JP7550426B1 - Method for indicating positioning accuracy in satellite navigation system and program for indicating positioning accuracy - Google Patents

Abstract

[Problem] To enable a user to grasp the positioning accuracy in a differential GPS (DGPS). [Solution] In satellite navigation systems including the US GPS and Japan's Quasi-Zenith Satellite System, when configuring a differential GPS (DGPS) in which a reference station is installed to correct positioning errors, correction information is obtained from multiple reference stations, and the maximum positioning error resulting from DGPS positioning performed at the position of a specific reference station using the correction information of each of the other reference stations is provided to the user station as an index of positioning accuracy when the specific reference station is used, the maximum positioning error resulting from DGPS positioning performed at the position of a reference station other than the specific reference station using the correction information of a specific reference station, or the maximum difference resulting from converting the correction information of each of the multiple reference stations into the amount of position correction at the position of the specific reference station. [Selected Figure] Figure 1

Description

This invention relates to a method for indicating positioning accuracy in a satellite navigation system and a program for indicating positioning accuracy.

Satellite navigation systems that use artificial satellites to measure position are collectively known as GNSS (Global Navigation Satellite System), and a representative example is the US's GPS (Global Positioning System). In general, GNSS uses a receiver to receive positioning signals transmitted by radio from artificial satellites called navigation satellites, and calculates the receiver's position by measuring the distance between the navigation satellite and the receiver. The receiver that determines the position is called the user receiver or user station. The error between the determined position and the true position is called the positioning error.

To calculate the receiver's position, it is necessary to know the position of the navigation satellite that is transmitting the positioning signal, but the orbital information required for this is transmitted by the navigation satellite itself by superimposing it on the positioning signal. Since the orbital information is created by prediction, it contains an error of about several meters, which causes positioning errors when calculating the receiver's position.

The timing at which navigation satellites transmit positioning signals is predetermined, and navigation satellites transmit positioning signals based on the time on their own clocks. High-precision atomic clocks are used for these clocks, but they contain errors equivalent to a few meters in distance, which causes positioning errors when calculating the receiver's position.

Before reaching the ground, the positioning signal passes through the ionosphere and troposphere in the sky, and delays occur when the radio signal passes through each of these regions. These delays are called the ionospheric propagation delay and the troposphere propagation delay, respectively. Therefore, when this radio signal is used as a positioning signal, these ionospheric propagation delay and troposphere propagation delay become a cause of positioning errors. The magnitude of the ionospheric propagation delay and the troposphere propagation delay converted into distance are called the ionospheric propagation delay and the troposphere delay, respectively.

In a satellite navigation system, the measured distance to a navigation satellite obtained by a receiver is the true distance plus all of the measurement errors caused by these error factors.

A receiver is installed at a fixed reference station on the ground, and the distance measured by this is used to create correction information for distance measurement errors. This information is then provided to the user, allowing the distance measured at the user station to be corrected based on the correction information, improving the position measurement accuracy (called "positioning accuracy") at the user station. This method is called Differential GPS (DGPS). To distinguish it from DGPS, the method of calculating the position of a user station without applying correction information is called standalone positioning.

There are several specific methods of DGPS, but the most common method uses the distance measured by a single reference station to generate distance correction values for each navigation satellite, and then compiles these for multiple navigation satellites and provides them to user stations as correction information. This method, sometimes called narrow-area differential GPS (LADGPS: Local Area DGPS), does not create correction information for each cause of positioning error, so as the distance between the user station and the reference station increases, the common components of the positioning error decrease, and positioning accuracy tends to deteriorate. It is generally recognized by those skilled in the art that it can be used within a range of approximately several hundred kilometers from the reference station, or up to several tens of kilometers depending on the ionospheric conditions.

The clock error of a navigation satellite appears as a uniform distance measurement error regardless of the position of the user station. The position error of a navigation satellite appears as a distance measurement error due to the inner product with the line of sight when the navigation satellite is seen from the user station. The amount of ionospheric propagation delay appears as a distance measurement error due to a quantity proportional to the integral of the density distribution of the ionospheric atmosphere on the path from which the positioning signal transmitted by the navigation satellite reaches the user station. The amount of tropospheric propagation delay appears as a distance measurement error due to a quantity proportional to the integral of the refractive index of the neutral atmosphere on the path from which the positioning signal transmitted by the navigation satellite reaches the user station. In other words, except for the clock error of the navigation satellite, the distance measurement error appears differently depending on the position of the user station. The distance correction value for a navigation satellite is the sum of the correction amounts corresponding to each of these measurement errors. Note that the amount of tropospheric propagation delay can be estimated with sufficient accuracy using a simple tropospheric propagation delay model.

The DGPS correction value for a navigation satellite is obtained by subtracting the distance measured by the reference station from the actual distance calculated from the navigation satellite's orbital information. This is then compiled for the navigation satellites from which the reference station is receiving positioning signals, and provided to the user station as correction information.

The correction information generated by the DGPS reference station can be converted into a position correction amount at any receiver position via the correspondence between the changes in distance of multiple navigation satellites contained in the correction information and the changes in receiver position.

We will confirm this using mathematical formulas. First, when determining the receiver position from the distances to multiple navigation satellites, because these relationships are nonlinear, iterative calculations are generally used. This involves repeatedly moving the receiver position by an amount corresponding to the difference between the measured distance to the navigation satellite and the distance to the navigation satellite at the provisional receiver position, via the correspondence relationship between the linearized distance and receiver position at the provisional receiver position, to determine a receiver position that satisfies the relationship with the measured distances to multiple navigation satellites.

Assume that N navigation satellites are used for positioning calculations. The correspondence between the linearized distance at the provisional receiver position and the receiver position is described by the following equation as the relationship between the change in distance Δr and the change in receiver position Δp.

(Equation 1)
G·Δp=Δr

Δp is a four-dimensional vector whose elements are the changes in the coordinate values of the receiver position Δx, Δy, and Δz, and the change in the receiver clock error Δc. That is, it is expressed as follows:

(Equation 2)
Δp=[Δx Δy Δz Δc]'

Here, "'" means the transpose of a matrix or vector. Δr is an N-dimensional vector, and its elements are the change in distance Δr(i) for each navigation satellite. That is, it is as follows.

(Equation 3)
Δr=[Δr(1)...Δr(i)...Δr(N)]'

The size of matrix G, which represents the geometric relationship between the distance and receiver position with respect to the navigation satellites, is N x 4. If the i-th row of matrix G is G(i), then it can be written as follows using the azimuth angle AZ(i) and elevation angle EL(i) of each navigation satellite.

(Equation 4)
G(i)=[-sinAZ(i)・cosEL(i)
-cosAZ(i)・cosEL(i)
-sinEL(i) 1]

To find Δp from Δr, it is common to solve (Equation 1) using the least squares method, as shown below.

(Equation 5)
Δp=inv(G'WG)・G'・W・△R=S・Δr

Here, inv(.) is a function that finds the inverse matrix. The NxN matrix W is used to obtain a weighted solution in the least squares method, and is generally the inverse matrix of the variance-covariance matrix for the distance measurements. If no weighting is required, a unit matrix can be used. The size of the matrix S is 4xN.

When a solution for the receiver position is obtained through repeated calculations, the receiver position does not change any further, so the change in the receiver position is |Δp| = 0. Here, "|·|" means the magnitude of the vector.

(Equation 6)
Δp=S·Δr=0

Let's consider applying correction information from DGPS. The correction information ΔR is composed of correction values ΔR(i) for each navigation satellite used. If the correction information ΔR is an N-dimensional vector, it is expressed as follows.

(Equation 7)
ΔR=[ΔR(1)...ΔR(i)...ΔR(N)]'

To apply the correction information, we simply add it to the distance measurement, which gives us the following relationship:

(Equation 8)
ΔP=S・(Δr+ΔR)=S・ΔR

That is, the correction information ΔR can be converted into a position correction amount ΔP via a matrix S. The position correction amount ΔP is a four-dimensional vector, and its elements are the correction amounts ΔX, ΔY, and ΔZ of the coordinate values of the receiver position and the correction amount ΔC of the receiver clock error. That is, it is as shown in the following formula.

(Equation 9)
ΔP=[ΔX ΔY ΔZ ΔC]'

The relationship in (Equation 1) is for a provisional receiver position in the receiver position calculation process, but since there are no particular restrictions on what the provisional receiver position is, the relationship in (Equation 1) holds for any receiver position. Therefore, the relationship in (Equation 8) also holds for any receiver position, so the correction information ΔR can be converted into a position correction amount ΔP for any receiver position.

Furthermore, consider multiplying the matrix S only by the correction value ΔR(i) for navigation satellite i contained in the correction information.

(Number 10)
ΔP=S・[0...ΔR(i)...0]'

The above formula means that the correction value ΔR(i) for each navigation satellite contained in the correction information can be converted to a position correction amount ΔP at any receiver position.

Strictly speaking, matrix G changes with changes in the receiver position, but the magnitude of the change in matrix G can be ignored in the vicinity of the receiver, for example, within the range of the change in receiver position due to the application of correction information. In other words, repeated calculations are not required when applying correction information.

Practical examples of DGPS include medium wave beacons for ships and FM multiplex digital broadcasting, but both have now been discontinued. Meanwhile, Japan's Quasi-Zenith Satellite System, which began operation in 2018, transmits DGPS correction information from its satellites as the Submeter-Level Augmentation Service (SLAS) service. The SLAS service has the advantage that by receiving a signal from a single satellite, correction information from 13 reference stations located throughout Japan can be obtained all at once. User stations using the SLAS service are required to select and use the correction information from the nearest reference station.

In addition to the above-mentioned system using individual reference stations, there is also a system called wide-area differential GPS, which combines measurement data from multiple reference stations to create wide-area correction information that is valid over a wide geographical area. As wide-area differential GPS services such as Japan's MSAS and the United States' WAAS have become widespread, there are currently no DGPS services other than the SLAS service of the Quasi-Zenith Satellite System that provide correction information from multiple reference stations.

In DGPS, there is no need to communicate the position of the reference station to the user station, but in the SLAS service, the user station is required to select and use correction information from the nearest reference station, so the approximate position of the reference station is transmitted along with the correction information.

In the field of GNSS, precise orbital ephemeris are created and used for each navigation satellite as accurate clock and orbital information. Precise orbital ephemeris are often created at 15-minute or 5-minute intervals, and users can obtain accurate time and position information at any point in time by interpolating between them. Precise orbital ephemeris created by an international organization called IGS (International GNSS Service), for example, are made public and are used in precision positioning fields such as surveying and geodesy.

There are three types of precise orbital almanac: Final Product and Rapid Product, which are not based on predictions, and Ultra Rapid Product, which is based on predictions. Final Product is the most accurate, with both navigation satellite position error and clock error within 2-3 centimeters, but requires about 2-3 weeks of analysis time from the date of measurement. Rapid Product has an accuracy similar to that of Final Product, and is released within 1-2 days from the date of measurement. Ultra Rapid Product includes predictions for up to several hours ahead from the time of release, and has an accuracy of about 5 centimeters for navigation satellite position error and about 1 meter for navigation satellite clock error.

Takeyasu Sakai and Kazunori Iemura, "DGPS Positioning Accuracy When Using Multiple Reference Stations," Technical Research Report of the Institute of Electronics, Information and Communication Engineers, SANE99-44, July 1999 Takeyasu Sakai and Kazunori Tadamura, "Improvement of GPS Positioning Accuracy by Using Multiple Reference Stations," Journal of the Japan Institute of Navigation, Vol. 101, pp. 15-20, September 1999 Toshiyuki Tanaka and Keita Kawamura, "Improvement of Positioning Accuracy in DGPS Using Long Baseline Reference Stations," Journal of the Institute of Positioning, Navigation and Navigation, Vol. 1, No. 1, pp. 1-8, 2010.

In general, with DGPS, the effect of correction information becomes smaller the further away from the reference station, so when using DGPS at a user station, it is either used within a limited range of the reference station, or, if multiple reference stations are available, the nearest reference station is selected and used.

For example, the SLAS service of the Quasi-Zenith Satellite System provides correction information from 13 reference stations located throughout Japan, and user stations are allowed to select and use the nearest reference station. The distance between a reference station and a user station can be more than 300 km, and can be even longer if some reference stations are out of service. However, even in such situations, the specified positioning accuracy can be achieved by using the nearest reference station.

In fact, it has recently become clear that the correction information provided by the SLAS service is not always effective enough to provide the required positioning accuracy. Ionosphere activity is affected by solar activity, which repeats in an 11-year cycle, and this issue has come to light during the most recent solar maximum. However, this has only been discovered through ex-post performance analysis, and there is no way for users of the SLAS service to ascertain the positioning accuracy in real time. For users, it is unclear whether the required positioning accuracy is being achieved, which makes it difficult to use the SLAS service.

In the case of SLAS services, correction information can be obtained from multiple reference stations, so by using the techniques of Non-Patent Documents 1 to 3 to interpolate and use the correction information from multiple reference stations, it may be possible to perform effective differential correction even at user stations located far from the reference station. However, none of Non-Patent Documents 1 to 3 provide any information about the positioning accuracy obtained as a result of applying the correction information. Therefore, these technical contents do not solve the problem of the present invention.

As described above, there was no means for determining the positioning accuracy in real time with DGPS. The objective of this invention is to enable users to determine the positioning accuracy in real time with DGPS.

In DGPS, the effect of correction by correction information generally decreases as the distance from the reference station increases, but the amount of tropospheric propagation delay can be estimated with sufficient accuracy using a simple tropospheric propagation delay model, so it is possible to correct the correction amount due to tropospheric propagation delay among the correction values for each navigation satellite to the correction amount at any receiver position. In addition, the amount of correction due to the position error of the navigation satellite can be estimated with sufficient accuracy using the precise orbital ephemeris (the very rapid ephemeris of [0041]), so it is possible to correct it to the correction amount at any receiver position as the line-of-sight component from the receiver position. Even if the distance to the reference station is, for example, around 500 km, the distance to the navigation satellite is more than 20,000 km, so not making this correction will not be a big problem. Note that the clock error of the navigation satellite is a constant distance error regardless of location, so such correction is not necessary.

Therefore, the problem with this invention is the remaining error factor, which is mainly caused by ionospheric propagation delay. The amount of ionospheric propagation delay appears as a distance measurement error due to the integral of the density distribution of the ionospheric atmosphere on the path taken by the positioning signal transmitted by the navigation satellite to reach the receiver, and the problem is the density distribution of the ionospheric atmosphere on the path taken by the positioning signal. Generally, this distribution is irregular and difficult to predict, so it is an error factor that cannot be fully corrected even with DGPS.

Consider the case where there are two DGPS reference stations. When the correction information generated by the second reference station is applied to the distance measurement value from the first reference station to determine the position, a calculation result including a positioning error is obtained, and the positioning error at the first reference station can be determined as the difference between this calculation result and the previously known position of the first reference station.

At this time, the correction values for each navigation satellite included in the correction information generated by the second reference station can be modified to correspond to the position of the first reference station, as described in [0048], for the amount of correction resulting from the position error of the navigation satellite and the tropospheric propagation delay. If this modification is then applied and used to calculate the position of the first reference station, the positioning error included in the calculation result can be suppressed.

However, if there is a difference in the amount of ionospheric propagation delay between the first and second reference stations, a large positioning error will occur because no correction for the amount of ionospheric propagation delay has been made. In other words, this positioning error reflects the difference in the amount of ionospheric propagation delay between the two reference stations. Therefore, when a user station located between or in the surrounding area of the two reference stations uses correction information from one of the two stations, this positioning error can be considered the maximum level of positioning error that cannot be corrected even by DGPS. The first method of solving the problem according to the present invention is to provide this to the user station as an index of positioning accuracy, allowing the user to grasp the positioning accuracy in real time in DGPS.

The above is true when two reference stations are available, but the same concept can be applied when there are multiple reference stations. In other words, if a specific reference station among multiple reference stations is targeted and the positioning error between the other reference stations and a specific reference station as described in [0050] to [0052] is calculated, the maximum value can be used as an index of positioning accuracy when user stations in the area surrounding those reference stations and their surrounding areas use the correction information from that specific reference station.

In the first method, the positioning error is calculated when the correction information generated by the second reference station is applied to the distance measurement value by the first reference station, or the positioning error is calculated when the correction information generated by another reference station is applied to the distance measurement value by a specific reference station, and the maximum value is provided to the user station as an index of positioning accuracy. However, by reversing this order, the positioning error is calculated when the correction information generated by the first reference station is applied to the distance measurement value by the second reference station, or the positioning error is calculated when the correction information generated by a specific reference station is applied to the distance measurement value by a reference station other than the specific reference station, and the maximum value is provided to the user station as an index of positioning accuracy. This is the second method of solving the problem by the present invention.

Consider again the case where there are two DGPS reference stations. As explained in [0011] to [0032], the correction information generated by each reference station can be converted into a position correction amount at any receiver position via the corresponding relationship between the change in distance of multiple navigation satellites contained in the correction information and the change in receiver position. Using this, the correction information generated by the second reference station can be converted into a position correction amount at the position of the first reference station. The magnitude of the difference between this result and the result of converting the correction information generated by the first reference station into a position correction amount at the position of the first reference station is calculated.

At this time, the correction values of each navigation satellite included in the correction information generated by the second reference station can be modified to correspond to the position of the first reference station, as described in [0048], for the correction amount due to the position error of the navigation satellite and the tropospheric propagation delay. If this modification is then applied and used to convert the position correction amount at the position of the first reference station, the difference between the correction amounts for the two positions can be reduced.

However, if there is a difference in the amount of ionospheric propagation delay between the first and second reference stations, the difference in the amount of position correction will be large because no correction for the amount of ionospheric propagation delay has been made. This difference in the amount of correction reflects the difference in the amount of ionospheric propagation delay between the two reference stations, as in [0052], and can be considered to be the maximum level of positioning error that cannot be corrected even by DGPS when a user station between the two reference stations or in the surrounding area uses correction information from one of the two stations. The third method of solving the problem according to the present invention is to provide this to the user station as an index of positioning accuracy, allowing the user to grasp the positioning accuracy in real time in DGPS.

The above is true when two reference stations are available, but the same concept can be applied when there are multiple reference stations. In other words, if a specific reference station among multiple reference stations is targeted and the difference in the position correction amount described in [0055] to [0057] is calculated between the other reference stations, the maximum value can be used as an index of positioning accuracy when user stations in the area surrounding those reference stations and the surrounding area use the correction information from that specific reference station.

Let us now consider again the case where there are two DGPS reference stations. As explained in [0011] to [0036], the correction value for each navigation satellite in the correction information generated by each reference station can be converted into a position correction amount for each navigation satellite at any receiver position via the corresponding relationship between the change in distance of the multiple navigation satellites contained in the correction information and the change in receiver position. Using this, the correction value for each navigation satellite in the correction information generated by the second reference station can be converted into a position correction amount at the position of the first reference station. The magnitude of the difference between this result and the result of converting the correction value for each navigation satellite in the correction information generated by the first reference station into a position correction amount at the position of the first reference station is calculated for each corresponding navigation satellite.

At this time, the correction values of each navigation satellite among the correction information generated by the second reference station can be modified to correspond to the position of the first reference station, as described in [0048], with respect to the amount of correction resulting from the position error of the navigation satellite and tropospheric propagation delay. If this modification is then used to convert the amount of correction for the position at the position of the first reference station, the magnitude of the difference between the correction amounts for the two positions will have the same properties as described in [0057].

The magnitude of this difference in position correction amount is calculated for each navigation satellite. The fourth method of solving the problem according to the present invention is to provide the maximum value to the user station as an index of positioning accuracy, allowing the user to grasp the positioning accuracy in real time in DGPS.

The above is true when two reference stations are available, but the same concept can be applied when there are multiple reference stations. In other words, if a specific reference station among multiple reference stations is targeted and the difference in the position correction amount described in [0059] to [0061] is calculated between the other reference stations, the maximum value can be used as an index of positioning accuracy when user stations in the area surrounding those reference stations and the surrounding area use the correction information from that specific reference station.

Comparing the four methods mentioned above, the first method requires distance measurements from the first reference station or a specific reference station, and the second method requires distance measurements from the second reference station or a reference station other than the specific reference station, whereas the third and fourth methods do not. Also, the first method requires that the position of the first reference station or a specific reference station, and the second method requires that the position of the second reference station or a reference station other than the specific reference station, be known accurately in advance, whereas the third and fourth methods require the position of the first reference station or a specific reference station, but do not require it to be very accurate. The reason for this is that in the third and fourth methods, when the correction information is converted into a position correction amount, the position correction amount does not change significantly even if the position accuracy of the point used as the receiver position is not very high.

In the first method, by using the calculated position obtained by applying correction information generated by the first reference station or the specific reference station to the distance measurement value by the first reference station or the specific reference station instead of the previously known position of the first reference station or the specific reference station, the accuracy of the previously known position of the first reference station or the specific reference station can be relaxed to the extent required by the third and fourth methods. However, even in this case, the first method still requires the distance measurement value by the first reference station or the specific reference station. The same situation applies to the second method.

As mentioned in [0048], position errors of navigation satellites are often not a big problem, and may be omitted when correcting the correction information in [0051], [0056], and [0060].

The invention according to claim 1 relates to a satellite navigation system comprising a plurality of navigation satellites that transmit positioning signals, a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them, a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each navigation satellite from the original distances calculated from the orbital information of each of the navigation satellites, and collectively providing the correction values to the user station as correction information for the navigation satellites, and an information providing station that provides the user station with an index of the positioning accuracy when a specific reference station among the plurality of reference stations is used, A method for indicating positioning accuracy in a satellite navigation system, characterized in that the correction information is obtained from each of the reference stations other than the specific reference station, the correction value of each navigation satellite contained therein is corrected to correspond to the position of the specific reference station with respect to the correction amount due to the position error of the navigation satellite and the tropospheric propagation delay, the corrected correction information is applied to the distance measurement value by the specific reference station to obtain the position of the specific reference station, the magnitude of the difference between this result and the previously known position of the specific reference station is obtained for each of the reference stations other than the specific reference station, and the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 2 is a satellite navigation system comprising: a plurality of navigation satellites that transmit positioning signals; a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each navigation satellite from the original distances calculated from the orbital information of each of the navigation satellites, and collectively providing the correction values to the user station as correction information for the navigation satellites; and an information providing station that provides the user station with an index of the positioning accuracy when a specific reference station among the plurality of reference stations is used, The information providing station obtains the correction information from each of the reference stations other than the specific reference station, corrects the correction value of each navigation satellite contained in the correction information for the amount of correction caused by tropospheric propagation delay so that it corresponds to the position of the specific reference station, applies the corrected correction information to the distance measurement value by the specific reference station to determine the position of the specific reference station, determines the magnitude of the difference between this result and the previously known position of the specific reference station for each of the reference stations other than the specific reference station, and provides the maximum value of the difference to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 3 is a satellite navigation system comprising a plurality of navigation satellites that transmit positioning signals, a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them, a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each corresponding navigation satellite from the original distances calculated from the orbital information of each of the navigation satellites, and collectively providing the correction values to the user station as correction information for the navigation satellites, and an information providing station that provides the user station with an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, the information providing station being operated This is a program for indicating the positioning accuracy in a satellite navigation system, which is characterized by obtaining the correction information from each of the reference stations other than the specific reference station, correcting the correction value of each navigation satellite contained therein for the amount of correction caused by the navigation satellite's position error and tropospheric propagation delay so that it corresponds to the position of the specific reference station, applying this corrected correction information to the distance measurement value by the specific reference station to obtain the position of the specific reference station, obtaining the magnitude of the difference between this result and the previously known position of the specific reference station for each of the reference stations other than the specific reference station, and providing the maximum value thereof to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 4 is a satellite navigation system comprising: a plurality of navigation satellites that transmit positioning signals; a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each corresponding navigation satellite from the original distances calculated from the orbital information of each of the navigation satellites, and collectively providing the correction values to the user station as correction information for the navigation satellites; and an information providing station that provides the user station with an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, A program for indicating the positioning accuracy in a satellite navigation system, which operates by obtaining the correction information from each of the reference stations other than the specific reference station, correcting the correction value of each navigation satellite contained therein for the amount of correction caused by tropospheric propagation delay so that it corresponds to the position of the specific reference station, applying this corrected correction information to the distance measurement value by the specific reference station to obtain the position of the specific reference station, determining the magnitude of the difference between this result and the previously known position of the specific reference station for each of the reference stations other than the specific reference station, and providing the maximum value of these to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 5 is a satellite navigation system comprising: a plurality of navigation satellites that transmit positioning signals; a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each corresponding navigation satellite from the original distances calculated from the orbital information of each of the navigation satellites, and collectively providing the correction values to the user station as correction information for the navigation satellites; and an information providing station that provides the user station with an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, The information providing station obtains the correction information from the specific reference station, corrects the correction values of each navigation satellite contained therein for the amount of correction caused by the position error of the navigation satellite and tropospheric propagation delay so that they correspond to the positions of each of the reference stations other than the specific reference station, applies the corrected correction information to the distance measurements of each of the corresponding reference stations to determine the positions of these reference stations, determines the magnitude of the difference between this result and the previously known positions of those reference stations for each of those reference stations, and provides the maximum value of these differences to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 6 relates to a satellite navigation system comprising: a plurality of navigation satellites that transmit positioning signals; a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each navigation satellite from the original distances calculated from the orbital information of each of the navigation satellites, and collectively providing the correction values to the user station as correction information for the navigation satellites; and an information providing station that provides the user station with an index of the positioning accuracy when a specific reference station among the plurality of reference stations is used. The information providing station obtains the correction information from the specific reference station, corrects the correction value of each navigation satellite contained therein for the amount of correction caused by tropospheric propagation delay so that it corresponds to the position of each of the reference stations other than the specific reference station, applies the corrected correction information to the distance measurement value of each corresponding reference station to determine the positions of these reference stations, determines the magnitude of the difference between this result and the previously known positions of these reference stations for each of the reference stations, and provides the maximum value of the difference to the user station as an index of the positioning accuracy when the specific reference station is used.

The invention according to claim 7 is a satellite navigation system comprising: a plurality of navigation satellites that transmit positioning signals; a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each navigation satellite from the original distances calculated from the orbital information of each of the navigation satellites, and collectively providing the correction values to the user station as correction information for the navigation satellites; and an information providing station that provides the user station with an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, This program operates in such a way that it obtains the correction information from the specific reference station, modifies the correction values of each navigation satellite contained therein for the amount of correction caused by the position error of the navigation satellite and tropospheric propagation delay so that they correspond to the positions of each of the reference stations other than the specific reference station, applies the modified correction information to the distance measurements of each of the corresponding reference stations to determine the positions of these reference stations, determines the magnitude of the difference between this result and the previously known positions of these reference stations for each of the reference stations, and provides the maximum value of these differences to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 8 is a satellite navigation system comprising: a plurality of navigation satellites that transmit positioning signals; a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each navigation satellite from the original distances calculated from the orbital information of each of the navigation satellites, and collectively providing the correction values to the user station as correction information for the navigation satellites; and an information providing station that provides the user station with an index of the positioning accuracy when a specific reference station among the plurality of reference stations is used, A program that operates in an information providing station, obtains the correction information from the specific reference station, modifies the correction value of each navigation satellite contained therein for the amount of correction caused by tropospheric propagation delay so that it corresponds to the position of each of the reference stations other than the specific reference station, applies the modified correction information to the distance measurement value of each corresponding reference station to determine the positions of these reference stations, determines the magnitude of the difference between this result and the previously known positions of these reference stations for each of these reference stations, and provides the maximum value of these differences to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 9 relates to a satellite navigation system including a plurality of navigation satellites that transmit positioning signals, a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them, a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each corresponding navigation satellite from the original distances calculated from the orbital information of each of the navigation satellites, as correction information for the navigation satellites, and an information providing station that provides the user station with an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, the correction information being provided by any one of the plurality of reference stations via a correspondence relationship between the change in distance for the navigation satellites included in the correction information and the change in receiver position. The information providing station obtains the correction information from each of the reference stations other than the specific reference station, corrects the correction value of each navigation satellite contained therein for the correction amount due to the position error of the navigation satellite and the tropospheric propagation delay so that it corresponds to the position of the specific reference station, converts this corrected correction information into a position correction amount at the position of the specific reference station, calculates the magnitude of the difference between this result and the result of converting the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station for each of the reference stations other than the specific reference station, and provides the maximum value of the difference to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 10 relates to a satellite navigation system including a plurality of navigation satellites that transmit positioning signals, a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them, a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each navigation satellite from the ideal distances calculated from the orbital information of each of the navigation satellites, and collectively providing the correction values to the user station as correction information for the navigation satellites, and an information providing station that provides the user station with an index of positioning accuracy when a specific reference station out of the plurality of reference stations is used, the correction information being a correspondence relationship between the change in distance for the navigation satellites included in the correction information and the change in receiver position. The information providing station obtains the correction information from each of the reference stations other than the specific reference station, corrects the correction value of each navigation satellite contained therein for the correction amount caused by tropospheric propagation delay so that it corresponds to the position of the specific reference station, converts the corrected correction information into a position correction amount at the position of the specific reference station, calculates the magnitude of the difference between this result and the result of converting the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station for each of the reference stations other than the specific reference station, and provides the maximum value of the difference to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 11 relates to a satellite navigation system including a plurality of navigation satellites that transmit positioning signals, a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them, a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each corresponding navigation satellite from the original distances calculated from the orbital information of each of the navigation satellites, and providing the user station with correction information for the navigation satellites as correction information, and an information providing station that provides the user station with an index of positioning accuracy when a specific reference station out of the plurality of reference stations is used, the correction information being provided to any receiver via a correspondence relationship between a change in distance for the navigation satellites included in the correction information and a change in receiver position. A program that indicates the positioning accuracy in a satellite navigation system, which operates at the information providing station, obtains the correction information from each of the reference stations other than the specific reference station, corrects the correction value of each navigation satellite contained therein for the correction amount due to the navigation satellite position error and tropospheric propagation delay so that it corresponds to the position of the specific reference station, converts this corrected correction information into a position correction amount at the position of the specific reference station, calculates the magnitude of the difference between this result and the result of converting the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station for each of the reference stations other than the specific reference station, and provides the maximum value to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 12 relates to a satellite navigation system including a plurality of navigation satellites that transmit positioning signals, a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them, a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each navigation satellite from the ideal distances calculated from the orbital information of each of the navigation satellites, and providing the user station with correction information for the navigation satellites as correction information, and an information providing station that provides the user station with an index of positioning accuracy when a specific reference station out of the plurality of reference stations is used, the correction information being calculated by calculating a correspondence between the change in distance for the navigation satellites included in the correction information and the change in receiver position, This program indicates the positioning accuracy in a satellite navigation system, and is characterized in that it can be converted into a position correction amount at any receiver position, operates at the information providing station, obtains the correction information from each of the reference stations other than the specific reference station, modifies the correction value of each navigation satellite contained therein for the correction amount caused by tropospheric propagation delay so that it corresponds to the position of the specific reference station, converts this modified correction information into a position correction amount at the position of the specific reference station, calculates the magnitude of the difference between this result and the result of converting the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station for each of the reference stations other than the specific reference station, and provides the maximum value to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 13 relates to a satellite navigation system including a plurality of navigation satellites that transmit positioning signals, a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them, a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each of the navigation satellites from the ideal distances calculated from the orbital information of each of the navigation satellites, and collectively providing the correction values to the user station as correction information for the navigation satellites, and an information providing station that provides the user station with an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, wherein the correction values for each navigation satellite included in the correction information are assigned to an arbitrary receiver position for each navigation satellite via a corresponding relationship between the change in distance for the navigation satellites included in the correction information and the change in receiver position. The information providing station obtains the correction information from each of the reference stations other than the specific reference station, corrects the correction value of each navigation satellite contained therein for the correction amount due to the navigation satellite's position error and tropospheric propagation delay so that it corresponds to the position of the specific reference station, converts each of the corrected correction values of the navigation satellite into a correction amount for the position at the position of the specific reference station, and calculates the magnitude of the difference between this result and the result of converting the correction value of each navigation satellite in the correction information obtained from the specific reference station into a correction amount for the position at the position of the specific reference station for each navigation satellite, for each of the reference stations other than the specific reference station, and provides the maximum value to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 14 relates to a satellite navigation system including a plurality of navigation satellites that transmit positioning signals, a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them, a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each of the navigation satellites from the original distances calculated from the orbital information of each of the navigation satellites, and collectively providing the correction values to the user station as correction information for the navigation satellites, and an information providing station that provides the user station with an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, wherein the correction values for each navigation satellite included in the correction information are determined arbitrarily for each navigation satellite via the corresponding relationship between the change in distance for the navigation satellites included in the correction information and the change in receiver position. The information providing station obtains the correction information from each of the reference stations other than the specific reference station, corrects the correction value of each navigation satellite contained therein for the correction amount caused by tropospheric propagation delay so that it corresponds to the position of the specific reference station, and converts each of the corrected correction values of the navigation satellite into a correction amount for the position at the position of the specific reference station. The information providing station obtains the correction information from each of the reference stations other than the specific reference station, corrects the correction amount caused by tropospheric propagation delay for each of the navigation satellites contained therein to correspond to the position of the specific reference station, and converts each of the corrected correction values of the navigation satellite into a correction amount for the position at the position of the specific reference station. The information providing station obtains the magnitude of the difference between this result and the result of converting the correction value of each navigation satellite in the correction information obtained from the specific reference station into a correction amount for the position at the position of the specific reference station for each navigation satellite, for each of the reference stations other than the specific reference station, and provides the maximum value to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 15 is a satellite navigation system including a plurality of navigation satellites that transmit positioning signals, a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them, a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each of the navigation satellites from the original distances calculated from the orbital information of each of the navigation satellites, and collectively providing the correction values to the user station as correction information for the navigation satellites, and an information providing station that provides the user station with an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, wherein the correction values for each navigation satellite included in the correction information are calculated based on the correspondence between the change in distance for the navigation satellites included in the correction information and the change in receiver position, and the correction values are calculated based on the position at an arbitrary receiver position for each navigation satellite, A program that indicates the positioning accuracy in a satellite navigation system, which operates at the information providing station, obtains the correction information from each of the reference stations other than the specific reference station, corrects the correction value of each navigation satellite contained therein for the correction amount due to the navigation satellite's position error and tropospheric propagation delay so that it corresponds to the position of the specific reference station, converts each corrected correction value of the navigation satellite into a position correction amount at the position of the specific reference station, and calculates the magnitude of the difference between this result and the result of converting the correction value of each navigation satellite in the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station for each navigation satellite, for each of the reference stations other than the specific reference station, and provides the maximum value to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 16 relates to a satellite navigation system including a plurality of navigation satellites that transmit positioning signals, a user station that receives the positioning signals transmitted by the navigation satellites and measures the distances between them, a plurality of reference stations that receive the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide the user station with correction values obtained by subtracting the correction values for each of the navigation satellites from the ideal distances calculated from the orbital information of each of the navigation satellites, and collectively providing the correction values to the user station as correction information for the navigation satellites, and an information providing station that provides the user station with an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, wherein the correction values for each navigation satellite included in the correction information are calculated based on the correspondence between the changes in distance and the changes in receiver position for the navigation satellites included in the correction information, and the correction values are calculated based on the correspondence between the changes in distance and the receiver position for each of the navigation satellites included in the correction information, A program that indicates the positioning accuracy in a satellite navigation system, which operates at the information providing station, obtains the correction information from each of the reference stations other than the specific reference station, corrects the correction value of each navigation satellite contained therein for the correction amount caused by tropospheric propagation delay so that it corresponds to the position of the specific reference station, converts each corrected correction value of the navigation satellite into a position correction amount at the position of the specific reference station, and calculates the magnitude of the difference between this result and the result of converting the correction value of each navigation satellite in the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station for each navigation satellite and each of the reference stations other than the specific reference station, and provides the maximum value to the user station as an index of positioning accuracy when the specific reference station is used.

The invention according to claim 17 is a method for indicating positioning accuracy in a satellite navigation system, characterized in that the information providing station is built into the user station in the invention according to any one of claims 1, 2, 5, 6, 9, 10, 13, and 14.

The invention according to claim 18 is a program for indicating the positioning accuracy in a satellite navigation system, characterized in that the information providing station is built into the user station in the invention according to any one of claims 3, 4, 7, 8, 11, 12, 15, and 16.

The inventions according to claims 1 to 18 are configured as described above, so that in a DGPS, users can grasp the positioning accuracy in real time. Previously, there was no means for users to grasp the positioning accuracy in real time.

1 is a schematic diagram illustrating a method for indicating positioning accuracy in a satellite navigation system according to an embodiment of the present invention. FIG.

Below, specific examples of the present invention will be described in detail with reference to the drawings.

A first embodiment of the present invention will be described in detail with reference to Figure 1. Note that while Figure 1 shows only two reference stations, this is merely an example, and a configuration with three or more reference stations is also possible. This embodiment corresponds to the inventions of claims 1 to 4.

In Figure 1, navigation satellite 1 (1x, 1y, etc.) each transmits a positioning signal.

The positioning signal transmitted by navigation satellite 1 (1x, 1y...) passes through the ionosphere 2.

The reference station 3 (3a, 3b, ...) receives the positioning signal transmitted by the navigation satellite 1 (1x, 1y, ...) and measures the distance from each navigation satellite.

The positioning signal received by the reference station 3 (3a, 3b...) is transmitted by the navigation satellite 1 (1x, 1y...), and then travels through route 31 (31a, 31b...), route 32 (32a, 32b...), and route 33 (33a, 33b...) to reach the reference station. Route 31 (31a, 31b...) is the portion before reaching the ionosphere, route 32 (32a, 32b...) is the portion during passage through the ionosphere, and route 33 (33a, 33b...) is the portion after passage through the ionosphere.

User station 4 receives the positioning signal transmitted by navigation satellite 1 (1x, 1y, ...) and measures the distance from each navigation satellite.

The positioning signal received by user station 4 is transmitted by navigation satellite 1 (1x, 1y, ...) and then passes through routes 41, 42, and 43 before reaching the user station. Route 41 is the portion before reaching the ionosphere, route 42 is the portion during passage through the ionosphere, and route 43 is the portion after passage through the ionosphere.

The information providing station 5 obtains correction information from the reference station 3 (3a, 3b, ...). For reference station 3a, this is the sum of the lengths of routes 31a, 32a, and 33a, and for reference station 3b, this is the sum of the lengths of routes 31b, 32b, and 33b, calculated from the orbital information of the navigation satellite minus the actually measured value.

The information providing station 5 corrects the correction values of each navigation satellite contained in the correction information obtained from the reference stations 3b, 3c, etc., so that the correction amount due to the position error of the navigation satellite corresponds to the position of the reference station 3a. In other words, the correction values, which include the correction amount due to the position error of the navigation satellite corresponding to the routes 31b, 31c, etc., are corrected to correspond to the route 31a. Since the position error of the navigation satellite can be estimated with sufficient accuracy by using the precise orbital ephemeris (the very rapid ephemeris in [0041]), it is possible to correct the correction amount at the positions of the reference stations 3b, 3c, etc. to the correction amount at the position of the reference station 3a. Note that the position error of the navigation satellite is often not a big problem as described in [0048], and this correction may be omitted.

The information providing station 5 corrects the correction values of each navigation satellite contained in the correction information obtained from the reference stations 3b, 3c, etc., so that the correction amount due to tropospheric propagation delay corresponds to the position of the reference station 3a. In other words, the correction values, which include the correction amount due to tropospheric propagation delay corresponding to the routes 33b, 33c, etc., are corrected to correspond to the route 33a. The amount of tropospheric propagation delay can be estimated with sufficient accuracy using a simple tropospheric propagation delay model, so it is possible to correct the correction amount at the positions of the reference stations 3b, 3c, etc. to the correction amount at the position of the reference station 3a.

The information providing station 5 applies the revised correction information to the distance measurements by the reference station 3a to determine the position of the reference station 3a, and determines the magnitude of the difference between this result and the previously known position of the reference station 3a. The magnitude of this difference is determined for the reference stations 3b, 3c, etc.

The information providing station 5 provides the maximum value of this difference to the user station 4 as an index of the positioning accuracy when the reference station 3a is used. In this case, the maximum value itself may be provided, but it is also acceptable to index it into several stages so that the user station can use it easily.

Next, we will explain how it works.

The information providing station 5 corrects the correction values for each navigation satellite contained in the correction information obtained from the reference stations 3b, 3c, etc., so that the correction amount due to the position error of the navigation satellite and the tropospheric propagation delay corresponds to the position of the reference station 3a. Therefore, the position of the reference station 3a obtained by the information providing station applying this corrected correction information to the distance measurement value by the reference station 3a and the previously known position of the reference station 3a should be almost the same, as long as there is no difference in the amount of ionospheric propagation delay between the reference station 3a and the reference stations 3b, 3c, etc. In other words, the positioning error is small.

On the other hand, if there is a difference in the amount of ionospheric propagation delay between reference station 3a and reference stations 3b, 3c, etc., a large positioning error will occur because the correction information obtained from reference stations 3b, 3c, etc. is not corrected for the amount of ionospheric propagation delay. In other words, this positioning error reflects the difference in the amount of ionospheric propagation delay between reference station 3a and reference stations 3b, 3c, etc. Therefore, when user stations in the area surrounding these reference stations and the surrounding areas use the correction information from reference station 3a, the maximum value of this positioning error can be considered the maximum level of positioning error that cannot be corrected even by DGPS. By providing this to user stations as an index of positioning accuracy, users can grasp the positioning accuracy in real time in DGPS.

Let us verify the above explanation using a formula. For navigation satellite i and reference station k, if the satellite position according to the navigation message is vector B(i), the correct satellite position is vector P(i), and the reference station position is vector R(k), then the correction value ΔR(i, k) is expressed by the following formula. The correction value ΔR(i, k) is a scalar quantity, and "|·|" means the magnitude of the vector.

(Equation 11)
ΔR(i,k)=|B(i)−R(k)|−|P(i)−R(k)|

Considering the causes of distance measurement errors, when the position error of the navigation satellite is expressed as vector E(i), the ionospheric propagation delay as I(i,k), and the tropospheric propagation delay as T(i,k), the correction value ΔR(i,k) can also be expressed by the following equation. The ionospheric propagation delay I(i,k) and the tropospheric propagation delay T(i,k) are scalar quantities.

(Equation 12)
ΔR(i,k)=E(i)・(B(i)−R(k))−I(i,k)−T(i,k)

The position error of a navigation satellite can be known if a precise orbital ephemeris is available, since the relationship E(i) = B(i) - P(i) holds. Therefore, the correction amount due to the position error of the navigation satellite, which is used to correct the correction value ΔR(i,j) of reference station j to the correction value at the position of reference station k, can be written as follows:

(Equation 13)
-E(i)・(B(i)−R(j))+E(i)・(B(i)−R(k))

In addition, since it is known that the amount of tropospheric propagation delay can be estimated using a simple model, the correction amount due to tropospheric propagation delay, which is used to correct the correction value ΔR(i, j) of reference station j to the correction value at the position of reference station k, can be written as follows:

(Equation 14)
+T(i,j)-T(i,k)

By combining these two, the following equation can be used to correct the correction value ΔR(i,j) of reference station j to the correction value at the position of reference station k.

(Equation 15)
ΔR(i, k)
ΔR(i, j)
-E(i)・(B(i)−R(j))+E(i)・(B(i)−R(k))
+T(i,j)-T(i,k)
=E(i)・(B(i)-R(k))-I(i,j)-T(i,k)

In other words, for the correction values of each navigation satellite contained in the correction information obtained from reference stations 3b, 3c, etc. (corresponding to symbol j), the correction amount due to the position error of the navigation satellite and the tropospheric propagation delay can be corrected to correspond to the position of reference station 3a (corresponding to symbol k), but the ionospheric propagation delay amount is not corrected, and the delay amount at reference stations 3b, 3c, etc. remains.

A second embodiment of the present invention will be described in detail with reference to Figure 1. Note that while Figure 1 shows only two reference stations, this is merely an example, and a configuration with three or more reference stations is also possible. This embodiment corresponds to the inventions of claims 5 to 8.

The explanations of [0088] to [0096] in Example 1 also apply to this example.

The information providing station 5 corrects the correction values of each navigation satellite contained in the correction information obtained from the reference station 3a so that the correction amount due to the position error of the navigation satellite corresponds to the positions of the reference stations 3b, 3c, etc. In other words, the correction value, which includes the correction amount due to the position error of the navigation satellite corresponding to the route 31a, is corrected to correspond to the routes 31b, 31c, etc. Since the position error of the navigation satellite can be estimated with sufficient accuracy by using the precise orbital ephemeris (the very rapid ephemeris of [0041]), it is possible to correct the correction amount at the position of the reference station 3a to the correction amount at the positions of the reference stations 3b, 3c, etc.

The information providing station 5 modifies the correction value of each navigation satellite contained in the correction information obtained from the reference station 3a so that the correction amount due to tropospheric propagation delay corresponds to the position of the reference station 3a. That is, the correction value includes a correction amount due to tropospheric propagation delay corresponding to the path 33a, and modifies it to correspond to the paths 33b, 33c, etc. The tropospheric propagation delay can be estimated with sufficient accuracy using a simple tropospheric propagation delay model, so it is possible to modify the correction amount at the position of the reference station 3a to the correction amount at the positions of the reference stations 3b, 3c, etc.

The information providing station 5 applies the revised correction information to the distance measurements by the reference stations 3b, 3c, etc. to determine the positions of the reference stations 3b, 3c, etc., and determines the magnitude of the difference between this result and the previously known positions of the reference stations 3b, 3c, etc. The magnitude of this difference is determined for the reference stations 3b, 3c, etc.

The information providing station 5 provides the maximum value of this difference to the user station 4 as an index of the positioning accuracy when the reference station 3a is used. In this case, the maximum value itself may be provided, but it is also acceptable to index it into several stages so that the user station can use it easily.

Next, we will explain how it works.

The information providing station 5 corrects the correction values of each navigation satellite contained in the correction information obtained from the reference station 3a so that the correction amount caused by the position error of the navigation satellite and the tropospheric propagation delay corresponds to the positions of the reference stations 3b, 3c, etc. Therefore, the positions of the reference stations 3b, 3c, etc. obtained by the information providing station applying this corrected correction information to the distance measurements by the reference stations 3b, 3c, etc. and the previously known positions of the reference stations 3b, 3c, etc. should be almost the same, as long as there is no difference in the amount of ionospheric propagation delay between the reference station 3a and the reference stations 3b, 3c, etc. In other words, the positioning error is small.

On the other hand, if there is a difference in the amount of ionospheric propagation delay between reference station 3a and reference stations 3b, 3c, etc., a large positioning error will occur because the correction information obtained from reference station 3a is not corrected for the amount of ionospheric propagation delay. In other words, this positioning error reflects the difference in the amount of ionospheric propagation delay between reference station 3a and reference stations 3b, 3c, etc. Therefore, when user stations in the area surrounding these reference stations and the surrounding areas use the correction information from reference station 3a, the maximum value of this positioning error can be considered the maximum level of positioning error that cannot be fully corrected even by DGPS. By providing this to user stations as an index of positioning accuracy, users can grasp the positioning accuracy in real time in DGPS.

A third embodiment of the present invention will be described in detail with reference to Figure 1. Note that while Figure 1 shows only two reference stations, this is merely an example, and a configuration with three or more reference stations is also possible. This embodiment corresponds to the inventions of claims 9 to 12.

The explanations of [0088] to [0096] in Example 1 also apply to this example.

The information providing station 5 converts the revised correction information into a position correction amount at the position of the reference station 3a, and calculates the magnitude of the difference between this result and the position correction amount obtained by converting the correction information obtained from the reference station 3a at the position of the reference station 3a. The magnitude of this difference is calculated for the reference stations 3b, 3c, etc.

The information providing station 5 provides the maximum value of this difference to the user station 4 as an index of the positioning accuracy when the reference station 3a is used. In this case, the maximum value itself may be provided, but it is also acceptable to index it into several stages so that the user station can use it easily.

Next, we will explain how it works.

The information providing station 5 corrects the correction information obtained from the reference stations 3b, 3c, etc., so that the correction amount due to the position error of the navigation satellite contained in the correction information and the tropospheric propagation delay corresponds to the position of the reference station 3a. Therefore, the result of the information providing station converting this corrected correction information into the position correction amount at the position of the reference station 3a and the position correction amount obtained by converting the correction information obtained from the reference station 3a into the position of the reference station 3a should be almost the same, as long as there is no difference in the amount of ionospheric propagation delay between the reference station 3a and the reference stations 3b, 3c, etc. In other words, the difference between them is small.

On the other hand, if there is a difference in the amount of ionospheric propagation delay between reference station 3a and reference stations 3b, 3c, etc., the difference in the amount of position correction will be large because the correction information obtained from reference stations 3b, 3c, etc. is not adjusted for the amount of ionospheric propagation delay. In other words, the difference in the amount of position correction reflects the difference in the amount of ionospheric propagation delay between reference station 3a and reference stations 3b, 3c, etc. Therefore, when user stations in the area surrounding these reference stations and the surrounding area use the correction information of reference station 3a, the maximum value of this difference in the amount of position correction can be considered as the maximum level of positioning error that cannot be corrected even by DGPS. By providing this to user stations as an index of positioning accuracy, users can grasp the positioning accuracy in real time in DGPS.

A fourth embodiment of the present invention will be described in detail with reference to Figure 1. Note that while Figure 1 shows only two reference stations, this is merely an example, and a configuration with three or more reference stations is also possible. This embodiment corresponds to the inventions of claims 13 to 16.

The explanations of [0088] to [0096] in Example 1 also apply to this example.

The information providing station 5 converts the correction value of each navigation satellite contained in the revised correction information into a position correction amount at the position of the reference station 3a, and calculates the magnitude of the difference for each corresponding navigation satellite between this result and the result of converting the correction value of each navigation satellite in the correction information obtained from the reference station 3a into a position correction amount at the position of the reference station 3a. The magnitude of this difference is calculated for each navigation satellite, for the reference stations 3b, 3c, etc.

The information providing station 5 provides the maximum value of this difference to the user station 4 as an index of the positioning accuracy when the reference station 3a is used. In this case, the maximum value itself may be provided, but it is also acceptable to index it into several stages so that the user station can use it easily.

Next, we will explain how it works.

The information providing station 5 modifies the correction values of each navigation satellite contained in the correction information obtained from the reference stations 3b, 3c, etc. to correspond to the position of the reference station 3a. Therefore, the results of the information providing station's conversion of the modified correction values of each navigation satellite into position correction amounts at the position of the reference station 3a and the results of the conversion of the correction values of each navigation satellite in the correction information obtained from the reference station 3a into position correction amounts at the position of the reference station 3a should be approximately the same for each corresponding navigation satellite, unless there is a difference in the amount of ionospheric propagation delay between the reference station 3a and the reference stations 3b, 3c, etc. In other words, the difference between them is small.

On the other hand, if there is a difference in the amount of ionospheric propagation delay between the reference station 3a and the reference stations 3b, 3c, etc., the difference in the amount of position correction will be large because the correction information obtained from the reference stations 3b, 3c, etc. is not adjusted for the amount of ionospheric propagation delay. In other words, the difference in the amount of position correction reflects the difference in the amount of ionospheric propagation delay between the reference station 3a and the reference stations 3b, 3c, etc. Therefore, when user stations in the area surrounding these reference stations and the surrounding area use the correction information of the reference station 3a, the maximum value of this difference in the amount of position correction can be regarded as the maximum level of positioning error that cannot be corrected even by DGPS. By providing this to the user station as an index of positioning accuracy, users can grasp the positioning accuracy in real time in DGPS.

In the first to fourth embodiments, the information providing station 5 is installed separately from the user station 4, but the functions of the information providing station can be performed in the user station, so it is also possible for the user station to have a built-in function of the information providing station. This embodiment corresponds to the inventions of claims 17 and 18.

Comparing Examples 1 to 4, Example 1 requires the distance measurement value from reference station 3a, and Example 2 requires the distance measurement value from reference stations 3b, 3c, etc., whereas Examples 3 and 4 do not require this. Also, Example 1 requires that the position of reference station 3a, and Example 2 requires that the positions of reference stations 3b, 3c, etc. be known accurately in advance, whereas Examples 3 and 4 require the position of reference station 3a, but this does not have to be so accurate. This corresponds to the explanation in [0063].

Therefore, when an information providing station 5 is provided on the service provider side to inform the user station 4 of the DGPS positioning accuracy, an information providing station 5 based on any of the embodiments 1 to 4 may be provided. On the other hand, when the user station 4 is configured as in this embodiment in which the function of the information providing station 5 is built in, the distance measurement value by the reference station is generally unknown, and as described in [0039], the exact position of the reference station is usually not given, so an information providing station based on embodiment 3 or embodiment 4 will be built in to the user station.

Next, we will explain how it works.

By incorporating the functionality of the information providing station 5 in the user station 4, the information providing station can know the operating status of the user station, and can apply the present invention to only the reference station that the user station intends to use among the available reference stations to know the DGPS positioning accuracy. This allows the user station to obtain information on reasonable positioning accuracy without being affected by reference stations that the user station does not use.

In a differential GPS (DGPS), there is no means for a user station to ascertain positioning accuracy in real time, and it is unclear whether the specified positioning accuracy is being achieved. The method of indicating positioning accuracy in a satellite navigation system of this invention allows users to ascertain positioning accuracy in real time in a DGPS, so that users can be informed if the positioning accuracy deviates from the specified accuracy, thereby contributing to ensuring user safety and improving the convenience of DGPS.

1 (1x, 1y...) Navigation satellite 2 Ionosphere 3 (3a, 3b...) Reference station 31 (31a, 31b...) Portion of the path of the positioning signal received by the reference station before it reaches the ionosphere 32 (32a, 32b...) Portion of the path of the positioning signal received by the reference station while passing through the ionosphere 33 (33a, 33b...) Portion of the path of the positioning signal received by the reference station after it passes through the ionosphere 4 User station 41 Portion of the path of the positioning signal received by the user station before it reaches the ionosphere 42 Portion of the path of the positioning signal received by the user station while passing through the ionosphere 43 Portion of the path of the positioning signal received by the user station after it passes through the ionosphere 5 Information providing station

Claims (18)

A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, and provide correction values obtained by subtracting the distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information for the plurality of navigation satellites;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
The information provider is:
obtaining the correction information from each of the reference stations other than the particular reference station;
The correction values of each navigation satellite included in these are corrected to correspond to the position of the specific reference station for the correction amount due to the position error of the navigation satellite and the tropospheric propagation delay,
applying the revised correction information to the distance measurements made by the particular base station to determine a position of the particular base station;
determining the magnitude of the difference between this result and the previously known position of said particular reference station for each of said reference stations other than said particular reference station;
A method for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, subtract the measured distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the correction values obtained by subtracting the measured distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
The information provider is:
obtaining the correction information from each of the reference stations other than the particular reference station;
For each of the navigation satellite correction values included therein, the amount of correction due to tropospheric propagation delay is corrected so as to correspond to the position of the specific reference station,
applying the revised correction information to the distance measurements made by the particular base station to determine a position of the particular base station;
determining the magnitude of the difference between this result and the previously known position of said particular reference station for each of said reference stations other than said particular reference station;
A method for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, and provide correction values obtained by subtracting the distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information for the plurality of navigation satellites;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
Operated by the information providing station,
obtaining the correction information from each of the reference stations other than the particular reference station;
The correction values of each navigation satellite included in these are corrected to correspond to the position of the specific reference station for the correction amount due to the position error of the navigation satellite and the tropospheric propagation delay,
applying the revised correction information to the distance measurements made by the particular base station to determine a position of the particular base station;
determining the magnitude of the difference between this result and the previously known position of said particular reference station for each of said reference stations other than said particular reference station;
A program for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, and provide correction values obtained by subtracting the distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information for the plurality of navigation satellites;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
Operated by the information providing station,
obtaining the correction information from each of the reference stations other than the particular reference station;
For each of the navigation satellite correction values included therein, the amount of correction due to tropospheric propagation delay is corrected so as to correspond to the position of the specific reference station,
applying the revised correction information to the distance measurements made by the particular base station to determine a position of the particular base station;
determining the magnitude of the difference between this result and the previously known position of said particular reference station for each of said reference stations other than said particular reference station;
A program for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, and provide correction values obtained by subtracting the distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information for the plurality of navigation satellites;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
The information provider is:
Obtaining the correction information from the specific reference station;
The correction values of each navigation satellite included therein are corrected for the amount of correction caused by the position error of the navigation satellite and the tropospheric propagation delay so as to correspond to the positions of each of the reference stations other than the specific reference station,
applying the revised correction information to the distance measurements made by each of the corresponding base stations to determine the positions of those base stations;
determining for each of those reference stations the magnitude of the difference between this result and the previously known positions of those reference stations;
A method for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, and provide correction values obtained by subtracting the distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information for the plurality of navigation satellites;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
The information provider is:
Obtaining the correction information from the specific reference station;
For each of the navigation satellite correction values included therein, the amount of correction due to tropospheric propagation delay is corrected so as to correspond to the position of each of the reference stations other than the specific reference station,
applying the revised correction information to the distance measurements made by each of the corresponding base stations to determine the positions of those base stations;
determining for each of those reference stations the magnitude of the difference between this result and the previously known positions of those reference stations;
A method for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, and provide correction values obtained by subtracting the distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information for the plurality of navigation satellites;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
Operated by the information providing station,
Obtaining the correction information from the specific reference station;
The correction values of each navigation satellite included therein are corrected for the amount of correction caused by the position error of the navigation satellite and the tropospheric propagation delay so as to correspond to the positions of each of the reference stations other than the specific reference station,
applying the revised correction information to the distance measurements made by each of the corresponding base stations to determine the positions of those base stations;
determining for each of those reference stations the magnitude of the difference between this result and the previously known positions of those reference stations;
A program for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, and provide correction values obtained by subtracting the distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information for the plurality of navigation satellites;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
Operated by the information providing station,
Obtaining the correction information from the specific reference station;
For each of the navigation satellite correction values included therein, the amount of correction due to tropospheric propagation delay is corrected so as to correspond to the position of each of the reference stations other than the specific reference station,
applying the revised correction information to the distance measurements made by each of the corresponding base stations to determine the positions of those base stations;
determining for each of those reference stations the magnitude of the difference between this result and the previously known positions of those reference stations;
A program for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, subtract the measured distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the correction values obtained by subtracting the measured distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
The correction information can be converted into a position correction amount at any receiver position through a correspondence relationship between changes in distances for multiple navigation satellites included in the correction information and changes in receiver position,
The information provider is:
obtaining the correction information from each of the reference stations other than the particular reference station;
For each of the navigation satellite correction values included therein, correction amounts due to the position error of the navigation satellite and the tropospheric propagation delay are corrected so as to correspond to the position of the specific reference station, and then the corrected correction information is converted into a position correction amount at the position of the specific reference station;
The magnitude of the difference between this result and the result of converting the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station is calculated for each of the reference stations other than the specific reference station;
A method for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, subtract the measured distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the correction values obtained by subtracting the measured distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
The correction information can be converted into a position correction amount at any receiver position through a correspondence relationship between changes in distances for multiple navigation satellites included in the correction information and changes in receiver position,
The information provider is:
obtaining the correction information from each of the reference stations other than the particular reference station;
For each of the navigation satellite correction values included therein, a correction amount due to tropospheric propagation delay is corrected so as to correspond to the position of the specific reference station, and then the corrected correction information is converted into a position correction amount at the position of the specific reference station;
The magnitude of the difference between this result and the result of converting the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station is calculated for each of the reference stations other than the specific reference station;
A method for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, subtract the measured distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the correction values obtained by subtracting the measured distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
The correction information can be converted into a position correction amount at any receiver position through a correspondence relationship between changes in distances for multiple navigation satellites included in the correction information and changes in receiver position,
Operated by the information providing station,
obtaining the correction information from each of the reference stations other than the particular reference station;
For each of the navigation satellite correction values included therein, correction amounts due to the position error of the navigation satellite and the tropospheric propagation delay are corrected so as to correspond to the position of the specific reference station, and then the corrected correction information is converted into a position correction amount at the position of the specific reference station;
The magnitude of the difference between this result and the result of converting the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station is calculated for each of the reference stations other than the specific reference station;
A program for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, and provide correction values obtained by subtracting the distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information for the plurality of navigation satellites;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
The correction information can be converted into a position correction amount at any receiver position through a correspondence relationship between changes in distances for multiple navigation satellites included in the correction information and changes in receiver position,
Operated by the information providing station,
obtaining the correction information from each of the reference stations other than the particular reference station;
For each of the navigation satellite correction values included therein, a correction amount due to tropospheric propagation delay is corrected so as to correspond to the position of the specific reference station, and then the corrected correction information is converted into a position correction amount at the position of the specific reference station;
The magnitude of the difference between this result and the result of converting the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station is calculated for each of the reference stations other than the specific reference station;
A program for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, and provide correction values obtained by subtracting the distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information for the plurality of navigation satellites;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
The correction value of each navigation satellite included in the correction information can be converted into a position correction amount at an arbitrary receiver position for each navigation satellite through a correspondence relationship between a change in distance for the navigation satellites included in the correction information and a change in receiver position,
The information provider is:
obtaining the correction information from each of the reference stations other than the particular reference station;
For each of the navigation satellite correction values included in the above, correction amounts due to the position error of the navigation satellite and the tropospheric propagation delay are corrected so as to correspond to the position of the specific reference station, and then the corrected correction values of each navigation satellite are converted into position correction amounts at the positions of the specific reference stations,
The magnitude of the difference between this result and the result of converting the correction value of each navigation satellite in the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station is calculated for each navigation satellite and for each of the reference stations other than the specific reference station;
A method for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, and provide correction values obtained by subtracting the distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information for the plurality of navigation satellites;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
The correction value of each navigation satellite included in the correction information can be converted into a position correction amount at an arbitrary receiver position for each navigation satellite through a correspondence relationship between a change in distance for the navigation satellites included in the correction information and a change in receiver position,
The information provider is:
obtaining the correction information from each of the reference stations other than the particular reference station;
Correcting the correction value of each navigation satellite included in the above so that the correction amount due to tropospheric propagation delay corresponds to the position of the specific reference station, and converting the corrected correction value of each navigation satellite into a position correction amount at the position of the specific reference station,
The magnitude of the difference between this result and the result of converting the correction value of each navigation satellite in the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station is calculated for each navigation satellite and for each of the reference stations other than the specific reference station;
A method for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, subtract the measured distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the correction values obtained by subtracting the measured distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
The correction value of each navigation satellite included in the correction information can be converted into a position correction amount at an arbitrary receiver position for each navigation satellite through a correspondence relationship between a change in distance for the navigation satellites included in the correction information and a change in receiver position,
Operated by the information providing station,
obtaining the correction information from each of the reference stations other than the particular reference station;
For each of the navigation satellite correction values included in the above, correction amounts due to the position error of the navigation satellite and the tropospheric propagation delay are corrected so as to correspond to the position of the specific reference station, and then the corrected correction values of each navigation satellite are converted into position correction amounts at the positions of the specific reference stations,
The magnitude of the difference between this result and the result of converting the correction value of each navigation satellite in the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station is calculated for each navigation satellite and for each of the reference stations other than the specific reference station;
A program for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A plurality of navigation satellites transmitting positioning signals;
a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween;
a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, and provide correction values obtained by subtracting the distances for each of the plurality of navigation satellites from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information for the plurality of navigation satellites;
In a satellite navigation system including an information providing station that provides an index of positioning accuracy when a specific reference station among the plurality of reference stations is used, to the user station,
The correction value of each navigation satellite included in the correction information can be converted into a position correction amount at an arbitrary receiver position for each navigation satellite through a correspondence relationship between a change in distance for the navigation satellites included in the correction information and a change in receiver position,
Operated by the information providing station,
obtaining the correction information from each of the reference stations other than the particular reference station;
Correcting the correction value of each navigation satellite included in the above so that the correction amount due to tropospheric propagation delay corresponds to the position of the specific reference station, and converting the corrected correction value of each navigation satellite into a position correction amount at the position of the specific reference station,
The magnitude of the difference between this result and the result of converting the correction value of each navigation satellite in the correction information obtained from the specific reference station into a position correction amount at the position of the specific reference station is calculated for each navigation satellite and for each of the reference stations other than the specific reference station;
A program for indicating positioning accuracy in a satellite navigation system, characterized in that the maximum value is provided to the user station as an index of positioning accuracy when the specific reference station is used. A method for indicating positioning accuracy in a satellite navigation system according to any one of claims 1, 2, 5, 6, 9, 10, 13, and 14, characterized in that the information providing station is built into the user station. A program for indicating the positioning accuracy in a satellite navigation system according to any one of claims 3, 4, 7, 8, 11, 12, 15, and 16, characterized in that the information providing station is built into the user station.

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