JPH0627215A - Portable gps receiver - Google Patents

Abstract

(57) [Summary] [Purpose] Convergence calculation for positioning is performed stably without oscillation. [Configuration] At the start of positioning, the position of the previous positioning result is set to the initial position for positioning calculation, and if the selected satellite is out of the field of view, other satellites are captured and the received power from the multiple captured satellites is received. The highest satellite number is output to the initial position setting means 12c. Accordingly, the initial position setting means 12c calculates the initial position from the position of the satellite having the maximum received power, and the obtained initial position is stored in the memory means 13.
Is output to and the initial position is changed. If the intensity of the incoming radio wave is the highest, it is predicted that the satellite will be in the position closest to the zenith, so the intersection of the line connecting the satellite position and the center of the earth and the surface of the earth is the most actual positioning point. Be close,
The intersection is the initial position. [Effects] With the above configuration, it is possible to stably perform the convergence calculation by the successive approximation calculation of the position positioning without oscillation and reduce the number of times of the convergence calculation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an independent positioning GPS receiver for position measurement using GPS satellites, and more particularly to a portable GPS receiver which frequently moves when the power is off.

[0002]

2. Description of the Related Art Conventionally, an independent positioning type GPS receiver that receives a radio wave from a GPS satellite alone to measure the current position has been known, and as the use expands and miniaturization technology advances, a portable type GPS receivers are emerging.

FIG. 3 is a block diagram of a conventional GPS receiver, and FIG. 4 is a flowchart showing an outline of operation of the conventional GPS receiver.

In FIG. 3, reference numeral 11 demodulates the modulated radio wave signals from a plurality of satellites to obtain satellite position information, radio wave propagation time, and general orbit outline information (hereinafter referred to as almanac).
Is a navigation data receiving means for outputting to the arithmetic unit 12.

Reference numeral 12 is an arithmetic unit. Reference numeral 12a is a current position measured by successive approximation calculation from an initial position based on a plurality of satellite position information and radio wave propagation time input from the navigation data receiving means 11, and the result is obtained. The positioning means for outputting to the memory means 13 and the display device 15, 12b outputs the almanac inputted from the navigation data receiving means 11 to the memory means 13, and at the time of starting positioning, the almanac from the memory means 13 and time data from the clock means 14. It is a satellite selection means that performs satellite selection by inputting and assuming that the current position is the initial position or the position of the previous positioning result.

Reference numeral 13 is a memory means for storing the positioning result, almanac, etc., 14 is a clock means for measuring the time by a backup power source even during a power failure, and outputting a rough time for predicting the arrival of satellites at the start of positioning, and 15 is a calculation. It is a display device that displays a positioning result or the like input from the device 12 on a CRT or the like.

Next, the conventional operation will be described. The satellite selection means 12b reads out the approximate time data from the clock means 14 at the start of positioning, reads out from the memory means 13 the almanac which is the orbital outline information of all the satellites and the previous positioning result used as the initial position or the initial position, and the initial position. The satellite arrival prediction at the time indicated by the clock means 14 at the position is performed, the navigation data receiving means 11 is notified of the numbers of three or four or more satellites to be used for position measurement, and the satellite acquisition operation start instruction is given. (Step 201).

The navigation data receiving means 11 is a satellite selecting means 1
The acquisition operation is sequentially started for the satellites designated by 2b. If the satellite cannot be captured, it outputs a satellite switching request to the satellite selecting means 12b, and the satellite selecting means 12b selects another satellite according to the almanac and outputs the satellite number to the navigation data receiving means 11 (steps 202 and 203).

When the satellite is captured and the radio wave of the satellite is received, the navigation data receiving means 11 demodulates the spread spectrum modulated satellite radio wave to measure the radio wave propagation time from the phase of the synchronized reception signal, and the The satellite information of the transmission time and the satellite position is extracted from the signal carried on the received radio wave and output to the positioning means 12a.

The positioning means 12a is the navigation data receiving means 1
Based on the radio wave propagation time, radio wave transmission time, and satellite position information input from 1, the current position is measured by the convergence calculation described later. Then, the positioning result is output and displayed on the display device 15 and also output and stored in the memory means 13 (step 204).

The principle of positioning by GPS is as follows. If there is a clock that is completely synchronized with the transmission point and reception point of the radio wave, and the transmission signal is controlled by that clock, if the reception timing is measured at the reception point, the propagation time of the radio wave between the transmission and reception points is obtained. It is possible to obtain the distance between the transmitting and receiving points by multiplying it by the speed of light.
Further, the GPS satellite transmits position information for calculating the position of the satellite itself on the receiving side.

Therefore, if the propagation time of the radio wave is measured at the receiving point to obtain the distance, the measuring point is located on a spherical surface having a fixed distance centered on the satellite. Further, the position of the satellite serving as the center is obtained based on the data and the satellite position information put on the received radio wave at that time. Then, if the measurement is performed for three satellites having different positions, the measurement position can be obtained as an intersection of three spherical surfaces centered on each of the three satellites.

However, if the radio waves from only three satellites are received in this way to obtain the intersections of the three spherical surfaces,
The clock at the receiving point must be accurately synchronized with the satellite clock. In reality, synchronizing the clock of the receiving point with the clock of the satellite is not only technically problematic, but also disadvantageous in reducing the cost of the receiver.

To solve this problem, the number of satellites to be received is increased by one. That is, the position of the receiving point can be obtained by receiving the signals of four satellites at the receiving point and solving the simultaneous equations in which four unknowns are the coordinates in the three directions and the four clock errors between the satellite and the receiver. If the height of the measurement point is known, the position can be obtained by receiving signals from three satellites.

However, in order to smoothly switch the receiving satellites when the GPS satellites, which are mobile satellites, disappear from the field of view or when the radio waves are blocked by an obstacle such as a building, the receiver is usually a spare satellite signal. Has a receiver circuit and 5 at the same time
Configure to receive radio waves from more than one satellite.

Now, as shown in FIG. 5, a three-dimensional structure having the z-axis with the earth center as the origin and the north direction as the positive direction along the earth's axis of rotation and the x-axis as the intersection of the meridian plane of Greenwich and the equatorial plane. Considering the right-handed Cartesian coordinate system, the coordinates of the measurement point are {x ₀ , y
₀ , z ₀ }, and the position of the satellite is {x _i , y _i , z _i }. Let i denote a number that identifies the satellite.

If the radio wave propagation time from the i-th satellite measured by the navigation data receiving means 1 is t _i , the measured distance r _i
Is expressed by the following (Equation 1) according to the Pythagorean theorem.

[0018]

[Equation 1]

Here, c is the speed of light, t _0i is the true radio wave propagation time, and δt is the clock shift of the receiver.

Since four numbers x ₀ , y ₀ , z ₀ and δt are unknowns, four satellites (i = 1, 2,
The position can be measured by establishing a simultaneous equation with four elements for (3, 4).

However, the above equation has a square or square root of an unknown number and is not linear, so that it cannot be easily solved. Therefore, in practice, the following method of converging the estimated value of the position to the true position is generally used.

That is, first, the estimated value of the position is calculated as (x _e , y
_e, and z _e), an estimate of the deviation of the clock and .DELTA.t _e, the error between the estimate and the true value Δx, Δy, Δz and Δt
Then, the relationship with the true value is as in the following (Equation 2).

[0023]

[Equation 2]

When the estimated distance is r _e , the following (Equation 3) is obtained.

[0025]

[Equation 3]

Here, since Δr _i is the difference between the estimated distance and the actually measured distance, this value can be obtained.

Here, by substituting (Equation 2) into (Equation 1) and performing Taylor expansion to omit the second and subsequent minute terms, further substituting (Equation 3) and rearranging, the following (Equation 4) is obtained. (The derivation is omitted).

[0028]

[Equation 4]

(Equation 4) is the error Δx, Δy, Δz of the estimated value.
Then, the value for each component is obtained by multiplying each direction cosine of the unit vector facing the satellite direction from the estimated position to obtain the value for each component, and adding the value obtained by multiplying the estimated time error Δt by the speed of light to the estimated distance r It is shown that it becomes equal to the difference Δr _i between _e and the measured distance r _i . The errors Δx, Δy, Δz of the estimated position and the estimated time error Δt can be obtained by establishing a four-dimensional simultaneous equation of four orders based on (Equation 4).

After that, each of the obtained errors is added to the estimated value, this is used as a new estimated value, and the iterative calculation is performed until the error converges to a predetermined minute value to obtain the true position and the clock error. This is the conventional convergence calculation method.

Here, when the height is known, Δ in (Equation 4)
The position z can be measured by establishing a three-dimensional simultaneous equation of the first order using z, which is known.

[0032]

However, in such a conventional method for calculating the positioning position of the GPS receiver, how to determine the estimated position (start the calculation with this estimated position as an initial value) when performing the calculation. Is an issue. For example, when positioning is interrupted, positioning is restarted after moving for a long distance, the actual measured position and estimated position will deviate significantly. If there is a large deviation, the position calculation results do not converge and the system may oscillate.

[0033]

Means for Solving the Problems The present invention is to solve the above-mentioned problems. First, the satellite arrival prediction at the positioning position at the time of the previous positioning is performed, the satellite is decided based on the prediction result, and an attempt is made to capture the satellite. When the radio wave can be captured, the previous positioning result is used as the initial position to perform the convergence calculation. If the satellite radio wave cannot be captured by the satellite arrival prediction, another satellite is newly searched to try to capture the satellite radio wave. The initial position setting means for changing the positioning initial position is provided in the vicinity of the intersection of the earth surface and the line connecting the acquisition satellite with the center of the earth when the acquisition of another satellite is successful.

[0034]

According to the present invention, when the satellite radio wave cannot be captured by the satellite arrival prediction, the present invention considers that the satellite has moved greatly from the previous positioning position, so that the process of changing the initial position can be started quickly. Since the changed position is near the intersection of the earth surface and the line connecting the acquisition satellite and the center of the earth, the convergence calculation can be performed stably.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a portable GPS receiver according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a portable G according to an embodiment of the present invention.
FIG. 2 is a block diagram of a PS receiver, and FIG. 2 is a flowchart showing an outline of operation of one embodiment of the present invention.

In FIG. 1, 11 is a navigation data receiving means for demodulating the modulated radio wave signals from a plurality of satellites and outputting satellite position information, radio wave propagation time and almanac to the arithmetic unit 12. Reference numeral 12 denotes an arithmetic unit, and 12a measures the current position by successive approximation calculation from the initial position based on a plurality of satellite position information and radio wave propagation time input from the navigation data receiving means 11, and stores the result in the memory means. 13 is a positioning means for outputting to 13 and the display device 15.

Reference numeral 12b is a satellite selecting means, and 13 is a memory means for storing the positioning result, almanac, and the like. The satellite selection means 12b mainly performs the following processing. That is, the almanac input from the navigation data receiving means 11 is output to the memory means 13. At the start of positioning, the almanac is read from the memory means 13, the time data is received from the clock means 14, satellite selection is performed assuming that the current position is the initial position, and the selected satellite number is output to the navigation data receiving means 11. If satellite acquisition is impossible and another satellite request signal is input from the navigation data receiving means 11,
The next satellite is selected, and the satellite number is used as the navigation data receiving means 11
And the initial position change request to the initial position setting means 12c.

The initial position setting means 12c mainly performs the following processing. That is, at the start of positioning, the position of the previous positioning result is set to the initial position for positioning calculation, and the satellite selecting means 1
When an initial position change request is input from 2b, the intersection of the earth surface and the line connecting the satellite position and the center of the earth is calculated from the satellite position information input from the navigation data receiving means 11, and this initial position is calculated. Change and set to the position data obtained by.

Reference numeral 14 is a clock means for measuring the time even with a power failure by the backup power source and outputting a rough time for predicting the satellite arrival at the start of positioning. Reference numeral 15 is a positioning result or the like input from the arithmetic unit 12 for CRT or the like. It is a display device for displaying.

Next, the operation of the portable GPS receiver of this embodiment will be described in detail. The initial position setting means 12c reads the position of the previous positioning result from the memory means 13 at the start of positioning, and outputs and stores it in the memory means 13 as an initial position for positioning calculation (step 101).

Next, the satellite selecting means 12b reads out the approximate time data from the clock means 4, reads out the almanac and the initial position which are the orbital outline information of all the satellites from the memory means 13, and the clock means 14 at the initial position. The satellite arrival prediction is performed at the time indicated by. Based on the result of the satellite arrival prediction, the navigation data receiving means 11 is notified of the numbers of three or four or more satellites predicted to be suitable for position measurement, and the satellite acquisition operation is started (step 102).

The navigation data receiving means 11 performs a satellite capturing operation instructed by the satellite selecting means 12b, and if there is a satellite that cannot be captured, requests another satellite selecting request to the satellite selecting means 12b (step 103). . The satellite selecting means 12b selects another satellite according to the almanac and notifies the navigation data receiving means 11 of the satellite number (step 10).
Along with 4), it is determined whether the selected satellite is within the field of view from the initial position (step 105).

When the selected satellite is out of the field of view, the initial position change is output to the initial position setting means 12c. The navigation data receiving means 11 measures the radio wave propagation time from the phase of the received signal synchronized by demodulating the satellite radio wave subjected to spread spectrum modulation, extracts the transmission time and satellite information of the satellite position from the received radio wave, and determines the positioning means. In addition to outputting to 12a, the number of the satellite with the highest received power is output to the initial position setting means 12c.

Next, the initial position setting means 12c obtains the initial position obtained from the position of the satellite having the maximum received power indicated by the navigation data receiving means 11 only when the initial position change request is inputted from the satellite selecting means 12b. Memory means 13
And change it (step 106).

Here, the reason for changing the initial position according to the position of the satellite having the maximum received power is that the distance to the satellite is the shortest and the propagation loss is the smallest when the satellite is in the zenith direction of the positioning point. It is predicted that the strength of the radio wave coming from the satellite will be maximum. In other words, if the strength of the incoming radio wave is maximum, it is predicted that the satellite will be in the position closest to the zenith, so the intersection of the line connecting the satellite position with the center of the earth and the earth's surface is the actual positioning point. Because it seems to be the closest to.

Further, the directional characteristics of the planar type microstrip antenna, which is the mainstream recently, has the maximum received radio wave intensity in the zenith direction. Therefore, if the incoming radio wave intensity is the maximum, the satellite is located at the position closest to the zenith direction. Something is expected.

The positioning means 12a is the navigation data receiving means 11
From the radio wave propagation time / radio wave transmission time / satellite position information input from, the current position is measured by the convergence calculation shown in the conventional example, the positioning result is output and displayed on the display device 15, and the positioning result is also stored in the memory means. It is output to 13 and stored (step 107).

[0049]

As described above, the present invention changes the initial position of the positioning calculation to the position where the satellite with the maximum received power is the zenith when the satellite coming out at the previous positioning position is predicted and the satellite outside the field of view is captured. By the configuration including the initial position setting means, it is possible to stably perform the convergence calculation by the successive approximation calculation of the position positioning without oscillation and reduce the number of times of the convergence calculation. Therefore, for example, even when the device is largely moved while the power is off, or when the stored initial position is lost, the positioning position convergence calculation can be stably performed, and the initial position and the positioning position can be calculated. Since the error with the position is small, the convergence calculation can be performed in a short time.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a portable GPS receiver according to the present invention.

FIG. 2 is a flowchart showing an operation outline of the embodiment.

FIG. 3 is a block diagram of a conventional GPS receiver.

FIG. 4 is a flowchart showing an operation outline of a conventional GPS receiver.

FIG. 5 is an explanatory diagram for explaining position measurement by GPS.

[Explanation of symbols]

 11 Navigation Data Receiving Means 12 Computing Device 12a Positioning Means 12b Satellite Selection Means 12c Initial Position Setting Means 13 Memory Means 14 Clock Means 15 Display Devices

Claims (1)

[Claims] 1. A navigation data receiving unit that demodulates a radio signal from a GPS satellite to measure a radio propagation time and receives navigation data, and an initial stage based on the radio propagation time and the navigation data obtained by the receiving unit. Positioning means for measuring the current position by successive approximation calculation from the position, memory means for accumulating general satellite orbit outline information obtained from the navigation data receiving means and the positioning result obtained from the positioning means, clock means, and current The position of is assumed to be the initial position, and the satellite selection means for predicting the incoming satellite from the time of the almanac of the memory means and the time of the clock means to select the acquisition satellite, the positioning result as the initial value of the next positioning calculation, Furthermore, when the predicted acquisition satellite cannot be acquired, it is configured to acquire other satellites, and when other satellites are acquired, the position closest to the zenith direction of the positioning point in the acquired satellites. A portable GPS receiver comprising an initial position setting means for updating an initial position to a position near an intersection of a line connecting the center of the earth with a capture satellite in the position of the earth and the surface of the earth.