ES2338393B1 - PROCEDURE FOR CORRECTION OF TRAVEL IONOSPHERIC DISTURBANCES IN SATELLITE NAVIGATION AND IN THE POSITIONING OF GNSS RECEPTORS. - Google Patents

Abstract

Correction procedure for traveling ionospheric disturbances in satellite navigation and in the positioning of GNSS receivers.

The procedure is applicable to navigation electronics based on satellites chosen from a group that includes GPS, Galileo, GLONASS and GNSS and understand the use of observations passes acquired from reference receivers, close to the user satellite receiver, according to a certain model of propagation provided from permanent stations, and / or an external seasonal or climatic model. All this can significantly increase the maximum applicability distance, with respect to the nearest permanent receiver, for the techniques of precise positioning and navigation with GPS, Galileo, GLONASS and GNSS in general, with any of the different techniques developed so far (RTK, VRS, WARTK, TCAR between others).

Description

Correction procedure for traveling ionospheric disturbances in satellite navigation and in the positioning of GNSS receivers.

Field of the Invention

The present invention relates to a correction procedure for ionospheric traveling disturbances ("Traveling lonospheric Disturbances", TIDs) applicable to the satellite navigation and satellite navigation receivers ("Global Navigation Satellite System" or GNSS in general, GPS, Glonass and Galileo in particular), intended in particular for facilitate very precise positioning based on the phase of carriers, through techniques such as "Real Time Kinematic" (RTK), "Virtual Referrer Station" (VRS), "Three Carrier Ambiguity Resolution "(TCAR)," Wide Area Real Time Kinematic "among others.

The correction procedure for traveling ionospheric disturbances in electronic navigation based on GPS, Galileo, GLONASS and GNSS satellites in general, it is given in the context of precise electronic navigation through satellite signals that are refracted by the Ionosphere, both for larger-scale variations as for more disturbances premises, objective of this procedure.

Background of the invention

The procedures designed to date for ionospheric correction in electronic navigation requires Satellite have been very simple. This has been mainly due to that the main field of application, GPS navigation, has been developed especially in the mid-90s, coinciding with the minimum of solar activity (which follows a cycle of approximately 11 years) and in which the error introduced by the ionosphere is noticeably smaller than it is and will be in situations of maximum.

Electronic radiation by the Sun is not something constant, but follows cycles of maximum and minimum of a period of approximately 11 years. This electronic radiation arrives to the Earth's atmosphere and provides such an electron density free in the ionosphere that affects the GPS or other satellite signal, contributing a degree of error to the measures of the order of meters.

The patent ES-A-2 255 446 discloses a procedure for autonomous determination of the orientation of a GNSS receiver with a single antenna based on your information ionospheric taking into account the phases of two carriers observed on two different frequencies from a given satellite.

In the application WO-A-2004/057364 describes a method and a system for real-time navigation using radio signals with three carriers and comprising the application of ionospheric corrections based on a model constantly updated ionospheric calculated by a station fixed terrestrial reference combined with geodetic data.

Application WO-A-03/069366 describes a server GPS capable of receiving information for use in determining ionospheric errors using mathematical formulas creating a ionospheric model for prediction of further errors ionospheric and for sending corrections to GPS receivers located at points suitable for receiving such information.

In the patent ES-A-2 168 920 discloses a procedure that makes use of the aforementioned WARTK technique for a very precise determination of ionospheric correction for electronic satellite navigation that provides the possibility of go from errors of the order of the meter to errors less than 10 cm. Most known models to treat the ionosphere before of said patent were two-dimensional, while the patent ES-A-2 168 920 is based in the real-time resolution of the ionospheric values of a model in which a three-dimensional distribution of the free electrons of the ionosphere. Currently, in the context of GNSS positioning and precision navigation (with few centimeters of error) GNSS users typically use a Single receiver and GNSS antenna to get your position three-dimensional in a correction service region precise differentials such as RTK or VRS, fed respectively by one or several reference receivers permanent

However, until now the modeling and correction of ionospheric disturbances travelers (or TIDs), one of the main effects that limit the distance to the nearest reference station. Although the ES-A-2 169 920 patent provides a solution to satellite signal variations due to ionospheric disturbances, large-scale, the most disturbances premises are pending resolution.

It is the objective of the present invention to give response to the need for a correction procedure for traveling ionospheric disturbances in electronic navigation more locals

The invention presented in this document comes to improve functionality to GNSS receivers or three-dimensional "satellite positioners", thanks to the real-time correction of ionospheric disturbances travelers, so that as a result of the improvement the user you can navigate precisely, with a few centimeters of error, to a greater distance from the reference stations, being able to be said distance of up to 40% higher (further) as shown preliminary results (or what is the same allows the duplication of the service area). We must also add that this new correction does not imply a need for devices electronic or additional "hardware", being the means of programming or additional software needed generally simple e integrated into the navigation software itself Username.

Exhibition of the invention

The present invention relates to a correction procedure for ionospheric disturbances traveling (TIDs) in satellite electronic navigation GPS, Galileo, GLONASS and GNSS in general, comprising the following stages for each GNSS satellite in view of the user and for each instant of observation:

to)

obtaining information about TID effect, at least on its elongation, in the observations previously acquired by one or more recipients permanent next to the user's GNSS receiver;

b)

obtaining information about TID propagation parameters comprising speed and TID propagation address; Y

C)

calculation based on information on the effect of the TID and its propagation parameters, of the correction to the effect of the TID on the observations acquired by the user for each GNSS satellite.

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Obtaining information from the aforementioned stage b) is made from a local network of permanent GNSS receivers deployed ad-hoc , or from any climate or seasonal model, or by a combination of both strategies.

This procedure is described in a manner sequential, in its main aspects and in greater detail, according to an implementation example, below:

one.

Be part of the existence of a corrections service that provide the user with real-time equipment, necessary values, such as ionospheric refraction, for the positioning and navigation with errors of few centimeters, thanks to the processing of the observations of one or in general several permanent stations close to the user, using techniques such as RTK, VRS, WARTK, TCAR, etc.

2.

Be part, in addition, of any user, who moves through the area covered by the corrections service mentioned above, and that is properly equipped with a GNSS receiver that you provide, in addition to code measurement, or pseudo distances, precise measurements of phase, for one, two or more frequencies.

3.

He corrections service provides the user, for example, a estimation of the speed and direction of propagation of the ionospheric traveling disturbances, for example from a sub-network of dedicated stations, or an estimate seasonal.

Four.

For each given GNSS satellite, a linear adjustment is made, for example, of the ionospheric corrections received from each reference station taking into account their spatial distribution, in terms for example of their sub-ionospheric points (intersection of each GNSS-satellite beam). receiver with a certain effective ionospheric height, typically between 300 and 600 km (for example 450 km).

5.

He user stores the waste resulting from each adjustment, at each time and for each satellite, performed as has commented previously among the ionospheric corrections, for the closest reference station you have experienced previously the effect of TID. For example during the day in winter, it is considered in the northern hemisphere the most season near to the north (to the south in the southern hemisphere), and during the night, in summer, the reference station is taken more close to the east. All this can be done only for satellites affected by TIDs according to station information permanent, and even these could transmit the series temporary corrections of TIDs, to further relax the receiver computing and memory requirements of Username.

6.

TO from the speed and direction of propagation of the ionospheric traveling disturbances, provided by the user calculate for each satellite affected by the view, the delay \ Deltat of the action of the TID on its observation with respect to that of the closest reference station that has detected it before, using for example a flat wave model (see figure 1).

7.

Finally the user calculates the ionospheric correction for each satellite in sight as the sum of: the correction provided by the adjustment (linear, for example) of the ionospheric corrections received, taking into account the relative spatial distribution of points sub-ionospheric reference stations and the sub-ionospheric point of observation of user, and the residual observation delayed a time \ Deltat of the closest reference station you have experienced before the TID corresponding to the delay of the TID calculated above between the observation of said station and that of the user. This form if the amplitude of the disturbance has not varied too much, between the observation at the reference station and the user mitigate (partially cancel) the effect of TID on the correction ionospheric to the user.

Brief description of the drawings

The above features and other advantages of the proposed procedure will be better understood from the following description made with help in the drawings attached.

Fig. 1. presents an example of the distribution of sub-ionospheric points (white circles) for different GPS satellites observed from a network of reference GPS receivers (black stars) and a user or rover receiver (rhombus), superimposed on a vertical ionospheric correction map (with a certain color code). The figure focuses on satellite 1, which illustrates both the direction of propagation of some alleged TIDs, and the effective distance between the corresponding sub-ionospheric point of the nearest reference station that has already been affected by the TID (circle with cross), and that of the user (circle with cross), which is used to calculate the corresponding delay, td, for example from the flat wave model (td \ approx [distance in the direction of propagation of the TID] / [ TID speed]).

In Fig. 2. it is presented, for each satellite GNSS in view of the user, an illustrative schematic diagram of the correction procedure for ionospheric disturbances travelers in the electronic navigation based on GPS satellites, Galileo, GLONASS and GNSS, according to the invention.

They have been indicated in this Fig. With some Numerical references the following elements:

one:

Precise position of the receivers permanent

2:

Position of each GNSS satellite

3:

Approximate position of Username

4:

Ionospheric corrections of permanent receivers

5:

Sub-ionospheric points of observations from permanent receivers

6:

Point sub-ionospheric observation from the Username

7:

TID features (at least speed and propagation direction)

8:

TID delay in the observation of user, regarding the observation of the permanent receiver more close already affected by TID.

9:

Standard ionospheric correction of Username

10:

User TID correction

eleven:

New ionospheric correction of Username.

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Description of a preferred embodiment

Described below, for each satellite GNSS in view of the user, an embodiment, by way of example, of the correction procedure for ionospheric disturbances travelers in the electronic navigation based on GPS satellites, Galileo, GLONASS and GNSS, which has been referred to this point. This procedure will be easily implemented, in practice, with the GPS and GLONASS equipment currently available, as well as with future Galileo and GPS equipment modernized among others.

one.

Be calculates or arranges (at the initial time) the coordinates of permanent receivers that make up the corrections service given (RTK, VRS, WARTK, TCAR, etc.).

2.

Be calculate the approximate coordinates of each GNSS satellite to the user view.

3.

Be Calculate the approximate position of the user.

Four.

A External corrections service provides corrections. ionospheric (very precise in the case of WARTK) of each satellite seen from the different permanent receivers.

5.

TO from the position of each permanent receiver and each satellite at sight, the coordinates of the points are calculated sub-ionospheric: corresponding.

6.

TO from the approximate position of the user and each satellite to the view, the coordinates of the points are calculated corresponding sub-ionospheres.

7.

The corrections service provides the characteristics of the TIDs affecting the observations at that time, for example by providing the wave number k and the circular frequency? Introduced previously. These values can be provided from seasonal or climatic estimates or real-time estimates from a local network of GNSS receivers deployed ad-hoc . These values can also be acquired by a combination of two such strategies.

8.

Based on the characteristics of the TIDs, and the subionospheric points of the permanent and user receivers, the delay to be applied to the effect of the TID on the user is estimated, with respect to the nearest permanent station that has been previously affected, for example from the expression \ Deltat = k \ cdot \ Delta r / \ omega associated with the flat wave approximation.

9.

He TID delay, which has just been explained, applies to select the residue corresponding to a time \ Deltat previous, corresponding to a previous \ Deltat, in the setting of the oblique ionospheric delays of each satellite seen from the permanent stations (for example in a Taylor development of first or second order), from the nearest permanent station, already affected, as indicated in point 5 above The value resulting. constitutes the user TID correction.

10.

Precisely from the adjustment (for example with a Taylor development) of the ionospheric delay delay values of the satellite signal visible from the permanent receivers, and taking into account the relative distribution of the sub-ionospheric points of the user and from the stations themselves, the user standard ionospheric correction is determined.

eleven.

Finally the new correction Total user ionospheric is calculated as the addition of the standard correction and TID correction (or equivalently the TID correction is subtracted from the current correction of the station reference).

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Any expert in the sector will understand that the invention described up to this point may be implemented with various modifications, as long as their essential characteristics that are included in the text of claims that follow, in particular the invention encompasses the use of other types of satellites and alternative measuring devices to acquire the values of the indicated parameters.

Claims (4)

1. Procedure for correcting traveling ionospheric disturbances in satellite navigation and in the positioning of GNSS receivers, said base being Navigation on satellites chosen from a group that includes GPS, Galileo, GLONASS and GNSS, characterized by understanding the following stages, for each GNSS satellite in the user's view, and for each instant of observation:

to)

obtaining information about TID effect, at least of its elongation, on the observations acquired by one or more permanent receivers near the receiver GNSS of the user;

b)

obtaining information about TID propagation parameters comprising at least one component of the speed and direction of propagation of said TID;

C)

Calculation based on information on the effect of the TID and its propagation parameters, of the correction to the effect of the TID on the observations acquired by the user for each GNSS satellite,

d)

points calculation sub-ionospheres seen from both receptors permanent as from the user receiver; Y

and)

TID delay calculation a consider, between user observation and that of the station permanent permanent that the TID has already experienced, as of TID model (including speed and direction of propagation obtained from a seasonal, climatic or network model dedicated location) and ionospheric corrections provided from of data from permanent stations.

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2. Method according to claim 1, characterized in that said information about TID parameters is obtained from a local network of permanent GNSS receivers deployed ad-hoc , or from any climatic or seasonal model, or by a combination of Both strategies 3. Method according to claim 1, characterized in that obtaining information about the effect of the TID further comprises its elongation for observations acquired by one or more permanent receivers close to the user's GNSS receiver, as waste after adjustment of the corrections. ionospheric calculated with a precise model for each of these permanent stations. 4. Method according to claim 1, characterized in that it further comprises:

and)

calculation of the correction to the TID, by applying the delay calculated above, to the residue of ionospheric adjustment, for the nearest reference station, in the adjustment mentioned above, and you have already experienced the TID effect; Y

F)

adding the correction to the TID together to the standard ionospheric correction from the corrections transmitted by permanent receivers, taking into account the relative distribution of sub-ionospheric points of observations from permanent recipients regarding the observations from the user.