Method for indicating positioning accuracy in satellite navigation system and program for indicating positioning accuracy

Abstract

To enable a user to grasp positioning accuracy in a differential GPS (DGPS).SOLUTION: In a satellite navigation system including a GPS in the United States and a quasi-zenith satellite system in Japan, when configuring a differential GPS (DGPS) in which a reference station is installed to correct a positioning error, after obtaining correction information from a plurality of reference stations, a maximum value of a positioning error as a result of performing DGPS positioning to which correction information of each of other reference stations is applied at a position of a specific reference station, a maximum value of a positioning error as a result of performing DGPS positioning to which correction information of the specific reference station is applied at a position of a reference station other than the specific reference station, or a maximum value of a difference as a result of converting correction information of each of the plurality of reference stations into a correction amount of a position at the position of the specific reference station is provided to a user station as an index of positioning accuracy when the specific reference station is used.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for indicating positioning accuracy in a satellite navigation system and a program for indicating positioning accuracy. [Background technology]

[0002] Satellite navigation systems that use satellites to measure position are collectively called GNSS (Global Navigation Satellite System), and a representative example is the US-based GPS (Global Positioning System). GNSS generally uses a receiver to receive positioning signals transmitted by radio from 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 a user receiver or user station. The error between the determined position and the true position is called the positioning error.

[0003] To calculate the receiver's position, it is necessary to know the position of the navigation satellite that is transmitting the positioning signal, and the orbital information required for this is transmitted by the navigation satellite itself by superimposing it on the positioning signal. Because the orbital information is created by prediction, it contains an error of several meters, which causes positioning errors when calculating the receiver's position.

[0004] The timing at which a navigation satellite transmits a positioning signal is predetermined, and the navigation satellite transmits the positioning signal based on the time on its own clock. This clock uses a highly accurate atomic clock, but it contains an error equivalent to several meters in distance, which causes positioning errors when calculating the receiver's position.

[0005] Before reaching the ground, a positioning signal passes through the ionosphere and troposphere above, and delays occur as 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.

[0006] In a satellite navigation system, the measured distance to a navigation satellite obtained by a receiver is the sum of all measurement errors due to these error factors compared to the true distance.

[0007] 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, thereby 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.

[0008] There are several specific DGPS methods, but the most common method uses distances measured by a single reference station to generate distance correction values ​​for each navigation satellite, which are then aggregated for multiple navigation satellites and provided to user stations as correction information. This method, sometimes called Local Area DGPS (LADGPS), does not generate correction information for each cause of positioning error. Therefore, 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 DGPS can be used within a range of approximately several hundred kilometers from the reference station, or up to several tens of kilometers depending on ionospheric conditions.

[0009] The clock error of a navigation satellite appears as a uniform distance measurement error regardless of the location of the user station. The position error of a navigation satellite appears as a distance measurement error due to the dot product with the line of sight when the navigation satellite is viewed from the user station. The ionospheric propagation delay appears as a distance measurement error, proportional to the integral of the density distribution of the ionospheric atmosphere along the path from which the positioning signal transmitted by the navigation satellite reaches the user station. The tropospheric propagation delay appears as a distance measurement error, proportional to the integral of the refractive index of the neutral atmosphere along 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 location of the user station. The distance correction value for a navigation satellite is the sum of the corrections corresponding to each of these measurement errors. Note that the tropospheric propagation delay can be estimated with sufficient accuracy using a simple tropospheric propagation delay model.

[0010] 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 receives positioning signals and provided to the user station as correction information.

[0011] The correction information generated by the DGPS reference station can be converted into a position correction amount at any receiver position through the correspondence between the changes in distance of multiple navigation satellites contained in the correction information and the changes in receiver position.

[0012] This will be confirmed 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 distance linearized at the provisional receiver position, to determine the receiver position that satisfies the relationship with the measured distances to multiple navigation satellites.

[0013] Assume that N navigation satellites are used for positioning calculation. The correspondence between the linearized distance and receiver position at the provisional receiver position is described by the following equation as the relationship between the change in distance Δr and the change in receiver position Δp.

[0014] (Number 1) G Δp=Δr

[0015] Δp is a four-dimensional vector, and its elements are the changes in the coordinate values ​​of the receiver position Δx, Δy, Δz and the change in the receiver clock error Δc. That is, as shown in the following equation.

[0016] (Number 2) Δp=[Δx Δy Δz Δc]'

[0017] 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, as shown in the following equation.

[0018] (Number 3) Δr=[Δr(1)…Δr(i)…Δr(N)]'

[0019] The size of the matrix G, which represents the geometric relationship between the distance and receiver position with respect to the navigation satellites, is N × 4. If the i-th row of the 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:

[0020] (Number 4) G(i)=[-sinAZ(i)·cosEL(i) -cosAZ(i)·cosEL(i) -sinEL(i) 1]

[0021] To find Δp from Δr, it is common to solve equation (1) using the least squares method, as shown below.

[0022] (Number 5) Δp=inv(G'WG)·G'·W·△R=S·Δr

[0023] Here, inv(·) is a function to find the inverse matrix. The N×N matrix W is used to obtain a weighted solution in the least squares method, and is generally taken as the inverse matrix of the variance-covariance matrix related to the distance measurements. If no weighting is required, a unit matrix can be used. The size of the matrix S is 4×N.

[0024] 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.

[0025] (Number 6) Δp=S·Δr=0

[0026] Let us consider applying correction information from DGPS. The correction information ΔR is composed of the correction value ΔR(i) of each navigation satellite used. If the correction information ΔR is an N-dimensional vector, it is expressed as follows:

[0027] (Number 7) ΔR=[ΔR(1)…ΔR(i)…ΔR(N)]'

[0028] To apply the correction information, we simply add it to the distance measurement, resulting in the following relationship:

[0029] (Number 8) ΔP=S·(Δr+ΔR)=S·ΔR

[0030] That is, the correction information ΔR can be converted into a position correction amount ΔP via the 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, as shown in the following equation.

[0031] (Number 9) ΔP=[ΔX ΔY ΔZ ΔC]'

[0032] 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 the position correction amount ΔP at any receiver position.

[0033] Furthermore, consider multiplying the matrix S only by the correction value ΔR(i) for the navigation satellite i contained in the correction information.

[0034] (Number 10) ΔP=S·[0…ΔR(i)…0]'

[0035] The above equation means that the correction value ΔR(i) for each navigation satellite contained in the correction information can be converted into a position correction amount ΔP at any receiver position.

[0036] Strictly speaking, matrix G changes as the receiver position changes, but within the vicinity of the receiver, for example, within the range of the change in receiver position due to the application of correction information, the magnitude of the change in matrix G can be ignored. In other words, iterative calculations are not required when applying correction information.

[0037] 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). The SLAS service has the advantage of receiving signals from a single satellite, allowing it to obtain correction information from 13 reference stations located throughout Japan all at once. User stations using the SLAS service are required to select and use the correction information from the nearest reference station.

[0038] In addition to the DGPS system using individual reference stations mentioned above, 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 MSAS in Japan and WAAS in the United States have become widespread, there are currently no DGPS systems that provide correction information from multiple reference stations other than the SLAS service of the Quasi-Zenith Satellite System.

[0039] In DGPS, there is no need to communicate the position of the reference station to the user station, but in SLAS services, the user station is required to select and use the correction information of the nearest reference station, so the approximate position of the reference station is transmitted along with the correction information.

[0040] In the field of GNSS, precise ephemeris are created and used for each navigation satellite as information on its accurate clock and orbit. Precise 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 ephemeris created by an international organization, for example, the International GNSS Service (IGS), are made public, and are used in fields of precision positioning such as surveying and geodesy.

[0041] There are three types of precise ephemeris: the Final Product and Rapid Product, which are not based on predictions, and the Ultra Rapid Product, which is based on predictions. The Final Product is the most accurate, with both the navigation satellite's position error and clock error having an accuracy of 2 to 3 centimeters from the date of measurement, but requires approximately 2 to 3 weeks for analysis. The Rapid Product has an accuracy similar to the Final Product and is released approximately 1 to 2 days from the date of measurement. The Ultra Rapid Product includes predictions for up to several hours ahead from the time of release, and has an accuracy of approximately 5 centimeters for the navigation satellite's position error and approximately 1 meter for the navigation satellite's clock error. [Prior art documents] [Non-patent literature]

[0042] [Non-Patent Document 1] Takeyasu Sakai and Kazunori Iemura, "DGPS Positioning Accuracy When Using Multiple Reference Stations," Institute of Electronics, Information and Communication Engineers Technical Research Report, SANE99-44, July 1999 [Non-patent document 2] Takeyasu Sakai and Kazunori Iemura, "Improvement of GPS Positioning Accuracy by Using Multiple Reference Stations," Journal of the Japan Institute of Navigation, No. 101, pp. 15-20, September 1999 [Non-patent document 3] 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 Summary of the Invention [Problem to be solved by the invention]

[0043] In DGPS, the effectiveness of correction information generally decreases the further away from the reference station. Therefore, when using DGPS at a user station, it is either used within a limited range from the reference station, or, if multiple reference stations are available, the nearest reference station is selected and used.

[0044] For example, the Quasi-Zenith Satellite System's SLAS service provides correction information from 13 reference stations located throughout Japan, and user stations are required to select and use the nearest reference station. The distance between a reference station and a user station can be 300 km or more, 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.

[0045] In fact, it has recently become clear that the effectiveness of corrections made by the SLAS service using correction information is sometimes insufficient, and that the desired positioning accuracy cannot be expected. Ionospheric activity is affected by solar activity, which repeats in an 11-year cycle, and this issue became apparent during the recent solar maximum. However, this situation was discovered through post-event performance analysis, and there is no way for SLAS service users to ascertain positioning accuracy in real time. For users, it is unclear whether the desired positioning accuracy is being achieved, which makes it difficult to use the SLAS service.

[0046] In the case of SLAS services, correction information can be obtained from multiple reference stations, and by using the techniques of Non-Patent Documents 1 to 3 to interpolate and use the correction information from multiple reference stations, effective differential correction can sometimes be performed 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.

[0047] As described above, there has been no means for determining the positioning accuracy in real time with DGPS. An object of the present invention is to enable a user to determine the positioning accuracy in real time with DGPS. [Means for solving the problem]

[0048] In DGPS, the effect of correction information generally decreases with increasing distance from the reference station. However, since tropospheric propagation delay can be estimated with sufficient accuracy using a simple tropospheric propagation delay model, 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. Furthermore, since the correction amount due to the position error of the navigation satellite can be estimated with sufficient accuracy using a precise ephemeris (the ultra-rapid ephemeris of

[0041] ), 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 kilometers, the distance to the navigation satellite is more than 20,000 kilometers, so not making this correction does not pose a major problem. Furthermore, since the clock error of the navigation satellite is a constant distance error regardless of location, such correction is not necessary.

[0049] Therefore, the problem to be solved by 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 along the path of the positioning signal transmitted by the navigation satellite until it reaches the receiver, and the density distribution of the ionospheric atmosphere along the path the positioning signal passes through is the problem. Generally, this distribution is irregular and difficult to predict, so it is an error factor that cannot be fully corrected even with DGPS.

[0050] Consider a case where there are two DGPS reference stations. If 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.

[0051] In this case, the correction values ​​of each navigation satellite contained 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 amounts resulting from the position error of the navigation satellite and tropospheric propagation delay. Therefore, if this modification is made and then used to calculate the position of the first reference station, the positioning error contained in the calculation result can be suppressed.

[0052] However, if there is a difference in the ionospheric propagation delay between the first and second reference stations, a large positioning error will occur because no correction for the ionospheric propagation delay is made. In other words, this positioning error reflects the difference in the ionospheric propagation delay between the two reference stations. Therefore, when a user station located between or in the surrounding area of ​​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 fully corrected even by DGPS. The first method for solving the problem according to the present invention is to provide this as an index of positioning accuracy to the user station, allowing the user to grasp the positioning accuracy in real time using DGPS.

[0053] The above is the case when two reference stations are available, but the same concept can also be applied when there are multiple reference stations. In other words, if the positioning error described in

[0050] to

[0052] is calculated between a specific reference station among multiple reference stations and 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 their surrounding areas use the correction information of that specific reference station.

[0054] In the first method, the positioning error is calculated when correction information generated by a second reference station is applied to a distance measurement value by a first reference station, or the positioning error is calculated when correction information generated by another reference station is applied to a distance measurement value by a specific reference station, and the maximum value thereof is provided to the user station as an index of positioning accuracy, but this order may be reversed to calculate the positioning error when correction information generated by the first reference station is applied to a distance measurement value by a second reference station, or the positioning error is calculated when correction information generated by a specific reference station is applied to a distance measurement value by a reference station other than the specific reference station, and the maximum value thereof is provided to the user station as an index of positioning accuracy. This is a second method for solving the problems according to the present invention.

[0055] Let us 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 through the correspondence 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.

[0056] In this case, the correction values ​​of each navigation satellite contained 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 amounts resulting from the position error of the navigation satellite and tropospheric propagation delay. Therefore, if this modification is made and then used to convert into the position correction amount at the position of the first reference station, the magnitude of the difference in the correction amounts for the two positions can be reduced.

[0057] However, if there is a difference in the ionospheric propagation delay between the first and second reference stations, the difference in the position correction amount will be large because no correction for the ionospheric propagation delay has been made. This difference in correction amount reflects the difference in the ionospheric propagation delay between the two reference stations, as in

[0052] , and can be considered the maximum level of positioning error that cannot be fully corrected even by DGPS 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. The third method for solving the problem according to the present invention is to provide this as an index of positioning accuracy to the user station, allowing the user to grasp the positioning accuracy in real time using DGPS.

[0058] The above is the case when two reference stations are available, but the same concept can also be applied when there are multiple reference stations. In other words, if the difference in the position correction amount described in

[0055] to

[0057] is calculated for a specific reference station among multiple 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 their surrounding areas use the correction information of that specific reference station.

[0059] Let us consider again the case where there are two DGPS reference stations. As explained in paragraphs

[0011] to

[0036] , the correction values ​​for each navigation satellite in the correction information generated by each reference station can be converted into position correction amounts for each navigation satellite at any receiver position via the correspondence between the changes in distance of the multiple navigation satellites contained in the correction information and the changes in receiver position. Using this, the correction values ​​for each navigation satellite in the correction information generated by the second reference station can be converted into position correction amounts at the position of the first reference station. The magnitude of the difference between this result and the result of converting the correction values ​​for each navigation satellite in the correction information generated by the first reference station into position correction amounts at the position of the first reference station is calculated for each corresponding navigation satellite.

[0060] In this case, 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 correction amount due to the position error of the navigation satellite and tropospheric propagation delay. Therefore, if this modification is made and then used to convert into the position correction amount at the position of the first reference station, the magnitude of the difference in the correction amounts for the two positions will have the same properties as described in

[0057] .

[0061] The magnitude of this difference in position correction amount is calculated for each navigation satellite. The fourth method for solving the problem according to the present invention is to provide the maximum value to the user station as an index of positioning accuracy, thereby enabling the user to grasp the positioning accuracy in real time in DGPS.

[0062] The above is the case when two reference stations are available, but the same concept can also be applied when there are multiple reference stations. That is, if the difference in the amount of position correction described in

[0059] to

[0061] is calculated for a specific reference station among multiple reference stations and 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 their surrounding areas use the correction information of that specific reference station.

[0063] Comparing the four methods described 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. Furthermore, the first method requires that the position of the first reference station or a specific reference station, and the second method requires that the positions 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 that it be very accurate. This is because, in the third and fourth methods, when converting correction information into a position correction amount, the amount of position correction does not change significantly even if the positional accuracy of the point used as the receiver position is not very high.

[0064] In the first method, instead of the previously known position of the first reference station or a specific reference station, the calculated position obtained by applying correction information generated by the first reference station or a specific reference station to the distance measurements made by the first reference station or a specific reference station is used, thereby allowing the accuracy of the previously known position of the first reference station or a specific reference station to be relaxed to the extent required in the third and fourth methods. However, even in this case, the first method still requires the distance measurements made by the first reference station or a specific reference station. The same applies to the second method.

[0065] Furthermore, as mentioned in

[0048] , position errors of navigation satellites are often not a major problem, and may be omitted when correcting the correction information in

[0051] ,

[0056] , and

[0060] .

[0066] The invention of claim 1 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 plurality of navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide correction values ​​obtained by subtracting the correction values ​​for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information; 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, is 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 in terms of the correction amount due to the position error of the navigation satellite and tropospheric propagation delay, and this corrected correction information is applied to the distance measurement value by the specific reference station to determine 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 determined for each of the reference stations other than the specific reference station, and the maximum value is provided to the user station as an indicator of positioning accuracy when the specific reference station is used.

[0067] The invention of 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 plurality of navigation satellites and measures the distance between them, a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground and measure the distance between them, and provide correction values ​​obtained by subtracting the correction values ​​for each corresponding navigation satellite from the actual distance calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information, 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 is a method for indicating positioning accuracy in a satellite navigation system, characterized in that the information providing station obtains the correction information from each of the reference stations other than the specific reference station, modifies the correction values ​​of each navigation satellite contained therein to correspond to the position of the specific reference station by adjusting the correction amount due to tropospheric propagation delay, and then applies this modified 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 these to the user station as an indicator of positioning accuracy when the specific reference station is used.

[0068] The invention of 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 plurality of navigation satellites and measures the distance between them, a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground and measure the distance between them, and subtract the distance for each corresponding navigation satellite from the actual distance calculated from the orbital information of each of the plurality of navigation satellites to obtain a correction value, which is provided to the user station as correction information for the plurality of 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 information providing station operates This is a program for indicating positioning accuracy in a satellite navigation system, characterized in that it obtains the correction information from each of the reference stations other than the specific reference station, modifies the correction values ​​of each navigation satellite contained therein to correspond to the position of the specific reference station for correction amounts due to navigation satellite position errors and tropospheric propagation delays, applies this modified 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 thereof to the user station as an indicator of positioning accuracy when the specific reference station is used.

[0069] The invention of 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 plurality of navigation satellites and measures the distance between them, a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground and measure the distance between them, and subtract the distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to obtain correction values, which are provided to the user station as correction information for the plurality of 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 positioning accuracy in a satellite navigation system, which operates at a user 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 amount of correction due to tropospheric propagation delay so that it corresponds to the position of the specific reference station, applies this modified 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 thereof to the user station as an indicator of positioning accuracy when the specific reference station is used.

[0070] The invention of 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 plurality of navigation satellites and measures the distance between them, a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground and measure the distance between them, and provide correction values ​​obtained by subtracting the correction values ​​for each corresponding navigation satellite from the actual distance 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, 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, modifies the correction values ​​of each navigation satellite contained therein to correspond to the positions of each of the reference stations other than the specific reference station, taking into account the position error of the navigation satellite and the correction amount due to tropospheric propagation delay, and then applies this modified correction information to the distance measurements 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 those reference stations for each of those reference stations, and provides the maximum value of this difference to the user station as an indicator of the positioning accuracy when using the specific reference station.This is a method for indicating positioning accuracy in a satellite navigation system, characterized in that the information providing station obtains the correction information from the specific reference station, modifies the correction values ​​of each of the navigation satellites contained therein to correspond to the positions of each of the reference stations other than the specific reference station, taking into account the position error of the navigation satellite and the correction amount due to tropospheric propagation delay, and then applies this modified correction information to the distance measurements of each corresponding reference station to determine the positions of those 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 this difference to the user station as an indicator of the positioning accuracy when using the specific reference station.

[0071] The invention of 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 plurality of navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide correction values ​​obtained by subtracting the correction values ​​for each corresponding navigation satellite from the actual distance 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; and an information providing station that provides the user station with an index of positioning accuracy when a specific reference station from the plurality of reference stations is used. The information providing station obtains the correction information from the specific reference station, modifies the correction values ​​of each navigation satellite contained therein for the amount of correction due to tropospheric propagation delay so that they correspond to the positions of each of the reference stations other than the specific reference station, applies this 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 those reference stations for each of those reference stations, and provides the maximum value of this difference to the user station as an indicator of the positioning accuracy when using the specific reference station.This is a method for indicating positioning accuracy in a satellite navigation system, characterized in that the information providing station obtains the correction information from the specific reference station, modifies the correction values ​​of each of the navigation satellites contained therein for the amount of correction due to tropospheric propagation delay so that they correspond to the positions of each of the reference stations other than the specific reference station, applies this modified correction information to the distance measurements of each of the corresponding reference stations to determine the positions of those reference stations, determines the magnitude of the difference between this result and the previously known positions of those reference stations for each of the reference stations, and provides the user station with the maximum value as an indicator of the positioning accuracy when using the specific reference station.

[0072] The invention of 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 plurality of navigation satellites and measures the distance between them; a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground and measure the distance between them, and subtract the resulting correction value for each corresponding navigation satellite from the original distance calculated from the orbital information of each of the plurality of navigation satellites to provide the correction value to the user station as correction information for the plurality of 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, and obtains the correction information from the specific reference station, modifies the correction values ​​of each navigation satellite contained therein to correspond to the positions of each of the reference stations other than the specific reference station in terms of the position error of the navigation satellite and the correction amount due to tropospheric propagation delay, and then applies this modified correction information to the distance measurements by 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 thereof to the user station as an indicator of the positioning accuracy when the specific reference station is used.

[0073] The invention of 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 plurality of navigation satellites and measures the distance between them; a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground and measure the distance between them, and subtract the distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites to obtain correction values, which are provided to the user station as correction information for the plurality of 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 for indicating positioning accuracy in a satellite navigation system operates in the information providing station, obtains the correction information from the specific reference station, modifies the correction values ​​of each navigation satellite contained therein for the amount of correction due to tropospheric propagation delay so that they correspond to the positions of each of the reference stations other than the specific reference station, applies this modified correction information to the distance measurements 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 those reference stations for each of those reference stations, and provides the maximum value of these differences to the user station as an indicator of positioning accuracy when using the specific reference station.

[0074] The invention of claim 9 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 plurality of navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide correction values ​​obtained by subtracting the correction values ​​for each corresponding navigation satellite from the ideal distance calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information; 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 information is obtained by adjusting the correction information to an arbitrary value via a correspondence relationship between the change in distance for the plurality of navigation satellites contained in the correction information and the change in receiver position. and the information providing station obtains the correction information from each of the reference stations other than the specific reference station, corrects the correction values ​​of each navigation satellite contained therein for correction amounts due to position errors of the navigation satellites and tropospheric propagation delays so that they correspond 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 thereof to the user station as an index of positioning accuracy when the specific reference station is used.

[0075] The invention of claim 10 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 plurality of navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide correction values ​​obtained by subtracting the correction values ​​for each corresponding navigation satellite from the actual distance calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information; 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 information is a correspondence between the change in distance for the plurality of navigation satellites included in the correction information and the change in receiver position. and 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 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 thereof to the user station as an index of positioning accuracy when the specific reference station is used.

[0076] The invention of claim 11 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 said plurality of navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by said plurality of navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide correction values ​​obtained by subtracting the correction values ​​for each corresponding navigation satellite from the original distance calculated from the orbital information of each of said plurality of navigation satellites to said user station as correction information; and an information providing station that provides said user station with an index of positioning accuracy when a specific reference station among said plurality of reference stations is used, said correction information being obtained by adjusting the correction information to any received position via a correspondence relationship between a change in distance for the plurality of navigation satellites included in said correction information and a change in receiver position. This program 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 correction amounts due to 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 of this difference to the user station as an indicator of positioning accuracy when using the specific reference station.

[0077] The invention of claim 12 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 plurality of navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the plurality of 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 actual distance calculated from the orbital information of each of the plurality of navigation satellites, and collectively providing the correction values ​​to the user station as correction information for the plurality of navigation satellites; and an information providing station that provides the user station with an indicator of the positioning accuracy when a specific reference station among the plurality of reference stations is used, wherein the correction information is calculated by using a correspondence relationship between the change in distance for the plurality of navigation satellites contained in the correction information and the change in receiver position, This is a program for indicating 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 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 this difference to the user station as an indicator of the positioning accuracy when the specific reference station is used.

[0078] The invention of claim 13 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 plurality of navigation satellites and measures the distances between them; a plurality of reference stations that receives the positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground and measures the distances between them, and provides the user station with correction values ​​obtained by subtracting the correction values ​​for each corresponding navigation satellite from the original distance calculated from the orbital information of each of the plurality of navigation satellites, and collectively providing the correction values ​​to the user station as correction information for the plurality of 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 contained in the correction information are calculated by adjusting an arbitrary receiver position for each navigation satellite through a correspondence relationship between a change in distance for the plurality of navigation satellites contained in the correction information and a change in receiver position. and 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 correction amounts due to navigation satellite position error and tropospheric propagation delay so that it corresponds to the position of the specific reference station, and then converts each corrected correction value of the navigation satellite into a position correction amount at the position of the specific reference station, and determines 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 thereof to the user station as an index of positioning accuracy when the specific reference station is used.

[0079] The invention of claim 14 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 plurality of navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the plurality of 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 ideal distance calculated from the orbital information of each of the plurality of navigation satellites, and collectively providing the correction values ​​to the user station as correction information for the plurality of 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 contained in the correction information are determined arbitrarily for each navigation satellite through the correspondence between the change in distance for the plurality of navigation satellites contained 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 tropospheric propagation delay so that it corresponds to the position of the specific reference station, and then converts each of these corrected correction values ​​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 thereof to the user station as an indicator of the positioning accuracy when the specific reference station is used.

[0080] The invention of claim 15 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 plurality of navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide correction values ​​obtained by subtracting the correction values ​​for each corresponding navigation satellite from the ideal distance calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information; 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 value for each navigation satellite contained in the correction information is calculated as the position at an arbitrary receiver position for each navigation satellite through the correspondence relationship between the change in distance for the plurality of navigation satellites contained in the correction information and the change in receiver position. and a program for indicating 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 correction amounts due to navigation satellite 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 correction amount for the position at the position of the specific reference station, calculates the magnitude of the difference between this result and the result of converting the correction value of each navigation satellite from 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 thereof to the user station as an index of positioning accuracy when the specific reference station is used.

[0081] The invention of claim 16 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 plurality of navigation satellites and measures the distances between them; a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground and measure the distances between them, and provide correction values ​​obtained by subtracting the obtained correction values ​​for each corresponding navigation satellite from the original distance calculated from the orbital information of each of the plurality of navigation satellites to the user station as correction information; 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 value for each navigation satellite contained in the correction information is calculated by calculating an arbitrary receiver position for each navigation satellite through a correspondence relationship between a change in distance for the plurality of navigation satellites contained in the correction information and a change in receiver position. a program that 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 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 correction amount for the position at the position of the specific reference station, 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 thereof to the user station as an index of positioning accuracy when the specific reference station is used.

[0082] The invention of claim 17 is a method for indicating positioning accuracy in a satellite navigation system, characterized in that in the invention described in any of claims 1, 2, 5, 6, 9, 10, 13, and 14, the information providing station is built into the user station.

[0083] The invention of claim 18 is a program for indicating positioning accuracy in a satellite navigation system, characterized in that in the invention described in any of claims 3, 4, 7, 8, 11, 12, 15, and 16, the information providing station is built into the user station. [Effects of the Invention]

[0084] The inventions according to claims 1 to 18 are configured as described above, so that in DGPS, the user can grasp the positioning accuracy in real time. Previously, there was no means for the user to grasp the positioning accuracy in real time. [Brief explanation of the drawings]

[0085] [Figure 1] 1 is a schematic diagram illustrating an embodiment of the present invention, for explaining a method for indicating positioning accuracy in a satellite navigation system of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0086] Specific embodiments of the present invention will be described in detail below with reference to the drawings. [Example]

[0087] A first embodiment of the present invention will be described in detail with reference to Fig. 1. Although Fig. 1 shows only two reference stations, this is 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.

[0088] In FIG. 1, navigation satellites 1 (1x, 1y...) each transmit a positioning signal.

[0089] The positioning signal transmitted by the navigation satellite 1 (1x, 1y···) passes through the ionosphere 2.

[0090] The reference stations 3 (3a, 3b...) receive the positioning signals transmitted by the navigation satellites 1 (1x, 1y...) and measure the distance from each navigation satellite.

[0091] The positioning signal received by the reference station 3 (3a, 3b...) is transmitted by the navigation satellite 1 (1x, 1y...) and then travels through path 31 (31a, 31b...), path 32 (32a, 32b...), and path 33 (33a, 33b...) before reaching the reference station. Path 31 (31a, 31b...) is the portion before reaching the ionosphere, path 32 (32a, 32b...) is the portion during passage through the ionosphere, and path 33 (33a, 33b...) is the portion after passage through the ionosphere.

[0092] The user station 4 receives the positioning signals transmitted by the navigation satellites 1 (1x, 1y...) and measures the distance from each navigation satellite.

[0093] The positioning signal received by the user station 4 is transmitted by the navigation satellite 1 (1x, 1y...), and then reaches the user station via route 41, route 42, and route 43. 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.

[0094] The information providing station 5 obtains correction information from the reference stations 3 (3a, 3b, etc.). This is the sum of the lengths of the routes 31a, 32a, and 33a for the reference station 3a, and the sum of the lengths of the routes 31b, 32b, and 33b for the reference station 3b, calculated from the orbital information of the navigation satellites minus the actually measured value.

[0095] 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., by adjusting the amount of correction caused by the position error of the navigation satellite to correspond to the position of the reference station 3a. In other words, the correction values, which include the amount of correction caused by the position error of the navigation satellite corresponding to the routes 31b, 31c, etc., are adjusted 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 adjust the amount of correction at the positions of the reference stations 3b, 3c, etc. to the amount of correction at the position of the reference station 3a. Note that, as stated in

[0048] , the position error of the navigation satellite is often not a major problem, and this correction may be omitted.

[0096] 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., by adjusting the amount of correction caused by tropospheric propagation delay so that it corresponds to the position of the reference station 3a. That is, the correction values, which include the amount of correction caused by tropospheric propagation delay corresponding to the paths 33b, 33c, etc., are adjusted to correspond to the path 33a. Because the amount of tropospheric propagation delay can be estimated with sufficient accuracy using a simple tropospheric propagation delay model, it is possible to adjust the amount of correction at the positions of the reference stations 3b, 3c, etc. to the amount of correction at the position of the reference station 3a.

[0097] 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.

[0098] 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 using the reference station 3a. In this case, the maximum value itself may be provided, but it may also be indexed into several stages to make it easier for the user station to use.

[0099] Next, the operation will be explained.

[0100] 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., to correspond to the position of the reference station 3a with respect to the correction amount resulting from the position error of the navigation satellite and the tropospheric propagation delay. 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 should almost match the previously known position of the reference station 3a, 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 positioning error is small.

[0101] 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 correction information obtained from the reference stations 3b, 3c, etc. is not corrected for the amount of ionospheric propagation delay, resulting in a large positioning error. In other words, this positioning error 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 their surrounding areas use the correction information from the 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 using DGPS.

[0102] Let us confirm 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) can be expressed by the following formula. The correction value ΔR(i,k) is a scalar quantity, and "|·|" means the magnitude of the vector.

[0103] (Number 11) ΔR(i,k)=|B(i)-R(k)|-|P(i)-R(k)|

[0104] Considering the causes of distance measurement errors separately, 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.

[0105] (Number 12) ΔR(i,k)=E(i)·(B(i)-R(k))-I(i,k)-T(i,k)

[0106] The position error of a navigation satellite can be determined by the precise orbital ephemeris, 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:

[0107] (Number 13) -E(i)·(B(i)-R(j))+E(i)·(B(i)-R(k))

[0108] Furthermore, 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:

[0109] (Number 14) +T(i,j)-T(i,k)

[0110] 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:

[0111] (Number 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)

[0112] 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 navigation satellite's position error and tropospheric propagation delay can be corrected to correspond to the position of reference station 3a (corresponding to symbol k), but this correction is not made to the ionospheric propagation delay amount, and the delay amount at reference stations 3b, 3c, etc. remains. [Example]

[0113] A second embodiment of the present invention will be described in detail with reference to Fig. 1. Although Fig. 1 shows only two reference stations, this is 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.

[0114] The explanations of

[0088] to

[0096] in the first embodiment also apply to this embodiment.

[0115] The information providing station 5 corrects the correction values ​​of each navigation satellite contained in the correction information received 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 path 31a, is corrected to correspond to the paths 31b, 31c, etc. The position error of the navigation satellite can be estimated with sufficient accuracy by using a precise orbital ephemeris (a very rapid ephemeris of

[0041] ), so 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.

[0116] The information providing station 5 corrects the correction values ​​of each navigation satellite contained in the correction information received 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, which includes the correction amount due to tropospheric propagation delay corresponding to the path 33a, is corrected 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 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.

[0117] The information providing station 5 applies the revised correction information to the distance measurements by the reference stations 3 b, 3 c, etc. to determine the positions of the reference stations 3 b, 3 c, etc., and determines the magnitude of the difference between this result and the previously known positions of the reference stations 3 b, 3 c, etc. The magnitude of this difference is determined for the reference stations 3 b, 3 c, etc.

[0118] 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 using the reference station 3a. In this case, the maximum value itself may be provided, but it may also be indexed into several stages to make it easier for the user station to use.

[0119] Next, the operation will be explained.

[0120] The information providing station 5 corrects the correction values ​​for each navigation satellite contained in the correction information received from the reference station 3a to correspond to the positions of the reference stations 3b, 3c, etc., for the amount of correction caused by the position error of the navigation satellite and the tropospheric propagation delay. 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. should be approximately the same as the previously known positions of the reference stations 3b, 3c, etc., 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 positioning error is small.

[0121] 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 correction information obtained from reference station 3a is not corrected for the amount of ionospheric propagation delay, resulting in a large positioning error. 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 their 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 using DGPS. [Example]

[0122] A third embodiment of the present invention will be described in detail with reference to Fig. 1. Although Fig. 1 shows only two reference stations, this is 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.

[0123] The explanations of

[0088] to

[0096] in the first embodiment also apply to this embodiment.

[0124] 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.

[0125] 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 using the reference station 3a. In this case, the maximum value itself may be provided, but it may also be indexed into several stages to make it easier for the user station to use.

[0126] Next, the operation will be explained.

[0127] Since the information providing station 5 corrects the correction information obtained from the reference stations 3b, 3c, etc., by adjusting the amount of correction caused by the position error of the navigation satellite and the tropospheric propagation delay contained in the correction information so that it corresponds to the position of the reference station 3a, the result of the information providing station converting this corrected correction information into the amount of position correction at the position of the reference station 3a and the amount of position correction obtained by converting the correction information obtained from the reference station 3a into the amount of ionospheric propagation delay at the position of the reference station 3a should be approximately the same, 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.

[0128] 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 their surrounding areas use the correction information from reference station 3a, the maximum value of this difference in the amount of position correction can be considered the maximum level of positioning error that cannot be fully corrected even by DGPS. By providing this as an index of positioning accuracy to user stations, DGPS allows users to grasp the positioning accuracy in real time. [Example]

[0129] A fourth embodiment of the present invention will be described in detail with reference to Fig. 1. Although Fig. 1 shows only two reference stations, this is 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.

[0130] The explanations of

[0088] to

[0096] in the first embodiment also apply to this embodiment.

[0131] 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 and for the reference stations 3b, 3c, etc.

[0132] 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 using the reference station 3a. In this case, the maximum value itself may be provided, but it may also be indexed into several stages to make it easier for the user station to use.

[0133] Next, the operation will be explained.

[0134] Since 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, the results of the information providing station converting this modified correction value of each navigation satellite into the correction amount for the position at the position of the reference station 3a and the results of the conversion of the correction value of each navigation satellite in the correction information obtained from the reference station 3a into the correction amount for the position 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 these should be small.

[0135] 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 their surrounding areas use the correction information from reference station 3a, the maximum value of this difference in the amount of position correction can be considered the maximum level of positioning error that cannot be fully corrected even by DGPS. By providing this as an index of positioning accuracy to user stations, DGPS allows users to grasp the positioning accuracy in real time. [Example]

[0136] 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 the functions of the information providing station built in. This embodiment corresponds to the inventions of claims 17 and 18.

[0137] 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 this is not required in Examples 3 and 4. Also, Example 1 requires the position of reference station 3a, and Example 2 requires the positions of reference stations 3b, 3c, etc. to be known accurately in advance, whereas Examples 3 and 4 require the position of reference station 3a, but do not require it to be very accurate. This differs from Example 1 in that it does not have to be very accurate. This corresponds to the explanation in

[0063] .

[0138] 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, it is sufficient to provide an information providing station 5 based on any of the embodiments 1 to 4. On the other hand, when the configuration of this embodiment is adopted in which the function of the information providing station 5 is built into the user station 4, the distance measurement value by the reference station is generally unknown, and as shown 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 into the user station.

[0139] Next, the operation will be explained.

[0140] By incorporating the functionality of the information providing station 5 into the user station 4, the information providing station can know the operating status of the user station, and therefore the present invention can be applied to only the available reference stations that the user station intends to use 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. [Industrial Applicability]

[0141] In differential GPS (DGPS), there is no means for user stations to grasp positioning accuracy in real time, and it is unclear whether the specified positioning accuracy is being achieved. The method for indicating positioning accuracy in a satellite navigation system of this invention allows users to grasp positioning accuracy in real time in DGPS, so that users can know if the positioning accuracy deviates from the specified accuracy, thereby contributing to ensuring user safety and improving the convenience of DGPS. [Explanation of symbols]

[0142] 1(1x,1y···) navigation satellite 2. Ionosphere 3(3a,3b...) Reference station 31(31a, 31b···) The portion of the path of the positioning signal received by the reference station before it reaches the ionosphere 32(32a, 32b...) The portion of the path of the positioning signal received by the reference station passing through the ionosphere 33(33a, 33b...) The portion of the path of the positioning signal received by the reference station after passing through the ionosphere 4 User Station 41 The portion of the path of the positioning signal received by the user station before it reaches the ionosphere 42 The portion of the path of the positioning signal received by the user station that passes through the ionosphere 43 The portion of the path of the positioning signal received by the user station after passing through the ionosphere 5 Information Bureau

Claims

1. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 shall: obtaining the correction information from each of the reference stations other than the specific 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 reference station to determine the position of the particular reference station; determining the magnitude of the difference between this result and the previously known position of the particular reference station for each of the reference stations other than the 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.

2. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 shall: obtaining the correction information from each of the reference stations other than the specific reference station; For each of the navigation satellite correction values ​​included therein, the correction amount due to tropospheric propagation delay is corrected to correspond to the position of the specific reference station, applying the revised correction information to the distance measurements made by the particular reference station to determine the position of the particular reference station; determining the magnitude of the difference between this result and the previously known position of the particular reference station for each of the reference stations other than the 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.

3. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 specific 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 reference station to determine the position of the particular reference station; determining the magnitude of the difference between this result and the previously known position of the particular reference station for each of the reference stations other than the 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.

4. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 specific reference station; For each of the navigation satellite correction values ​​included therein, the correction amount due to tropospheric propagation delay is corrected to correspond to the position of the specific reference station, applying the revised correction information to the distance measurements made by the particular reference station to determine the position of the particular reference station; determining the magnitude of the difference between this result and the previously known position of the particular reference station for each of the reference stations other than the 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.

5. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 shall: obtaining the correction information from the specific reference station; The correction values ​​of each navigation satellite included therein are corrected to correspond to the positions of each of the reference stations other than the specific reference station with respect to the position error of the navigation satellite and the correction amount due to the tropospheric propagation delay, applying the revised correction information to the distance measurements made by each of the corresponding reference stations to determine the positions of those reference stations; determining for each of the reference stations the magnitude of the difference between this result and the previously known positions of the 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.

6. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 shall: 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 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 reference stations to determine the positions of those reference stations; determining for each of the reference stations the magnitude of the difference between this result and the previously known positions of the 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.

7. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 to correspond to the positions of each of the reference stations other than the specific reference station with respect to the position error of the navigation satellite and the correction amount due to the tropospheric propagation delay, applying the revised correction information to the distance measurements made by each of the corresponding reference stations to determine the positions of those reference stations; determining for each of the reference stations the magnitude of the difference between this result and the previously known positions of the 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.

8. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 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 reference stations to determine the positions of those reference stations; determining for each of the reference stations the magnitude of the difference between this result and the previously known positions of the 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.

9. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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, The information provider shall: obtaining the correction information from each of the reference stations other than the specific reference station; For each of the navigation satellite correction values ​​included therein, the correction amount due to the position error of the navigation satellite and the tropospheric propagation delay is corrected so as to correspond to the position of the specific reference station, and then this 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.

10. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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, The information provider shall: obtaining the correction information from each of the reference stations other than the specific reference station; For each of the navigation satellite correction values ​​included therein, the correction amount due to tropospheric propagation delay is corrected so as to correspond to the position of the specific reference station, and then this 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.

11. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 specific reference station; For each of the navigation satellite correction values ​​included therein, the correction amount due to the position error of the navigation satellite and the tropospheric propagation delay is corrected so as to correspond to the position of the specific reference station, and then this 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.

12. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 specific reference station; For each of the navigation satellite correction values ​​included therein, the correction amount due to tropospheric propagation delay is corrected so as to correspond to the position of the specific reference station, and then this 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.

13. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 any receiver position for each navigation satellite through a correspondence relationship between a change in distance and a change in receiver position for the plurality of navigation satellites included in the correction information, The information provider shall: obtaining the correction information from each of the reference stations other than the specific reference station; The correction values ​​of each navigation satellite included in these are corrected so that the amount of correction caused by the position error of the navigation satellite and the tropospheric propagation delay corresponds to the position of the specific reference station, and then the corrected correction values ​​of each navigation satellite are converted into the amount of position correction 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 from 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.

14. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 any receiver position for each navigation satellite through a correspondence relationship between a change in distance and a change in receiver position for the plurality of navigation satellites included in the correction information, The information provider shall: obtaining the correction information from each of the reference stations other than the specific reference station; Correcting the correction value of each navigation satellite included therein for the amount of correction caused by tropospheric propagation delay so as to correspond to the position of the specific reference station, and then 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 from 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.

15. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 any receiver position for each navigation satellite through a correspondence relationship between a change in distance and a change in receiver position for the plurality of navigation satellites included in the correction information, Operated by the information providing station, obtaining the correction information from each of the reference stations other than the specific reference station; The correction values ​​of each navigation satellite included in these are corrected so that the amount of correction caused by the position error of the navigation satellite and the tropospheric propagation delay corresponds to the position of the specific reference station, and then the corrected correction values ​​of each navigation satellite are converted into the amount of position correction 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 from 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.

16. a plurality of navigation satellites that transmit 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 that receive positioning signals transmitted by the plurality of navigation satellites using receivers fixed on the ground, measure the distances between them, subtract the measured distances for each corresponding navigation satellite from the actual distances calculated from the orbital information of each of the plurality of navigation satellites, and provide the resulting correction values ​​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 any receiver position for each navigation satellite through a correspondence relationship between a change in distance and a change in receiver position for the plurality of navigation satellites included in the correction information, Operated by the information providing station, obtaining the correction information from each of the reference stations other than the specific reference station; Correcting the correction value of each navigation satellite included therein for the amount of correction caused by tropospheric propagation delay so as to correspond to the position of the specific reference station, and then 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 from 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.

17. 15. The method for indicating positioning accuracy in a satellite navigation system according to claim 1, 2, 5, 6, 9, 10, 13, or 14, wherein said information providing station is built into said user station.

18. 17. The program for indicating positioning accuracy in a satellite navigation system according to claim 3, 4, 7, 8, 11, 12, 15, or 16, wherein said information providing station is built into said user station.

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