Method for generating correction information in a satellite navigation system, information processing apparatus for generating correction information, and program

Abstract

Restore the distance information measured by the reference station from the correction information provided by the DGPS service. 【Solution means】 In a satellite navigation system including GPS by the United States and the quasi-zenith satellite system in Japan, what is usually provided to the user station by the DGPS service is correction information, not the distance information measured by the reference station. Therefore, the distance information measured by those reference stations is not provided to the user station, and in the case of WADGPS (Wide Area DGPS), existing DGPS reference stations could not be used. By restoring the distance information measured by the reference station from the correction information provided by the existing DGPS service, it becomes possible to provide the distance information measured by the DGPS reference station to the user station, and also to configure WADGPS using the DGPS reference station.

Description

Technical Field

[0001] This invention relates to a method for generating correction information in a satellite navigation system, an information processing apparatus for generating correction information, and a program.

Background Art

[0002] A satellite navigation system that measures positions using artificial satellites is generally referred to as GNSS (Global Navigation Satellite System), and a representative example thereof is GPS (Global Positioning System) by the United States. In general, GNSS receives positioning signals transmitted by artificial satellites called navigation satellites by a receiver, measures the distance between the navigation satellite and the receiver, and calculates the position of the receiver by calculation. A receiver for which the position is to be determined is called a user receiver or a user station, etc. An error with respect to the true position of the obtained position is called a positioning error.

[0003] In order to calculate the position of the receiver, it is necessary to know the position of the navigation satellite that transmits the positioning signal. However, the orbit information required for this is transmitted by the navigation satellite itself by superimposing it on the positioning signal. Since the orbit information is created by prediction, it includes an error of about several meters, which becomes a factor of the positioning error when calculating the receiver position.

[0004] The timing at which the navigation satellite transmits the positioning signal is determined in advance, and the navigation satellite transmits the positioning signal based on the time of the clock it has. Although a highly accurate atomic clock is used as this clock, a slight time deviation is inevitable, so the user receiver needs information on the time indicated by the navigation satellite's clock. This information is transmitted by the navigation satellite itself included in the orbit information as a transmitter clock error. Since the transmitter clock error is created by prediction, the transmission timing of the positioning signal calculated thereby includes an error corresponding to up to about several meters in terms of distance, which becomes a factor of the positioning error when calculating the position of the user receiver as an estimation error of the transmitter clock error of the navigation satellite (simply referred to as the clock error).

[0005] Before the positioning signal reaches the ground, it passes through the ionosphere and the troposphere in the sky, and a delay occurs when the positioning signal passes through each region. These delays are respectively called the ionospheric propagation delay and the tropospheric propagation delay. Since the positioning signal arrives late, the distance measured by the positioning signal becomes longer than the original, and both become factors of positioning error. The magnitudes of the ionospheric propagation delay and the tropospheric propagation delay converted into distance are respectively called the ionospheric propagation delay amount and the tropospheric delay amount.

[0006] The clock error of the navigation satellite appears uniformly as a distance measurement error regardless of the position of the receiver. The position error of the navigation satellite appears as the inner product component with the line-of-sight direction from the receiver to the navigation satellite as a distance measurement error. The ionospheric propagation delay amount appears as the integral of the electron density distribution of the ionosphere on the path until the ranging signal transmitted by the navigation satellite reaches the receiver as a distance measurement error. The tropospheric propagation delay amount appears as the integral of the refractive index of the atmosphere on the path until the ranging signal transmitted by the navigation satellite reaches the receiver as a distance measurement error. That is, except for the clock error of the navigation satellite, the distance measurement error appears differently depending on the position of the receiver.

[0007] By the way, a receiver is installed at a reference station fixed on the ground, and a correction value for the above-described distance measurement error is created from the distance measured thereby, and this is provided to the user as correction information, so that the distance measured at the user station is corrected by the correction value, and the measurement accuracy of the position at the user station (referred to as "positioning accuracy") is improved. This method is called differential GPS (DGPS). A numerical value for correcting the distance measurement error for each individual navigation satellite is called a correction value, and a set of correction values for a plurality of navigation satellites is called correction information.

[0008] When simply referred to as DGPS, it usually means providing correction information generated by a single reference station. This DGPS by individual reference stations may be called LADGPS (Local Area DGPS) in order to distinguish it from WADGPS described later. The LADGPS correction information generated by reference stations at different positions generally differs from each other because the measurement errors of distances regarding each navigation satellite appear differently at those positions.

[0009] As practical examples of LADGPS, there were those by medium-wave beacons for ships and FM multiplex digital broadcasts, but both have now been abolished. On the other hand, Japan's quasi-zenith satellite system, which started operation in 2018, transmits LADGPS correction information from artificial satellites as SLAS (Submeter-Level Augmentation Service). In the SLAS service, by receiving signals from a single artificial satellite, it is possible to obtain correction information at 13 reference stations located throughout Japan all at once. Receivers using the SLAS service are supposed to select and use the correction information of the nearest reference station. In the SLAS service, user stations are supposed to be equipped with receivers corresponding to a positioning signal of a single frequency.

[0010] In addition to the method by individual reference stations described above, there is a method called Wide Area Differential GPS (WADGPS) that integrates measurement data from multiple reference stations to create wide-area correction information effective over a wide geographical area. In this method, using the distances measured by reference stations, correction information is generated for each factor of positioning error such as the clock error of navigation satellites, the position error of navigation satellites, the ionospheric propagation delay, and the tropospheric propagation delay, and provided to user stations. Since each of these error factors appears as a distance measurement error depending on the position of the user station, at the user station, the correction value to be used is calculated from the correction information according to its own position and used for correction.

[0011] As a practical example of WADGPS, SBAS (Satellite-Based Augmentation System) has been standardized for aircraft. In the SBAS standard, the transmission format of correction information is defined. After accommodating correction information for each factor of positioning error such as the clock error of navigation satellites, the position error of navigation satellites, and the ionospheric propagation delay, it is transmitted from artificial satellites. Regarding the tropospheric propagation delay, since it can be corrected with sufficient accuracy by a tropospheric propagation delay model, it is not included in the transmission format of the SBAS standard, and correction is performed using a tropospheric propagation delay model defined in advance for both the master station that generates the correction information and the user station that uses the correction information.

[0012] As an example of SBAS, MSAS (Michibiki-Based Satellite Augmentation System) operated by the Japanese aeronautical agency is in practical use. There are also WAAS (Wide Area Augmentation System) by the United States, EGNOS (European Geostationary Navigation Overlay Service) in Europe, and GAGAN (GPS-Aided GEO-Augmented Navigation) in India. Recently, South Korea has started the operation of KASS (Korea Augmentation Satellite System).

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0014]

Non-Patent Document 1

[0015] The first problem of the present invention will be described. In both LADGPS and WADGPS, what is provided to the user station by the DGPS service is correction information, not the distance information measured by the reference station. Although the user station can expect to improve the positioning accuracy by applying the correction information, the procedure for applying the correction information is predefined, and there is no room for the user station to perform its own correction process.

[0016] In view of recent advances in satellite navigation technology, particularly the improvement in the modeling accuracy of ionospheric propagation delay and tropospheric propagation delay, there is a possibility that the positioning performance can be improved by performing an independent correction process at the user station. For this purpose, it is necessary to use the distance information measured by the reference station of DGPS instead of the correction information of DGPS.

[0017] As a practical example of LADGPS, there is the SLAS service, in which 13 reference stations provide the user stations with the LADGPS correction information generated individually. If the information on the distances measured by these reference stations could be utilized, there would be room for the user stations to perform their own correction processes. However, since the SLAS service provides only correction information, the information on the distances measured by each reference station is not provided, making it impossible for the user stations to perform their own correction processes.

[0018] In the case of the SLAS service, since correction information from multiple reference stations can be obtained, it is possible to improve the positioning accuracy by interpolating and using the correction information of multiple reference stations by the methods of Patent Document 1 and Non-Patent Documents 1 to 3. However, in none of Patent Document 1 and Non-Patent Documents 1 to 3 is a method for restoring the information on the distances measured by the reference stations described.

[0019] Patent Document 2 describes a method of approximating the distance measurement values measured by a reference station with a polynomial and then transmitting the coefficients of the polynomial and the residuals from the polynomial. By this method, there is a possibility of reducing the amount of information to be transmitted compared with the case of transmitting the distance measurement values as they are, but it is necessary to transmit the coefficients of the polynomial in addition to the residuals of the distance measurement values. That is, even by using this method, it is not possible to restore the information on the distances measured by the reference stations only from the correction information provided by the reference stations.

[0020] The second problem of the present invention will be described. In WADGPS, using the distances measured by reference stations, correction information is generated for each factor of positioning error such as the clock error of the navigation satellite, the position error of the navigation satellite, the ionospheric propagation delay, and the tropospheric propagation delay. Among these, the clock error of the navigation satellite is independent of the position of the user station. Also, for the tropospheric propagation delay, sufficient accuracy can be achieved by the tropospheric propagation delay model for correction.

[0021] Regarding the position error of the navigation satellite and the ionospheric propagation delay, the measurement error of the distance appears differently depending on the position of the user station. Since it is necessary to generate correction information reflecting such characteristics, in WADGPS, generally, four or more, typically six or more, reference stations are geographically separated and arranged within the service area.

[0022] Here, the minimum number of four reference stations is due to the number of unknowns combining the clock error and position error of the navigation satellite. Regarding the ionospheric propagation delay, each reference station can measure it individually, but to correctly separate and extract the clock error and position error of the navigation satellite from the measurement error of the distance, four or more reference stations are required corresponding to the four unknowns.

[0023] Also, in order to generate effective WADGPS correction information within the service area, calculation processing is performed using the fact that the way the position error of the navigation satellite and the ionospheric propagation delay appear as the measurement error of the distance differs depending on the position of the reference station. Therefore, it is necessary to geographically separate the reference stations to such an extent that a sufficient difference occurs in the way the measurement error of the distance appears. Generally, a distance of about 500 to 1,000 kilometers is often provided between the reference stations. Such a configuration of WADGPS reference stations places a heavy burden on installation and operation.

[0024] As a practical example of LADGPS, there is the SLAS service, which provides LADGPS correction information generated by 13 reference stations to user stations. If these reference stations can be used, WADGPS can be configured without installing reference stations for WADGPS. However, since the SLAS service only provides correction information, the distance information measured by each reference station is not provided and cannot be used as a reference station for WADGPS.

[0025] In the case of the SLAS service, since correction information from multiple reference stations can be obtained, it is possible to improve the positioning accuracy by interpolating and using the correction information of multiple reference stations by the methods of Patent Document 1 and Non-Patent Documents 1 to 3. However, in none of Patent Document 1 and Non-Patent Documents 1 to 3 is there a description of a method for restoring the distance information measured by the reference station so that it can be used by WADGPS.

[0026] Regarding Patent Document 2, as described in

[0019] , a method is described in which the distance measurement values measured by the reference station are approximated by a polynomial and then transmitted as the coefficients of the polynomial and the residuals from the polynomial. However, even by using this method, it is not possible to restore the distance information measured by the reference station only from the correction information provided by the reference station. Therefore, it is not possible to configure WADGPS using the reference station of LADGPS.

[0027] As described above, in LADGPS, there is a first problem that the distance information measured by the reference station is not provided to the user station, and in WADGPS, there is a second problem that existing LADGPS reference stations cannot be used. The problem of the present invention is to solve these problems by using the correction information provided by the existing LADGPS service, so that the distance information measured by the reference station of LADGPS can be provided to the user station, and also to configure WADGPS using the reference station of LADGPS.

Means for Solving the Problem

[0028] The present invention solves the above problems by using the correction information provided by the existing LADGPS service. Since all of the above problems require the distance information measured by the reference station, if the distance information measured by the reference station of LADGPS can be restored from the correction information provided by the existing LADGPS service, the above problems can be solved.

[0029] That is, in the correction station, the distance information measured by the reference station is restored from the correction information provided by the existing LADGPS service and provided to the user station. Further, in the correction station, the distance information measured by a plurality of reference stations is restored from the correction information provided by the existing LADGPS service, and the correction information of WADGPS is generated using this, thereby configuring WADGPS using the reference stations of LADGPS. A method for generating the correction information of WADGPS using the distance information measured by a large number of reference stations in the correction station is described in detail in Non-Patent Document 4, for example.

[0030] In order to restore the distance information measured by each reference station from the correction information provided by the LADGPS service, first, the properties of the correction values in LADGPS will be described. Let the code representing the reference station be r. Then, the pseudorange measured by this reference station for the navigation satellite i can be written as follows. Here, R(i,r) is the geometric distance between the navigation satellite i and the reference station r, B(i) is the transmitter clock error of the navigation satellite i, I(i,r) is the ionospheric propagation delay between the navigation satellite i and the reference station r, T(i,r) is the tropospheric propagation delay between the navigation satellite i and the reference station r, and S(r) is the receiver clock error of the reference station r.

[0031] (Equation 1) P(i,r) =R(i,r)-B(i)+I(i,r)+T(i,r)+S(r)

[0032] At the reference station r, using the orbit information of the navigation satellite i, the estimated value of the distance measured with the navigation satellite i is obtained by the following equation. Here, R’(i,r) is the distance between the navigation satellite i and the reference station r calculated from the orbit information of the navigation satellite i, B’(i) is the transmitter clock error of the navigation satellite i calculated from the orbit information of the navigation satellite i, and S’(r) is the estimated value of the receiver clock error of the reference station r.

[0033] (Equation 2) P’(i,r) =R’(i,r)-B’(i)+S’(r)

[0034] The correction value C(i,r) for the navigation satellite i by the reference station r is obtained as follows by subtracting (Equation 1) from (Equation 2). Here, let the estimated error in distance due to the error included in the orbit information of the navigation satellite i be ΔR(i,r)=R’(i,r)-R(i,r), the transmitter clock error due to the error included in the orbit information of the navigation satellite i be ΔB(i)=B’(i)-B(i), and the estimated error in the receiver clock error of the reference station r be ΔS(r)=S’(r)-S(r).

[0035] (Equation 3) C(i,r) =P’(i,r)-P(i,r) =△R(i,r)-ΔB(i)-I(i,r)-T(i,r)+ΔS(r)

[0036] Generally, when the user station applies the correction value, since the receiver clock error is estimated in the process of calculating the position of the user station, ΔS(r) can be arbitrarily offset. Since this is a function of the reference station r and not a function of the navigation satellite i, this means that the correction values generated by a certain reference station for N satellites can all be offset by an arbitrary same value. Utilizing this, even under the property that I(i,r) and T(i,r) are always positive, the maximum value of the absolute values of the N correction values can be suppressed.

[0037] Let the symbol representing the user station be u. Then, the pseudo-range measured by the user station u can be written as follows.

[0038] (Equation 4) P(i,u) =R(i,u)-B(i)+I(i,u)+T(i,u)+S(u)

[0039] At the user station u, it receives the provision of the correction value C(i,r) and adds this to the pseudo-range measured by the user station u. At this time, if the distance between the user station u and the reference station r is not large, the distance estimation errors ΔR(i,r) and ΔR(i,u) caused by the errors included in the orbit information of the navigation satellite i are almost the same, the ionospheric propagation delays I(i,u) and I(i,r) are also almost the same, and the tropospheric propagation delays T(i,u) and T(i,r) can also be regarded as almost the same. Therefore, the corrected pseudo-range becomes as follows. When compared with (Equation 4), the ionospheric propagation delay and the tropospheric propagation delay are eliminated. This can be said to be the basic principle of DGPS.

[0040] (Equation 5) P(i,u)+C(i,r) =R(i,u)-B(i)+I(i,u)+T(i,u)+S(u) +△R(i,r)-ΔB(i)-I(i,r)-T(i,r)+ΔS(r) =R’(i,u)-B’(i)+S(u)+ΔS(r)

[0041] Here, the geometric distance R(i,u) between the navigation satellite i and the user station u is replaced by the distance R’(i,u) between the navigation satellite i and the user station u calculated from the orbit information of the navigation satellite i, and the transmitter clock error B(i) of the navigation satellite i is replaced by the transmitter clock error B’(i) calculated from the orbit information of the navigation satellite i. However, since the user station u calculates its own position based on the position of the navigation satellite i and the transmitter clock error calculated from the orbit information of the navigation satellite i, it will no longer be affected by the errors included in the orbit information of the navigation satellite i.

[0042] Also, in (Equation 5), the component ΔS(r) corresponding to the receiver clock error at the reference station r remains in the corrected pseudo-range. However, this is only because the receiver clock error S(u) is replaced by S(u)+ΔS(r). Therefore, if the user station u treats S(u)+ΔS(r) as the receiver clock error in the process of calculating the position, it can calculate the position without any problem.

[0043] In the correction station, consider restoring the distance information measured by the reference station from the correction value (Equation 3) provided by the reference station. If the position of the reference station r is known, the estimated value of the distance measured between the dead reckoning satellite i calculated from the orbit information of the dead reckoning satellite i at the reference station r is as shown in (Equation 2), but since this includes the receiver clock error at the reference station r, it cannot be calculated by the correction station.

[0044] Therefore, instead of (Equation 2), the following equation that does not include the receiver clock error at the reference station r is used.

[0045] (Equation 6) P’(i,r) - S’(r) = R’(i,r) - B’(i)

[0046] Since the right side of (Equation 6) does not include the receiver clock error of the reference station r, it can be calculated by the correction station from the position of the reference station r and the orbit information of the dead reckoning satellite i. At the correction station, if the correction value (Equation 3) is subtracted from this (Equation 6), the distance information (Equation 1) measured by the reference station r can be restored as follows.

[0047] (Equation 7) P’(i,r) - S’(r) - C(i,r) = R’(i,r) - B’(i) - ΔR(i,r) + ΔB(i) + I(i,r) + T(i,r) - ΔS(r) = P(i,r) - S’(r)

[0048] Here, the estimated value S’(r) of the receiver clock error at the reference station r remains. However, since the receiver clock error S(r) at the reference station r and its estimated value S’(r) are unknown to the user station, it is the same for the user station regardless of the value of S’(r). From this perspective, with (Equation 7), the distance information measured by the reference station can be restored to a necessary and sufficient extent for the user station.

[0049] Note that Patent Document 2 is as described in

[0019] . According to the method of this document, P(i,r) including the receiver clock error at the reference station is restored without the remaining S’(r). In the method of the present invention, since there is no information corresponding to the coefficients of the polynomial in the method of Patent Document 2, the receiver clock error at the reference station is not restored, but this is sufficient for the user station.

[0050] By this method, the distance information measured by the reference station of LADGPS can be restored from the correction information provided by the LADGPS service. By providing the restored distance information measured by the reference station to the user station, the user station can utilize the distance information. Also, if a plurality of reference stations can be used, by using the method described in Non-Patent Document 4 and generating the correction information of WADGPS using this restored distance information, WADGPS can be configured using the reference station of LADGPS.

[0051] In the 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 therebetween, and a reference station that receives the positioning signals transmitted by the plurality of navigation satellites by a receiver fixed on the ground, measures the distances therebetween, generates a correction value for the measurement error of the distance for each navigation satellite, and provides this correction value to the correction station as correction information for the plurality of navigation satellites, and the correction station that processes the correction information obtained from the reference station and provides it to the user station, the correction station calculates, for each of the plurality of navigation satellites, an estimated value excluding the component corresponding to the receiver clock error of the distance measured at the position of the reference station using the orbit information of the navigation satellite, and subtracts the correction value provided for the navigation satellite from this, thereby restoring the distance information measured by the reference station for the navigation satellite, and providing this restored distance information to the user station. This is a method for generating correction information in a satellite navigation system.

[0052] The invention according to claim 2 is a satellite navigation system comprising a plurality of navigation satellites that transmit positioning signals, a user station that receives the positioning signals transmitted by the plurality of navigation satellites and measures the distances thereto, and a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites by a receiver fixed on the ground, measure the distances thereto, generate correction values regarding measurement errors of the distances for each navigation satellite, and collectively provide the correction values for the plurality of navigation satellites to a correction station as correction information, and the correction station that processes the correction information obtained from the plurality of reference stations and provides it to the user station. In the satellite navigation system, the correction station calculates, for each of the plurality of reference stations and the plurality of navigation satellites, an estimated value excluding a component corresponding to a receiver clock error of the distance measured at the position of the reference station using the orbit information of the navigation satellite, subtracts the correction value provided for the navigation satellite from this, restores the distance information measured by the reference station for the navigation satellite, and uses this restored distance information to generate new correction information for each factor of positioning errors such as the clock error and position error of the navigation satellite, the ionospheric propagation delay amount, and the tropospheric propagation delay amount, and provides this new correction information to the user station. This is a method for generating correction information in a satellite navigation system.

[0053] The invention according to claim 3 is a satellite navigation system including a plurality of navigation satellites that transmit positioning signals, a user station that receives the positioning signals transmitted by the plurality of navigation satellites and measures the distances thereto, a reference station that receives the positioning signals transmitted by the plurality of navigation satellites by a receiver fixed on the ground, measures the distances thereto, generates a correction value for the measurement error regarding the distance for each navigation satellite, and collectively provides this correction value as correction information to a correction station for the plurality of navigation satellites, and the correction station that processes the correction information obtained from the reference station and provides it to the user station. In the satellite navigation system, for each of the plurality of navigation satellites operating at the correction station, an estimated value excluding a component corresponding to the receiver clock error of the distance measured at the position of the reference station using the orbit information of the navigation satellite is calculated, and by subtracting the correction value provided for the navigation satellite from this, the distance information measured by the reference station for the navigation satellite is restored, and the restored distance information is provided to the user station. It is an information processing device for generating correction information in a satellite navigation system, characterized in that

[0054] The invention according to claim 4 is a satellite navigation system comprising a plurality of navigation satellites that transmit positioning signals, a user station that receives the positioning signals transmitted by the plurality of navigation satellites and measures the distances thereto, and a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites by a receiver fixed on the ground, measure the distances thereto, generate correction values regarding the measurement errors of the distances for each navigation satellite, and collectively provide these correction values as correction information to a correction station for the plurality of navigation satellites, and the correction station that processes the correction information obtained from the plurality of reference stations and provides it to the user station. In the satellite navigation system, for each of the plurality of reference stations and the plurality of navigation satellites operating at the correction station, an estimated value is calculated using the orbit information of the navigation satellite, excluding the component corresponding to the receiver clock error of the distance measured at the position of the reference station, and by subtracting the correction value provided for the navigation satellite from this, the distance information measured by the reference station for the navigation satellite is restored. Using this restored distance information, new correction information is generated for each factor of the positioning error such as the clock error and position error of the navigation satellite, the ionospheric propagation delay amount, and the tropospheric propagation delay amount, and this new correction information is provided to the user station. It is an information processing device for generating correction information in a satellite navigation system.

[0055] The invention according to claim 5 is a satellite navigation system comprising: a plurality of navigation satellites that transmit positioning signals; a user station that receives the positioning signals transmitted by the plurality of navigation satellites and measures the distances thereto; a reference station that receives the positioning signals transmitted by the plurality of navigation satellites by a receiver fixed on the ground, measures the distances thereto, generates a correction value regarding the measurement error of the distance for each navigation satellite, and provides this correction value as correction information to the correction station for the plurality of navigation satellites in a lump; and the correction station that processes the correction information obtained from the reference station and provides it to the user station. In the satellite navigation system, for each of the plurality of navigation satellites operating in the correction station, an estimated value excluding a component corresponding to the receiver clock error of the distance measured at the position of the reference station using the orbit information of the navigation satellite is calculated, and by subtracting the correction value provided for the navigation satellite from this, the information on the distance measured by the reference station for the navigation satellite is restored, and this restored distance information is provided to the user station. A program for generating correction information in a satellite navigation system, characterized in that it is such as described above.

[0056] The invention according to claim 6 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 thereto; a plurality of reference stations that receive the positioning signals transmitted by the plurality of navigation satellites by a receiver fixed on the ground, measure the distances thereto, generate correction values for the measurement errors regarding the distances for each navigation satellite, and collectively provide these correction values as correction information to a correction station for the plurality of navigation satellites; and the correction station that processes the correction information obtained from the plurality of reference stations and provides it to the user station. In the satellite navigation system, for each of the plurality of reference stations and the plurality of navigation satellites operating at the correction station, an estimated value excluding a component corresponding to the receiver clock error of the distance measured at the position of the reference station using the orbit information of the navigation satellite is calculated, and by subtracting the correction value provided for the navigation satellite from this, the information on the distance measured by the reference station for the navigation satellite is restored. Using this restored distance information, new correction information is generated for each factor of the positioning error such as the clock error and position error of the navigation satellite, the ionospheric propagation delay amount, and the tropospheric propagation delay amount, and this new correction information is provided to the user station. It is a program for generating correction information in a satellite navigation system, characterized by the above.

Effect of the Invention

[0057] Since the inventions according to claims 1, 3, and 5 are configured as described above, the information on the distances measured by the reference stations of LADGPS can be provided to the user station.

[0058] Since the inventions according to claims 2, 4, and 6 are configured as described above, WADGPS can be configured using the reference stations of LADGPS.

Brief Description of the Drawings

[0059]

Figure 1

Figure 2

Embodiment for Carrying Out the Invention

[0060] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

Example

[0061] A first embodiment of the present invention will be described in detail with reference to FIG. 1. This embodiment corresponds to claims 1, 3, and 5. Although only three navigation satellites are shown in FIG. 1, this is for illustration, and there may be cases with four or more satellites. Also, although one reference station is shown in FIG. 1, this is for illustration, and in this embodiment, a configuration with any number of reference stations of one or more is possible.

[0062] Navigation satellites 1 (1a, 1b...) each transmit a positioning signal.

[0063] User station 2 receives the positioning signals transmitted by navigation satellites 1 (1a, 1b...) and measures the distance from each navigation satellite.

[0064] The LADGPS reference station 3 has a function of receiving the positioning signals transmitted by navigation satellites 1 (1a, 1b...), measuring the distance from each navigation satellite, generating a correction value regarding the measurement error of the distance for each navigation satellite, and providing this as correction information 4 to the correction station 5.

[0065] The correction station 5 calculates, for each of the navigation satellites 1 (1a, 1b...), an estimated value excluding the component corresponding to the receiver clock error of the distance measured at the position of the reference station 3 using the orbit information of the navigation satellite, and subtracts the correction value provided for the navigation satellite from this to restore the distance information measured by the reference station 3 for the navigation satellite. The distance information restored here is the one in which the estimated value of the receiver clock error of the reference station 3 is subtracted from the measured value of the distance by the reference station 3.

[0066] The correction station 5 provides the restored distance information 6 to the user station 2.

[0067] Next, the operation will be described.

[0068] The user station 2 obtains the distance information 6 measured by the reference station 3 that provides the LADGPS service and has been restored by the correction station 5. This information is the information on the distance measured by the reference station, and is different from the correction information generated by the reference station. This information is obtained by subtracting the estimated value of the receiver clock error of the reference station 3 from the measured value of the distance by the reference station 3. However, since the receiver clock error of the reference station 3 is originally unknown to the user station 2, it does not matter particularly.

[0069] The user station 2 can use this distance information 6 to perform its own correction process by a method different from that of generating correction values by the LADGPS reference station for the distance to the navigation satellite measured by itself.

[0070] In this embodiment, the correction station 5 is assumed to be installed separately from the user station 2, but a configuration in which the function of the correction station 5 is incorporated in the user station 2 is also possible.

Embodiment

[0071] The second embodiment of the present invention will be described in detail with reference to FIG. 2. This embodiment corresponds to claims 2, 4, and 6. Although only three navigation satellites are shown in FIG. 2, this is for illustration, and there may be four or more. Also, although four reference stations are shown in FIG. 2, this is for illustration, and in this embodiment, a configuration with an arbitrary number of reference stations of four or more is possible.

[0072] The navigation satellites 1 (1a, 1b ···) each transmit a positioning signal.

[0073] The user station 2 receives the positioning signals transmitted by the navigation satellites 1 (1a, 1b ···) and measures the distances from each navigation satellite.

[0074] The LADGPS reference station 3 (3a, 3b ···) receives the positioning signals transmitted by the navigation satellite 1 (1a, 1b ···), measures the distances from each navigation satellite, generates correction values for the measurement errors of the distances for each navigation satellite, and provides this as correction information 4 (4a, 4b ···) to the correction station 5.

[0075] For each of the reference station 3 (3a, 3b ···) and the navigation satellite 1 (1a, 1b ···), the correction station 5 calculates an estimated value excluding the component corresponding to the receiver clock error of the distance measured at the position of the reference station using the orbit information of the navigation satellite, and subtracts the correction value provided for the navigation satellite from this, thereby restoring the distance information measured by the reference station for the navigation satellite. Here, the restored distance information is such that the estimated value of the receiver clock error of the reference station is subtracted from the measured value of the distance by the reference station.

[0076] Using this restored distance information, the correction station 5 generates new correction information 7 for each factor of the positioning error such as the clock error and position error of the navigation satellite 1 (1a, 1b ···), the ionospheric propagation delay amount, and the tropospheric propagation delay amount. Although the restored distance information is such that the estimated value of the receiver clock error of the reference station 3 (3a, 3b ···) is subtracted from the measured value of the distance by the reference station, since the receiver clock error of the reference station (3a, 3b ···) is originally unknown to the correction station 5, there is no particular problem.

[0077] The correction station 5 provides this new correction information 7 to the user station 2 as WADGPS correction information.

[0078] Next, the operation will be described.

[0079] The user station 2 obtains the WADGPS correction information 7 from the correction station 5. Since this correction information is generated for each factor of the positioning error such as the clock error and position error of the navigation satellite 1 (1a, 1b ···), the ionospheric propagation delay amount, and the tropospheric propagation delay amount, when the user station applies this correction information, the correction process of WADGPS will be executed.

[0080] According to its own position, the user station 2 calculates the correction value to be used by itself from this WADGPS correction information 7, and applies this to the distance to the navigation satellite measured by itself. Thereby, correction processing adapted to its own position can be executed by the WADGPS method.

[0081] In this embodiment, the correction station 5 is assumed to be installed separately from the user station 2, but a configuration in which the function of the correction station 5 is incorporated in the user station 2 is also possible.

Industrial Applicability

[0082] By the method for generating correction information in the satellite navigation system of this invention, in LADGPS, the information on the distance measured by the reference station is not provided to the user station, and in WADGPS, where an existing LADGPS reference station could not be used, by restoring the information on the distance measured by the reference station from the correction information provided by the existing LADGPS service, the information on the distance measured by the reference station of LADGPS can be provided to the user station, and also, WADGPS can be configured using the reference station of LADGPS.

Explanation of Signs

[0083] 1 (1a, 1b ···) Navigation satellite 2 User station 3 (3a, 3b ···) Reference station 4 (4a, 4b ···) Correction information generated by the reference station 5 Correction station 6 Distance information 7 New correction information

Claims

1. A plurality of navigation satellites transmitting positioning signals; a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween; a reference station that receives the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground, measures the distances between them, generates a correction value for each navigation satellite with respect to the distance measurement error, and provides the correction values ​​for the navigation satellites together as correction information to a correction station; In a satellite navigation system including the correction station, the correction information obtained from the reference station is processed and provided to a user station, The said Bureau of Corrections: For each of the plurality of navigation satellites, calculate an estimate of the distance measured at the position of the reference station using the orbital information of the navigation satellite, excluding a component corresponding to a receiver clock error, and recover the distance information measured for the navigation satellite by the reference station by subtracting the correction value provided for the navigation satellite from the estimate; A method for generating correction information in a satellite navigation system, comprising providing the restored distance information to the user station.

2. A plurality of navigation satellites transmitting positioning signals; a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween; a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, generate correction values ​​for distance measurement errors for each navigation satellite, and provide the correction values ​​for the plurality of navigation satellites together as correction information to a correction station; In a satellite navigation system including the correction station, the correction information obtained from the plurality of reference stations is processed and provided to a user station, The said Bureau of Corrections: For each of the plurality of reference stations and the plurality of navigation satellites, calculate an estimate of the distance measured at the position of the reference station using the orbital information of the navigation satellite, excluding a component corresponding to a receiver clock error, and restore information of the distance measured by the reference station for the navigation satellite by subtracting from the estimate an adjustment value provided for the navigation satellite; A method for generating correction information in a satellite navigation system, characterized in that new correction information is generated for each cause of positioning error, such as the clock error and position error of the navigation satellite, ionospheric propagation delay, and tropospheric propagation delay, using this restored distance information, and providing this new correction information to the user station.

3. A plurality of navigation satellites transmitting positioning signals; a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween; a reference station that receives the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground, measures the distances between them, generates a correction value for each navigation satellite with respect to the distance measurement error, and provides the correction values ​​for the navigation satellites together as correction information to a correction station; In a satellite navigation system including the correction station, the correction information obtained from the reference station is processed and provided to a user station, Operates in the correction station, For each of the plurality of navigation satellites, calculate an estimate of the distance measured at the position of the reference station using the orbital information of the navigation satellite, excluding a component corresponding to a receiver clock error, and recover the distance information measured for the navigation satellite by the reference station by subtracting the correction value provided for the navigation satellite from the estimate; An information processing device for generating correction information in a satellite navigation system, which provides the restored distance information to the user station.

4. A plurality of navigation satellites transmitting positioning signals; a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween; a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, generate correction values ​​for distance measurement errors for each navigation satellite, and provide the correction values ​​for the plurality of navigation satellites together as correction information to a correction station; In a satellite navigation system including the correction station, the correction information obtained from the plurality of reference stations is processed and provided to a user station, Operates in the correction station, For each of the plurality of reference stations and the plurality of navigation satellites, calculate an estimate of the distance measured at the position of the reference station using the orbital information of the navigation satellite, excluding a component corresponding to a receiver clock error, and restore information of the distance measured by the reference station for the navigation satellite by subtracting from the estimate an adjustment value provided for the navigation satellite; An information processing device that generates correction information in a satellite navigation system, which uses this restored distance information to generate new correction information for each cause of positioning error, such as the clock error and position error of the navigation satellite, ionospheric propagation delay, and tropospheric propagation delay, and provides this new correction information to the user station.

5. A plurality of navigation satellites transmitting positioning signals; a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween; a reference station that receives the positioning signals transmitted by the navigation satellites using a receiver fixed on the ground, measures the distances between them, generates a correction value for each navigation satellite with respect to the distance measurement error, and provides the correction values ​​for the navigation satellites together as correction information to a correction station; In a satellite navigation system including the correction station, the correction information obtained from the reference station is processed and provided to a user station, Operates in the correction station, For each of the plurality of navigation satellites, calculate an estimate of the distance measured at the position of the reference station using the orbital information of the navigation satellite, excluding a component corresponding to a receiver clock error, and recover the distance information measured for the navigation satellite by the reference station by subtracting the correction value provided for the navigation satellite from the estimate; A program for generating correction information in a satellite navigation system, characterized in that the restored distance information is provided to the user station.

6. A plurality of navigation satellites transmitting positioning signals; a user station that receives positioning signals transmitted from the plurality of navigation satellites and measures the distances therebetween; a plurality of reference stations which receive positioning signals transmitted by the plurality of navigation satellites using a receiver fixed on the ground, measure the distances between them, generate correction values ​​for distance measurement errors for each navigation satellite, and provide the correction values ​​for the plurality of navigation satellites together as correction information to a correction station; In a satellite navigation system including the correction station, the correction information obtained from the plurality of reference stations is processed and provided to a user station, Operates in the correction station, For each of the plurality of reference stations and the plurality of navigation satellites, calculate an estimate of the distance measured at the position of the reference station using the orbital information of the navigation satellite, excluding a component corresponding to a receiver clock error, and restore information of the distance measured by the reference station for the navigation satellite by subtracting from the estimate an adjustment value provided for the navigation satellite; A program for generating correction information in a satellite navigation system, which uses this restored distance information to generate new correction information for each cause of positioning error, such as the clock error and position error of the navigation satellite, ionospheric propagation delay, and tropospheric propagation delay, and provides this new correction information to the user station.

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