Protection level calculation device, protection level calculation system, position determination system and protection level calculation method

Abstract

Protection level calculation device (3), comprising: a distortion error model unit (13) to output an upper and lower limit of a distortion error that is assumed to be contained in a measurement obtained from a position determination signal; and a protection level calculation unit (14) to calculate a protection level for determining the validity of a position determination solution calculated on the basis of measurement, using the upper limit and the lower limit.

Description

Technical field

[0001] The present disclosure relates to a protection level calculation device, a protection level calculation system, a position determination system and a protection level calculation method for calculating a protection level to determine the validity of a position determination solution. State of the art

[0002] For advanced applications, such as autonomous driving, positioning systems exist that determine the application's position using signals transmitted by Global Positioning System (GPS) satellites, wireless communication base stations, or similar devices. To enable the safe, application-controlled use of a position solution calculated from measurements, these positioning systems use a level of protection to determine whether the calculated position solution is valid.

[0003] For example, a protection level calculation device described in patent literature 1 derives a multivariate probability distribution model in advance, which includes distance measurement errors and measurement quality indicators of distance measurements. When performing a position determination, the protection level calculation device described in patent literature 1 determines the conditional probability density of a measurement error with respect to the values ​​of the simultaneously obtained measurement quality indicators for a distance measurement from each of a plurality of signal sources transmitting a position determination signal and calculates the protection level of a position determination solution based on the relationship between the measurement errors and a position determination error.Patent literature 2 describes a method for vector phase tracking of a multitude of global positioning satellite carrier signals, in which, for a tracked satellite, a discriminator generates phase tracking error signals at different frequencies, which are assigned to the different carrier signals of the tracked satellite, and in which a multi-frequency estimation of the disturbances is performed based on the phase tracking error signal supplied by the discriminator unit. The method takes the ionospheric error into account when determining the output phase error signals. Patent literature 3 discloses a pseudo-range-based reliable positioning method for a multimode GNSS receiver.The multimode GNSS receiver receives GNSS satellite signals, primarily to obtain pseudo-ranges and navigation messages from the GNSS satellite signals. Different types of pseudo-ranges and navigation messages are unified to the same time and space coordinates, and the pseudo-ranges and the navigation messages transformed into coordinates are subjected to error correction.

[0004] Patent literature 4 discloses a method for predicting the performance of a satellite navigation system comprising at least one constellation of satellites for a GNSS receiver. The method is characterized in that it additionally includes the steps of acquiring third-party data (Pfa, Pmd) from the receiver, which indicate the probability of a false alarm and the probability of a false message according to the requirements for the predetermined RAIM method, and creating a database (7) of this third-party data according to predetermined scenarios.

[0005] Patent literature 5 discloses a method for determining the reliability of position information based on an intelligent device, which determines the reliability of the accuracy of position information provided to an intelligent device in order to provide it, and a system for determining the same.To achieve this purpose, the method for determining the reliability of position information based on a smart device according to the present invention comprises: a first step enabling an analysis unit to analyze a navigationally hazardous environment at sea; a second step enabling a computation unit to calculate a level of protection based on the data analyzed by the analysis unit; a third step in which a fault modeling unit models a fault generated from a satellite navigation signal and an inertial sensor of the smart device; and a fourth step in which a comparison unit compares an alarm threshold (AL) that prevents a user's navigation solution, to which the calculated level of protection and the fault modeled by the fault modeling unit are applied, from being exceeded. List of quotations Patent literature Patent literature 1: Japanese patent no. 6855580 Patent literature 2: WO 2009 / 125 011 A1 Patent Literature 3: CN 1 04 035 113 A Patent literature 4: EP 1 965 219 A1 Patent literature 5: KR 10 2023 0 083 466A Brief description of the invention Problem to be solved by the invention

[0006] According to the conventional technique disclosed in patent literature 1, if an abnormal measurement is present at the time of using the multivariate probability distribution model, the protection level calculation device rejects the abnormal measurement for calculating the protection level. Therefore, the conventional technique has a problem in that the protection level calculation device cannot calculate the effective protection level if it does not reject an abnormal measurement.

[0007] The present disclosure was prepared in light of the foregoing and one of its objectives is to provide a protection level calculation device capable of calculating a protection level that is effective for determining the validity of a position determination solution calculated on the basis of measurements. Means to solve the problem

[0008] To solve the problems described above and to fulfill the task, a protection level calculation device according to the present disclosure includes: a distortion error model unit to output an upper limit and a lower limit of a distortion error that is assumed to be contained in a measurement obtained from a position determination signal; and a protection level calculation unit to calculate a protection level for determining the validity of a position determination solution calculated on the basis of the measurement using the upper limit and the lower limit. Effects of the invention

[0009] The protection level calculation device according to the present disclosure has the effect of being able to calculate the protection level that is effective for determining the validity of the position determination solution calculated on the basis of the measurements. Brief description of the drawings Fig. Figure 1 is a representation illustrating a configuration example of a positioning system according to a first embodiment. Fig. Figure 2 is a representation illustrating a configuration example of a protection level calculation system included in the position determination system according to the first embodiment. Fig. Figure 3 is a representation illustrating a configuration example of a control circuit according to the first embodiment. Fig. Figure 4 is a representation illustrating a configuration example of a dedicated hardware circuit according to the first embodiment. Fig. Figure 5 is a flowchart illustrating an operating sequence for the protection level calculation system included in the position determination system according to the first embodiment. Fig. Figure 6 is a representation to explain a non-centrality parameter used in the calculation of a degree of protection in the first embodiment. Fig. Figure 7 is a representation illustrating an example of an arrangement of satellites to explain a process for calculating a horizontal degree of protection in the first embodiment. Fig. Figure 8 is a representation illustrating a first modification of the protection level calculation system in the first embodiment. Fig. Figure 9 is a representation illustrating a second modification of the protection level calculation system in the first embodiment. Fig. Figure 10 is a representation illustrating a third modification of the protection level calculation system in the first embodiment. Fig. Figure 11 is a representation illustrating a fourth modification of the protection level calculation system in the first embodiment. Fig. Figure 12 is a representation illustrating a configuration example of a positioning system according to a second embodiment. Fig. Figure 13 is a representation illustrating a configuration example of a protection level calculation system included in the position determination system according to the second embodiment. Fig. Figure 14 is a representation illustrating a configuration example of a protection level calculation system included in a position determination system according to a third embodiment. Fig. Figure 15 is a representation illustrating an example of upper and lower limit models of a distortion error used by the protection level calculation system of the third embodiment. Fig. Figure 16 is a representation illustrating a modification of the protection level calculation system included in the position determination system according to the third embodiment. Fig. Figure 17 is a representation illustrating a configuration example of a protection level calculation system included in a position determination system according to a fourth embodiment. Description of embodiments

[0010] A protection level calculation device, a protection level calculation system, a position determination system and a protection level calculation method according to embodiments are described in more detail below with reference to the drawings. First embodiment.

[0011] Fig. Figure 1 is a diagram illustrating a configuration example of a positioning system 100 according to a first embodiment. The positioning system 100 includes an application 101, which is a positioning object, a positioning terminal 102 installed in the application 101, a plurality of satellites 103, which are positioning satellites, base stations 104 for wireless communication, and a server 105, which is connected to the base stations 104 via a communication network. The positioning satellites are, for example, GPS satellites used in GPS or quasi-zenith satellites used in the quasi-zenith satellite system (QZSS). In the case shown in Figure 1, the positioning system 100 is a positioning terminal 102 installed in the application 101, a plurality of satellites 103, which are positioning satellites, base stations 104 for wireless communication, and a server 105, which is connected to the base stations 104 via a communication network. The positioning satellites are, for example, GPS satellites used in GPS or quasi-zenith satellites used in the quasi-zenith satellite system (QZSS). Fig. In the illustrated example 1, application 101 is a vehicle. The positioning terminal 102 can communicate with the base stations 104 via wireless communication and with the server 105 via a communication network.

[0012] The satellites 103 transmit positioning signals. The positioning terminal 102 receives the positioning signals and determines the position of the application 101. Instead of the satellites 103, the base stations 104 can transmit positioning signals to the positioning terminal 102. That is, the signal sources for the positioning signals can be either the satellites 103 or the base stations 104.

[0013] Upon receiving position signals from the signal sources, the position terminal 102 extracts information about the positions of the signal sources and information about the distances between the application 101 and the signal sources as measurements. The position terminal 102 calculates the position solution for the application 101 by performing a position calculation using these measurements. That is, the position terminal 102 performs a position calculation. The position solution includes information about the horizontal position and information about the vertical position.

[0014] The measurements extracted using the positioning signals contain errors. Errors in the measurements, when Satellite 103 are the signal sources, include, for example, errors due to Satellite 103, such as satellite clock errors or satellite orbital errors; errors due to the atmosphere, such as ionospheric or tropospheric delays; errors due to a receiving environment, such as multipath errors or radio wave interference; and errors due to a receiver, such as receiver clock errors or receiver distortion between signals.

[0015] Therefore, the positioning terminal 102 uses a protection level to determine the validity of the calculated positioning solution. The positioning terminal 102 calculates the protection level using an observation model that corresponds to the measurements used in the positioning calculation and weightings in the positioning calculation. That is, the positioning terminal 102 calculates the protection level. A specific procedure for calculating the protection level is described later.

[0016] In the positioning system 100, a limit value is defined that specifies the boundary of a positioning error within which the application 101 can effectively use the positioning solution calculated by the positioning terminal 102. This limit value is referred to as the alarm limit and is specified by the application 101. The positioning terminal 102 compares the calculated level of protection with the limit value to determine the validity of the calculated positioning solution. Based on the result of determining the validity of the calculated positioning solution, the positioning terminal 102 determines whether the calculated positioning solution can be used or not.

[0017] The Position Determination System 100 includes a protection level calculation system that calculates the protection level. A configuration of the protection level calculation system is described here. Fig. Figure 2 is a representation illustrating a configuration example of a protection level calculation system 1, which is included in the position determination system 100 according to the first embodiment. The in Fig. 2 Illustrated protection level calculation system 1 includes a position determination device 2, which performs a position determination, and a protection level calculation device 3, which calculates the protection level.

[0018] Here, a case is described in which both the position determination device 2 and the protection level calculation device 3 are used in the Fig. The positioning terminal 102 illustrated in Figure 1 is integrated. It should be noted that, as described later, the positioning device 2 can be integrated into the positioning terminal 102, and the protection level calculation device 3 can be integrated into a server 105 or the like, i.e., a device outside the positioning terminal 102. Alternatively, both the positioning device 2 and the protection level calculation device 3 can be integrated into an external device, such as the server 105. If the positioning device 2 is integrated into a device other than the positioning terminal 102, a positioning signal receiving unit 10, described below, is included in the positioning device 2.

[0019] The positioning device 2 includes the positioning signal receiver 10, which receives the positioning signals transmitted by the signal sources, a positioning calculation unit 11, which performs a positioning calculation, and a storage unit 12, which stores information. The positioning signal receiver 10 includes an antenna and a receiver. The antenna and receiver are not shown. The storage unit 12 stores the positioning solution calculated by the positioning calculation unit 11.

[0020] The protection level calculation device 3 includes a distortion error model unit 13, which outputs the upper and lower limits of distortion errors assumed to be present in measurements obtained from the position determination signals; a protection level calculation unit 14, which calculates the protection level of the position determination solution; and a storage unit 15, which stores information. The protection level calculation unit 14 calculates the protection level to determine the validity of the position determination solution calculated on the basis of the measurements, using the upper and lower limits output by the distortion error model unit 13. The storage unit 15 stores the calculated protection level.The upper and lower bounds of the distortion errors can, for example, be contained in information called Integrity Assistance Data in the standard defined by the 3rd Generation Partnership Project (3GPP). The Integrity Assistance Data, which includes the upper and lower bounds, is transferred from the distortion error model unit 13 to the protection level calculation unit 14. In the [document / section]... Fig. In the 2 illustrated example, the position determination calculation unit 11, the distortion error model unit 13 and the protection degree calculation unit 14 are integrated into the position determination terminal 102.

[0021] Upon receiving the positioning signals, the positioning signal receiver 10 extracts information about the positions of the signal sources and information about the distances between the application 101 and the signal sources as measurements. The positioning signal receiver 10 outputs the measurements to the positioning calculation unit 11. The measurements output by the positioning signal receiver 10 may include carrier phase measurements, Doppler frequency measurements, or the like.

[0022] Position Calculation Unit 11 calculates the position solution using the input measurements. In addition to the position solution, Position Calculation Unit 11 outputs information about the observation model, corresponding to the measurements from the signal sources used in the position calculation and the weights applied in the calculation. The position solution calculated by Position Calculation Unit 11 may include information about velocity, acceleration, or similar parameters.

[0023] Position determination device 2 sends the position determination solution, the observation model, and the weights for the position determination calculation, output by position determination calculation unit 11, to the protection level calculation device 3. The information about the position determination solution, the observation model, and the weights for the position determination calculation is entered into protection level calculation unit 14. The upper and lower limits of the distortion errors, output by distortion error model unit 13, are also entered into protection level calculation unit 14. Protection level calculation unit 14 calculates the protection level of the position determination solution using the observation model, the weights for the position determination calculation, and the upper and lower limits of the distortion errors.The degree of protection calculated by the protection calculation unit 14 is stored in the storage unit 15.

[0024] This section describes a hardware configuration for implementing the position determination device 2 and the protection level calculation device 3. As described above, the position determination signal receiving unit 10 of the position determination device 2 includes the antenna and the receiver. Of the components described in Fig. In the two illustrated components of the position determination device 2, the position determination calculation unit 11 is implemented by a processing circuit. Part of the position determination signal receiving unit 10 can be a processing circuit. These processing circuits can be a circuit in which a processor executes software, or they can be a dedicated circuit.

[0025] If the processing circuit is implemented by software, the processing circuit is, for example, one in Fig. 3 illustrated control circuits. Fig. Figure 3 is a diagram illustrating a configuration example of a control circuit 50 according to the first embodiment. The control circuit 50 includes an input unit 51, a processor 52, a memory 53, and an output unit 54.

[0026] The input unit 51 is an interface circuit that receives data input from outside the control circuit 50 and provides the data to the processor 52. The output unit 54 is an interface circuit that sends data from the processor 52 or the memory 53 to an external location outside the control circuit 50. When the processing circuit receives the data in Fig. In the illustrated control circuit 50, the processor 52 reads and executes a program corresponding to each component of the positioning device 2, which is stored in the memory 53, thereby implementing each component. The processor 52 outputs data, such as calculation results, to a volatile memory of the memory 53. The memory 53 is also used as temporary storage during each process performed by the processor 52. The processor 52 can output data, such as calculation results, to the memory 53 and store the data in the memory 53, or it can store data, such as calculation results, in an auxiliary storage device via the volatile memory of the memory 53. The memory unit 12 is implemented by the memory 53 or the auxiliary storage device. The illustration of the auxiliary storage device is omitted.

[0027] The processor 52 is a central processing unit (CPU, also referred to as a central processor, processing device, computing device, microprocessor, microcomputer, processor, or digital signal processor (DSP)). The memory 53 corresponds, for example, to non-volatile or volatile semiconductor memory, such as random-access memory (RAM), read-only memory (ROM), flash memory, erasable programmable read-only memory (EPROM), or electrically erasable programmable read-only memory (EEPROM) (registered trademark), or to a magnetic disk, a flexible disk, an optical disk, a compact disc, a mini-disc, a digital versatile disc (DVD), or the like.

[0028] From the in Fig. The components of the protection level calculation device 3 illustrated above, the distortion error model unit 13 and the protection level calculation unit 14, are implemented by the control circuit 50, as described above. The storage unit 15 is implemented by the memory 53 or the auxiliary storage device.

[0029] Fig. Figure 3 is an example of hardware where the position determination calculation unit 11, the distortion error model unit 13, and the protection level calculation unit 14 are implemented by the general-purpose processor 52 and the memory 53. However, the position determination calculation unit 11, the distortion error model unit 13, and the protection level calculation unit 14 can also be implemented by a dedicated hardware circuit. Fig. Figure 4 is a representation illustrating a configuration example of a dedicated hardware circuit 55 according to the first embodiment.

[0030] The dedicated hardware circuit 55 includes the input unit 51, the output unit 54, and the processing circuit 56. The processing circuit 56 can be a single circuit, a combined circuit, a programmed processor, a parallel programmed processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a circuit combining these. It should be noted that the position determination calculation unit 11, the distortion error modeling unit 13, and the protection level calculation unit 14 can be implemented by combining the control circuit 50 and the hardware circuit 55.

[0031] Next, an operating procedure for the protection level calculation system 1 of the first embodiment is described. Fig. Figure 5 is a flowchart illustrating the operating procedure for the protection level calculation system 1, which is included in the position determination system 100 according to the first embodiment. Here, an operating procedure for calculating the protection level by the protection level calculation system 1 is described.

[0032] In step S1, the protection level calculation system 1 receives the position determination signals at the position determination signal receiver unit 10 of the position determination device 2. Upon receiving the position determination signals, the protection level calculation system 1 obtains measurements in step S2 by extracting the measurements from the position determination signals at the position determination signal receiver unit 10. The position determination signal receiver unit 10 extracts information about the positions of the signal sources and information about the distances between the application 101 and the signal sources as measurements.

[0033] In step S3, the distortion error model unit 13 of the protection level calculation device 3 outputs the upper and lower limits of distortion errors assumed to be included in the measurements. In step S4, the protection level calculation unit 14 of the protection level calculation device 3 calculates the protection level using the upper and lower limits of the distortion errors. The calculated protection level is stored in the memory unit 15. Thus, the protection level calculation system 1 excludes operation according to the Fig. The process is illustrated in section 5.

[0034] Next, a method for calculating the degree of protection in the first embodiment is described. The position determination calculation unit 11 provides a coefficient matrix H∈R. m×n as an observational model that measures y∈R mfrom each signal source used in the position determination calculation. The coefficient matrix H∈R m×n is obtained by linearizing a nonlinear observation model h(x)∈R m for measurements based on state variables x∈R n to use state variables x0∈R as a reference n The state variables x∈R are obtained. m include three-dimensional position information which specifies the three-dimensional position of the position determination terminal 102.

[0035] Furthermore, the position determination calculation unit 11 provides an error covariance matrix R∈R m×m of observation errors as weights in the position determination calculation. The position determination calculation unit 11 can be defined as a positive definite symmetric matrix W, in which the sum of eigenvalues ​​m is, together with the variance σ0. 2The observation error is expressed with respect to the unit weighting. In this case, the error covariance matrix R of the observation error is determined according to the relationship W=σ0. 2 R -1 determined. Here, m represents the number of dimensions of the measurements used in the position determination calculation. n represents the number of dimensions of the state variables estimated by the position determination calculation.

[0036] The distortion error model unit 13 gives the upper limit b max ∈R m of a distortion error and the lower limit b min ∈R m of the distortion error. This distortion error is a distortion error that is assumed to be present in every measurement used in the position determination calculation and varies from measurement to measurement.

[0037] The protection level calculation unit 14 calculates the horizontal protection level HPL using the observation model and the position determination calculation weights inputted by the position determination calculation unit 11, and the upper and lower limits of the distortion errors inputted by the distortion error model unit 13. The horizontal protection level HPL is obtained by solving a nonlinear programming problem, which is described below in (1) for a distortion vector b∈R m The nonlinear programming problem shown in (1) can be solved by a general nonlinear programming solver. Formula 1: Maximize HPL=(M1b)2+(M2b)2 Subject to the constraints bTGb≤λ bi,min≤bi≤bi,max(i=1,…,m)

[0038] Here, difference coefficients relating to the positions, which are difference coefficients contained in the coefficient matrix H, are expressed in a local horizontal coordinate system based on a three-dimensional position specified by the state variables x0, which serve as a reference. The local horizontal coordinate system is also known as the East-North-Up (ENU) coordinate system. If a coordinate transformation of the difference coefficients is required, the Position Determination Calculation Unit 11 or the Protection Degree Calculation Unit 14 performs the coordinate transformation.

[0039] In the nonlinear programming problem shown in (1), M1∈R 1×m a row that refers to a positional component in the east-west direction with respect to the three-dimensional reference position in a matrix M= (H T R -1 H) -1 HT R -1 ∈R n×m refers to M2∈R 1×m is a row that refers to a positional component in the north-south direction with respect to the three-dimensional reference position in the matrix M= (H T R -1 H) -1 H T R -1 ∈R n×m refers to a matrix G∈R. m×m is defined as G= (R -1 -R -1 H (H T R -1 H) -1 H T R -1 ) expressed. b i,min and b i,max are elements of b min and b maxi is a measurement index. λ is a non-centrality parameter determined from a false alarm rate, a failure rate, and the degrees of freedom mn in determining whether the positioning solution can be used. The false alarm rate is the probability that the positioning solution is determined to be unusable when it is. The failure rate is the probability that the positioning solution is determined to be usable when it should not be. The value of the non-centrality parameter λ is stored in memory 53 or the like, for example, by creating a table in which the value of the non-centrality parameter λ is associated with the degree of freedom value, where the false alarm rate and the failure rate are fixed values.Alternatively, the value of the non-centrality parameter λ can be obtained by calculation each time the false alarm rate and the non-detection rate change according to a change in the environment in which the position determination is performed.

[0040] Next, the non-centrality parameter λ will be determined with reference to Fig. 6 described. Fig. Figure 6 is a diagram illustrating the non-centrality parameter used in calculating the degree of protection in the first embodiment. The horizontal axis of a Fig. The diagram in Figure 6 shows a test statistic of the position determination solution. The vertical axis of the diagram in Figure 6 represents the position of the product. Fig. The diagram in Figure 6 illustrates the probability density of the test statistic for the position determination solution. Here, the weighted sum of squares error (WSSE) of the observation residuals of the position determination solution is used as the test statistic. The WSSE of the observation residuals of a position determination solution x^∈R n is defined as WSSE=(yh(x^)) T R - 1(yh(x^)). If all measurements are normal, the test statistic follows a chi-square distribution. If one or more measurements are abnormal, the test statistic follows a non-central chi-square distribution. If the value of the test statistic exceeds a threshold T, which is determined based on the false alarm rate, the positioning terminal 102 determines that the positioning solution cannot be used without calculating the protection level. If the test statistic is less than or equal to the threshold T, the positioning terminal 102 calculates the protection level and determines, by comparison with the alarm limit, whether the positioning solution can be used. The positioning terminal 102 determines the validity of the positioning solution by determining whether the positioning solution can be used.

[0041] Here, for example, it is assumed that the false alarm rate is 10 -4 The non-detection rate is 10 -3 where the degree of freedom is 6. In this example, the value of the noncentrality parameter λ is approximately 63.632324. The false alarm rate is a value obtained by integrating the probability density function of the 6-degree-of-freedom chi-square distribution from the threshold T to infinity. The failure rate is a value obtained by integrating the probability density function of the 6-degree-of-freedom noncentral chi-square distribution from 0 to the threshold T. Fig. Figure 6 illustrates the chi-square distribution curve and the non-central chi-square distribution curve. First, the threshold T, at which the false alarm rate becomes a given value, is determined numerically. Then, the non-centrality parameter λ is obtained by numerically determining the non-centrality parameter of the non-central chi-square distribution, where the failure rate becomes a given value.

[0042] As with the calculation of the horizontal protection level HPL, the protection level calculation unit 14 calculates the vertical protection level VPL using the observation model and the position determination calculation weights inputted by the position determination calculation unit 11, and the upper and lower limits of the distortion errors inputted by the distortion error model unit 13. The vertical protection level VPL is obtained by solving a nonlinear programming problem, which is described below in (2) for a distortion vector b∈R m The nonlinear programming problem shown in (2) can be solved by a general nonlinear programming solver. Formula 2: MaximizeVPL=M3bSubject to the constraints bTGb≤λ bi,min≤bi≤bi,max(i=1,…,m)

[0043] In the nonlinear programming problem shown in (2), M3∈R 1×ma row that refers to a position component in the top-and-bottom direction with respect to the three-dimensional reference position in the matrix M.

[0044] Next, a specific procedure for calculating the horizontal protection level of HPL will be described with reference to Fig. 7 described. Fig. Figure 7 is a representation illustrating an example of an arrangement of the satellites 103 to explain the procedure for calculating the horizontal degree of protection in the first embodiment. Fig. Figure 7 illustrates a sky plot diagram showing the positions of ten GPS satellites on the celestial sphere. The in Fig. Figure 7 illustrates G14, G16, G21, G23, G25, G26, G27, G29, G31, and G32 as representing satellites 103. It is assumed that the positioning calculation unit 11, at the point where the position determination is performed, uses only single-frequency pseudo-distance measurements of signals transmitted by the ten GPS satellites. That is, m = 10. The positioning calculation unit 11 uses only three-dimensional position information and a receiver clock offset as state variables. That is, n = 4. Thus, the protection level calculation unit 14 calculates the protection level using an observational model for the four state variables across the ten measurements, the weightings in the position determination calculation, and the upper and lower limits of the distortion errors. A coefficient matrix H∈R linearized around an approximate position is used. 10×4In an ENU coordinate system, which is a local horizontal coordinate system, it is expressed as below in equation (3). Note that for each numerical value contained on the right-hand side of equation (3), five or more decimal places are omitted. Formula 3: H=[−0.0789−0.85340,51521,000−0.69050,13990,70961,0000,8252−0, 33400,45541,000−0.70860,59510,37911,0000,94640,31450,07371.00 0−0.22020.35070.91021.000−0.4585−0.78620.41431.0000.60970.67410.41691.0000.3806−0.06500.92251.0000.0694−0.96890.23741.000]

[0045] The coefficient matrix H represents the observation model. The rows of the coefficient matrix H correspond to the respective GPS satellites. In each row of the matrix shown in (3), values ​​of an east-west direction vector, a north-south direction vector, and an up-and-down direction vector, and a coefficient of the receiver clock offset are shown in order from left to right.

[0046] If the variance of the observation errors σ 2 =1.0[m 2 ] independent of the altitude angles of the satellites 103, is a covariance matrix R∈R 10×10 The observation error is a diagonal matrix σ 2 I 10 with σ 2 =1,0 as a diagonal element. The covariance matrix R∈R 10×10 This reflects the weighting used in the position determination calculation. Here, I is... m However, an identity matrix of m×m. From the coefficient matrix H and the covariance matrix R of the observation errors, M1∈R are obtained. 1×10 , M2∈R1×10 and G∈R 10×10 expressed by equations (4), (5) and (6), respectively. It should be noted that in each numerical value contained on the right-hand side of equation (4), each numerical value contained on the right-hand side of equation (5), and each numerical value contained on the right-hand side of equation (6), five or more decimal places have been omitted. Formula 4: M1=[−0.0170−0.21660.2558−0.32220.1775−0.0152−0.17390,13320.2088−0.0304] M2=[−0.22960,0762−0.09800,25780,14400,0978−0.18150,2255−0.0553−0.2367] G=[0.7221−0.0754−0.13860.05450.0420−0.0346−0.26110.0922−0.1207−0.2803 ⋮ ⋮ −0.28030.0027−0.1504−0.0032−0.12390.1356−0.31050.06850.05970.6017]

[0047] If the false alarm rate is 10 -4 is and the non-detection rate is 10 -3If the degree of freedom is mn=6, which is equal to the value of the degree of freedom described above. Therefore, the value of the non-centrality parameter λ is also equal to the value described above. For example, if the minimum value of the distortion error is 0 [m] and the maximum value is 10 [m] for all of the measurements, then b min and b max expressed by the following equations (7) and (8). Formula 5: bmin=[0.00000,00000,00000,00000,00000,00000,00000,00000,00000,0000] bmax=[10,000010,000010,000010,000010,000010,000010,000010,000010,000010,0000]

[0048] If the nonlinear programming problem shown in (1) above for a distortion vector b∈R 10Once solved, the distortion vector b is expressed using these values ​​by equation (9) below. Note that for each numerical value on the right-hand side of equation (9), five or more decimal places are omitted. Formula 6: b=[0.000010,00000,000010,00000,000010,00008,546610,00000,00000,0000]

[0049] The horizontal protection level for HPL is 7.591439 [m].

[0050] Here, the example for calculating the horizontal protection level (HPL) was described using only GPS satellites; however, the positioning system 100 can calculate the horizontal protection level (HPL) using Galileo satellites or quasi-zenith satellites. In such a case, the positioning system 100 can add a receiver distortion between satellite systems to the state variables, according to the types of satellites used.

[0051] The example described here illustrates how to calculate the horizontal protection level (HPL) using only single-frequency pseudo-distance measurements. However, the Position Determination System 100 can calculate the horizontal protection level (HPL) using two or more frequencies. In such a case, the Position Determination System 100 can add receiver distortion between frequencies to the state variables according to the number of frequencies used.

[0052] Furthermore, a reference satellite can be determined for each satellite system, and a measurement based on a signal from each satellite 103 can be a simple difference value with respect to the reference satellite. In such a case, the positioning system 100 can remove the receiver clock offset and the distortion between satellite systems and the distortion between receiver frequencies from the state variables.

[0053] The example for calculating the horizontal protection level HPL using pseudo-distance measurements was described here; however, carrier phase measurements can be added. In such a case, the positioning system 100 can add the carrier phase ambiguity to the state variables. Furthermore, the velocity or acceleration of the receiver can be added to the state variables.

[0054] In the example for calculating the horizontal protection level of HPL, the minimum and maximum values ​​of the distortion error are common to all measurements; however, these values ​​can be changed for each measurement individually. Furthermore, the minimum distortion error can be specified as a value other than zero or as a negative value. Similarly, the maximum distortion error can be specified as zero or as a negative value.

[0055] In the example for calculating the horizontal protection level (HPL), satellites 103 are used as the signal sources for the positioning signals; however, the signal sources can be either satellites 103 or base stations 104. The signal sources can also be a combination of satellites 103 and base stations 104.

[0056] The position determination calculation unit 11 can improve the position determination solution by an observation update using the Kalman filter or the like, using previous prediction values ​​x pre ∈R nThe protection level calculation unit 14 further calculates the protection level using the weights of the previous predicted values ​​of the state variables, which are the weights used in the calculation of the position determination solution, and the upper and lower bounds of distortion errors assumed to be contained in the previous predicted values. In this case, each of the position determination calculation unit 11, the distortion error model unit 13, and the protection level calculation unit 14 is extended as follows.

[0057] The position determination calculation unit 11 gives a coefficient matrix H∈R m×n as an observational model that measures y∈R m from each signal source used in the position determination calculation. The position determination calculation unit 11 gives the error covariance matrix R∈R m×mThe weightings for observation errors in the position determination calculation are also used. Furthermore, the position determination calculation unit 11 outputs an error covariance matrix Q∈R. n×n as the weights of previous predicted values ​​of the state variables. As in the case described above, the position determination calculation unit 11 can be the positive definite symmetric matrix W, in which the sum of eigenvalues ​​m is, together with the variance σ0, as the weights in the position determination calculation. 2 The observation error is expressed with respect to the unit weighting. In this case, the error covariance matrix R of the observation error is determined according to the relationship W=σ0. 2 R -1determined. Here, m represents the number of dimensions of the measurements used in the position determination calculation. n represents the number of dimensions of the state variables estimated by the position determination calculation. The test statistic of the position determination solution is WSSE=(yh (x pre )) T (HQH+R) -1 (yh (x pre )) used.

[0058] Furthermore, the position determination calculation unit can calculate 11 previous prediction values ​​of the state variables and the error covariance matrix Q using a measurement from an inertial sensor, such as an accelerometer or a gyroscope. In particular, if the time intervals in which the signal sources can be used are long, using an inertial sensor measurement can prevent the accumulation of errors in previous prediction values ​​due to the passage of time. In this case, the values ​​of the error covariance matrix Q also decrease, and the weights of the previous state variable prediction values ​​increase. Moreover, when an inertial sensor measurement is used, the upper and lower limits can be set such that the distortion errors assumed to be contained in the previous prediction values ​​decrease. Consequently, the degree of protection decreases.

[0059] The distortion error model unit 13 outputs the upper and lower bounds of the distortion error assumed to be contained in each measurement used in the position determination calculation, and the upper and lower bounds of the distortion errors assumed to be contained in the previous prediction values. The upper bound is b max of the two types of distortion errors b max ∈R m+n The lower limit b min of the two types of distortion errors is b min ∈R m+n.

[0060] The protection level calculation unit 14 calculates the horizontal protection level HPL using the observation model, the weights in the position determination calculation, and the weights of the previous predicted values ​​of the state variables inputted by the position determination calculation unit 11, and the upper and lower bounds of the distortion errors inputted by the distortion error model unit 13. The horizontal protection level HPL is obtained by solving a nonlinear programming problem, which is described below in (10) for a distortion vector b∈R m+n The nonlinear programming problem shown in (10) can be solved by a general nonlinear programming solver. Formula 7: Maximize HPL=(M1b)2+(M2b)2 Subject to the constraints bTGb≤λ bi,min≤bi≤bi,max(i=1,…,m)

[0061] Here, difference coefficients relating to the positions, which are difference coefficients contained in the coefficient matrix H, are expressed in an ENU coordinate system, a local horizontal coordinate system that specifies three-dimensional positions, with the state variables x0 serving as a reference. If a coordinate transformation of the difference coefficients is required, the position determination calculation unit 11 or the protection degree calculation unit 14 performs the coordinate transformation.

[0062] In the nonlinear programming problem presented in (10), M1∈R 1×(m+n) a row that refers to a positional component in the east-west direction with respect to the three-dimensional reference position in a matrix M∈R n×(m+n) refers to M2∈R 1×(m+n)is a row that refers to a positional component in the north-south direction with respect to the three-dimensional reference position in the matrix M∈R n×(m+n) refers to.

[0063] Here, the matrix M is expressed by the following equation (11). Formula 8: M=([HTI][R−1OOQ−1][HI])−1[HTI][R−1OOQ−1]

[0064] A matrix G∈R (m+n)×(m+n) is expressed by the following equation (12). Formula 9: G=[R−1−R−1H(HTR−1H+Q−1)−1HTR−1−R−1H(HTR−1H+Q−1)−1Q−1−Q−1(HTR−1H+Q−1)−1HTR−1Q−1−Q−1(HTR−1H+Q−1)−1Q−1]

[0065] As with the calculation of the horizontal protection level HPL, the protection level calculation unit 14 calculates the vertical protection level VPL using the observation model, the weights in the position determination calculation, and the weights of the previous predicted values ​​of the state variables inputted by the position determination calculation unit 11, and the upper and lower bounds of the distortion errors inputted by the distortion error model unit 13. The vertical protection level VPL is obtained by solving a nonlinear programming problem, which is described below in (13) for a distortion vector b∈R m+n The nonlinear programming problem shown in (13) can be solved by a general nonlinear programming solver. Formula 10: Maximize VPL=M3b under the constraints bTGb≤λ bi,min≤bi≤bi,max(i=1,…,m)

[0066] In the nonlinear programming problem presented in (13), M3∈R 1×(m+n) a row that refers to a position component in the top-and-bottom direction with respect to the three-dimensional reference position in the matrix M.

[0067] As described above, the positioning system 100 according to the first embodiment includes the protection level calculation system 1. The protection level calculation system 1 includes the protection level calculation device 3, which calculates the protection level used to determine the validity of the positioning solution. The protection level calculation device 3 calculates the protection level using the upper and lower limits of a distortion error assumed to be present in each measurement. Therefore, if a measurement contains an abnormal value, and if a distortion error in that measurement lies within the range between the upper and lower limits, the protection level calculation system 1 can calculate the protection level effective for determining the validity of the positioning solution using that measurement.

[0068] Previously, the description focused on the case where both the position determination device 2 and the protection level calculation device 3 are integrated into the position determination terminal 102, and the position determination terminal 102 calculates the position determination solution and the protection level. As described above, the position determination device 2 can be integrated into the position determination terminal 102, and the protection level calculation device 3 can be integrated into an external device, such as the server 105. Alternatively, both the position determination device 2 and the protection level calculation device 3 can be integrated into an external device, such as the server 105.

[0069] For example, if both the position determination device 2 and the protection level calculation device 3 are integrated into the position determination terminal 102, the position determination terminal 102 calculates the protection level using the upper and lower limits of a distortion error assumed to be present in each measurement, and determines the validity of the position determination solution calculated using this measurement, based on the protection level. A component for determining the validity of the position determination solution is not illustrated.

[0070] When the positioning terminal 102 calculates the degree of protection and determines the validity of the positioning solution, the positioning terminal 102 can pre-store in its memory the upper and lower limits of a distortion error assumed to be present in each measurement. Alternatively, as described below in Fig. Figure 8 illustrates that the position determination terminal 102 receives the upper and lower limits of a distortion error from an external device, such as the server 105, as integrity support data. Although the example in which the protection level calculation system 1 determines the validity of the position determination solution within the position determination terminal 102 has been described, the present invention is not limited thereto. The protection level calculation system 1 can determine the validity of the position determination solution outside the position determination terminal 102. The validity of the position determination solution can be determined within the protection level calculation device 3 or can be determined outside the protection level calculation device 3.

[0071] Fig. Figure 8 is a representation illustrating a first modification of the protection level calculation system 1 in its first embodiment. In the Fig. In the protection level calculation system 1 illustrated in Figure 8, the position determination device 2, the protection level calculation unit 14, and the storage unit 15 are provided in the position determination terminal 102, which is a first device. The distortion error model unit 13 is provided in the server 105, which is a second device that can communicate with the first device. The protection level calculation device 3 includes the protection level calculation unit 14 and the storage unit 15 of the position determination terminal 102 and the distortion error model unit 13 of the server 105. In the Fig. In the configuration shown in Figure 8, the positioning terminal 102 receives the upper and lower limits of a distortion error from the server 105 as integrity support data.

[0072] Fig. Figure 9 is a representation illustrating a second modification of the protection level calculation system 1 in the first embodiment. In the Fig. In the protection level calculation system 1 illustrated in Figure 9, the position determination device 2 is integrated into the position determination terminal 102, and the protection level calculation device 3 is integrated into the server 105. That is, the position determination calculation unit 11 is integrated into the position determination terminal 102, which is a first device, and the distortion error model unit 13 and the protection level calculation unit 14 are integrated into the server 105, which is a second device. The position determination device 2 transmits measurement information to the server 105. The server 105 calculates the protection level at the protection level calculation unit 14 using the upper and lower limits of distortion errors assumed to be present in the received measurements. The server 105 then transmits information about the calculated protection level to the position determination terminal 102.When the information about the level of protection is received, the positioning terminal 102 determines the validity of the positioning solution.

[0073] Instead of the positioning terminal 102 determining the validity of the positioning solution, an external device, such as the server 105, can determine the validity of the positioning solution, as described below. Fig. 10 illustrated. Fig. Figure 10 is a representation illustrating a third modification of the protection level calculation system 1 in the first embodiment.

[0074] At the in Fig. In the protection level calculation system 1 illustrated in Figure 10, the position determination device 2 is integrated into the position determination terminal 102, and the protection level calculation device 3 is integrated into the server 105. That is, the position determination calculation unit 11 is integrated into the position determination terminal 102, which is a first device, and the distortion error model unit 13 and the protection level calculation unit 14 are integrated into the server 105, which is a second device. The position determination terminal 102 transmits information about the position determination solution calculated by the position determination calculation unit 11 to the server 105. The server 105 determines the validity of the position determination solution using the protection level calculated in the protection level calculation unit 14. The server 105 transmits the validity determination result to the position determination terminal 102.

[0075] At the in Fig. In the protection level calculation system 1 illustrated in Figure 1, the positioning terminal 102 transmits the limit value determined by the application 101 to the server 105. Alternatively, the server 105 can retrieve the limit value via a communication network from a device other than the positioning terminal 102. Thus, by outsourcing the processing for calculating the protection level or determining the validity of the positioning solution to an external device, the processing load on the positioning terminal 102 is reduced. Consequently, the protection level calculation system 1 allows the positioning terminal 102 to have a cost-effective configuration.

[0076] Fig. Figure 11 is a representation illustrating a fourth modification of the protection level calculation system 1 in the first embodiment. In the Fig. In the protection level calculation system 1 illustrated in Figure 11, both the position determination device 2 and the protection level calculation device 3 are integrated into the server 105. That is, the position determination calculation unit 11, the distortion error model unit 13, and the protection level calculation unit 14 are integrated into the server 105. The position determination signal receiver unit 10 is provided in the position determination terminal 102. Upon receiving the position determination signals, the position determination signal receiver unit 10 extracts measurements from the position determination signals. The position determination terminal 102 transmits the extracted measurements to the server 105.

[0077] When server 105 receives the measurements, the positioning device 2 calculates the positioning solution. The protection level calculation device 3 calculates the protection level using the upper and lower limits of distortion errors assumed to be present in the measurements. Server 105 compares the calculated protection level with the limit value determined by application 101 to determine the validity of the positioning solution. Server 105 transmits the validity determination result to the positioning terminal 102.

[0078] At the in Fig. In the protection level calculation system 1 illustrated in Figure 1, the positioning terminal 102 transmits the limit value determined by the application 101 to the server 105. Alternatively, the server 105 can retrieve the limit value via a communication network from a device other than the positioning terminal 102. Thus, by outsourcing the processing for calculating the protection level or determining the validity of the positioning solution to an external device, the processing load on the positioning terminal 102 is reduced. Consequently, the protection level calculation system 1 allows the positioning terminal 102 to have a cost-effective configuration.

[0079] Even if both the positioning device 2 and the protection level calculation device 3 are integrated into an external device, such as the server 105, the positioning terminal 102 can calculate the positioning solution. In this case, the positioning terminal 102, which has calculated the positioning solution, can receive information about the protection level from an external device, such as the server 105, and determine the validity of the positioning solution.

[0080] Each of the in Fig. 10 and Fig. The protection level calculation system 1, illustrated in Figure 11, determines the validity of the position determination solution within the protection level calculation device 3 in the server 105 and outputs the determination result from the protection level calculation device 3. However, the present invention is not limited to this. The protection level calculation system 1 can determine the validity of the position determination solution outside the protection level calculation device 3 in the server 105 and output the determination result from outside the protection level calculation device 3 in the server 105.

[0081] Regardless of whether the position determination device 2 and the protection level calculation device 3 are each integrated into the position determination terminal 102 or an external device, such as the server 105, the position determination calculation unit 11, the distortion error model unit 13 and the protection level calculation unit 14 are controlled by the in Fig. 3 illustrated control circuit 50 or the one in Fig. 4 illustrated hardware circuit 55 implemented.

[0082] As described above, the protection level calculation system 1 calculates the protection level using the upper and lower limits of a distortion error assumed to be present in each measurement, regardless of whether the position determination device 2 and the protection level calculation device 3 are integrated into the position determination terminal 102 or an external device such as the server 105. Consequently, if a distortion error is present in each measurement used in the calculation of the position determination solution within the range between the upper and lower limits of this distortion error, and if a measurement contains an abnormal value, the protection level calculation system 1 can calculate the protection level effective for determining the validity of the position determination solution using that measurement.Thus, in a situation where measurements may contain an abnormal value, the protection level calculation system 1 can calculate the protection level that is effective for determining the validity of the position determination solution calculated on the basis of the measurements. Second embodiment.

[0083] Errors due to positioning satellites or atmospheric conditions, which are inherent in measurements, are usually corrected and then used in the position calculation. A second embodiment describes a case in which measurements are corrected using correction information uniformly distributed by a quasi-zenith satellite or correction information provided by a reference station 202 described below via a communication network, and a degree of protection is calculated for the corrected measurements. In the second embodiment, the same reference numerals are assigned to the same components as in the first embodiment, and a configuration is described that differs mainly from the first embodiment.

[0084] Fig. Figure 12 is a diagram illustrating a configuration example of a positioning system 200 according to the second embodiment. The positioning system 200 includes a positioning augmentation satellite 201 and a reference station (a continuously operating reference station: CORS) 202, in addition to the same configuration as the positioning system 100 according to the first embodiment. The reference station 202 is a station equipped with a positioning terminal whose precise position is known.

[0085] The positioning augmentation satellite 201 and the reference station 202 buffer correction information and transmit it to the positioning terminal 102 at a preset time. This correction information is used to correct errors contained in measurements. The correction information is distributed uniformly by a quasi-zenith satellite, which is an example of the positioning augmentation satellite 201, or provided by the reference station 202 via the communication network. The correction information provided by the reference station 202 differs from the correction information that is distributed uniformly by the positioning augmentation satellite 201 and repeatedly transmitted by the base station 104.

[0086] Satellites 103 transmit positioning signals. The positioning terminal 102 receives the positioning signals and determines the position of the application 101. The positioning augmentation satellite 201 transmits a correction information signal. The positioning terminal 102 receives the correction information signal and corrects its measurements. It should be noted that the base stations 104 or the server 105 can repeatedly transmit the correction information from the positioning augmentation satellite 201 to the positioning terminal 102 via a communication network in preparation for a case where the positioning terminal 102 does not receive the correction information signal from the positioning augmentation satellite 201 due to its entry into the shadow of a building or the like.

[0087] Upon receiving positioning signals from the signal sources, the positioning terminal 102 extracts information about the positions of the signal sources and information about the distances between the application 101 and the signal sources as measurements. Since the measurements contain errors, the positioning terminal 102 corrects the extracted measurements using correction information received from the positioning augmentation satellite 201 or the reference station 202. The positioning terminal 102 then calculates the positioning solution of the application 101 using the corrected measurements. The errors corrected using the correction information are at least either errors due to the positioning satellites or errors due to the atmosphere.

[0088] The measurements also include errors due to the receiving environment or the receiver. Therefore, the positioning terminal 102 uses the degree of protection to determine the validity of the calculated positioning solution. The positioning terminal 102 calculates the degree of protection using an observational model that corresponds to the measurements used in the positioning calculation and weights applied to the positioning calculation. That is, the positioning terminal 102 calculates the degree of protection. Then, the positioning terminal 102 compares the calculated degree of protection with a limit value of the application 101 and determines whether the calculated positioning solution can be used or not. A specific procedure for calculating the degree of protection is described later.

[0089] The Position Determination System 200 includes a protection level calculation system that calculates the protection level. This section describes one configuration of the protection level calculation system. Fig. Figure 13 is a representation illustrating a configuration example of a protection level calculation system 1A, which is included in the position determination system 200 according to the second embodiment. The in Fig. 13 Illustrated protection level calculation system 1A includes a position determination device 2A, which performs a position determination, and a protection level calculation device 3A, which calculates the protection level.

[0090] This describes a case in which both the position determination device 2A and the protection level calculation device 3A are used in the Fig. The position determination device 102 is illustrated in Figure 12. It should be noted that the position determination device 2A may be integrated into the position determination device 102, and the protection level calculation device 3A may be integrated into the server 105 or the like, which is a device outside the position determination device 102. Alternatively, both the position determination device 2A and the protection level calculation device 3A may be integrated into an external device such as the server 105. If the position determination device 2A is integrated into a device other than the position determination device 102, a position determination signal receiving unit 10, described below, is included in the position determination device 2A.

[0091] The positioning device 2A includes the positioning signal receiver 10, which receives positioning signals transmitted by the signal sources, a positioning calculation unit 11A, which performs a positioning calculation, and the storage unit 12, which stores information. The positioning signal receiver 10 includes an antenna and a receiver. A correction information receiver 16 can use at least one of the antenna and receiver in conjunction with the positioning signal receiver 10. Alternatively, the correction information receiver 16 can include an antenna and a receiver that differ from those of the positioning signal receiver 10. The antenna and receiver are not illustrated. The storage unit 12 stores the positioning solution calculated by the positioning calculation unit 11A.

[0092] The position determination device 2A includes the correction information receiving unit 16 in addition to the same configuration as that of the one in Fig. 2. Positioning device 2. The correction information receiving unit 16 includes the antenna and the receiver. The antenna and receiver are not illustrated. The correction information receiving unit 16 receives the correction information transmitted by the position determination augmentation satellite 201 and the reference station 202, respectively. The position determination augmentation satellite 201 and the reference station 202 are each a signal source of a correction information signal.

[0093] The protection level calculation device 3A includes a distortion error model unit 13A, which outputs the upper and lower limits of a distortion error, a protection level calculation unit 14A, which calculates the protection level of the position determination solution, and the storage unit 15, which stores information. The protection level calculation device 3A has the same configuration as the one in Fig. 2 illustrated protection level calculation device 3. This distortion error is a distortion error that remains even when a correction is performed based on the correction information, of distortion errors that are assumed to be contained in measurements obtained from the position determination signals.

[0094] The position determination calculation unit 11A, the distortion error model unit 13A and the protection level calculation unit 14A of the protection level calculation system 1A are replaced by the in Fig. 3 illustrated control circuit 50 or the one in Fig. 4. Illustrated hardware circuit 55 is implemented. Part of the position determination signal receiving unit 10 and part of the correction information receiving unit 16 can form a processing circuit.

[0095] The following describes a case in which the signal sources for the positioning signals are the satellites 103. Upon receiving the positioning signals from the satellites 103, the positioning signal receiver 10 extracts information about the positions of the satellites 103 and information about the distances between the application 101 and the satellites 103 as measurements. The positioning signal receiver 10 outputs the extracted measurements to the positioning calculation unit 11.Each measurement output by the positioning signal receiving unit 10 includes at least one distortion error due to satellite 103, such as satellite clock error, orbit error or satellite distortion between signals, distortion error due to the atmosphere, such as ionospheric delay or tropospheric delay, or distortion error due to the receiver, such as receiver clock error or receiver distortion between signals.

[0096] The correction information receiver 16 receives the correction information signal transmitted by the positioning augmentation satellite 201 or the reference station 202 and outputs the correction information to the positioning calculation unit 11A. The correction information received by the correction information receiver 16 includes, for example, information transmitted by the centimeter level augmentation service provided by the quasi-zenith satellite system. Using this correction information, the positioning calculation unit 11A corrects the distortion errors due to satellites 103 and the distortion errors due to the atmosphere from the distortion errors included in the measurements.

[0097] The Position Determination Unit 11A calculates the position determination solution using the corrected measurements. In addition to the position determination solution, the Position Determination Unit 11A outputs information about the observation model, corresponding to the measurements from the signal sources used in the position determination calculation and the weights applied in the calculation. The position determination solution calculated by the Position Determination Unit 11A may include information about velocity, acceleration, or similar parameters.

[0098] If the reference station 202 is located near the positioning terminal 102, the positioning calculation unit 11A can correct the measurements input by the positioning signal receiver 10 using measurements from the reference station 202 instead of the correction information received from the positioning augmentation satellite 201, the base stations 104, or the server 105. Specifically, the correction information receiver 16 receives measurements from the reference station 202 and outputs the received measurements directly to the positioning calculation unit 11A. Communication between the reference station 202 and the positioning device 2A is carried out, for example, by wireless communication via a mobile phone network or the like.

[0099] The Position Determination Computing Unit 11A uses the measurements inputted by the Correction Information Receiving Unit 16 at the Reference Station 202 as correction values ​​and subtracts these correction values ​​from the measurements input by the Position Determination Signal Receiving Unit 10. In this way, the Position Determination Computing Unit 11A obtains the measurements corrected for distortion errors due to the satellites 103 and distortion errors due to the atmosphere. The Position Determination Computing Unit 11A performs a position determination calculation using these corrected measurements to calculate the position determination solution.

[0100] When measurements at reference station 202 are used as correction information, the corrected measurements include distortion errors due to the environment of reference station 202. Therefore, reference station 202 is usually installed in an open-air environment to be able to ignore distortion errors due to the environment.

[0101] Position determination device 2A sends the position determination solution, the observation model, and the weights for the position determination calculation, output by position determination calculation unit 11A, to the protection level calculation device 3A. The information about the position determination solution, the observation model, and the weights for the position determination calculation is entered into protection level calculation unit 14A. The upper and lower limits of the distortion error, output by distortion error model unit 13A, are entered into protection level calculation unit 14A. Protection level calculation unit 14A calculates the protection level of the position determination solution using the observation model, the weights for the position determination calculation, and the upper and lower limits of the distortion error.The degree of protection calculated by the protection calculation unit 14A is stored in the storage unit 15.

[0102] Next, a method for calculating the degree of protection in the second embodiment is described. The position determination calculation unit 11A provides a coefficient matrix H∈R. m×n as an observational model that uses corrected measurements y c ∈R m This corresponds to the coefficients used in the position determination calculation. The coefficient matrix H∈R m×n is obtained by linearizing a nonlinear observation model h(x)∈R m for measurements based on state variables x∈R n to use state variables x0∈R as a reference n obtained. It should be noted that the state variables x∈R mThree-dimensional position information is provided via the position determination terminal 102. Here, m represents the number of dimensions of the measurements used in the position determination calculation. n represents the number of dimensions of the state variables estimated by the position determination calculation.

[0103] For example, each diagonal element of the error covariance matrix σ yi 2 +σ ci 2 , i.e., the sum of the error variance σ yi 2 each measurement yi∈y and the error variance σ ci 2 a correction value c i , which has been corrected for the distortion error due to satellite 103 and the distortion error due to the atmosphere. The correction value here is c. i a value obtained by correcting the measurement y received from the position determination signal receiver unit 10 iusing the correction information received by the correction information receiving unit 16.

[0104] If the positioning calculation unit 11A calculates the positioning solution using measurements yr at the reference station 202 instead of the correction information received from the positioning augmentation satellite 201 or the reference station 202, each diagonal element of the error covariance matrix σ yi 2 +σ yri 2 , i.e., the sum of the error variance σ yi 2 a measurement at the position determination terminal 102 and the error variance σ yri 2 a measurement at the reference station 202, i.e. a measurement from the same signal source as the measurement at the position determination terminal 102.

[0105] The error variance σ yi 2The error variance σ of a measurement at the position determination terminal 102 can, for example, be determined using a pre-generated model as a function of the signal type or the signal elevation angle. ci 2 a correction value that is corrected for the distortion error due to satellite 103 and the distortion error due to the atmosphere, and the error variance σ yri 2 The error variances of a measurement at reference station 202, i.e., a measurement from the same signal source as a measurement at position determination terminal 102, can be determined using a model that is generated in advance depending on the signal type or the signal elevation angle. If the values ​​of these error variances are included in the correction information, the values ​​contained in the correction information can be used.

[0106] The distortion error model unit 13A provides the upper limit b env_max∈R m of a distortion error and the lower limit b env_min ∈R m of the distortion error. This distortion error is an environmental distortion error that is assumed to be present in every measurement used in the position determination calculation and varies from measurement to measurement. That is, it is assumed here that of the distortion errors contained in the measurements, the distortion errors due to Satellite 103 and the distortion errors due to the atmosphere are removed by the correction, leaving only the environmental distortion errors.

[0107] The protection level calculation unit 14A calculates the horizontal protection level HPL using the observation model and the position determination calculation weights inputted by the position determination calculation unit 11A, and the upper and lower limits of the distortion error inputted by the distortion error model unit 13A. The horizontal protection level HPL is obtained by solving a nonlinear programming problem, which is described below in (14) for a distortion vector b. env ∈R m The nonlinear programming problem shown in (14) can be solved by a general nonlinear programming solver. Formula 11: Maximize HPL=(M1benv)2+(M2benv)2 Subject to the constraints benvTGBenv≤λ bi,env_min≤bi,env≤bi,env_max(i=1,…,m)

[0108] Here, difference coefficients relating to the positions, which are difference coefficients contained in the coefficient matrix H, are expressed in an ENU coordinate system, which is a local horizontal coordinate system, on the basis of a three-dimensional position specified by state variables x0, which serve as a reference.

[0109] In the nonlinear programming problem presented in (14), M1∈R 1×. a row that refers to a positional component in the east-west direction with respect to the three-dimensional reference position in a matrix M= (H T R -1 H) -1 H T R -1 ∈R n×m refers to M2∈R 1×m is a row that refers to a positional component in the north-south direction with respect to the three-dimensional reference position in the matrix M= (H T R -1 H) -1 H T R -1 ∈Rn×m refers to a matrix G∈R. m×m is defined as G= (R -1 -R -1 H (H T R -1 H) -1 H T R -1 ) expressed. b i,env_min is an element of b env_min . b i,env_max is an element of b env_max . i is a measurement index.

[0110] As with the calculation of the horizontal protection level HPL, the protection level calculation unit 14A calculates the vertical protection level VPL using the observation model and the position determination calculation weights inputted by the position determination calculation unit 11A, and the upper and lower limits of the distortion error inputted by the distortion error model unit 13A. The vertical protection level VPL is obtained by solving a nonlinear programming problem, which is described below in (15) for a distortion vector b env ∈R mThe nonlinear programming problem shown in (15) can be solved by a general nonlinear programming solver. Formula 12: Maximize VPL=M3b under the constraints bTGb≤λ bi,min≤bi≤bi,max(i=1,…,m)

[0111] In the nonlinear programming problem presented in (15), M3∈R 1×m a row that refers to a position component in the top-and-bottom direction with respect to the three-dimensional reference position in the matrix M.

[0112] The protection level calculation unit 14A can calculate the protection level, furthermore using the standard distortion errors in the correction values ​​to correct the measurements. For example, limitations of the nonlinear programming problem, as shown below in (16), can be addressed using the standard distortion error µ. ci >0 in each correction value. Formula 13: Under the constraints benvTGbenv≤λ bi,env_min−μci≤bi,env≤bi,env_max+μci(i=1,…,m)

[0113] The standard distortion error µ ci Each correction value can be determined using a pre-generated model depending on the signal type or signal elevation angle. If the value of the standard distortion error µ ci Since each correction value is contained in the correction information, the value contained in the correction information can be used. For example, the literature "J. Rife et al., "Paired Overbounding and Application to GPS Augmentation", PLANS 2004. Position, Location and Navigation Symposium" discloses a method in which an error in a correction value derived from correction information is expressed by a paired Gaussian distribution, and the error variance σ ci 2a correction value, i.e., a correction value that is corrected for a distortion error due to a satellite and a distortion error due to the atmosphere, and a parameter corresponding to the standard distortion error µ ci Each correction value corresponds to a value that is provided as part of the correction information.

[0114] As described above, the Protection Level Calculation System 1A calculates the protection level by adding the standard distortion errors in the correction values ​​when calculating the protection level, taking into account the distortion errors due to Satellite 103 and the distortion errors due to the atmosphere, which may remain even after a correction based on the correction information, in addition to the distortion errors due to the environment. Therefore, the Protection Level Calculation System 1A can calculate the protection level effective for determining the validity of the positioning solution.

[0115] The position determination calculation unit 11A can calculate the position determination solution by means of an observation update using the Kalman filter or the like, based on previous prediction values ​​of the state variables. In this case, each of the position determination calculation unit 11A, the distortion error model unit 13A, and the protection level calculation unit 14A is extended as in the first embodiment.

[0116] As described above, the positioning system 200 according to the second embodiment includes the positioning supplement satellite 201 and the reference station 202 in addition to the same configuration as the positioning system 100. The protection level calculation system 1A, which includes the protection level calculation device 3A, corrects measurements at the positioning device 2A using correction information to correct distortion errors due to the satellites 103 and distortion errors due to the atmosphere or measurements at the reference station 202.

[0117] In the conventional protection level calculation device, which uses the multivariate probability distribution model, the types and reliability of measurement quality indicators recorded by the receiver are values ​​that are unique to the receiver. However, some indicators are not output externally, and the available range is limited. In contrast, the protection level calculation device 3A of the second embodiment focuses, for example, on distortion errors due to the environment around the positioning terminal 102 and calculates the protection level using the upper and lower limits of a distortion error assumed to be present in every corrected measurement. The environment is, for example, the blocking of the direct wave of a signal by a building or a multipath path.

[0118] The upper and lower limits of a distortion error for each measurement are obtained from a geometric environment model, which is a model of the environment. The distortion error model unit 13A determines both the upper and lower limits of a distortion error based on an environment model, which is a model of the environment surrounding the application 101, which is a position determination object. Consequently, the protection level calculation system 1A, using the protection level calculation device 3A, can calculate the protection level effective for determining the validity of the position determination solution without being dependent on the type or performance of the receiver, in addition to the effects described in the first embodiment. The protection level calculation system 1A can calculate the protection level that reflects the individual environment using the geometric environment model, which is a model of the environment.

[0119] Previously, the description focused on the case where the signal sources for the positioning signals are the 103 satellites. If the signal sources are the 104 base stations, measurements do not include errors due to the satellites or errors due to the atmosphere, and therefore the protection level calculation system 1A does not perform any correction using correction information. However, even when the signal sources are the 104 base stations, distortion errors due to the environment are included in measurements. Therefore, the protection level calculation system 1A calculates the protection level using the upper and lower limits of a distortion error that is assumed to be present in every measurement, as in the case where the signal sources for the positioning signals are the 103 satellites. Third embodiment.

[0120] A third embodiment describes a case in which time information, indicating the time at which application 101 passed, and position information about the roadside unit or application 101 are received from a roadside unit installed at the roadside, and a protection level is calculated using this information and map information. In the third embodiment, the same reference numerals are assigned to the same components as in the first or second embodiment, and a configuration is described that differs mainly from that of the first or second embodiment.

[0121] Fig. Figure 14 is a representation illustrating a configuration example of a protection level calculation system 1B included in a position determination system 300 according to the third embodiment. The position determination system 300 according to the third embodiment includes a protection level calculation system 1B, which differs from the one described in Figure 14. Fig. The protection level calculation system 1A is illustrated in Figure 13. The protection level calculation system 1B includes a position determination device 2B, which performs a position determination, a protection level calculation device 3B, which calculates the protection level, and a street-side unit 18.

[0122] This describes a case in which both the position determination device 2B and the protection level calculation device 3B are integrated into the position determination terminal 102. It should be noted that the position determination device 2B may be integrated into the position determination terminal 102, and the protection level calculation device 3B may be integrated into the server 105 or the like, which is a device outside the position determination terminal 102. Alternatively, both the position determination device 2B and the protection level calculation device 3B may be integrated into an external device such as the server 105. If the position determination device 2B is integrated into a device other than the position determination terminal 102, the position determination signal receiving unit 10 is contained within the position determination device 2B.

[0123] The roadside unit 18 is a device equipped with a sensor, such as a camera and a clock, and is installed at the roadside. The roadside unit 18 detects the application 101 using its sensor, such as the camera. When the roadside unit 18 detects the application 101 passing by, the unit outputs position information about itself as position information about the application 101 at the time the application 101 passed by. It should be noted that the roadside unit 18 can measure the relative position between itself and the application 101 to determine the application 101's absolute position and output information about this determined position as position information about the application 101.

[0124] The positioning device 2B includes the positioning signal receiving unit 10, which receives positioning signals transmitted by signal sources, namely the satellites 103 or the base stations 104; a positioning calculation unit 11B, which performs a positioning calculation; the storage unit 12, which stores information; and the correction information receiving unit 16. The positioning device 2B has the same configuration as the positioning device 2A of the protection level calculation system 1A. It should be noted that the positioning device 2B has the same configuration as the positioning device 2 of the in Fig. 2 illustrated protection level calculation system 1 can exhibit.

[0125] The protection level calculation device 3B includes a distortion error model unit 13B, which outputs the upper and lower limits of a distortion error, a protection level calculation unit 14B, which calculates the protection level of a positioning solution, the storage unit 15, which stores information, and a map information unit 17. The storage unit 15 stores the protection level and map information.

[0126] The positioning terminal 102 receives position information transmitted by the roadside unit 18. The received position information is entered into the map information unit 17. Furthermore, the positioning solution output by the positioning calculation unit 11B of the positioning device 2B is entered into the map information unit 17. The map information unit 17 reads the map information stored in the memory unit 15. The map information unit 17 references the map information using the entered positioning solution or position information via the application 101 and determines the class of the environment around the application 101.Here, environments are classified into a variety of categories, such as suburbs, semi-urban areas, and urban areas, according to differences in the magnitude and frequency of environmental distortion errors, such as multipath distortion. Environmental distortion errors are smallest in suburbs and largest in urban areas. In other words, the environmental category reflects the magnitude or frequency of environmental distortion errors.

[0127] Map Information Unit 17 determines the class to which the environment around Application 101 corresponds and outputs the determined result to Distortion Error Model Unit 13B. Thus, Map Information Unit 17 references the map information using the positioning solution or the positioning information about Application 101, thereby determining the class that represents the magnitude or frequency of the distortion error due to the environment for the environment around Application 101.

[0128] The distortion error model unit 13B contains models for the upper and lower limits of the distortion error for the respective environment classes. Based on the class determined by the map information unit 17, the distortion error model unit 13B selects the appropriate model for the upper and lower limits of the distortion error. The distortion error model unit 13B calculates the upper and lower limits of the distortion error using an environment model that is the selected model. That is, the distortion error model unit 13B determines the upper and lower limits of the distortion error using an environment model that corresponds to the class determined by the map information unit 17.

[0129] In this way, the distortion error model unit 13B calculates the upper and lower limits of the distortion error due to the environment surrounding the application 101, based on the distortion errors assumed to be present in the measurements. The distortion error model unit 13B outputs the results of the upper and lower limit distortion error calculations to the protection level calculation unit 14B.

[0130] The position determination calculation unit 11B, the distortion error model unit 13B, the protection level calculation unit 14B, and the map information unit 17 of the protection level calculation system 1B are replaced by the in Fig. 3 illustrated control circuit 50 or the one in Fig. 4 illustrated hardware circuit 55 implemented.

[0131] Here, an example of the models for the upper and lower limits of the distortion error is described, which are different for each environment class. Fig. Figure 15 is a representation illustrating an example of the models for the upper limit and the lower limit of the distortion error used by the protection level calculation system 1B of the third embodiment. Fig. 15 illustrates an example of the model of each class for each of the upper bound b. i,env_max and the lower limit b i,env_min , with the surrounding area being classified into suburbs, semi-urban areas and urban areas.

[0132] For example, the literature "GSG-5 / 6 Series GNSS Simulator User Manual with SCPI Guide" classifies the elevation angle into the Open Sky Zone, the Multipath Zone, and the Obstruction Zone to model distortion errors due to the environment. In the Open Sky Zone, there are no multipath errors and no distortion errors due to the environment. In the Multipath Zone, direct waves from the positioning satellites are not blocked, but multipath errors occur. In the Obstruction Zone, direct waves from the positioning satellites are blocked, and only indirect waves are received, leading to errors due to a lack of line of sight (NLOS).

[0133] The environmental classes differ in elevation angles, at which the three zones change. Therefore, for example, if the upper limit b i,env_max and the lower limit b i,env_min of the distortion error due to a multipath error as functions b i,env_mp_max(el i ) or b i,env_mp_min (el i ) of the altitude angle el i of satellite 103 and the upper and lower limits of the distortion error due to an NLOS error as functions b i,env_nlos_max (el i ) or b i,env_nlos_min (el i ) of the altitude angle el i of satellite 103, the upper limit b i,env_max and the lower limit b i,env_min of the distortion error, which is different for each environment class, expressed as in Fig. 15 illustrated.

[0134] As described above, according to the third embodiment, the positioning system 300 includes the roadside unit 18 in addition to the same configuration as the positioning system 100 or the positioning system 200. The protection level calculation device 3B included in the protection level calculation system 1B is a device that calculates the protection level to be used to determine the validity of the positioning solution and includes the distortion error model unit 13B and the map information unit 17. The map information unit 17 references the map information using the positioning solution output by the positioning calculation unit 11B or the position information output by the roadside unit 18 via the application 101 and determines the class of the environment.The distortion error model unit 13B selects the upper limit distortion error model and the lower limit distortion error model according to the class determined by the map information unit 17. The distortion error model unit 13B calculates the upper and lower limits of the distortion error based on the environment using the selected model. The protection level calculation unit 14B calculates the protection level using the upper and lower limits of the distortion error calculated by the distortion error model unit 13B. Therefore, even if a measurement contains an anomalous value, the protection level calculation unit 14B can not only determine the validity of the positioning solution using that measurement, but can also calculate the protection level, which reflects the magnitude or frequency of multipath error or NLOS error.By using the protection level calculation device 3B, the protection level calculation system 1B can calculate the more precise protection level in addition to the effects described in the first or second embodiment.

[0135] The map information unit 17 can reference the map information stored in the memory unit 15 and output a three-dimensional model of the environment via application 101, based on the positioning solution output by the positioning calculation unit 11B or the positioning information output by the roadside unit 18. The map information is three-dimensional map information, such as a dynamic map. In this case, the distortion error model unit 13B determines the upper and lower limits of an error for each measurement using an environment model, which is the three-dimensional model output by the map information unit 17. The environment model is a geometric model derived from the information of a three-dimensional map.

[0136] By using the geometric model obtained from the three-dimensional map as the environmental model, the protection level calculation system 1B can calculate a more accurate protection level that reflects the specific environment, compared to using a coarse, step-by-step model. By using the protection level calculation device 3B, the protection level calculation system 1B can calculate an even more accurate protection level in addition to the effects described in the first or second embodiment.

[0137] Generally, when calculating the upper and lower limits of a distortion error using a three-dimensional map or similar tool, it is costly to have access to the most up-to-date map and to calculate the upper and lower limits of the distortion error based on the height of a building and the distance from Application 101 to the building. For example, if the protection level calculation device 3B is located in Server 105, Application 101 can reduce costs in addition to the effects described above.

[0138] Previously, the description focused on the case in which both the position determination device 2B and the protection level calculation device 3B are integrated into the position determination terminal 102. As in the first embodiment, the position determination device 2B can be integrated into the position determination terminal 102, and the protection level calculation device 3B can be integrated into an external device, such as the server 105. Alternatively, both the position determination device 2B and the protection level calculation device 3B can be integrated into an external device, such as the server 105.

[0139] In the protection level calculation system 1B, the application 101, equipped with the positioning terminal 102, can receive the upper and lower limits of a distortion error for each measurement calculated by the server 105 as integrity support data in order to calculate the protection level. Alternatively, the application 101, equipped with the positioning terminal 102, can receive the result of the protection level calculation from the server 105 or the like, or it can receive the result of the determination of whether the positioning solution can be used or not, based on a comparison between a limit value determined by the application 101 and the protection level.

[0140] Fig. Figure 16 is a representation illustrating a modification of the protection level calculation system 1B, which is included in the position determination system 300 according to the third embodiment. In the Fig. In the protection level calculation system 1B illustrated in Figure 16, the positioning device 2B, the protection level calculation unit 14B, and the storage unit 15, which stores the protection level, are provided in the positioning terminal 102, which is a first device. The distortion error model unit 13B, the map information unit 17, and the storage unit 15, which stores the map information, are provided in the server 105, which is a second device. The protection level calculation device 3B includes the protection level calculation unit 14B and the storage unit 15 of the positioning terminal 102 and the distortion error model unit 13B, the map information unit 17, and the storage unit 15 of the server 105. In the Fig. In the configuration shown in Figure 16, the positioning terminal 102 receives the upper and lower limits of a distortion error from the server 105 as integrity support data.

[0141] At the in Fig. In the configuration illustrated in Figure 16, Server 105 can retrieve position information about Application 101 from the roadside unit 18 via a communication network, such as a mobile phone network, without involving Application 101. Consequently, if Server 105 has orbital information about the satellites 103, Positioning System 300 can calculate the upper and lower limits of distortion errors for measurements corresponding to all of the satellites 103 that can be measured by Application 101. It should be noted that Application 101 can receive the upper and lower limits of a distortion error for each measurement as integrity support data without transmitting measurement information and the positioning solution to Server 105. Fourth embodiment.

[0142] The first to third embodiments describe the case in which the degree of protection of the positioning solution is calculated using pseudo-distance measurements. In a fourth embodiment, a degree of protection is calculated by taking into account errors due to integer ambiguities, which are resolved by positioning a calculation using carrier phase measurements in addition to pseudo-distance measurements. Carrier phase measurements are suitable for accurate distance measurement. However, if an error exists in a resolved integer, this becomes a distortion error. In the fourth embodiment, the same reference numerals are assigned to the same components as in the first to third embodiments, and a configuration that differs from that of the first to third embodiments is described.

[0143] Fig. Figure 17 is a diagram illustrating a configuration example of a protection level calculation system 1C, which is included in a positioning system 400 according to the fourth embodiment. The positioning system 400 according to the fourth embodiment has the same configuration as the positioning system 200 according to the second embodiment or the positioning system 300 according to the third embodiment.

[0144] The protection level calculation system 1C includes a positioning device 2C, which performs a position determination, and a protection level calculation device 3C, which calculates a protection level. The positioning device 2C includes the positioning signal receiving unit 10, which receives positioning signals transmitted by signal sources, namely the satellites 103 or the base stations 104; a positioning calculation unit 11C, which performs a position determination calculation; the storage unit 12, which stores information; and the correction information receiving unit 16. That is, the positioning device 2C has the same configuration as the one in Fig. Figure 13 illustrates the position determination device 2A. The protection level calculation device 3C includes a distortion error model unit 13C, which outputs the upper and lower limits of a distortion error, a protection level calculation unit 14C, which calculates the protection level of the position determination solution, and the storage unit 15, which stores information. That is, the protection level calculation device 3C has the same configuration as the one in Fig. Figure 13 illustrates the protection level calculation device 3A. Thus, the protection level calculation system 1C has the same configuration as the protection level calculation system 1A of the second embodiment. It should be noted that the protection level calculation system 1C has the same configuration as the protection level calculation system 1B of the third embodiment.

[0145] The position determination calculation unit 11C, the distortion error model unit 13C and the protection level calculation unit 14C of the protection level calculation system 1C are replaced by the in Fig. 3 illustrated control circuit 50 or the one in Fig. 4. Illustrated hardware circuit 55 is implemented. Part of the position determination signal receiving unit 10 and part of the correction information receiving unit 16 can form a processing circuit.

[0146] The distortion error model unit 13C processes an integer error, assumed to be contained in an integer ambiguity resolved for a measurement of each carrier phase, as a distortion error assumed to be contained in the carrier phase measurement. The carrier phase measurement here is a measurement corrected using correction information provided by the Positioning Supplement Satellite 201 or the Reference Station 202.

[0147] When receiving positioning signals, the positioning signal receiver 10 extracts information about the positions of the signal sources and information about the distances between the application 101 and the signal sources as measurements of the pseudo-distances. The positioning signal receiver 10 extracts information about the carrier phases as measurements of the carrier phases. The positioning signal receiver 10 outputs the measurements of the pseudo-distances and the measurements of the carrier phases to the positioning calculation unit 11C. These measurements output by the positioning signal receiver 10 may include Doppler frequency measurements.

[0148] The correction information receiving unit 16 receives a signal containing correction information transmitted by the positioning augmentation satellite 201 or the reference station 202 and extracts the correction information from the received signal. The correction information receiving unit 16 outputs the correction information to the positioning calculation unit 11C.

[0149] Using the correction information, the Positioning Computing Unit 11C corrects distortion errors due to Satellite 103 and distortion errors due to the atmosphere from distortion errors present in the measurements. The Positioning Computing Unit 11C performs a position calculation using the corrected measurements to compute the position solution. In addition to the position solution, the Positioning Computing Unit 11C outputs information about an observation model corresponding to the measurements from the signal sources used in the position calculation and weights applied during the position calculation. The position solution calculated by the Positioning Computing Unit 11C may include information about velocity, acceleration, or similar parameters.

[0150] Position determination device 2C sends the position determination solution, the observation model, and the weights for the position determination calculation, output by position determination calculation unit 11C, to the protection level calculation device 3C. The information about the position determination solution, the observation model, and the weights for the position determination calculation is entered into protection level calculation unit 14C. The upper and lower limits of the distortion error, output by distortion error model unit 13C, are entered into protection level calculation unit 14C. Protection level calculation unit 14C calculates the protection level of the position determination solution using the observation model, the weights for the position determination calculation, and the upper and lower limits of the distortion error.The degree of protection calculated by the protection calculation unit 14C is stored in the storage unit 15.

[0151] Next, a method for calculating the degree of protection in the fourth embodiment is described. The position determination calculation unit 11C corrects the measurements y. p ∈R m The carrier phases input by the position determination signal receiving unit 10 are used, along with the correction information input by the correction information receiving unit 16. Then, the position determination calculation unit 11C calculates the position determination solution using the corrected measurements y. pc ∈R m of the carrier phases. In addition, the position determination calculation unit 11C performs a calculation to resolve an integer uncertain quantity that is in the corrected measurement y. pc,i ∈y pcThe carrier phase is included, i.e., the integer ambiguity of the carrier phase. The ambiguity of the carrier phase is obtained by determining a reference satellite for each satellite system, converting a simple difference between satellites for these reference satellites into an integer, and performing a position determination calculation.

[0152] An observation equation for the measurement y pc,i The carrier phase corrected for the distortion error due to satellite 103 and the distortion error due to the atmosphere is expressed as below in (17) using a nonlinear observation model h(x). Formula 14: ypc,i=h(x)=ρ(possvi,pos)+dt+cf∇Nl,ref¯+cfNref +εpc,i

[0153] Here, ∇ indicates that the set to which ∇ is applied is the simple difference between satellites for the reference satellite. ρ is a geometric distance and is calculated using the three-dimensional position pos. svi of satellite 103 and the three-dimensional position pos of the positioning terminal 102. dt represents the receiver clock offset of the positioning terminal 102. ∇N i,re A checkmark above it indicates the ambiguity of the simple difference between satellites, which is converted into an integer. N ref represents the ambiguity of the reference satellite. f represents the frequency of the signal, c represents a high speed, and ε pc,i represents a measurement error. pos, dt and N ref are contained in the state variables x.

[0154] For the reference satellite, i.e., satellite 103 with i=ref, an observation equation of a corrected measurement y is used.pc,ref the carrier phase as expressed below in (18) using a nonlinear observation model h(x). Formula 15: ypc,ref=h(x)=ρ(possvref,pos)+dt+cfNref+εpc,ref

[0155] Alternatively, if a measurement of the simple difference between satellites is used in the position determination calculation, an observation equation of a corrected measurement ∇y is used. pc,i,ref the carrier phase as expressed below in (19) using a nonlinear observation model h(x). Formula 16: ∇ypc,i,ref=ypc,i−ypc,ref=h(x)=ρ(possvi,pos)−ρ(possvref,pos)+cf∇Nl,ref¯+∇εpc,i,ref

[0156] The position determination calculation unit 11C gives a coefficient matrix H∈R m×n as an observational model that corresponds to the corrected measurements y pc ∈R m or ∇y pc ∈R mwhich corresponds to the carrier phases. Here, m represents the number of dimensions of the measurements used in the position determination calculation. n represents the number of dimensions of the state variables estimated by the position determination calculation. Therefore, if ∇y pc The value m is used in the corrected measurements of the carrier phases, which are smaller than in the measurements taken before simple differences between satellites are made using the number of reference satellites. The coefficient matrix H∈R m×n is obtained by linearizing a nonlinear observation model h(x)∈R m for measurements based on state variables x∈R n to use state variables x0∈R as a reference n obtained. It should be noted that the state variables x∈R m three-dimensional position information is included via the position determination terminal 102.

[0157] Furthermore, the position determination calculation unit 11C provides the error covariance matrix R∈R m×m observation errors are represented as weights in the position determination calculation. For example, each diagonal element of the error covariance matrix σ ypi 2 +σ cpi 2 , i.e., the sum of the error variance σ ypi 2 each measurement y pi ∈y and the error variance σ jpi 2 a correction value c pi , which has been corrected for the distortion error due to satellite 103 and the distortion error due to the atmosphere. The correction value here is c. pi a correction value calculated based on the correction information received by the correction information receiving unit 16.

[0158] If the position determination calculation unit 11C measurements yr pThe carrier phases at reference station 202 are used as the correction information instead of the correction information received from satellite 103 or the like, each diagonal element of the error covariance matrix σ ypi 2 +σ yrpi 2 , i.e., the sum of the error variance σ ypi 2 each measurement y pi ∈y and the error variance σ yrpi 2 a measurement of the carrier phase at reference station 202, i.e. a measurement from the same signal source as the measurement of the carrier phase.

[0159] The error variance σ ypi 2 The error variance σ can be determined, for example, using a pre-generated model as a function of the signal type or the signal elevation angle. cpi 2a correction value that is corrected for the distortion error due to satellite 103 and the distortion error due to the atmosphere, and the error variance σ yrpi 2 Error variances in a carrier phase measurement at reference station 202, i.e., a measurement from the same signal source as the carrier phase measurement, can be determined using a model generated in advance as a function of the signal type or signal elevation angle. If the values ​​of these error variances are included in the correction information, they can be used.

[0160] The distortion error model unit 13C provides the upper limit b amb_max ∈R m a distortion error b amb_ and the lower limit b amb_min ∈R m of the distortion error b ambThis distortion error is a value obtained by multiplying an integer error, assumed to be contained in the ambiguity of the carrier phase of the simple difference between satellites (converted to an integer at each measurement during the position calculation), by c / f, and varies from measurement to measurement.

[0161] The protection level calculation unit 14C calculates the horizontal protection level HPL using the observation model and the position determination calculation weights inputted by the position determination calculation unit 11C, and the upper and lower limits of the distortion error inputted by the distortion error model unit 13C. The horizontal protection level HPL is obtained by solving a nonlinear programming problem, which is described below in (20) for a distortion vector b. amb ∈R m The nonlinear programming problem shown in (20) can be solved by a general nonlinear programming solver. Formula 17: Maximize HPL=(M1bamb)2+(M2bamb)2Under the constraints bambTGbamb≤λ bi,amb_min≤bi,amb≤bi,amb_max(i=1,…,m)

[0162] Here, difference coefficients relating to the positions, which are difference coefficients contained in the coefficient matrix H, are expressed in an ENU coordinate system, which is a local horizontal coordinate system, on the basis of a three-dimensional position specified by state variables x0, which serve as a reference.

[0163] In the nonlinear programming problem presented in (20), M1∈R 1×m a row that refers to a positional component in the east-west direction with respect to the three-dimensional reference position in a matrix M= (H T R -1 H) -1 H T R -1 ∈R n×m refers to M2∈R 1×m is a row that refers to a positional component in the north-south direction with respect to the three-dimensional reference position in the matrix M= (H T R -1 H) -1 H T R -1 ∈Rn×m refers to a matrix G∈R. m×m is defined as G= (R -1 -R -1 H(H T R -1 H) -1 H T R -1 ) expressed. b i,amb_min is an element of b amb_min . b i,amb_max is an element of b amb_max . i is a measurement index.

[0164] As with the calculation of the horizontal protection level HPL, the protection level calculation unit 14C calculates the vertical protection level VPL using the observation model and the position determination calculation weights inputted by the position determination calculation unit 11C, and the upper and lower limits of the distortion error inputted by the distortion error model unit 13C. The vertical protection level VPL is obtained by solving a nonlinear programming problem, which is described below in (21) for a distortion vector b amb ∈R mThe nonlinear programming problem shown in (21) can be solved by a general nonlinear programming solver. Formula 18: MaximizeVPL=M3bSubject to the constraints bTGb≤λ bi,amb_min≤bi≤bi,amb_max(i=1,…,m)

[0165] In the nonlinear programming problem presented in (21), M3∈R 1×m a row that refers to a position component in the top-and-bottom direction with respect to the three-dimensional reference position in the matrix M.

[0166] The upper limit b i,amb_max and the lower limit b i,amb_min The distortion error can also be determined by the following equations (22) and (23). Formula 19: bi,amb_min=−cf⋅ceil(K⋅σ∇Ni,ref) bi,amb_max=cf⋅ceil(K⋅σ∇Ni,ref)

[0167] That is, the upper limit b i,amb_max and the lower limit b i,amb_minThe distortion error is determined by calculating the standard deviation σ. ∇Ni,ref the ambiguity ∇N i,ref The carrier phase of the simple difference between satellites is multiplied by a preset coefficient K before being converted into an integer estimated by the Positioning Calculation Unit 11C. It should be noted that the coefficient K depends on an algorithm for converting the ambiguity of the carrier phase into an integer. The coefficient K is set to reflect a range of values ​​assumed by the algorithm to be the integer error.

[0168] As described above, the position determination system 400 according to the fourth embodiment uses measurements of the carrier phases in addition to measurements of the pseudo-distances when calculating the degree of protection.

[0169] In measurements of the pseudo-paths, errors due to the environment around the positioning terminal 102, such as the blocking of direct signal waves by a building or a multipath, are predominant. In contrast, in measurements of the carrier phases, integer errors in the ambiguities solved for the carrier phase measurements are predominant. During the position calculation, the carrier phase ambiguities are converted into integers. Thus, in the weighting of the measurements, those related to the carrier phase measurements increase, and those related to the pseudo-path measurements decrease.This means that in an early phase of the position determination calculation, the effect of distortion errors is more strongly attributable to the environment, whereas, after the position determination calculation has progressed to some extent, the effect is more strongly attributable to the integer errors in the ambiguities of the carrier phases.

[0170] The 1C protection level calculation system calculates the protection level of the carrier phase measurements assuming integer errors in the carrier phase ambiguities. Consequently, even in a phase where the processing of the position determination calculation has progressed and the carrier phase ambiguities of the measurements have been converted into integers, the 1C protection level calculation system can still calculate the protection level that is effective for determining the validity of the measurements.

[0171] Depending on the processing stage of the position determination calculation, distortion error factors include both the signals from satellites 103, where integer errors in the ambiguities solved for the carrier phase measurements are predominant, and the signals from satellites 103, where distortion errors due to the environment, included in the pseudo-path measurements, are predominant. In this case, the protection level calculation system 1C can use the functions of the protection level calculation system 1A or 1B, described in the second or third embodiment, in combination with the functions described in the fourth embodiment. In this case, the protection level calculation unit 14C can determine the protection level using an observation model that is based on the corrected measurements y. c ∈R m, which are used in the position determination calculation, to the measurements of the pseudo-distances of the signals of satellites 103, where the ambiguities of the carrier phases are not converted into integers, and to the measurements of the carrier phases of the signals of satellites 103, where the ambiguities of the carrier phases are converted into integers, of observation weights and a distortion vector.

[0172] As in equations (24) and (25) below, the upper limit b max ∈R m1+m2 and the lower limit b min ∈R m1+m2 The distortion error reflects distortion errors due to the environment for measurements of the pseudo-distances and can reflect integer errors in the ambiguities of the carrier phases for measurements of the carrier phases. Formula 20: bmax=[benv_maxTbamb_maxT]T bmin=[benv_minTbamb_minT]T

[0173] The upper and lower limits of the distortion error due to the environment are b env_max and b env_min ∈R m1 The upper and lower limits of the distortion error due to the ambiguity of the carrier phase are b amb_max and b amb_min ∈R m2 Here, m1 represents the number of measurements of the pseudo-distances used in the position determination calculation. m2 represents the number of measurements of the carrier phases where the ambiguities of the carrier phases are converted into integers, among the carrier phases used in the position determination calculation.

[0174] As described above, even if distortion error factors include both the signals of satellites 103 where carrier phase measurements are predominant and the signals of satellites 103 where pseudo-distance measurements are predominant, the positioning system 400 according to the fourth embodiment can calculate the degree of protection effective for determining the validity of measurements by using the upper and lower limits of the distortion error due to the environment and the ambiguities of the carrier phases.

[0175] The configuration described in each of the foregoing embodiments illustrates an example of the subject matter of the present disclosure. The configuration of each embodiment can be combined with another known technique. The respective configurations of the embodiments can optionally be combined. The configuration of each embodiment can be partially omitted or modified without departing from the core of the present disclosure. List of reference symbols

[0176] 1, 1A, 1B, 1C Protection level calculation system; 2, 2A, 2B, 2C Position determination device; 3, 3A, 3B, 3C Protection level calculation device; 10 Position determination signal receiving unit; 11, 11A, 11B, 11C Position determination calculation unit; 12, 15 Storage unit; 13, 13A, 13B, 13C Distortion error model unit; 14, 14A, 14B, 14C Protection level calculation unit; 16 Correction information receiving unit; 17 Map information unit; 18 Roadside unit; 50 Control circuit; 51 Input unit; 52 Processor; 53 Memory; 54 Output unit; 55 Hardware circuit; 56 Processing circuit; 100, 200, 300, 400 Positioning system; 101 Application; 102 Positioning terminal; 103 Satellite; 104 Base station; 105 Server; 201 Positioning supplement satellite; 202 Reference station.

Claims

Protection level calculation device (3) comprising: a distortion error model unit (13) for outputting an upper limit and a lower limit of a distortion error assumed to be contained in a measurement obtained from a position determination signal; and a protection level calculation unit (14) for calculating a protection level for determining the validity of a position determination solution calculated on the basis of the measurement, using the upper limit and the lower limit. Protection level calculation device (3A, 3B) according to claim 1, wherein the distortion error model unit (13A, 13B) determines both the upper limit and the lower limit based on an environment model which is a model of an environment around a position determination object (101). Protection level calculation device (3B) according to claim 2, comprising a map information unit (17) for referencing map information using the positioning solution or positioning information about the positioning object (101) to determine a class that represents a magnitude or occurrence frequency of the distortion error due to the environment for the environment around the positioning object (101), wherein the distortion error model unit (13B) determines the upper limit and the lower limit using the environment model that corresponds to the class determined by the map information unit (17). Protection level calculation device (3C) according to one of claims 1 to 3, wherein the protection level calculation unit (14C) further calculates the protection level using an upper limit and a lower limit of a distortion error, which is assumed to be contained in a measurement of a carrier phase, and both the upper limit and the lower limit of the distortion error, which is assumed to be contained in the measurement of the carrier phase, are a value obtained from a model of an integer error in an ambiguity of the carrier phase. Protection level calculation device (3C) according to claim 1, wherein the protection level calculation unit (14C) further calculates the protection level using an upper limit and a lower limit of a distortion error, which is assumed to be contained in a measurement of a carrier phase, both the upper limit and the lower limit of the distortion error, which is assumed to be contained in the measurement used to calculate the position determination solution, and the measurement of a pseudo-path between a signal source of the position determination signal and a position determination object (101), are a value obtained from a model of an environment around the position determination object (101), and both the upper limit and the lower limit of the distortion error, which is assumed to be contained in the measurement of the carrier phase, are a value,which is obtained using a model of an integer error in an ambiguity of the carrier phase. Protection level calculation device (3A, 3B) according to claim 2, 3 or 5, wherein the environment model is a geometric model obtained from three-dimensional map information. Protection level calculation device (3) according to one of claims 1 to 6, wherein the protection level calculation unit (14) further calculates the protection level using a weighting of a previous prediction value of a state variable, which is a weighting used in the calculation of the position determination solution, and an upper limit and a lower limit of a distortion error, which is assumed to be contained in the previous prediction value. Protection level calculation device (3) according to claim 7, wherein the previous prediction value is calculated using a measurement of an inertial sensor. Protection level calculation device (3A) according to one of claims 1 to 6, wherein the protection level calculation unit (14A) further calculates the protection level using a standard distortion error in a correction value to correct the measurement. Protection level calculation system (1), comprising: a position determination calculation unit (11) for calculating a position determination solution based on a measurement obtained from a position determination signal; a distortion error model unit (13) for outputting an upper limit and a lower limit of a distortion error assumed to be contained in the measurement; and a protection level calculation unit (14) for calculating a protection level to determine a validity of the position determination solution using the upper limit and the lower limit. Protection level calculation system (1) according to claim 10, wherein the position determination calculation unit (11) is contained in a first device (102) and the distortion error model unit (13) and the protection level calculation unit (14) are contained in a second device (105) which can communicate with the first device (102). Position determination system (100, 200) comprising the protection level calculation system (1) according to claim 10 or 11 . Protection level calculation method, comprising: a step to output an upper limit and a lower limit of a distortion error assumed to be contained in a measurement obtained from a positioning signal; and a step to calculate a protection level to determine a validity of a positioning solution calculated on the basis of the measurement, using the upper limit and the lower limit.

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