RTK-GNSS positioning system and RTK-GNSS positioning method

Abstract

This invention provides an RTK-GNSS positioning system and an RTK-GNSS positioning method that can derive error estimation information for correcting errors in mobile station reception information without using RTK correction information. [Solution] An RTK-GNSS positioning system according to one aspect of the present disclosure includes a base station having a first receiving unit for receiving base station reception information from a satellite, a mobile station having a second receiving unit for receiving mobile station reception information from a satellite, a first calculation unit for deriving RTK correction information based on the base station reception information, a second calculation unit for deriving error estimation information for correcting errors in the mobile station reception information based on the RTK correction information and the mobile station reception information, and a storage unit for storing the error estimation information.

Description

Technical Field

[0001] The present disclosure relates to an RTK-GNSS positioning system and an RTK-GNSS positioning method.

Background Art

[0002] As a technique for realizing high-precision positioning, RTK-GNSS positioning using the RTK method is known. In RTK-GNSS positioning, information from satellites received by a mobile station such as an agricultural machine or a construction machine (hereinafter sometimes simply referred to as "mobile station reception information") is corrected based on RTK correction information including information from satellites received by a base station fixed on the ground (hereinafter sometimes simply referred to as "base station reception information") and information regarding the base station coordinates and the like, so that a Fix-time position coordinate of the mobile station with an error of 3 cm or less from the actual coordinate of the mobile station can be obtained. For example, Patent Document 1 discloses a positioning system that can easily obtain the position of a base station in RTK-GNSS positioning of a mobile station applied to automatic driving of a mobile station such as an agricultural machine or a construction machine.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the automated operation of mobile stations for agricultural and construction machinery, high-precision location information of the mobile station is required to ensure safety in workplaces such as fields and construction sites. In RTK-GNSS positioning, if the base station is unable to receive base station reception information, RTK correction information cannot be derived. In this case, it becomes impossible to obtain high-precision mobile station location information through correction based on RTK correction information. Similarly, if the mobile station is unable to receive RTK correction information based on base station reception information, it becomes impossible to obtain high-precision mobile station location information through correction based on RTK correction information. Therefore, in situations where base station reception information or RTK correction information cannot be received, the automated operation of the mobile station is stopped to ensure safety in the workplace. Stopping the automated operation of the mobile station may lead to a decrease in work efficiency in the workplace. Furthermore, not only for safety reasons, but also when base station reception information or RTK correction information cannot be received, it may lead to a decrease in work accuracy in the workplace.

[0005] To prevent mobile stations from stopping their autonomous driving, high-precision positioning using the PPP-RTK method is known. In positioning using the PPP-RTK method, if the base station is unable to receive base station reception information, or if the mobile station is unable to receive RTK correction information based on base station reception information, the mobile station reception information is corrected based on PPP correction information received by the mobile station from satellites instead of RTK correction information, thereby obtaining highly accurate mobile station location information. However, when adopting the PPP-RTK method, a dedicated receiver that supports the reception of PPP correction information must be additionally installed at the mobile station, increasing the cost of the positioning system.

[0006] In view of the aforementioned conventional problems, this disclosure aims to provide an RTK-GNSS positioning system and an RTK-GNSS positioning method that can derive error estimation information for correcting errors in mobile station reception information without using RTK correction information. [Means for solving the problem]

[0007] An RTK-GNSS positioning system according to one aspect of the present disclosure includes a base station having a first receiving unit for receiving base station reception information from a satellite, a mobile station having a second receiving unit for receiving mobile station reception information from a satellite, a first calculation unit for deriving RTK correction information based on the base station reception information, a second calculation unit for deriving error estimation information for correcting errors in the mobile station reception information without using the RTK correction information, based on the RTK correction information and the mobile station reception information, and a storage unit for storing the error estimation information.

[0008] Furthermore, RTK-GNSS positioning methods according to other aspects of this disclosure include the steps of: receiving base station reception information and mobile station reception information from a satellite; deriving RTK correction information based on the base station reception information; and deriving error estimation information for correcting errors in the mobile station reception information without using the correction information, based on the RTK correction information and the mobile station reception information. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide an RTK-GNSS positioning system and an RTK-GNSS positioning method that can derive error estimation information for correcting errors in mobile station reception information without using RTK correction information. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing the overall configuration of an RTK-GNSS positioning system according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a conceptual diagram of the derivation of positioning location information. [Figure 3] Figure 3 is a conceptual diagram of the derivation of error estimation information. [Figure 4] Figure 4 is a conceptual diagram of the derivation of the first estimated location information. [Figure 5] Figure 5 is a conceptual diagram of the derivation of the second estimated location information. [Figure 6] Figure 6 is an explanatory diagram illustrating the details of Equation I. [Figure 7] FIG. 7 is a conceptual diagram showing the relationship between the reception state of RTK correction information of a mobile station and each derived information. [Figure 8] FIG. 8 is a flowchart showing the flow of derivation of each information shown in FIG. 7. [Figure 9] FIG. 9 is an explanatory diagram when positioning position information is preferentially adopted as the position information of the mobile station. [Figure 10] FIG. 10 is an explanatory diagram when first estimated position information is preferentially adopted as the position information of the mobile station. [Figure 11] FIG. 11 is an explanatory diagram when shifting and adopting from positioning position information to first estimated position information as the position information of the mobile station. [Figure 12] FIG. 12 is a flowchart showing the flow of the process executed in S11 of FIG, 8 in the shifting adoption of FIG. 11. [Figure 13] FIG. 13 is an explanatory diagram of the derivation of estimated RTK correction information.

Mode for Carrying Out the Invention

[0011] <Summary of Embodiments of the Present Disclosure> Hereinafter, the summary of the embodiments of the present disclosure will be listed and described. (1) The RTK-GNSS positioning system according to the present embodiment includes a base station having a first receiving unit for receiving base station reception information from satellites, a mobile station having a second receiving unit for receiving mobile station reception information from satellites, a first calculation unit for deriving RTK correction information based on the base station reception information, a second calculation unit for deriving error estimation information for correcting the error of the mobile station reception information based on the RTK correction information and the mobile station reception information, a storage unit for storing the error estimation information, and includes.

[0012] According to the RTK-GNSS positioning system of the present embodiment, without using RTK correction information, error estimation information for correcting the error of the mobile station reception information can be derived without additionally arranging a dedicated receiver such as a positioning system using the above-described PPP-RTK method. Therefore, it is possible to provide a positioning system that enables acquisition of high-precision position information of a mobile station based on information other than RTK correction information while suppressing an increase in cost.

[0013] (2) In the RTK-GNSS positioning system of (1) described above, the base station has a transmission unit for transmitting the RTK correction information to the mobile station, the mobile station has a third reception unit for receiving the RTK correction information transmitted from the base station, the second calculation unit in a state where the mobile station can receive the RTK correction information transmitted from the base station, derives the positioning position information of the mobile station based on the RTK correction information and the mobile station reception information, derives the first estimated position information of the mobile station based on the RTK correction information, the error estimation information derived based on the mobile station reception information, and the mobile station reception information, in a state where the mobile station cannot receive the RTK correction information transmitted from the base station, the second estimated position information of the mobile station may be derived based on the error estimation information stored in the storage unit and the mobile station reception information.

[0014] According to the RTK-GNSS positioning system of (2) described above, high-precision position information of the mobile station can be derived regardless of the reception status of the first reception unit. Thereby, even in a state where the mobile station cannot receive the RTK correction information transmitted from the base station (hereinafter, may be simply referred to as "a state where the RTK correction information cannot be received"), the automatic driving of the mobile station can be continued. Therefore, the work efficiency and work accuracy at the work site are improved.

[0015] (3) In the RTK-GNSS positioning system described in (2) above, The above-mentioned second arithmetic unit is, When the above mobile station is in a state where it can receive the above RTK correction information transmitted from the above base station, the above positioning location information is adopted as the location information of the above mobile station. If the mobile station is unable to receive the RTK correction information transmitted from the base station, the second estimated location information may be used as the location information of the mobile station.

[0016] According to the RTK-GNSS positioning system described in (3) above, the accuracy of the mobile station's position information can be ensured when the mobile station is in a state where it can receive RTK correction information transmitted from the base station (hereinafter sometimes simply referred to as "the state in which RTK correction information can be received").

[0017] (4) In the RTK-GNSS positioning system described in (2) above, The above-mentioned second arithmetic unit is, When the above mobile station is in a state where it can receive the above RTK correction information transmitted from the above base station, the first estimated position information is adopted as the position information of the above mobile station. If the mobile station is unable to receive the RTK correction information transmitted from the base station, the second estimated location information may be used as the location information of the mobile station.

[0018] According to the RTK-GNSS positioning system described in (4) above, the continuity of the mobile station's position information is improved when switching between the state in which RTK correction information can be received and the state in which it cannot be received.

[0019] (5) In the RTK-GNSS positioning system described in (2) above, The above-mentioned second arithmetic unit is, When the above mobile station is in a state where it can receive the above RTK correction information transmitted from the above base station, Based on the above error estimation information, estimated RTK correction information is derived. The difference information between the above RTK correction information and the above estimated RTK correction information is derived, Until the above difference information satisfies the predetermined conditions, the above positioning location information will be adopted as the location information of the above mobile station. If the above difference information satisfies the predetermined conditions, the first estimated location information may be adopted as the location information of the mobile station.

[0020] According to the RTK-GNSS positioning system described in (5) above, the accuracy and continuity of the mobile station's position information are improved.

[0021] (6) In any of the RTK-GNSS positioning systems described in (1) to (5) above, the error estimation information may include estimation information of errors that change over time.

[0022] According to the RTK-GNSS positioning system described in (6) above, it is possible to derive error estimation information that can accurately correct errors in mobile station reception information.

[0023] (7) In the RTK-GNSS positioning system described in (6) above, the time-varying error may include at least an ionospheric delay error and a tropospheric delay error.

[0024] According to the RTK-GNSS positioning system described in (7) above, error estimation information can be derived that can more accurately correct errors in mobile station reception information.

[0025] (8) In any of the RTK-GNSS positioning systems described in (1) to (7) above, the base station has the first processing unit, The above mobile station may also have a configuration that includes the above second processing unit and the above storage unit.

[0026] According to the RTK-GNSS positioning system described in (8) above, the system configuration becomes simpler, and the cost of the positioning system can be reduced.

[0027] (9) In any of the RTK-GNSS positioning systems described in (1) to (8) above, the second calculation unit may derive the error estimation information based on the relation shown in Equation I. [Observation vector] = Amn × [State vector] + [Noise vector] ... Equation I (In formula I, A is an m x n matrix, The elements of the observation vector include the mobile station reception information, the RTK correction information including the base station reception information and base station coordinates, and the mobile station's fixed position coordinates. The elements of the state vector include at least the above error estimation information, The elements of the noise vector include the observed noise.

[0028] According to the RTK-GNSS positioning system described in (9) above, error estimation information can be derived that can accurately correct errors in mobile station reception information.

[0029] (10) In the RTK-GNSS positioning system described in (9) above, the base station received information includes at least pseudo-distance and carrier phase, The above mobile station reception information may include at least pseudo-distance, carrier phase, and satellite coordinates.

[0030] According to the RTK-GNSS positioning system described in (10) above, error estimation information can be derived that can correct errors in mobile station reception information with greater accuracy.

[0031] (11) In the RTK-GNSS positioning system described in (9) or (10) above, the error estimation information may include at least an ionospheric delay error and a tropospheric delay error.

[0032] According to the RTK-GNSS positioning system described in (11) above, error estimation information can be derived that can correct the error in mobile station reception information with even greater accuracy.

[0033] (12) The RTK-GNSS positioning method according to another embodiment is The steps include receiving base station reception information and mobile station reception information from a satellite, The steps include: deriving RTK correction information based on the above base station reception information; Based on the above RTK correction information and the above mobile station reception information, the step of deriving error estimation information for correcting the error in the above mobile station reception information without using the above RTK correction information, Includes.

[0034] According to another embodiment of the RTK-GNSS positioning method, error estimation information for correcting errors in mobile station reception information can be derived without using RTK correction information, and without receiving other correction information such as PPP correction information. Therefore, it becomes possible to derive correction information that can serve as an alternative to RTK correction information while suppressing cost increases.

[0035] (13) The RTK-GNSS positioning method described in (12) above may include a step of deriving the estimated position information of the mobile station based on the error estimation information and the mobile station reception information.

[0036] According to the RTK-GNSS positioning method described in (13) above, highly accurate positional information of the mobile station can be continuously acquired. As a result, the frequency of stopping the mobile station's automatic movement is reduced. This improves work efficiency and accuracy in the workplace.

[0037] <Details of the embodiments of this disclosure> The embodiments of this disclosure will be described in detail below with reference to the drawings. At least some of the embodiments described below may be combined in any way.

[0038] [Overall configuration of the RTK-GNSS positioning system] Figure 1 is a schematic diagram showing the overall configuration of an RTK-GNSS positioning system 1 according to one embodiment of the present disclosure. The RTK-GNSS positioning system 1 comprises a base station 10 and a mobile station 20. In this embodiment, the mobile station 20 is a tractor 22 equipped with a positioning detection device 21. The tractor 22 is an example of a work vehicle, and the present disclosure is not limited to the tractor 22, but may also be other work vehicles such as agricultural machinery, construction machinery, and utility vehicles.

[0039] The base station 10 comprises a first receiving unit 11, a first storage unit 12, a first calculation unit 13, and a transmitting unit 14. The base station 10 is, for example, a fixed base station that is fixed at a predetermined location. However, if a virtual reference point system (network-type RTK-GNSS positioning) is available, the base station 10 may be a virtual reference point. The first receiving unit 11 has a receiving function for receiving base station reception information from the satellite SAT. The first storage unit 12 has a storage function for storing the coordinates on which the base station 10 is fixed (hereinafter sometimes simply referred to as "base station coordinates"), a program for deriving RTK correction information based on the base station reception information and base station coordinates, etc. The first calculation unit 13 has a calculation function for deriving RTK correction information based on the above program for deriving RTK correction information. The transmitting unit 14 has a transmitting function for transmitting the RTK correction information derived by the first calculation unit 13 to the mobile station 20.

[0040] The positioning detection device 21 comprises a second receiving unit 211, a second storage unit 212, a second calculation unit 213, and a third receiving unit 214. The second receiving unit 211 has a receiving function for receiving mobile station reception information from the satellite SAT. The second storage unit 212 has a program for deriving error estimation information and location information of the mobile station 20, and a storage function for storing the derived error estimation information, etc. The second calculation unit 213 has a calculation function for deriving error estimation information and location information of the mobile station 20, etc., based on the above program. The third receiving unit 214 has a receiving function for receiving RTK correction information transmitted from the transmitting unit 14.

[0041] The tractor 22 is connected to the positioning detection device 21 by wire or wireless connection. The tractor 22 is equipped with components 221 for automatic driving based on the position information of the mobile station 20 from the positioning detection device 21. For example, as disclosed in Patent Document 1, work vehicles equipped with components for automatic driving based on the position information of a mobile station acquired by an RTK-GNSS positioning system are known. Components 221 can be the same as those used in the above-mentioned known work vehicle.

[0042] In the RTK-GNSS positioning system 1, the base station 10 has a first memory unit 12 and a first calculation unit 13, and the mobile station 20 has a second memory unit 212 and a second calculation unit 213. This allows the RTK-GNSS positioning system 1 to be built with a simple configuration of a base station 10 and a mobile station 20. However, the RTK-GNSS positioning system of this disclosure is not limited to this configuration. For example, the RTK-GNSS positioning system of this disclosure can also be configured to include a server that can communicate with the base station 10 and the mobile station 20, in addition to the base station 10 and the mobile station 20. In this case, instead of the base station 10 and the mobile station 20, the server can be configured to have a first memory unit 12, a first calculation unit 13, a second memory unit 212, and a second calculation unit 213. However, from the viewpoint of cost reduction, the simple configuration shown in the RTK-GNSS positioning system 1 is preferred.

[0043] [Derivation of positioning location information] Figure 2 is a conceptual diagram of the derivation of positioning location information. The positioning location information is derived by a positioning calculation based on RTK correction information performed by the second calculation unit 213. The second calculation unit 213 in this disclosure derives the fixed position coordinates of the mobile station 20 as positioning location information. In the above positioning calculation, RTK correction information received by the third receiving unit 214 and mobile station reception information received by the second receiving unit 211 are used as input information. The RTK correction information used to derive the positioning location information includes at least the pseudo-distance and carrier phase of the base station reception information and the base station coordinates. The mobile station reception information used to derive the positioning location information includes at least the pseudo-distance, carrier phase, and satellite coordinates. The derivation of positioning location information in this disclosure can be performed by a positioning calculation similar to that used in known RTK-GNSS positioning.

[0044] [Derivation of error estimation information] Figure 3 is a conceptual diagram of the derivation of error estimation information. The error estimation information is derived by a prediction calculation performed by the second calculation unit 213 based on RTK correction information, mobile station reception information, and fixed position coordinates. The RTK correction information used to derive the error estimation information includes at least the pseudo-distance and carrier phase of the base station reception information, and the base station coordinates. The mobile station reception information used to derive the error estimation information includes at least the pseudo-distance, carrier phase, and satellite coordinates.

[0045] Error estimation information includes satellite orbit error, satellite clock error, receiver clock error, ionospheric delay error, tropospheric delay error, integer bias, and position offset. The error estimation information of this disclosure includes at least one selected from satellite orbit error, satellite clock error, receiver clock error, ionospheric delay error, tropospheric delay error, integer bias, and position offset. In the error estimation information, error estimation information that changes over time is information that is likely to affect the derivation of the estimated position information of the mobile station 20, as described later. Therefore, it is preferable that the error estimation information includes error estimation information that changes over time.

[0046] Errors that vary over time include satellite orbit errors, satellite clock errors, receiver clock errors, ionospheric delay errors, and tropospheric delay errors. In particular, ionospheric delay errors and tropospheric delay errors have a significant impact on the derivation of the estimated position information of the mobile station 20, as described later. Therefore, it is more preferable that the error estimation information includes at least ionospheric delay errors and tropospheric delay errors.

[0047] [Derivation of estimated location information]

[0048] The estimated position information is the position information of the mobile station 20, derived by correcting the error in the mobile station reception information with error estimation information, without using RTK correction information. The estimated position information can be applied to the automatic driving of the tractor 22 as the position information of the mobile station 20, in place of the fixed position coordinates, which are the positioning position information described above. The estimated position information includes first estimated position information and second estimated position information.

[0049] Figure 4 is a conceptual diagram of the derivation of the first estimated position information. Figure 5 is a conceptual diagram of the derivation of the second estimated position information. Both the first estimated position information and the second estimated position information are derived by a positioning calculation based on error estimation information performed by the second calculation unit 213. In the positioning calculation for deriving the first estimated position information, the input information used is the mobile station reception information received by the mobile station 20 and the error estimation information derived by the prediction calculation performed by the second calculation unit 213, as shown in Figure 3. In the positioning calculation for deriving the second estimated position information, the input information used is the mobile station reception information received by the mobile station 20 and the error estimation information stored in the second storage unit 212. The mobile station reception information used for deriving the estimated position information includes at least pseudo-distance, carrier phase, and satellite coordinates. The error estimation information used for deriving the estimated position information preferably includes the above-mentioned time-varying error estimation information, and is particularly preferably at least ionospheric delay error and tropospheric delay error.

[0050] The RTK-GNSS positioning system 1 can derive the position information of the mobile station 20 as positioning position information, first estimated position information, and second estimated position information. The positioning position information is corrected using RTK correction information, while the first estimated position information and second estimated position information are corrected using error estimation information. Therefore, the positioning position information, first estimated position information, and second estimated position information are more accurate position information for the mobile station 20 than the position information obtained by GNSS positioning alone. Furthermore, the second estimated position information is derived using error estimation information stored in the second memory unit 212. Therefore, even if at least one of the following becomes impossible—receiving base station reception information at the first receiving unit 11 of the base station 10, transmitting RTK correction information at the transmitting unit 14 of the base station 10, and receiving RTK correction information at the third receiving unit 214 of the mobile station 20—the RTK-GNSS positioning system 1 can still derive the second estimated position information. In other words, the RTK-GNSS positioning system 1 can derive highly accurate positional information of the mobile station 20 regardless of the communication status of the first receiving unit 11, the transmitting unit 14, and the third receiving unit 214. Therefore, with the RTK-GNSS positioning system 1, the tractor 22 can continue to drive automatically even when the mobile station 20 is unable to receive RTK correction information transmitted from the base station 10. As a result, the work efficiency and accuracy of the tractor 22 are improved.

[0051] [Calculation formula for prediction calculation] As shown in Figure 3, the error estimation information prediction calculation performed by the second calculation unit 213 is carried out using, for example, the relational expression shown in equation I below. [Observation vector] = Amn × [State vector] + [Noise vector] ... Equation I (In formula I, for example, Amn is an m x n matrix, The elements of the observation vector include the base station reception information, the mobile station reception information, the RTK correction information, the fixed position coordinates of the mobile station, and the base station coordinates. The elements of the state vector include the error estimation information, The elements of the noise vector include the observed noise. It may also include other elements or content, or some of these elements or content may be omitted.

[0052] Figure 6 is an explanatory diagram illustrating the details of Equation I. For illustrative purposes, Amn is shown in Figure 6 as a 7x7 matrix, but it is not limited to this; Amn may also be a 12n+6x12n+13 matrix (where n is the number of satellites), etc. The contents of each element of the observation vector, state vector, and noise vector shown in Figure 6 are described below. Note that other elements or contents may be included, and some of these elements or contents may be omitted.

[0053] (Observation vector) BPD: False distance received by the base station BCP: Carrier phase received by the base station BCO: Base station coordinates MPD: False distance received by the mobile station MCP: Carrier phase received by the mobile station MSC: Satellite coordinates received by the mobile station FIX: Mobile station's fixed position coordinates MCE: Satellite clock error received by the mobile station

[0054] (State vector) SOE: Satellite orbit error SCE: Satellite Clock Error RCE: Receiving Clock Error IDE: Ionospheric delay error TDE: Tropospheric Delay Error IVB: Integer Bias PSO: Position Offset MCO: Mobile station coordinates SCO: Satellite coordinates MSD: The amount of deviation in the satellite clock received by the mobile station.

[0055] (Noise vector) BDN: Observation noise of pseudo-range received by base station BPN: Observed noise of carrier phase received by the base station BON: Observation noise of base station coordinates MDN: Pseudo-range observation noise received by a mobile station MPN: Observed noise of carrier phase received by a mobile station. MCN: Observation noise of satellite coordinates received by the mobile station FIN: Observation noise of the mobile station's fixed position coordinates MSN: Observational noise of satellite clock error received by mobile stations

[0056] Equation I can be set appropriately based on RTK-GNSS positioning using the conventional RTK method and information obtained from satellite SAT. The elements of the observation vector and noise vector correspond to the input information for the prediction calculation in the derivation of error estimation information shown in Figure 3. The elements of the state vector correspond to the error estimation information output in the prediction calculation in the derivation of error estimation information shown in Figure 3.

[0057] In Figure 6, the state vector includes, but is not limited to, satellite orbit error, satellite clock error, receiver clock error, ionospheric delay error, tropospheric delay error, integer bias, position offset, mobile station coordinates, satellite coordinates, and the amount of deviation of the satellite clock error received by the mobile station. As described above, the elements of the state vector correspond to error estimation information. Therefore, it is preferable that the state vector includes at least one error that changes over time. It is particularly preferable that the state vector includes at least the ionospheric delay error and the tropospheric delay error.

[0058] [Relationship between base station reception status and various types of information, and the process for deriving each type of information] Figure 7 is a conceptual diagram showing the relationship between the reception status of RTK correction information at the mobile station 20 and the information derived therefrom. Each line shown in Figure 7 indicates the start, interruption, recovery, and end of reception of RTK correction information from the base station 10's transmitter 14 by the mobile station 20's third receiver 214. The mobile station's received information from the satellite SAT, received by the mobile station 20's second receiver 211, is in a receivable state from the start to the end of reception as described above (not shown).

[0059] As shown in Figure 7, RTK correction information is received by the third receiving unit 214 of the mobile station 20 at any time other than from the time reception is interrupted until reception is restored. When RTK correction information is available, the first calculation unit 13 derives the RTK correction information, and the second calculation unit 213 derives the positioning location information, error estimation information, and first estimated location information.

[0060] As shown in Figure 7, the RTK correction information becomes unreceivable in the third receiving unit 214 of the mobile station 20 from the time reception is interrupted until reception is restored. When the RTK correction information is unreceivable, the second estimated position information is derived in the second calculation unit 213.

[0061] Figure 8 is a flowchart showing the derivation process for each piece of information shown in Figure 7. The RTK-GNSS positioning system 1 is configured to execute steps S1 to S13 shown in Figure 8 from start (reception start) to end (reception end).

[0062] As shown in Figure 8, when the RTK-GNSS positioning system 1 starts receiving base station reception information, the first receiving unit 11 of the base station 10 performs step S1, which is the step of receiving base station reception information from the satellite SAT. Next, the first calculation unit 13 of the base station 10 performs step S2, which is the step of determining whether or not base station reception information was received in S1. If it is determined in S2 that base station reception information has been received, the first calculation unit 13 performs step S3, which is the step of deriving RTK correction information. If it is determined in S2 that base station reception information has not been received, the determination result is transmitted by the transmitting unit 14 of the base station 10 and received by the third receiving unit 214 of the positioning detection device 21 of the mobile station 20.

[0063] In the position detection device 21 of the mobile station 20, the second calculation unit 213 executes step S3, which determines whether or not the RTK correction information derived in S3 has been received by the third receiving unit 214. In S4, if it is determined that the RTK correction information has been received, the second calculation unit 213 executes step S5, which derives the Fix time position coordinates as positioning position information for the mobile station 20, based on the RTK correction information derived in S3 and the mobile station reception information received by the second receiving unit 211 of the position detection device 21. Next, the second calculation unit 213 executes step S6, which derives error estimation information based on the RTK correction information derived in S3, the Fix time position coordinates derived in S5, and the mobile station reception information. The error estimation information derived in S6 is stored in the second storage unit 212 of the position detection device 21 by executing step S7, which stores the error estimation information in the second storage unit 212 of the position detection device 21. Furthermore, the second calculation unit 213 executes step S8, which derives the first estimated position information of the mobile station 20 based on the mobile station reception information and the error estimation information derived in S6.

[0064] If, in S2 or S4, it is determined that no base station reception information or RTK correction information has been received, the second calculation unit 213 of the positioning detection device 21 executes S9, which is a step of determining whether or not error estimation information is stored in the second storage unit 212. If, in S9, it is determined that error estimation information is stored, the second calculation unit 213 executes S10, which is a step of deriving the second estimated position information of the mobile station 20 based on the mobile station reception information and the error estimation information stored in the second storage unit 212.

[0065] If it is determined in S9 that there is no stored error estimation information, the process returns to S1, in which the first receiving unit 11 of the base station 10 receives base station reception information. Although not shown in Figure 8, if the RTK-GNSS positioning system 1 continues to determine that there is no stored error estimation information in S9 for a predetermined number of times or a predetermined period of time, it will consider this a base station reception error and terminate reception.

[0066] After S8 or S10, the second calculation unit 213 executes S11, which is the step of identifying the location information of the mobile station 20 based on the positioning location information derived in S5, the first estimated location information derived in S8, and the second estimated location information derived in S10. Details of identifying the location information of the mobile station 20 in S11 will be explained later in the section on identifying the location information of the mobile station. After S11, S12 is executed, which is the step of determining whether or not the reception of base station reception information has ended. If it is determined in S12 that reception has not ended, the process returns to S1. If it is determined in S12 that reception has ended, S13 is executed, which is the step of erasing the error estimation information stored in the second storage unit 212, and the reception of base station reception information in the RTK-GNSS positioning system 1 ends.

[0067] [Identifying the location information of the mobile station] (Priority given to positioning information or first estimated location information) Figure 9 is an explanatory diagram illustrating the case where positioning location information is prioritized as the location information of the mobile station 20. Figure 10 is an explanatory diagram illustrating the case where first estimated location information is prioritized as the location information of the mobile station 20. Both Figures 9 and 10 are diagrams that add information used to identify the location information of the mobile station 20 in the cases where RTK correction information can be received and where RTK correction information cannot be received, to the relationship between the reception status of the RTK correction information of the mobile station 20 and each of the derived pieces of information shown in Figure 7.

[0068] In the RTK-GNSS positioning system 1, when RTK correction information cannot be received, second estimated position information is derived as the mobile station's position information. In other words, when RTK correction information cannot be received, neither the positioning position information nor the first estimated position information is derived. Therefore, in the RTK-GNSS positioning system 1, when RTK correction information cannot be received, the second estimated position information is used to identify the mobile station 20's position information. That is, in Figure 8 above, if it is determined in S2 or S4 that there is no reception of base station reception information or RTK correction information, the second estimated position information is used as the mobile station 20's position information in the S11 mobile station 20 position information identification step. As mentioned above, the second estimated position information is the mobile station 20's position information with higher accuracy than the position information obtained by GNSS standalone positioning. Furthermore, the second estimated position information is derived even when RTK correction information cannot be received. Therefore, even when RTK correction information cannot be received, the tractor 22 can continue to drive automatically. As a result, the work efficiency and precision of tractor 22 are improved.

[0069] When RTK correction information is receivable, the positioning location information and the first estimated location information are derived as the mobile station's location information. As shown in Figure 9, when positioning location information is prioritized, when RTK correction information is receivable, the positioning location information is adopted as the location information of the mobile station 20. That is, in the method that prioritizes the adoption of positioning location information, if it is determined that RTK correction information is receivable in S4 of Figure 8 above, the positioning location information is adopted as the location information of the mobile station 20 in the mobile station 20 location information identification step of S11. In other words, when RTK correction information is receivable, the Fix time position coordinates corrected based on the RTK correction information are used as the location information of the mobile station 20, similar to the conventional RTK-GNSS positioning system using the RTK method. Therefore, the RTK-GNSS positioning system 1 that prioritizes the adoption of positioning location information can guarantee the accuracy of the mobile station 20's location information when RTK correction information is receivable.

[0070] As shown in Figure 10, when the first estimated position information is prioritized, the first estimated position information is adopted as the position information of the mobile station 20 when RTK correction information is receivable. That is, in the method of prioritizing the first estimated position information, if it is determined that RTK correction information is receivable in S4 of Figure 8 above, the first estimated position information is adopted as the position information of the mobile station 20 in the mobile station 20 position information identification step of S11. In this case, regardless of the reception status of the base station reception information, the position information of the mobile station 20 will be either the first estimated position information or the second estimated position information derived based on the error estimation information and the mobile station reception information. When switching between the state in which RTK correction information can be received and the state in which it cannot be received, in the method of prioritizing the positioning position information shown in Figure 9 above, there may be a discrepancy in the position information of the mobile station 20 between the positioning position information and the second estimated position information. The main reason for this discrepancy is that the information used to correct the mobile station reception information is different: the positioning position information is RTK correction information, while the second estimated position information is error estimation information. The first and second estimated position information are both error estimation information used to correct the mobile station's received information. Therefore, the deviation of the mobile station 20's position information during the above switching is suppressed. Thus, the RTK-GNSS positioning system 1, which prioritizes the first estimated position information, improves the continuity of the mobile station 20's position information.

[0071] As shown in Figures 9 and 10, the RTK-GNSS positioning system 1 derives both the positioning location information and the first estimated location information when RTK correction information is available, even when prioritizing either the positioning location information or the first estimated location information. However, the RTK-GNSS positioning system of this disclosure is not limited to deriving both the positioning location information and the first estimated location information, and only needs to derive RTK correction information and error estimation information when RTK correction information is available. For example, the RTK-GNSS positioning system of this disclosure may not derive the first estimated location information when prioritizing the positioning location information. Similarly, the RTK-GNSS positioning system of this disclosure may not derive the positioning location information when prioritizing the first estimated location information.

[0072] (Adoption of transition from positional location information to first estimated location information) As described above, when positioning location information is prioritized, the accuracy of the mobile station 20's location information is guaranteed when RTK correction information can be received, but the continuity of the mobile station 20's location information may decrease when switching between the state where RTK correction information can be received and the state where it cannot. Conversely, when the first estimated location information is prioritized, the continuity of the mobile station 20's location information improves when switching between the state where RTK correction information can be received and the state where it cannot, but the accuracy of the mobile station 20's location information may decrease when RTK correction information can be received. The decrease in accuracy and continuity of the mobile station 20's location information is mainly due to the difference between the positioning location information and the first estimated location information.

[0073] The inventors have found that (i) the difference between the measured position information and the first estimated position information is large immediately after the start of reception by the RTK-GNSS positioning system 1, and decreases with the passage of time since the start of reception; (ii) the reduction in the difference between the measured position information and the first estimated position information with the passage of time is due to the stabilization of the error estimation information; and (iii) once the error estimation information is stabilized, there is almost no further expansion of the difference between the measured position information and the first estimated position information. Based on the inventors' findings above, when RTK correction information is receivable, by adopting a method of transitioning from measured position information to first estimated position information, where the measured position information is adopted as the position information of the mobile station 20 before the error estimation information stabilizes, and the first estimated position information is adopted as the position information of the mobile station 20 after the error estimation information stabilizes, it is possible to improve the accuracy and continuity of the position information of the mobile station 20.

[0074] Figure 11 is an explanatory diagram illustrating the case where the mobile station 20 transitions from positioning location information to first estimated location information as its location information. Figure 12 is a flowchart showing the processing flow executed in S11 of Figure 8 during the transition and adoption in Figure 11. Figure 13 is an explanatory diagram illustrating the derivation of estimated RTK correction information.

[0075] As shown in Figure 11, when RTK correction information is receivable, the position information of the mobile station 20 is transitioned from the positioning position information to the first estimated position information (hereinafter sometimes simply referred to as "transition adoption"). In the RTK-GNSS positioning system 1, the difference information is derived from the start of reception until the difference information described later satisfies predetermined conditions. Then, from the start of reception until the difference information satisfies predetermined conditions, the positioning position information is adopted as the position information of the mobile station 20 when RTK correction information is receivable. Note that from the start of reception until the difference information satisfies predetermined conditions, the second estimated position information is adopted as the position information of the mobile station 20 when RTK correction information is not receivable (not shown). After the difference information satisfies predetermined conditions, similar to the method of prioritizing the adoption of the first estimated position information shown in Figure 10 above, the first estimated position information is adopted as the position information of the mobile station 20 when RTK correction information is receivable, and the second estimated position information is adopted as the position information of the mobile station 20 when RTK correction information is not receivable.

[0076] As shown in Figure 12, when the transitional adoption method is applied, the RTK-GNSS positioning system 1 executes steps S111 to S119 in S11 of Figure 8. S111 is the step of deriving estimated RTK correction information. As shown in Figure 13, the estimated RTK correction information is derived based on the first estimated position information, base station coordinates, and mobile station reception information. The pseudo-distance included in the mobile station reception information is derived using receiver coordinates, satellite clock error deviation, position offset, receiver clock error, satellite coordinates, satellite orbit error, satellite clock error, ionospheric delay error, and tropospheric delay error. The carrier phase included in the mobile station reception information is derived using these in addition to integer bias. The estimated RTK correction information derivation calculation, which is the calculation for deriving the estimated RTK correction information, can be constructed based on the positioning calculation based on RTK correction information shown in Figure 2. More specifically, a calculation formula is constructed that uses positioning calculations based on RTK correction information as a foundation, and then uses positioning location information and mobile station reception information to calculate the RTK correction information in reverse. The above calculation formula for calculating the RTK correction information in reverse can be applied as an estimated RTK correction information derivation calculation.

[0077] In S111, after the estimated RTK correction information is derived, step S112 is executed, which determines whether or not the second estimated position information has been derived. If it is determined in S112 that the second estimated position information has been derived, the process moves to S113, and the second estimated position information is adopted as the position information of the mobile station 20.

[0078] If it is determined in S112 that there is no second estimated position information to be derived, then step S114 is executed, which is a step in which it is determined whether or not there is a record of stabilization information, which will be described later, in the second storage unit 212 of the position detection device 21. If it is determined in S114 that there is a record of stabilization information, the process moves to S115, and the first estimated position information is adopted as the position information of the mobile station 20.

[0079] If it is determined in S114 that there is no record of stabilization information, then S116 is executed, which is a step to derive difference information, which is information about the difference between the RTK correction information and the estimated RTK correction information. As shown in Figure 2, the RTK correction information includes at least the pseudo-distance and carrier phase of the base station reception information, and the base station coordinates. As shown in Figure 13, the estimated RTK correction information includes at least the estimated pseudo-distance and estimated carrier phase of the estimated base station reception information, and the base station coordinates. Both the RTK correction information and the estimated RTK correction information include base station coordinates. Therefore, the base station coordinates cancel each other out in the difference information. Thus, the difference information is information about the difference between the base station reception information and the estimated base station reception information. More specifically, the difference information includes at least information about the difference between the pseudo-distance and the estimated pseudo-distance, and information about the difference between the carrier phase and the estimated carrier phase.

[0080] In S116, after the difference information is derived, step S117 is performed, which is a step in which it is determined whether or not the difference information satisfies predetermined conditions. In the RTK-GNSS positioning system 1, in S117, the second calculation unit 213 compares the pseudo-distance and carrier phase of the mobile station received information with the pseudo-distance and carrier phase of the base station received information to determine whether or not the difference information satisfies predetermined conditions.

[0081] In S117, if it is determined that the difference information satisfies predetermined conditions, step S118 is executed, which is the step of storing stabilization information indicating that the difference information satisfies predetermined conditions in the second storage unit 212. After the stabilization information is stored in the second storage unit 212 in S118, the process moves to S114, and the first estimated position information is adopted as the position information of the mobile station 20. In the RTK-GNSS positioning system 1 to which transition adoption is applied, in S13 of Figure 8, in addition to the error estimation information, the stabilization information is also deleted from the second storage unit 212 (not shown).

[0082] If, in S117, it is determined that the difference information does not satisfy the predetermined conditions, the process moves to S119, and the positioning location information is adopted as the location information of the mobile station 20.

[0083] [Other variations] The embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments described above, and includes all modifications within the scope equivalent to the configurations described in the claims. [Explanation of Symbols]

[0084] 1. Positioning system 10 base station 11 First receiving unit 12 First memory section 13 First calculation section 14. Transmitter 20 Mobile Stations 21 Positioning detection device 211 Second receiving unit 212 Second memory section 213 Second calculation section 214 Third receiving unit 221 Components 22 tractors

Claims

1. A base station having a first receiving unit for receiving base station reception information from a satellite, A mobile station having a second receiving unit for receiving mobile station reception information from a satellite, A first calculation unit for deriving RTK correction information based on the base station reception information, A second calculation unit for deriving error estimation information for correcting errors in the mobile station reception information based on the RTK correction information and the mobile station reception information, A storage unit for storing the aforementioned error estimation information, An RTK-GNSS positioning system, including the above.

2. The base station has a transmitting unit for transmitting the RTK correction information to the mobile station. The mobile station has a third receiving unit for receiving the RTK correction information transmitted from the base station, The second arithmetic unit is, When the mobile station is in a state where it can receive the RTK correction information transmitted from the base station, Based on the RTK correction information and the mobile station reception information, the positioning location information of the mobile station is derived. Based on the RTK correction information and the mobile station reception information, the error estimation information is derived, and based on the mobile station reception information, the first estimated position information of the mobile station is derived. When the mobile station is in a state where it cannot receive the RTK correction information transmitted from the base station, Based on the error estimation information stored in the memory unit and the mobile station reception information, a second estimated position information of the mobile station is derived. The RTK-GNSS positioning system according to claim 1.

3. The second arithmetic unit is, When the mobile station is in a state where it can receive the RTK correction information transmitted from the base station, the positioning location information is adopted as the location information of the mobile station. When the mobile station is unable to receive the RTK correction information transmitted from the base station, the second estimated location information is used as the location information of the mobile station. The RTK-GNSS positioning system according to claim 2.

4. The second arithmetic unit is, When the mobile station is in a state where it can receive the RTK correction information transmitted from the base station, the first estimated position information is adopted as the position information of the mobile station. When the mobile station is unable to receive the RTK correction information transmitted from the base station, the second estimated location information is used as the location information of the mobile station. The RTK-GNSS positioning system according to claim 2.

5. The second arithmetic unit is, When the mobile station is in a state where it can receive the RTK correction information transmitted from the base station, Based on the aforementioned error estimation information, estimated RTK correction information is derived. The difference information between the aforementioned RTK correction information and the estimated RTK correction information is derived. Until the aforementioned difference information satisfies the predetermined conditions, the positioning location information will be used as the location information of the mobile station. After the aforementioned difference information satisfies the predetermined conditions, the first estimated location information is adopted as the location information of the mobile station. The RTK-GNSS positioning system according to claim 2.

6. The RTK-GNSS positioning system according to claim 1, wherein the error estimation information includes estimation information of errors that change over time.

7. The RTK-GNSS positioning system according to claim 6, wherein the time-varying error includes at least an ionospheric delay error and a tropospheric delay error.

8. The base station has the first processing unit, The mobile station has the second processing unit and the storage unit, The RTK-GNSS positioning system according to claim 1.

9. The RTK-GNSS positioning system according to any one of claims 1 to 8, wherein the second calculation unit derives the error estimation information based on the relational expression shown in formula I. [Observation vector] = Amn × [State vector] + [Noise vector] ... Equation I (In formula I, A is an m x n matrix, The elements of the observation vector include the mobile station reception information, the RTK correction information including the base station reception information and base station coordinates, and the mobile station's fixed position coordinates. The elements of the state vector include at least the error estimation information, The elements of the noise vector include the observed noise.

10. The base station received information includes at least the pseudo-distance and the carrier phase. The mobile station received information includes at least the pseudo-distance, carrier phase, and satellite coordinates. The RTK-GNSS positioning system according to claim 9.

11. The RTK-GNSS positioning system according to claim 9, wherein the error estimation information includes at least an ionospheric delay error and a tropospheric delay error.

12. The steps include receiving base station reception information and mobile station reception information from a satellite, The steps include: deriving RTK correction information based on the base station reception information; The steps include: deriving error estimation information for correcting errors in the mobile station reception information without using the RTK correction information, based on the RTK correction information and the mobile station reception information; An RTK-GNSS positioning method, including the above.

13. The RTK-GNSS positioning method according to claim 12, comprising the step of deriving estimated position information of the mobile station based on the error estimation information and the mobile station reception information.

Images