JP7443500B2 - Reference station selection device, reference station selection method, and program - Google Patents

Description

The present invention relates to a technique for measuring the position of a mobile station with high precision.

In recent years, positioning using a navigation satellite system, GNSS (Global Navigation Satellite System), has been utilized in a wide range of applications.

In the GNSS carrier phase positioning method (or GNSS interferometric positioning method: hereinafter referred to as carrier phase positioning), a mobile station uses multiple GNSS satellite signals (hereinafter referred to as satellite signal receiving device) received by its own GNSS satellite signal receiving device (hereinafter referred to as satellite signal receiving device). , satellite signals), observation data of satellite signals received by a satellite signal receiving device at a fixed station (reference station) located at a reference point with a known position, and position information of the fixed station (reference station). In order to calculate the relative displacement (baseline vector) of the station with respect to the fixed station, baseline analysis by carrier phase positioning calculation (hereinafter referred to as carrier phase positioning calculation) is performed. Here, observation data is information on the results of pseudorange and carrier phase measurement in signal processing of a satellite signal receiving device, and is also called raw data. In the following description, it is assumed that observation data includes information necessary for positioning (information included in navigation messages, etc.) obtained by receiving satellite signals. For example, a real time kinematic method is used as a carrier phase positioning method.

In carrier wave phase positioning, as the distance (baseline length) between the mobile station and the fixed station becomes longer, the convergence (fix) rate and positioning accuracy of the positioning solution in carrier wave phase positioning calculation deteriorates, so as the mobile station moves, It is necessary to switch fixed stations (that is, select a fixed station). Note that in addition to using a stationary fixed station as a reference station, a mobile body can also be used as a moving base station.

Research on network RTK-GPS positioning Master's degree thesis, 2003 Tokyo University of Mercantile Marine, Graduate School of Merchant Marine, Department of Distribution Information Engineering, Shinji Tanaka

In a system using a plurality of geographically distributed reference stations, a mobile station generally selects the reference station closest to the mobile station (having the shortest baseline length). However, there is a problem in that when a reference station is selected based only on the baseline length, high positioning accuracy may not necessarily be obtained. For example, if the satellite signal reception condition is poor at the reference station with the shortest baseline length from the mobile station, higher positioning accuracy may be obtained by selecting another reference station with a longer baseline length from the mobile station. be.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a technology that allows a mobile station to dynamically and appropriately select a reference station so that a mobile station can stably obtain high positioning accuracy. With the goal.

According to the disclosed technology, there is provided a reference station selection device that selects a reference station to be used for carrier phase positioning in a mobile station from a plurality of geographically distributed reference stations,
The plurality of reference stations are fixed stations or mobile bodies,
an information acquisition unit that acquires information of each reference station in the plurality of reference stations;
Among the one or more reference stations whose baseline length is equal to or less than a predetermined threshold among the plurality of reference stations, at least information regarding the position accuracy index of the reference station, information regarding the comparison result of the reception state of satellite signals of the mobile station and the reference station, and a selection unit that selects a reference station to be used for carrier phase positioning in the mobile station based on one or more of the information regarding the reliability index of the reference station. provided.

According to the disclosed technique, a technique is provided that enables a mobile station to dynamically and appropriately select a reference station so that a mobile station can stably obtain high positioning accuracy.

FIG. 3 is a diagram for explaining an example of selecting a reference station based on a baseline length. FIG. 2 is a diagram for explaining an overview of processing in an embodiment of the present invention. FIG. 2 is a configuration diagram of a reference station selection device. 3 is a flowchart illustrating an example of the operation of the reference station selection device. FIG. 6 is a diagram illustrating an example in which a candidate for a reference station is a mobile body. FIG. 2 is a diagram illustrating an overview of operations when a mobile station has the function of a reference station selection device. FIG. 2 is a diagram illustrating an example of the configuration of a mobile station in a case where the mobile station has a function of a reference station selection device. It is a diagram showing an example of the hardware configuration of the device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention (this embodiment) will be described below with reference to the drawings. The embodiments described below are merely examples, and the embodiments to which the present invention is applied are not limited to the following embodiments.

In this embodiment, a station located at a reference point used in carrier phase positioning by a mobile station is referred to as a "reference station." Furthermore, a target for positioning (one whose location is unknown) is called a "mobile station."

The reference station may be a fixed station fixed to the ground or the like, or may be a moving body. Hereinafter, when clearly indicating that a reference station is a fixed station, it may be written as a reference station (fixed station), and when clearly indicating that a reference station is a mobile body, it may be written as a reference station (mobile body).

(Summary of embodiment)
In this embodiment, a reference station selection device 100, which will be described later, dynamically and appropriately selects a reference station to be used for carrier phase positioning of the mobile station 10 from a plurality of candidates based on the baseline length and other information.

First, for comparison, an example in which a reference station is selected based only on the baseline length will be described with reference to FIG. In the example shown in FIG. 1, reference station A, reference station B, and reference station C exist as reference station candidates used by the mobile station 10 for carrier phase positioning.

For example, the mobile station 10 receives position information of each of reference station A, reference station B, and reference station C from a server on the network. Note that the mobile station 10 may hold the position information of each of the base station A, base station B, and base station C in advance, or may receive the position information of each base station A, base station B, and base station C from the base station A, base station B, and base station C. You may receive it.

The mobile station 10 determines the straight-line distance (baseline The reference station with the shortest length) is selected as the reference station to be used for carrier phase positioning.

In the example of FIG. 1, reference station B is selected. However, for example, when the reference station B is a fixed station, if the reception condition of the satellite signal is not good, the accuracy of the relative position obtained as a result of the carrier phase positioning calculation (baseline length analysis) by the mobile station 10 may be Deteriorate. Further, for example, when the reference station B is a mobile object, while the reference station B is traveling in an environment where satellite signals cannot be received well (e.g., an urban canyon environment), the mobile station 10 performs carrier phase positioning calculation convergence (Fix). ) solution may not be obtained, and only a float solution or a differential solution (DGNSS solution) may be obtained.

In the future, in applications such as automatic driving, it is expected that both reference stations (fixed stations) and reference stations (mobile objects) will be arranged at a higher density. In that case, a plurality of reference stations (candidate reference stations) may exist within the maximum allowable baseline length (eg, 10 km). Furthermore, a reference station in an urban canyon reception environment where many buildings exist does not necessarily ensure a good reception environment similar to an open sky. In such a situation, there is a possibility that an appropriate reference station cannot be selected simply on the condition that the baseline length is the shortest. In other words, even though there is a more suitable reference station available, there is a possibility that the reference station cannot be selected.

Therefore, in the present embodiment, in addition to the baseline length, a reference station to be used by the mobile station 10 for carrier phase positioning is appropriately selected based on information other than the baseline length.

With reference to FIG. 2, an example of the configuration and operation of the present embodiment when the mobile station 10 and reference stations A to C are present will be described. As shown in FIG. 2, this embodiment includes a reference station selection device 100. The reference station selection device 100 is capable of communicating with each reference station and the mobile station 10 via a communication network such as a mobile network or the Internet.

The reference station selection device 100 collects reference station information from each reference station in real time (S1 to S3). Collecting in real time means collecting information at that point in time, for example, at a predetermined period or at a timing when there is a change in information. Note that information that does not change dynamically, such as position information of a reference station (fixed station), may be collected at long intervals (for example, once a day) in addition to being collected in real time. The collected information is stored in the data storage unit 130 in the reference station selection device 100, which will be described later.

The information to be collected is information used to make decisions for selecting a reference station, and specific examples of the information will be described later.

In S4, the mobile station 10 transmits a "selection request" to the reference station selection device 100, requesting that the reference station most suitable for the mobile station 10 be selected for use in carrier phase positioning. This selection request includes information about the mobile station 10 (eg, location information of the mobile station 10, satellite signal reception status of the mobile station 10, etc.) used to determine reference station selection. Note that the information used for determining reference station selection by the mobile station 10 may be transmitted to the reference station selection device 100 at a timing other than the timing of S4 (eg, periodic timing).

The reference station selection device 100 selects the most suitable reference station for the mobile station 10 at that time based on the information collected from each reference station in S1 to S3 and the information included in the selection request received in S4, and selects the selection result. is transmitted to the mobile station 10 (S5). The mobile station 10 executes a carrier phase positioning calculation using the reference station notified as the selection result.

The reference station selection device 100 selects the optimal reference station for the mobile station 10 using the baseline length and other information. The configuration and operation example for this purpose will be described below. Although the "modified example" will be explained at the end, the example explained before the "modified example" is referred to as the "basic example."

(Example of configuration of reference station selection device 100)
FIG. 3 shows an example of the functional configuration of the reference station selection device 100. As shown in FIG. 3, the reference station selection device 100 includes an information acquisition section 110, a selection section 120, a data storage section 130, and an information provision section 140.

The information acquisition unit 110 acquires information transmitted from each reference station and also acquires information transmitted from the mobile station 10. These acquired pieces of information are stored in the data storage unit 130.

The selection unit 120 reads information from the data storage unit 130, and uses the read information to select the most suitable reference station for the mobile station 10 at that time. The information providing unit 140 transmits information on the reference station selected by the selecting unit 120 to the mobile station 10.

Note that when the mobile station 10 performs carrier phase positioning calculation using the selected reference station, the mobile station 10 may receive observation data and position information of the selected reference station directly from the reference station, or may receive it directly from the reference station. It may be received from the selection device 100 or may be received from a server on a network other than the reference station selection device 100.

(Example of operation of reference station selection device)
Next, an example of the operation of the reference station selection device 100 will be described in accordance with the procedure of the flowchart in FIG. 4. It is assumed that the data storage unit 130 of the reference station selection device 100 has already stored information on each reference station necessary for selection of a reference station. The reference station information includes reference station position information and reference station information necessary for selecting a reference station.

<S101>
In S101, the information acquisition unit 110 of the reference station selection device 100 receives a reference station selection request from the mobile station 10. The selection request includes at least the position information of the mobile station 10 and information about the mobile station 10 (information on the satellite signal reception state, etc.) necessary for selecting the reference station. Note that the information acquisition unit 110 may acquire the location information of the mobile station 10 from a mobile network to which the mobile station 10 is connected.

<S102>
In S102, the selection unit 120 calculates the baseline length between the mobile station 10 and each reference station using the location information of the mobile station 10 and the location information of a plurality of reference stations around the mobile station 10, and calculates the baseline length between the mobile station 10 and each reference station. A reference station whose length is less than or equal to a threshold value is extracted. In this embodiment, it is assumed that a plurality of reference stations are extracted here. The threshold value is, for example, 10 km.

<S103-S106>
In S103, one or more reference stations are selected from among the plurality of reference stations extracted in S102 based on criteria described later. In S104, it is determined whether two or more reference stations have been selected. If two or more reference stations are selected, S104 becomes Yes and the process proceeds to S105, and if one reference station is selected, the process proceeds to S106.

In S105, the selection unit 120 selects the reference station with the shortest baseline length from among the two or more reference stations. In S106, the information providing unit 140 notifies the mobile station 10 of information on the selected one reference station.

(Example of criteria for selecting reference station)
An example of the criteria (judgment method) for selecting a reference station by the selection unit 120 will be described below. For convenience, an example of selecting a reference station based on individual criteria will be described below, followed by an example of combinations of criteria such as condition selection and scoring. Information used in each of the following determination methods is collected from each reference station and mobile station 10 and stored in the data storage section 130, and the selection section 120 selects a reference station based on the information read from the data storage section 130. I do.

<(Example 1) Baseline length>
In Example 1, the selection unit 120 selects a reference station to be used for carrier phase positioning of the mobile station 10 based on the straight-line distance (baseline length) between the mobile station 10 and the reference station.

In this embodiment, as described above, the baseline length is used when narrowing down the candidates for the reference station, such as by setting a threshold value for the baseline length and selecting one or more reference stations within the range of the threshold value. In addition, when multiple reference stations are selected based on criteria other than baseline length, the baseline length may be changed when ultimately determining the reference station, such as selecting the reference station with the shortest baseline length from among the multiple reference stations. You can also use

<(Example 2) Position accuracy>
The mobile station 10 calculates the baseline length and obtains its own absolute position by performing a carrier phase positioning calculation using its own observation data, the observation data from the selected reference station, and the position information of the selected reference station. . The location information of the reference station is notified to the mobile station 10 from the reference station. Alternatively, the reference station selection device 100 may receive position information from the reference station and notify the mobile station 10 of it, or the mobile station 10 may receive the location information of the reference station from a server on a network other than the reference station selection device 100. You may also receive information.

If the positional accuracy of the reference station used in the carrier phase positioning calculation (baseline length analysis) of the mobile station 10 is low, the accuracy of the resulting positioning solution of the mobile station 10 will also be low.

Therefore, in Example 2, the selection unit 120 selects a reference station to be used for carrier phase positioning of the mobile station 10 based on the positional accuracy of the reference station.

For example, each reference station maintains its own position accuracy index value (accuracy index value) and notifies the reference station selection device 100 of the accuracy index value, and the reference station selection device 100 stores the accuracy index value in the data storage unit 130. Suppose that it is held at .

As an example, assume that the accuracy index value takes a value from 0 to 100, and the larger the value, the better (higher) the accuracy. Assume that there are four reference stations, reference station A, reference station B, reference station C, and reference station D, as reference station candidates used by the mobile station 10, and the accuracy index values of each are as follows: reference station A = 90, reference station B = 85, reference station C = 75, and the reference station D=60.

For example, the selection unit 120 selects the reference station A as the reference station with the best (highest) positional accuracy. Alternatively, a threshold value of the accuracy index value may be set, and a reference station whose accuracy is equal to or higher than the threshold value may be selected. As an example, if the threshold value=80, the selection unit 120 selects the reference station A and the reference station B.

Regarding the setting of the above-mentioned accuracy index value, for example, when the reference station is an electronic reference point, a high value such as accuracy index value = 100 is set. In addition, if the reference station (reference station other than the electronic reference point) is a fixed station and the electronic reference point is used as a reference station to obtain its own position information based on a fix solution based on carrier phase positioning calculation, the electronic reference point Since the traceability to the point is high, a high value such as accuracy index value=90 is set, for example. On the other hand, if a convergence (fix) solution is not obtained for the same reference station and only a float solution is obtained, a slightly lower value such as accuracy index value = 70 is set. In this way, the accuracy index value is not constant over time, but may be set dynamically.

Also, for example, even if the reference station (reference station other than the electronic reference point) is a fixed station, it may be a reference station that uses the electronic reference point as a reference station and obtains its own position information by performing carrier phase positioning calculations. If the reference station obtains its own position information by performing carrier phase positioning calculations using observation data, the traceability to the electronic reference point will be lower than in the above case, so for example, accuracy index value = 80. A value such as this is set.

Further, for example, when the reference station is a mobile body, a lower value is usually set as the accuracy index value than when the reference station is a fixed station. However, if a mobile object is equipped with an absolute positioning unit (GNSS carrier wave phase positioning means) and a high-precision relative positioning unit (IMU (Inertial Measurement Unit), LiDAR (Light Detection and Ranging), etc.), and these are linked If highly accurate positioning can be performed at all times by providing a complex positioning mechanism that is operated in a complex manner, the accuracy index value is set to a higher value that takes this into consideration.

The accuracy index value described above may be set manually by the owner of the reference station or the service provider of the reference station selection device 100, or by programming the rules as shown in the example above. Alternatively, the reference station itself or the reference station selection device 100 may automatically set the accuracy index value. Further, as described above, the accuracy index value may be dynamically set.

When selecting a reference station based on the positional accuracy of the reference station, using the accuracy index value as described above is an example. For example, the higher the traceability to the electronic reference point (the number of hops to the electronic reference point, etc.), the higher the traceability to the electronic reference point (how many hops to the electronic reference point, etc.) The reference station may be selected by assuming that the smaller the value is, the better the position accuracy is.

Regarding how to understand the traceability of a certain reference station to an electronic reference point (how many hops away it is to an electronic reference point), for example, the information acquisition unit 110 can identify the position of each reference station from each reference station. This can be determined by receiving information about the reference station used for carrier phase positioning. For example, if we know that base station A uses an electronic reference point for carrier phase positioning, and that base station B uses reference station A for carrier phase positioning, then the number of hops to the electronic reference point of base station A is 1. It can be seen that the value of reference station B is 2.

<(Example 3) Satellite signal reception status>
Basically, the higher the degree of coincidence between the satellite signal received by the mobile station 10 and the satellite signal received by the reference station, the higher the carrier wave phase by the mobile station 10 is. It is expected that the precision and convergence (fix) rate of positioning calculations will increase. Example 3 is an example based on this viewpoint, and Examples 3-1 to 3-3 will be explained below. Note that Examples 3-1, 3-2, and 3-3 may be used alone, or a plurality of them (including all of them) may be used in combination.

<Example 3-1>
In Example 3-1, the selection unit 120 selects the carrier wave phase of the mobile station 10 based on the degree of coincidence between the satellite signal that is well received by the mobile station 10 and the satellite signal that is well received by the reference station. Select the reference station used for positioning. Note that "receiving well" means, for example, the reception quality of the satellite signal (e.g. CNR (Carrier-to-Noise Ratio) or SNR (Signal-to-Noise Ratio). It can be determined that the ratio)) is equal to or greater than a predetermined threshold value. Hereinafter, as an example, CNR will be used as reception quality.

For example, the mobile station 10 and each reference station each transmit identification information (code) of a received satellite signal and its CNR to the reference station selection device 100 as real-time information. The selection unit 120 selects a reference station based on the information.

As an example, assume that there are two candidate reference stations, reference station X and reference station Y, and that the satellite signals received by reference station , S5), (reference station Y=S3, S4, S5, S6, S7, S8), (mobile station 10=S1, S2, S5, S6, S7, S8).

In this case, between the reference station Select reference station Y.

In the above example, a satellite signal with a high CNR is used, but the reason for this is that the satellite signal with a high CNR may be a visible satellite signal (a signal that arrives directly from a GNSS satellite without being obstructed by buildings, etc.). This is because it can be estimated that the

Instead of using CNR, position information of each reference station, position information of the mobile station 10 (position information based on code positioning may be used), orbit information of each GNSS satellite, and structures around each reference station and mobile station are used. Based on the geospatial information (dynamic map, 3D building map, sky image information, etc.) of The reference station may also be selected by

In addition, CNR is used for the mobile station 10 and the reference station (mobile object), and for the reference station (fixed station), the position information of each reference station, the orbit information of each GNSS satellite, and the geospatial information of the structures around the reference station are used. (dynamic map, three-dimensional building map, sky image information, etc.) may be used to calculate visible satellite signals at the current time. Since it is thought that changes over time in the geospatial information of structures around the reference station (fixed station) are small, elevation angle threshold information for each direction of structures around the GNSS antenna of the reference station (fixed station) is displayed on the sky plot. If the (azimuth mask) is held in advance, visible satellite signals can be determined with less processing.

<Example 3-2>
In Example 3-2, the selection unit 120 selects the DOP (Dilution of A reference station is selected based on the Precision) value. The DOP value is a value that indexes the placement state of satellites, and indicates a tendency that the smaller the value, the higher the expected positioning accuracy.

The "satellite signal that is well received" in Example 3-2 may be a satellite signal selected based on reception quality (CNR, SNR, etc.), or may be a satellite signal that is selected based on reception quality (CNR, SNR, etc.), or may be a satellite signal that is selected based on reception quality (CNR, SNR, etc.), It may be a visible satellite signal obtained by calculation from orbit information of each GNSS satellite, mobile station, geospatial information of structures around each reference station, etc.

As an example, suppose there are two candidate reference stations, reference station X and reference station Y, and the satellite signals that are well received by reference station X, reference station Y, and mobile station 10 are (reference station , (reference station Y=S3, S5, S6, S7, S8), (mobile station 10=S1, S2, S3, S4, S5, S6, S7, S8).

At this time, the satellite signals that match between the reference station X and the mobile station 10 are S1, S2, S4, and S5. The satellite signals that match between the reference station Y and the mobile station 10 are S3, S5, S6, S7, and S8. If the DOP values at S1, S2, S4, and S5 are 2, and the DOP values at S3, S5, S6, S7, and S8 are 3, the selection unit 120 selects one of the reference stations X and Y. Select reference station X.

<Example 3-3>
If the degree of coincidence between the satellite types and frequency bands of the satellite signals used is high, it can be expected that the accuracy of the carrier phase positioning solution of the mobile station 10 will be high. Therefore, in Example 3-3, the selection unit 120 selects the mobile station based on the degree of coincidence between the satellite type and frequency band of the satellite signal used by the mobile station 10 and the satellite type and frequency band of the satellite signal used by each reference station. A reference station to be used for carrier phase positioning of station 10 is selected.

As an example, assume that there are two candidate reference stations, reference station _{, F3 ) , ( base station _ _ _ _ _} (Mobile station 10=A _F1 , A _F2 , B _F1 , B _F2 , C _F1 ). Note that "A _F1 " means that frequency band F1 is used for satellite type A. The same applies to others.

In this case, between the reference station Select reference station Y from Y.

<(Example 4) Reliability>
It is preferable that the reliability of the reference station used by the mobile station 10 to perform carrier phase positioning is higher than that of low reliability from the viewpoint of stably maintaining high positioning accuracy.

As indicators of reliability, past performance of the base station's availability (operation rate), quality of the connected network (link status, packet loss rate, propagation delay, etc.), reception status of the base station's interference signal, and convergence (Fix) are used as indicators of reliability. ) rate, cycle slip rate, convergence (Fix) state, etc. Note that these are just examples, and indicators other than these may be used as indicators of reliability.

Each of these pieces of information is transmitted from each reference station to the reference station selection device 100 as real-time information. However, information with low real-time characteristics (for example, availability results) may be transmitted to the reference station selection device 100 from, for example, a server that manages each reference station. The reference station selection device 100 selects the most reliable reference station from among the plurality of candidate reference stations. Alternatively, the reference station selection device 100 selects one or more reference stations whose reliability is higher than a predetermined threshold.

Specific examples of the above indicators will be explained below. The availability performance, network quality (link status, packet loss rate, propagation delay, etc.), interference signal reception status, convergence (Fix) rate, cycle slip rate, convergence (Fix) status, etc. explained below are as follows: Each of them may be used alone, or a plurality of them (including all of them) may be combined to obtain one index value of reliability.

<Availability track record>
The availability of a reference station is the probability of being able to receive service from that reference station at a given time. In this example, receiving a service means being able to obtain observation data and position information used by the mobile station 10 from the reference station. For example, if the reference station is old and frequently breaks down, availability will be low. Furthermore, even if the equipment is somewhat old, if it has a redundant configuration such as hot standby, the decline in availability can be suppressed.

<Network quality>
The "network" in network quality refers to a network to which a reference station is connected, and observation data and position information obtained at the reference station are transmitted to the mobile station 10 or the reference station selection device 100 via the network. If the quality of the network is low (e.g., links are disconnected irregularly, packets are frequently lost, propagation delays are large), the mobile station 10 may not be able to receive observation data and position information of the reference station. arise. Therefore, the higher the quality of the network, the better.

<Reception status of interference signal>
For example, if a base station of a mobile network exists near a reference station, a downlink signal from the base station may regularly affect satellite signals received by the reference station as an interference signal. Various other sources of interference signals are also assumed. When the reference station receives an interference signal, the reception quality of the satellite signal received by the reference station deteriorates, and the phase of the carrier wave of the satellite signal may not be accurately observed. Therefore, it is better that the intensity of the interference signal is smaller. Note that the influence of the strength of the interference signal can be reduced when receiving the satellite signal by means such as implementing a frequency filter that reduces signals outside the band of the satellite signal.

<Convergence (Fix) rate>
The convergence (Fix) rate is the ratio of time in the convergence (Fix) state during a certain period in the past. The convergence (Fix) rate depends on the satellite signal reception status of the reference station (and the reference station used (referenced) by the reference station for carrier phase positioning calculations) and the carrier phase positioning performance of the reference station. If the convergence (Fix) rate is high, it is assumed that the reference station is in a relatively good reception environment (a reception environment with a high open space ratio, close to an open sky reception environment), and that the carrier phase positioning performance of the reference station is high. , it is expected that the convergence (Fix) rate will be high in the future as well. Therefore, when the convergence (Fix) rate is high, the reliability of the reference station is high. The higher the convergence (Fix) rate, the better.

<Cycle slip rate>
A cycle slip is a cycle slip that occurs when an instantaneous change in transmission path length due to a momentary interruption or multipath occurs in satellite signal reception during satellite signal observation by a reference station, and the satellite signal reception device temporarily loses synchronization with the carrier wave phase of the satellite signal. This is because the phase data is interrupted, causing a shift (jump) in the phase data. Cycle slip rate is the rate at which cycle slips occur. If the cycle slip rate of a certain reference station is high, the reliability of that reference station is low. The lower the cycle slip rate, the better.

<Convergence (Fix) state>
At the reference station, when a fix solution for carrier phase positioning with the reference station (electronic reference point, etc.) is not obtained and only a float solution is obtained, the ambiguity of the integer value bias of the wave number is caused. This is an unresolved state, and the position accuracy obtained in that state is estimated to be low. Therefore, the convergence (Fix) state indicating whether a convergence (Fix) solution has been obtained is an indicator of the reliability of the accuracy of the reference station. Note that, as described above, information on the convergence (Fix) state may be used as an index of position accuracy.

<Example of indicator usage>
For each of the above-mentioned indicators, each value or state itself may be used as a condition for selecting a reference station, or it may be converted into a unified index value (referred to as a reliability index value here) and used for selecting a reference station. Good too. Conversion from each index value to a unified reliability index value may be performed manually or automatically by determining rules. Alternatively, one reliability index value (metrics) may be derived by combining a plurality of index values. For example, the reliability index value may be "Availability x A + Packet loss rate x B + Interference signal strength x C + Cycle slip rate x D" (A, B, C, and D are predetermined constants).

As an example, assume that the reliability index value takes a value from 0 to 100, and the larger the value, the higher the reliability. Assume that there are four reference stations, reference station A, reference station B, reference station C, and reference station D, as reference station candidates used by the mobile station 10, and the respective reliability index values are: reference station A = 99, reference station B = 85, and reference station C. =75, and reference station D=50.

For example, the selection unit 120 selects the reference station A as the reference station with the highest reliability. Alternatively, a threshold value of the reliability index value may be set, and a reference station whose accuracy is equal to or higher than the threshold value may be selected. As an example, if the threshold value=80, the selection unit 120 selects the reference station A and the reference station B.

(Example of using a combination of criteria for standard station selection)
The reference station selection device 100 may narrow down the reference stations based on at least each condition based on the criteria of Examples 1 to 4 described above. Further, by combining at least any one or more (or all) of the judgment criteria in Examples 1 to 4 described above and scoring it, the mobile station 10 can select the carrier wave phase from among the plurality of reference stations whose baseline length is equal to or less than the threshold value. It is also possible to select a reference station to be used for positioning.

For example, the score S is calculated as "S = Baseline length index value x α + Position accuracy index value x β + Satellite signal reception status index value x δ + Reliability index value x γ" (α, β, δ, γ are predetermined constants). Calculate and select the reference station with the largest S. α, β, δ, and γ are determined in advance through experiments, for example. Note that one or more constants of α, β, δ, and γ may be zero. For example, the baseline length may be used only to initially narrow down the reference station candidates, and α may be set to 0 in the above score calculation. That is, the baseline length index value may be excluded from the calculation of the score.

Furthermore, the combination of criteria used to select a reference station may be changed depending on the use case. In addition, for each item (e.g., reliability) used to calculate the score S, it is determined which specific indicators to use (e.g., whether to use the convergence (Fix) state) depending on the use case. It's okay. Use cases 1 to 3 will be described below as examples of use cases.

(Use case 1)
Use case 1 is an example where the reference station to be selected is a mobile object. This moving object is, for example, a vehicle. In this case, for example, as shown in FIG. 5, a reference station (mobile object) 20 and a reference station (mobile object) 30 are used as reference station candidates (reference stations whose baseline length is equal to or less than a threshold value) used by the mobile station 10 for carrier phase positioning. , is traveling near the mobile station 10 in the direction shown. Similarly to the case shown in FIG. 2, in this case as well, the information necessary for selecting a reference station is transmitted from the mobile station 10, the reference station (mobile object) 20, and the reference station (mobile object) 30 to the reference station selection device 100. Suppose that

In this case, the selection unit 120 of the reference station selection device 100 selects the reference station (mobile ) 20 and the reference station (mobile object) 30, and select the reference station (mobile object) with higher S. However, in use case 1, regarding "reliability," if the reference station (mobile) has obtained a fixed solution by carrier phase positioning using another reference station A (fixed station), The score for the "gender index value x γ" section is set to be high.

Regarding the "position accuracy index value," the reference station (mobile object) is equipped with a relative positioning section (IMU, LiDAR, etc.) in addition to an absolute positioning section, and its performance (accuracy) is high and the absolute If the positioning accuracy is high when relative positioning is performed based on position information, the score of "position accuracy index value x β" will be high. Since the score value of a reference station (mobile object) changes over time, the reference station can be dynamically selected based on the score after setting a protection time as appropriate.

(Use case 2)
Use case 2 is a use case in which the mobile station 10 is a drone (flying object), and the mobile station 10 is controlled to stop (hover) in the air.

Even in this case, the selection unit 120 of the reference station selection device 100 selects the above-mentioned "S = baseline length index value x α + position accuracy index value x β + satellite signal reception state index value x δ + reliability index value x γ", The calculation is performed for each of a plurality of reference stations for which S is less than or equal to the threshold value, and the reference station with the highest S is selected. However, in use case 2, the accuracy of the absolute position of the mobile station 10 is not important, but it is important that it is stationary relative to something fixed. Therefore, regarding the "position accuracy index value", the score S is higher when the reliability (network quality, etc.) of the candidate reference station (fixed station) is higher than whether the reference station is traceable to the electronic reference point.

(Use case 3)
Use case 3 is a use case for monitoring displacement (tilting, subsidence, deformation, etc.) of a structure such as a bridge. In this use case, sensors (herein referred to as "mobile station 10") are installed at one or more locations on the structure to be monitored, and the results of carrier phase positioning of the mobile station 10 are used to Monitor displacement.

Even in this case, the selection unit 120 of the reference station selection device 100 selects the above-mentioned "S = baseline length index value x α + position accuracy index value x β + satellite signal reception state index value x δ + reliability index value x γ", The calculation is performed for each of a plurality of reference stations for which S is less than or equal to the threshold value, and the reference station with the highest S is selected. However, in use case 3, from the perspective of "location accuracy index value", if the reference station is a mobile object, the score of "location accuracy index value x β" will be very low, and in reality, the reference station that is a mobile object is a candidate. removed from On the other hand, a reference station (fixed station) with high reliability and high traceability to an electronic reference point is more likely to be selected.

In addition, since real-time performance is not important, for example, if there is a reference station whose position accuracy and reliability are higher only during a certain time of the day than the position accuracy and reliability of other reference stations at any time of the day. , carrier phase positioning may be performed using that reference station during that time period.

(Modified example)
In the basic example described above, the reference station selection device 100 is provided separately from the mobile station 10, as shown in FIG. However, this is just an example. The function of the reference station selection device 100 may be included in the mobile station 10. This form will be explained as a modified example.

As shown in FIG. 6, in the modified example, the mobile station 10 collects information necessary for base station selection from each base station, and selects the base station that it uses for carrier phase positioning based on the collected information. do. The information to be collected and the method for selecting a reference station are the same as the information collected and the selection method implemented by the reference station selection device 100 in the basic example. In addition, in a modified example, since the mobile station 10 selects a reference station, the mobile station 10 may be referred to as a "reference station selection device."

FIG. 7 shows a functional configuration diagram of the mobile station 10 in a modified example. As shown in FIG. 7, the mobile station 10 in the modified example includes an information acquisition section 11, a selection section 12, a data storage section 13, an absolute positioning section 14, a relative positioning section 15, a positioning control section 16, and an output section 17. have

The information acquisition unit 11 acquires information (information necessary for selecting a reference station) transmitted from each reference station. The acquired information is stored in the data storage section 13. The data storage unit 13 also stores information necessary for selecting a reference station on the mobile station 10 side. The information acquisition unit 11 also receives observation data and position information from the selected reference station. The observation data and position information are used for carrier phase positioning calculation by the mobile station 10.

The selection unit 12 reads information from the data storage unit 13 and selects the optimal reference station for the mobile station 10 using the read information. The operation of the selection section 12 is the same as the operation of the selection section 120 of the reference station selection device 100 in the basic example.

The absolute positioning unit 14 receives the satellite signal and performs code positioning or carrier phase positioning. The relative position measuring unit 15 is a vehicle speed pulse measuring device, an IMU, an on-vehicle camera, LiDAR, a GNSS Doppler shift measuring device, or the like. A vehicle speed pulse measuring device determines the speed of the vehicle, that is, the distance traveled per unit time. Three-dimensional angular velocity and acceleration are determined by the three-axis gyro and three-direction accelerometer mounted on the IMU. The relative position of the vehicle can be determined from the movement of objects in image data captured by an on-vehicle camera. With LiDAR, by irradiating a target object with scanning laser light and observing the scattered and reflected light, it is possible to measure the distance to the target object and determine the relative position of the vehicle. With GNSS Doppler shift, relative displacement in position can be determined by temporally integrating vehicle speed obtained by measuring changes in carrier wave frequency.

The relative positioning unit 15 may be a plurality of positioning means such as a vehicle speed pulse measuring device, an IMU, an on-vehicle camera, LiDAR, a GNSS Doppler shift measuring device, or a single positioning means. good. When the relative positioning unit 15 has a plurality of positioning means, it may be provided with a mechanism for selecting and outputting the most accurate positioning result from among the positioning results obtained by each of the plurality of positioning means. However, a mechanism may be provided in which all or part of the positioning results obtained by each are coupled using a Kalman filter or the like and output.

Further, the relative position positioning section 15 is supplied with a high precision clock signal obtained by time synchronization with the GNSS signal from the absolute position positioning section 14 . Even when the high-precision clock signal is interrupted, the relative positioning unit 15 can maintain the accuracy of the clock signal through holdover (free-running operation of the oscillator) without relying on time synchronization with the GNSS signal.

The positioning control unit 16 switches the positioning means to the relative positioning unit 15 and performs positioning when the absolute positioning unit 14 is unable to obtain a fixed solution, for example in an urban canyon environment. Execute ongoing control.

The output unit 17 outputs the current position, which is the positioning solution output from the positioning control unit 16, to the outside of the device. The current position is expressed in three-dimensional coordinates (x, y, z), but the output information may be the three-dimensional coordinates themselves in a geographic coordinate system or a projected coordinate system, or may be other information. It's okay. For example, a control signal may be output to the control unit of the autonomous vehicle, or image information showing the position on a map may be output.

The mobile station 10 may be a single physically integrated device, or may be a device in which several functional units are physically separated and the separated functional units are connected via a network. It's okay.

Furthermore, the mobile station 10 may include all the functions shown in FIG. 7, or some functions may be provided on the network (for example, on the cloud) and the remaining functions may be installed and used in the mobile station 10. It's okay.

For example, by outputting observation data (also called raw data) from a GNSS carrier phase positioning receiver provided in the mobile station 10 and transmitting the observation data to a carrier phase positioning calculation processing function unit provided on the cloud, The carrier phase positioning calculation may be performed on the cloud. In this case, the positioning calculation result is returned from the carrier phase positioning calculation processing function unit on the cloud to the positioning control unit 16 via the information acquisition unit 11.

(Hardware configuration example)
FIG. 8 is a diagram showing an example of the hardware configuration of a computer that can be used as the reference station selection device 100 or the information acquisition unit 11 and selection unit 12 of the mobile station 10 in the embodiment of the present invention. The computer in FIG. 8 includes a drive device 1000, an auxiliary storage device 1002, a memory device 1003, a CPU 1004, an interface device 1005, a display device 1006, an input device 1007, an output device 1008, etc., which are interconnected by a bus B. .

A program for realizing processing by the computer is provided, for example, by a recording medium 1001 such as a CD-ROM or a memory card. When the recording medium 1001 storing the program is set in the drive device 1000, the program is installed from the recording medium 1001 to the auxiliary storage device 1002 via the drive device 1000. However, the program does not necessarily need to be installed from the recording medium 1001, and may be downloaded from another computer via a network. The auxiliary storage device 1002 stores installed programs as well as necessary files, data, and the like.

The memory device 1003 reads the program from the auxiliary storage device 1002 and stores it when there is an instruction to start the program. The CPU 1004 implements functions related to the information acquisition unit 11, selection unit 12, etc. of the reference station selection device 100 or the mobile station 10, according to a program stored in the memory device 1003. The interface device 1005 is used as an interface for connecting to a network. A display device 1006 displays a GUI (Graphical User Interface) or the like based on a program. The input device 1007 is composed of a keyboard, a mouse, buttons, a touch panel, or the like, and is used to input various operation instructions. An output device 1008 outputs the calculation result. Note that the display device 1006 is an example of an output unit.

(Effects of embodiment)
As described above, according to the embodiments of the present invention, a mobile station dynamically performs carrier phase positioning using an optimal reference station, thereby achieving stable and high positioning performance at low cost. It becomes possible.

(Summary of embodiments)
In this embodiment, at least the reference station selection device, reference station selection method, and program described in the following sections are provided.
(Section 1)
A reference station selection device that selects a reference station used for carrier phase positioning in a mobile station from a plurality of geographically distributed reference stations,
an information acquisition unit that acquires information of each reference station in the plurality of reference stations;
Select a reference station to be used for carrier phase positioning in the mobile station based on one or more information including information other than the baseline length from among the one or more reference stations whose baseline length is equal to or less than a predetermined threshold among the plurality of reference stations. A reference station selection device comprising: a selection section for selecting;
(Section 2)
The one or more pieces of information are at least one or more of the following: information regarding the positional accuracy of the reference station, information regarding the reception status of satellite signals at the reference station, and information regarding the reliability of the reference station. The reference station selection device according to item 1.
(Section 3)
The reference station selection device according to claim 1 or 2, wherein the selection unit calculates a score from the one or more pieces of information, and selects a reference station to be used for carrier phase positioning in the mobile station based on the score.
(Section 4)
A reference station selection method executed by a reference station selection device that selects a reference station to be used for carrier phase positioning in a mobile station from a plurality of geographically distributed reference stations, the method comprising:
an information acquisition step of acquiring information of each reference station among the plurality of reference stations;
Select a reference station to be used for carrier phase positioning in the mobile station based on one or more information including information other than the baseline length from among the one or more reference stations whose baseline length is equal to or less than a predetermined threshold among the plurality of reference stations. A reference station selection method comprising a selection step of selecting.
(Section 5)
A program for causing a computer to function as each part of the reference station selection device according to any one of items 1 to 3.

Although the present embodiment has been described above, the present invention is not limited to such specific embodiment, and various modifications and changes can be made within the scope of the gist of the present invention as described in the claims. It is possible.

11 Information acquisition section 12 Selection section 13 Data storage section 14 Absolute positioning section 15 Relative positioning section 16 Positioning control section 17 Output section 100 Reference station selection device 110 Information acquisition section 120 Selection section 130 Data storage section 140 Information provision section 1000 Drive device 1001 Recording medium 1002 Auxiliary storage device 1003 Memory device 1004 CPU
1005 Interface device 1006 Display device 1007 Input device 1008 Output device

Claims (4)

A reference station selection device that selects a reference station used for carrier phase positioning in a mobile station from a plurality of geographically distributed reference stations,
The plurality of reference stations are fixed stations or mobile bodies,
an information acquisition unit that acquires information of each reference station in the plurality of reference stations;
Among the one or more reference stations whose baseline length is equal to or less than a predetermined threshold among the plurality of reference stations, at least information regarding the position accuracy index of the reference station, information regarding the comparison result of the reception state of satellite signals of the mobile station and the reference station, and a selection unit that selects a reference station to be used for carrier phase positioning in the mobile station based on one or more of the information regarding the reliability index of the reference station. The reference station selection device according to claim 1, wherein the selection unit calculates a score from the one piece of information or the plurality of pieces of information, and selects a reference station to be used for carrier phase positioning in the mobile station based on the score. A reference station selection method executed by a reference station selection device that selects a reference station to be used for carrier phase positioning in a mobile station from a plurality of geographically distributed reference stations, the method comprising:
The plurality of reference stations are fixed stations or mobile bodies,
an information acquisition step of acquiring information of each reference station among the plurality of reference stations;
Among the one or more reference stations whose baseline length is equal to or less than a predetermined threshold among the plurality of reference stations, at least information regarding the position accuracy index of the reference station, information regarding the comparison result of the reception state of satellite signals of the mobile station and the reference station, and a selection step of selecting a reference station to be used for carrier phase positioning in the mobile station based on one or more of the information regarding the reliability index of the reference station. A program for causing a computer to function as each part of the reference station selection device according to claim 1 or 2.

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