JP6431467B2 - Displacement monitoring system and displacement monitoring method - Google Patents

Description

  The present invention relates to a system and a displacement monitoring method for monitoring the displacement of an observation point using a satellite navigation system (GNSS: Global Navigation Satellite System) such as GPS (Global Positioning System).

  Conventionally, various monitoring technologies have been proposed to predict in advance disasters caused by the collapse of a ground with slopes or landslides, and to prevent damage in advance, and in recent years, GPS reception that becomes observation stations at multiple locations in the monitored area There is known a displacement monitoring system in which a machine is installed, a positional shift relative to a reference station is detected in time series on the monitoring center side, and an abnormality of the ground is monitored.

  Patent Documents 1 and 2 describe a static positioning method using a base line vector between each receiver obtained from a positioning signal received from a satellite, and a real-time kinema using a base line vector between receivers of an observation station and a reference station. A displacement monitoring system has been proposed in which a tick (RTK: Real Time kinematic) positioning method is selectively used according to the ground fluctuation situation to perform positioning in the temporal direction. More specifically, when the ground fluctuation is small, the static positioning method with high accuracy is used although it takes time to measure. When the fluctuation is large, measurement is possible in a short time considering the responsiveness although the accuracy is inferior. The RTK positioning method is used.

JP 2004-045158 A JP 2004-144623 A

  According to Patent Document 1, the static positioning method is generally several millimeters (1 hour measurement interval) according to Patent Document 1, when the L1 wave (1575.72 MHz carrier) is used as the positioning radio wave. Compared to the high accuracy of 1 cm, it is set to several cm (measurement interval of 1 second). Therefore, when it is necessary to repeat measurement at short time intervals, such as when the ground fluctuation exceeds a threshold value, there is a certain limitation in application in the positioning accuracy of the current RTK positioning method.

  In addition, observation data such as pseudorange and carrier phase and navigation message data necessary for positioning require 400 to 800 bytes in the case of the GPS L1C / A code most used for civilian use. As in Patent Documents 1 and 2, when the number of observation stations increases, in the mode of transmitting these pieces of information to the monitoring center, the amount of data increases in proportion to the number of stations, and transmission takes a long time. At the same time, the burden of positioning calculation processing at the monitoring center increases.

  The present invention provides a displacement monitoring system and method for obtaining positioning results from a plurality of observation stations with a required accuracy while reducing the burden on data processing and data transmission in a short time.

  A displacement monitoring system according to the present invention includes a reference station that is installed at a predetermined position and receives a positioning signal broadcast from each satellite, and an observation station that is installed within a monitoring target range and receives a positioning signal from the satellite. A monitoring unit that monitors positional displacements of the plurality of observation stations, and the reference station includes reference side communication means for transmitting the positioning signals received by the own station to the plurality of observation stations, and the observation station Receives a positioning calculation means for obtaining a positioning result of the local station from the positioning signal received by the local station and the positioning signal received by the reference station by kinematic baseline analysis, and a positioning signal of the reference station. And observation side communication means for transmitting a station positioning result to the monitoring unit.

  Further, the displacement monitoring method according to the present invention includes a reference station that is installed at a predetermined position and receives a positioning signal broadcast from each satellite, and a plurality of positioning stations that are installed within a monitoring target range and receive a positioning signal from the satellite. An observation station, and a monitoring unit that monitors positional displacement of the observation station, the process of transmitting the positioning signal received by the reference station to the plurality of observation stations, and the positioning received by each observation station A step of obtaining a positioning result of each observation station by kinematic baseline analysis in the observation station from a signal and a positioning signal transmitted from the reference station; and a step of transmitting the positioning result of each observation station to the monitoring unit; Is included.

  According to these inventions, the positioning signal received at the reference station is transmitted to the observation station, and each of the positioning signal received from the observation station and the positioning signal transmitted from the reference station is analyzed by kinematic baseline analysis at the observation station. The positioning result of the observation station is obtained. Then, the positioning result of each observation station is transmitted to the monitoring unit. Therefore, although there is a burden of transmitting a positioning signal from the reference station to the observation station, the observation station obtains each positioning result and transmits the data to the monitoring unit with a small data capacity. Positioning results from observation stations can be obtained with the required accuracy in a time-consuming manner with reduced burden on data processing and data transmission. The transmission of the positioning result of each observation station to the monitoring unit may be transmitted directly to the monitoring unit or may be transmitted via a reference station.

  The positioning calculation means includes averaging processing means that averages a plurality of positioning results immediately before obtained in the time series direction and uses the result as the positioning result. According to this configuration, a more accurate positioning result can be obtained in a relatively short period.

  Further, the reference station and the observation station include satellite selection means for selecting a satellite to be used. According to this configuration, it is possible to further improve the positioning accuracy by simply selecting and using a satellite that does not cause a failure such as a multipath or selectively using a weight.

  In addition, the monitoring unit includes a difference calculation unit that obtains at least one of a time-series difference in time-series positioning results and a relative difference between stations. According to this configuration, the displacement of the position and the relative displacement between the stations are monitored, and it is possible to eliminate damage from a disaster or the like.

  The monitoring unit may include monitoring means for outputting an alarm when the difference exceeds a threshold value. According to this configuration, it is possible to eliminate damage from a disaster or the like by an alarm that notifies evacuation or the like.

  Further, the observation side communication unit receives the positioning result from the upstream observation station, transmits the received positioning result together with the received positioning result of the upstream observation station to the downstream observation station, The observation-side communication unit of each of the observation stations transmits its own positioning result to the monitoring unit together with the received positioning results of all the upstream-side observation stations. This configuration is effective when it is difficult for radio waves to reach the reference station directly due to undulations or the like at the location where the observation station is installed.

Further, a plurality of the reference stations are selected as a selection reference station, and a reference station selection unit that sequentially determines a reference station from among the selected reference stations is provided. The reference station selection unit determines a reference station from the selected reference stations. It is characterized by changing every period. According to this configuration,
By providing a plurality of reference stations, even if a measurement error becomes large at the time of positioning at a certain reference station, it is possible to maintain and ensure measurement accuracy as a whole by switching to another reference station. The reference station selection means may be provided in the monitoring unit or may be provided in common to each station. Further, a functional part for selecting the selected reference station and a functional part for determining the reference station from among them may be provided separately. For example, a functional part for selecting a selected reference station may be provided in the monitoring unit, and a functional part for determining a reference station from the functional part may be provided in each station.

  Further, the reference station selection means performs positioning accuracy evaluation for each combination of the plurality of reference stations, and selects the selected reference station from the evaluation result. According to this configuration, it is not easy to evaluate the presence / absence of an error with one reference station, but the measurement accuracy is always maintained by performing the positioning accuracy evaluation when setting the combination of the selected reference stations.

  Further, the reference station selecting means performs the positioning accuracy evaluation at every one of a predetermined period and at a predetermined timing. According to this configuration, since the positioning accuracy is evaluated and the combination of the selected reference stations can be changed periodically when an error occurs or the variation becomes large (timing), the positioning accuracy is maintained as a whole. The

  In addition, since the selected reference station is two reference stations, it is possible to efficiently maintain and ensure accuracy.

  According to the present invention, positioning results from a plurality of observation stations can be obtained with a required accuracy while reducing the burden on data processing and data transmission in a short time.

1 is a schematic diagram of a displacement monitoring system according to the present invention. It is a figure which shows the structure of a sensor part, (A) is a block diagram which shows an example of the functional block of a reference station, (B) is a block diagram which shows an example of the functional block of an observation station. It is a block diagram which shows an example of the functional block of a monitoring part. It is a term chart which shows an example of the timing of reception and data transmission of a reference station and an observation station. It is a figure of the memory map explaining the buffering process of a positioning result. It is a flowchart of the starting process by power-on of a reference station and an observation station. It is a flowchart which shows the process which a reference | standard station performs. It is a flowchart which shows the process for the positioning calculation which an observation station performs. It is a flowchart of the timer process which a reference station and an observation station perform. It is a flowchart which shows the averaging process which an observation station performs It summarizes the results of experiments using the GPS receiver applied to this system. (A) is the latitude direction, (b) is the longitude direction, (c) is the average time and standard deviation in the height direction. It is a chart which shows the relationship. It is a figure explaining the contents of initialization by change of a reference station in a 2nd embodiment. It is a structure of the sensor part which concerns on 2nd Embodiment, Comprising: It is a block diagram which shows an example of the functional block of the station provided with the function of the reference station and the observation station. It is a flowchart which shows an example of the selection process of the reference station which a monitoring part performs. It is a flowchart which shows an example of the transmission process of the reception data which a selection reference station performs. It is a time chart which shows an example of the simultaneous transmission timing of the received signal of a selection reference station. It is a flowchart which shows an example of the RTK positioning calculation process in an observation station with respect to the determined reference station. It is a flowchart which shows the other example of the selection process of the reference station performed in each station.

  FIG. 1 is a schematic diagram of a displacement monitoring system according to the present invention. In FIG. 1, Sat ... is an artificial satellite, for example, a GPS (Global Positioning System) satellite, orbiting the earth in a known orbit. As is well known, the GPS satellites Sat ... transmit (broadcast) radio waves having different frequencies (L1, L2, L5, etc.) as positioning signals. In the present embodiment, as an example, a positioning process in a case where radio waves of L1 waves (1575.42 MHz, wavelength 19.03 cm carrier) are used will be described. The radio wave is composed of a carrier wave in which positioning codes called codes are arranged as a predetermined data string, and the L1 wave has a C / A code as a positioning code including satellite identification information, GPS time, and orbit information. A navigation message consisting of information on emerifest information and ionospheric delay is included. More specifically, radio waves are used primarily to measure the distance between a satellite and a receiver, whose carrier is called a code. The code is 1023 chips long, with a pseudo-noise code with a period of 1 ms, and two-phase phase modulation (BPSK: Bi-Phase Shift Keying). It has been done.

  The sensor unit 1 includes a reference station 10 and an observation station 20 that are GPS receivers, and receives positioning signals broadcast from GPS satellites Sat. The reference station 10 is installed in the monitoring target area or in the vicinity thereof. The observation stations 20 are dispersed in the monitoring target area and installed as observation points. The reference station 10 and the observation station 20 generally perform positioning processing using broadcast radio waves from four or more GPS satellites Sat. Each of the reference station 10 and the observation station 20 is set with ID information for identifying its own station, and when transmitting a signal or data as will be described later, its own ID information is used as transmission source information. Attach.

  The reference station 10 and the observation station 20 may all be communicable wirelessly, but all or part of them may be communicably connected by wire as necessary. In the present embodiment, as shown in FIG. 1, the reference station 10 can wirelessly communicate with some of the observation stations 20 (ID = 01 to ID = i), while the remaining observation stations 20 ( ID = n−1, ID = n) can be communicated by wire via a data aggregating unit 31 described later. Note that the observation station 20 (ID = n−1, ID = n) is serially connected to the downstream observation station 20 (ID = n) from the upstream observation station 20 (ID = n−1). The positioning result may be transmitted to the monitoring unit 3 side via the route. The same applies to the observation station 20 (ID = 01 to ID = i). In the wired system, for example, the communication protocol of RS-485 can be used. In the monitoring target area, a wireless system is basically used, but a portion where the slope is undulated and a radio wave cannot be expected to be circulated (low reception sensitivity) is a wired system.

  The monitoring unit 3 includes a data aggregation unit 31 and a monitoring processing unit 32. The monitoring unit 3 is disposed in the vicinity of the sensor unit 1 or at a predetermined location. The data aggregating unit 31 is preferably installed in the vicinity of the sensor unit 1 and mainly receives data sent from the sensor unit 1 to execute the aggregating process of the received data, and also monitors the file data. In response to a request from 32, output processing is performed. The monitoring processing unit 32 performs displacement information processing using the data filed by the data aggregation unit 31 and distributes processing results to the monitoring subject and the user as necessary.

  2A and 2B are diagrams illustrating a configuration of the sensor unit, in which FIG. 2A is a configuration diagram illustrating an example of a functional block of a reference station, and FIG. 2B is a configuration diagram illustrating an example of a functional block of an observation station. The reference station 10 and the observation station 20 have a configuration for executing a function as a reference station and a function as an observation station. Note that the reference station 10 and the observation station 20 may be manufactured as the same general-purpose configuration, and the functions on either side may be selectively executed when used.

  The reference station 10 includes a control unit 11 and a GPS receiving unit 12. A memory unit 112, a communication unit 113, and a power supply unit 114 are connected to the control unit 11. The GPS receiving unit 12 includes an antenna 121 that receives positioning signals periodically broadcast from GPS satellites Sat. The reference station 10 is configured in such a manner that each of these parts is housed in a substantially cylindrical casing shown in FIG. A power switch (not shown) that can be operated from the outside is provided at an appropriate position of the housing. The communication unit 113 transmits and receives signals and data between the observation station 20 and the monitoring unit 3. The power supply unit 114 operates each unit of the reference station 10, and may use a renewable energy such as a solar cell in addition to the secondary battery.

  The memory unit 112 is a program data memory unit 1121 that stores a processing program for executing processing as the reference station 10, a received signal memory unit 1122 that stores a positioning signal from the GPS satellite Sat as a received signal received by the own station, A reference station position data memory unit 1123 that stores position data (latitude, longitude, height) where the reference station 10 is installed as reference station position data is provided. In addition, the memory unit 112 includes a satellite selection list memory unit 1124 that stores a list of satellites recommended (or thinned out) from the viewpoint of positioning accuracy among GPS satellites used for positioning processing. The reference station position data in the reference station position data memory unit 1123 may be obtained from a map, or may be a method in which the reference station 10 executes a single positioning process in advance for a predetermined period to obtain highly accurate position information.

  The satellite selection information stored in the satellite selection list memory unit 1124 is obtained, for example, as follows. Since positioning accuracy mainly depends on multipath and the like, it is preferable to exclude satellites having a small elevation angle and close to the horizon at the time of positioning. Since each GPS satellite broadcasts orbit information, it is possible to specify in advance a GPS satellite with a low degree of recommendation corresponding to the time zone using the relationship with the installation position of the reference station 10. In addition, since multipath is affected by topography and buildings, a GPS satellite that flies at a position where a reflected wave that causes multipath is generated can be specified in advance as a GPS satellite with low recommendation. The GPS satellite Sat has a revolution cycle and makes two rounds of the earth in 23 hours and 56 minutes. Therefore, the GPS satellite position (or time zone) when multipath effects occur is obtained in advance through at least one day of testing, so that the subsequent multipath occurrence time and It becomes possible to know the corresponding satellite, and by storing such information in the satellite selection list memory unit 1124, it is possible to disable a GPS satellite having a low recommendation level including time information. Note that the information registered in the satellite selection list memory unit 1124 is preferably used while being shifted by 4 minutes every day. Each of these circumstances is the same for the NGSS satellite, and a similar list can be created and applied even in an aspect using each satellite.

  The control unit 11 functions as a reception signal processing unit 1101 and a communication processing unit 1102 by executing a processing program. The received signal processing unit 1101 performs a process of receiving a predetermined (one packet) positioning signal from a plurality of GPS satellites Sat, and performs a process of temporarily storing the received signal in the received signal memory unit 1122. Note that the control unit 11 may perform a process of removing a positioning normal signal from an unused GPS satellite from the GPS time and a GPS satellite registered in the satellite selection list memory unit 1124. Alternatively, the control unit 11 associates the received GPS satellite positioning signal with the recommended information and transmits it to the observation station 20, and collates with the satellite selection list memory unit 2124 of the observation station 20 on each observation station 20 side. You may make it utilize only the positioning signal of a GPS satellite with a high recommendation degree in both.

  The communication processing unit 1102 performs processing for simultaneously transmitting the reception signal for one packet stored in the reception signal memory unit 1122 to all the observation stations 20 for each epoch and the positioning result received from each observation station 20. Process to send to. In the simultaneous transmission, the data is transmitted to the observation station 20 (see FIG. 1) connected by wire via the data aggregating unit 31 according to the RS-485 communication protocol. In addition, the communication processing unit 1102 suffices to transmit the reference station position data to all the observation stations 20 at least once after activation. In this embodiment, as described later, for example, every few epochs for every epoch. Simultaneous transmission to the observation station 20 is performed.

  The observation station 20 includes a control unit 21 and a GPS reception unit 22. A memory unit 212, a communication unit 213, and a power supply unit 214 are connected to the control unit 21. The GPS receiver 22 includes an antenna 221 that receives positioning signals periodically broadcast from GPS satellites Sat. The observation station 20 is configured in such a manner that each of these parts is housed in a substantially cylindrical casing shown in FIG. A power switch (not shown) that can be operated from the outside is provided at an appropriate position of the housing. The communication unit 213 transmits and receives signals and data to and from the reference station 1. The power supply unit 214 operates each unit of the observation station 20, and may use a renewable energy such as a solar cell in addition to the secondary battery.

  The memory unit 212 is a program data memory unit 2121 that stores a processing program for executing processing as the observation station 20, and a received signal memory unit that receives a positioning signal from the GPS satellite Sat at its own station and stores it as a received signal 2122, a positioning result memory unit 2123 for temporarily storing the results of the RTK positioning process, and a satellite selection list memory unit 1124 for storing a list of GPS satellites recommended from the viewpoint of positioning accuracy among the GPS satellites used for the positioning process; It has. The satellite selection information may be obtained in the same manner as in the case of the reference station 10, but different GPS satellites may be listed depending on the installation location of each observation station 20.

  The control unit 21 functions as a reception signal processing unit 2101, an RTK positioning calculation unit 2102, an averaging processing unit 2103, and a communication processing unit 2104 by executing a processing program. The received signal processing unit 2101 performs a process of receiving a predetermined positioning signal (for one packet) from the GPS satellite Sat every broadcast, and a process of temporarily storing the received signal in the received signal memory unit 1122. Do.

  The RTK positioning calculation unit 2102 executes an RTK positioning process for performing kinematic baseline analysis using the received signal of each GPS satellite Sat transmitted from the reference station 10 and the received signal of each GPS satellite Sat at its own station. Results (C / A code data and carrier phase data), for example, position data relative to the reference station (latitude / longitude and height values in each direction) are obtained, and the positioning results are associated with time-series directions (buffering). Execute the storing process. The absolute position may be calculated using the reference station position data, and the above is collectively referred to as a positioning result.

  The averaging processing unit 2103 executes calculation for obtaining an average value of the plurality of buffered positioning results. The average value may be a weighted average or a simple average. In addition, for example, a process of thinning out positioning results with poor measurement accuracy that vary more than a certain threshold value of the standard deviation σ may be considered. The communication processing unit 2104 performs a process of receiving a distribution signal from the reference station 10 and returning a calculated positioning result.

  FIG. 3 is a configuration diagram illustrating an example of functional blocks of the monitoring unit. The data aggregation unit 31 includes a communication processing unit 311 and a positioning result storage unit 312. The communication processing unit 311 transmits / receives signals and data to / from the reference station 10 and the observation station 20 and transmits a positioning result to the monitoring processing unit 32. The positioning result storage unit 312 functions as a storage unit for various data in the data aggregation unit 31 as needed, and mainly stores the positioning results of all the observation stations 20. The reference station selection unit 314 is used in a second embodiment to be described later.

  The monitoring processing unit 32 compares the position displacement of each installation location from the positioning results from each observation station 20 in time series, or compares the position displacement with a threshold value, and according to other needs and according to the application. A monitoring information generation unit 321 that performs various fluctuation analyzes and monitors the presence or absence of ground abnormality, and a data distribution unit 322 that distributes to a monitoring subject or a user who needs monitoring information are provided. More specifically, the monitoring information generation unit 321 determines whether or not each observation station 20 has undergone a positional deviation from the positioning results of each observation station 20 sent in time series, and to what extent the positional deviation has occurred. Or a relative position shift between stations, and functions as a difference calculating means for calculating a time-series direction difference. The monitoring information generation unit 321 may perform further analysis of ground abnormality based on the displacement amount and displacement time information of each observation station 20 in addition to the calculation of the difference value. The data distribution unit 322 can distribute the calculated difference value and analysis information as they are, or can be distributed with alarm information when the difference value exceeds a predetermined threshold, and also data distribution according to both aspects can be adopted. It is. A predetermined network, for example, a telephone line (wireless or wired) such as FOMA (Freedom Of Mobile multimedia Access) is used between the data aggregation unit 31 and the monitoring processing unit 32.

  FIG. 4 is a term chart showing an example of signal reception and transmission timings at the reference station and the observation station. In the figure, P-ID0 indicates the processing timing of the reference station 10, and P-IDn (n> 1) indicates the processing timing of the last of the n observation stations 20. FIG. 4 shows an example in which n = 9, that is, one reference station and nine observation stations 20. The epoch of reception is every 1 second, and as will be described later, the processing is distributed between the first half up to 0.5 seconds (500 ms) and the second half thereafter.

  As shown in P-ID0, the reference station 10 receives a positioning signal from the Sat satellite in its own station during 0 second to 0.5 seconds indicated by a high level in each 1 second period. Packet reception is determined and stored, and the received signal of the reference station 10 is simultaneously transmitted to all the observation stations 20. Further, the reference station 10 receives the positioning result returned from the observation station 20 in the latter half of 0.5 seconds to 1 second indicated by the low level, and transmits it to the monitoring unit 3.

  As shown by P-ID1, the first observation station 20 receives a positioning signal from the Sat satellite in its own station in the first half of each 1-second cycle, as well as from the reference station 10. A PTK positioning calculation is executed using the distributed received signal, and the result is stored in the positioning result memory unit 2123. In the latter half of the time, a predetermined averaging process, which will be described later, is executed, and a positioning result as a result is returned to the reference station 10 (via the monitoring unit 3). Each observation station 20, that is, the second and subsequent observation stations 20 executes the first half of the above processing for each epoch, and the second half of the processing is the result of positioning 10 times in its positioning result memory unit 2123. Executes in response to the epoch when stored. For example, the P-ID1 observation station 20 transmits a positioning result in 1.5 seconds to 2.0 seconds, and the P-ID2 observation station 20 transmits a positioning result in 2.5 seconds to 3.0 seconds. In the P-IDn observation station 20, the positioning result is transmitted in 9.5 seconds to 10 seconds (= 0 seconds). That is, in this embodiment, the nine observation stations 20 send an average value for 10 seconds to the monitoring unit 3 as a positioning result with an epoch period of 1 second. In the first epoch, in 0.5 seconds to 1.0 seconds, as will be described later, the reference station position data is simultaneously transmitted.

  FIG. 5 is a memory map for explaining positioning result buffering processing. The RTK positioning calculation unit 2102 of each observation station 20 stores (ten) time-series positioning results for 10 seconds in the positioning result memory unit 2123 in association with file locations. As for the positioning result, the latest data is updated to the data of the oldest file portion so that the latest 10 data always remain.

  Next, processing executed by each unit will be described with reference to the flowcharts of FIGS. FIG. 6 shows processing after power-on for the sensor unit 1 (reference station and observation station). When the sensor unit 1 receives power-on, first, initialization of the system is started (step S1). In the initialization of the system, ID setting, output cycle (averaging cycle) setting, various buffer (RAM) clear processing, and the like are performed. The ID and output cycle are set by an operator when installed in the monitoring target area or in advance (at the time of carrying in the field, for example), or set at the manufacturing or shipping stage by de facto.

  Next, it is determined whether the ID is 0, that is, whether it is a reference station (step S3). If the ID is 0, that is, the reference station, the process as the reference station is started (step S5). If the ID is other than 0, that is, the observation station, the process as the observation station according to the ID is started (step S7). ). With this process, all the sensor units 1 that are powered on are put into operation.

  FIG. 7 shows processing executed in the control unit 11 of the reference station 10. First, positioning signals from a plurality of GPS satellites Sat are received and taken in (step S11). Then, it is determined whether or not one packet each having a predetermined data amount (400 to 800 bytes) has been captured (step S13). When one packet is captured, the received signal for the one packet received this time is transmitted to all the observation stations 20 all at once (step S15). In the present embodiment, the processing so far is performed in the first half of one epoch. On the other hand, if one packet is not captured, step S15 is skipped. In this case, the previous reception signal may be retransmitted from the reference station 10, or the reception signal sent from the reference station 10 at the previous time may be used by the observation station 20.

  Next, in accordance with the order, the positioning result (after averaging) transmitted from a certain observation station 20 is taken in (step S17). Then, it is determined whether or not one packet having a predetermined data amount (48 to 50 bytes) has been captured (step S19). When one packet is captured, the positioning result for this one packet is sent to the monitoring unit 3. It is transmitted (step S15). On the other hand, if one packet is not captured, step S21 is skipped. In this case, the previous positioning result of the observation station 20 may be retransmitted from the reference station 10, or the monitoring unit 3 may use the positioning result of the observation station 20 sent from the reference station 10 last time. Good. Then, the process returns to step S11, and the same process is repeatedly executed every time a positioning signal of the GPS satellite Sat broadcast periodically is received.

  FIG. 8 shows processing for positioning calculation executed in the control unit 21 of the observation station 20. First, the local station receives positioning signals from a plurality of GPS satellites Sat and captures them (step S31). Subsequently, a received signal having a data amount (400 to 800 bytes) is fetched from the reference station 10 (step S33). Then, it is determined whether or not a reception signal at the local station has been captured, and whether or not a reception signal for one packet has been captured from the reference station 10 (step S35). If both signals are captured, the RTK positioning calculation is executed from the received signals at the reference station 10 and the own station (step S37). Next, the TDMA counter for counting time is reset to 0 (step S39).

  Note that TDMA (Time Division Multiple Access) is one of the methods used for wireless communication and refers to time division multiple access in which one frequency is alternately shared by a plurality of callers for a short time. Next, the positioning result is buffered, that is, associated with the memory address, and stored in the positioning result memory unit 313 (step S41). Then, the process returns to step S31, and the same process is repeatedly executed every time a positioning signal of the GPS satellite Sat broadcast periodically is received.

  FIG. 9 shows timer processing executed in the control unit of the reference station and the observation station. First, calculation for obtaining the output timing value t is performed (step S51). That is, the GPS time (for example, second) included in the positioning signal is divided by the output period (in this embodiment, 10 seconds) to obtain the “remainder”. By this calculation, the value of “remainder” is repeatedly obtained in order of “0, 1, 2,..., 9, 0, 1,. This “remainder” is defined as a value t. Then, the value t can be associated with an ID (= 0 to 10) for identifying the reference station and the observation station.

  The timer processing is set so that a call is generated at a short cycle compared to the epoch cycle, here, every 10 ms.

  When a value t is determined in a certain epoch in step S51, it is determined whether or not t = ID (step S53). That is, it is determined whether or not it matches the own station ID. If they do not match, this flow is exited because it is not the local station.

  On the other hand, if it matches the ID of the own station, the TDMA counter is incremented by 1 (step S55). Here, the count value of the TDMA counter reaches 50, that is, 500 ms (= calls every 10 ms × 50 times). Is determined (step S57). This flow is exited until it reaches 500 ms. This is because in the first half of one second of the epoch, each station receives a positioning signal and performs a simultaneous transmission process of the received signal at the reference station, so it waits in consideration of such processing time (ensures normal operation of the process). In the latter half, the processing described later is performed. The determination in step S57 may be set in consideration of the processing time executed in the first half of the epoch cycle, and is not limited to 500 ms. However, in the present embodiment, it is preferable to set the time to 1/2 or more of one epoch so that Step S57 does not become Yes twice in the second half.

  On the other hand, when 500 ms elapses in step S57, it is determined whether or not ID = 0 (step S59). This is to determine whether the own station is a reference station or an observation station. If the own station is a reference station, the reference station position data is simultaneously transmitted to all the observation stations (step S61). Then, the TDMA counter is reset to 0 (step S67), and this flow is exited.

  On the other hand, if the own station is an observation station, an averaging process is executed (step S63), and then the average result is output as a positioning result to the reference station (step S65). The average result is transmitted to the monitoring unit 3 via the reference station 10 as described above. Then, the TDMA counter is reset to 0 (step S67), and this flow is exited.

  According to the above, when there are nine observation stations 20, the positioning results obtained by averaging the positioning results for the latest 10 times are transmitted to the monitoring unit 3 in order from each observation station 20 every 10 epochs. Will be. Note that steps S59 and S61 may be omitted in a mode in which the reference station position data is transmitted only once immediately after activation. In this case, the averaging process by the nine observation stations 20 is nine times, and the transmission cycle of the positioning result after averaging is also advanced by 1 second.

  FIG. 10 shows the averaging process (step S63) executed by the observation station. First, the averaging counter is cleared (step S71). Next, the presence / absence of buffering data is determined (step S73). If there is buffering data, it is determined whether the positioning status is Fix (step S75). The positioning status indicates whether or not the data stored in the corresponding buffer has a predetermined accuracy, and Fix means that the data has a predetermined accuracy (normal).

  If the positioning status of the buffering data is Fix, the positioning result of the first buffer is fetched (step S77), then the averaging counter is incremented by 1 (step S79), and the process returns to step S73 to sequentially Steps S75 to S79 are repeated until the positioning results for 10 times are finally accumulated in the buffer. If the positioning status is not “Fix”, the error may be inadvertently increased, and the positioning result of the buffer is excluded from the averaging process target.

  When all the fixed buffering data are cumulatively added, it is determined whether or not the averaging counter is 0 (step S81). If the averaging counter is not 0, an average calculation is performed to divide the data added value by the number of times (step S83). On the other hand, if the averaging counter is 0, the calculation is impossible and this flow is exited. When the averaging process is completed, the process proceeds to step S65, and the positioning result after the averaging process is transmitted to the monitoring unit 3 through the reference station 10.

  FIG. 11 summarizes the results of experiments using the sensor unit 1 (GPS receiver) applied to this system. (A) is the latitude direction, (b) is the longitude direction, and (c) is the height. It is a graph which shows the relationship between each average frequency | count in a direction, and a standard deviation. This experiment was conducted in a positional relationship in which two GPS receivers were installed 10 m apart. The static positioning process indicates an average value of the positioning process performed in a session for 60 minutes every epoch 30 seconds. The RTK positioning process indicates an average value of the positioning process performed at 0.5 minutes, 10 minutes, 30 minutes, and 60 minutes. 11 (a) and 11 (b), regarding latitude and longitude, it can be seen that the standard deviation σ in the 0.5 minute averaging process in the RTK positioning process is about twice as large as the standard deviation in the static positioning process. In the height direction, there are about five times as shown in FIG.

  On the other hand, in the RTK positioning process, the standard deviation change state between 0.5 minutes and 10 minutes has a relative parameter ratio compared to the corresponding change states from 10 minutes to 30 minutes and 30 minutes to 60 minutes. Although it is small, it can be seen that there is not much difference as seen in the slopes of the line segments shown in FIGS. Specifically, the average processing for 30 measurement data is 0.5 minutes average, 600 for 10 minutes average, 1800 for 30 minutes average, and 3600 for 60 minutes average. Therefore, the parameter ratio of 60 minutes and 30 minutes is 1/2 times, 30 minutes and 10 minutes is 1/3 times, and 10 minutes and 0.5 minutes is 1/20 relatively. small. Thus, it can be said that the standard deviation σ is not a linear change but shows a tendency of non-linear variations less at 0.5 minutes, that is, around 30 seconds. Therefore, high positioning accuracy can be expected even in a short time of about 30 seconds.

  The present invention can adopt the following modes. For example, in the present embodiment, the communication units 113 and 213 of the sensor unit 1 are communication between the reference station 10 and the observation station 20, Instead of this, network communication such as a mesh type, a tree type, a star type, a ring type, or a mixed type (hybrid) thereof can be employed.

  In this embodiment, it is used for monitoring the collapse of slopes and landslides, but is also applicable to monitoring the change in shape of large structures such as dams.

  In addition, although the present embodiment has been described including a GPS satellite navigation system operated by the United States, it is compatible with a GNSS satellite navigation system including a satellite navigation system (Global Navigation Satellite System) such as GALILEO in Europe and GLONASS in Russia. Also good.

  In addition, although the satellite selection list memory units 1124 and 2124 have been described as a list of selectable satellites, the positioning result may be weighted according to the recommendation level.

  In addition, although the averaging processing unit 2103 uses a simple average, weighting may be performed based on a comparison with variations in positioning results and a standard deviation σ. By applying such weighting, it is possible to further improve the accuracy of the positioning result.

  In the present embodiment, the monitoring unit 3 is arranged separately from the sensor unit 1. However, for example, the functional unit of the monitoring unit 3 may be provided in the reference station 10. According to this, a suitable aspect can be adopted according to the purpose, application and the like.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to FIGS. In the above-described embodiment, the reference station 10 is used as one. However, in the second embodiment, the reference station is dynamically changed. By dynamically changing the reference station, it is possible to ensure the reliability of the positioning result (maintain accuracy).

  In RTK positioning, initialization processing is performed over several minutes to several tens of minutes in order to eliminate carrier slip. For example, in the RTK positioning system shown in FIG. 12 (A), the baseline vectors that can be observed when the reference station (# 0) is set to n are 0- # 1, 0- # 2,..., 0- # n. . These n baseline vectors are independent of each other, and even if the initialization at the observation station is wrong, the improperness cannot be determined from the baseline vector information. FIG. 12B shows n baseline vectors 1- # 0, 1- # 2,..., 1- # n that can be observed when the reference station is changed to the observation station (# 1). FIG. 12C shows both base line vectors in association with each other. By changing the reference station, two sets of base line vectors by completely independent initialization can be obtained. If there is a discrepancy in one of the positioning results of the two sets of stations (# 0,... #N), it is not known which set of initialization failed. When the initialization success rate in one set is 95%, the success rate in the two sets is improved to 99.75%.

  In the following, since the observation station 20 is selected as the reference station and operates as the reference station, in the second embodiment, unless otherwise specified, the reference station and the observation station are the stations (# 0, # 1,..., #N). Further, the selected reference station is called a selected reference station, and the other stations are called other stations.

  FIG. 13 is a functional block diagram of a station 20a having both functions of a reference station and an observation station. The station 20a includes the functional blocks shown in FIGS. 2 (A) and 2 (B). 2 (A) and 2 (B) are structurally the same, and the functions are a processing program for executing processing as the reference station 10 and a processing program for executing processing as the observation station 20 in the memory unit 212a. This is realized by having the program data memory unit 2121a. The program data memory unit 2121a stores a change program that dynamically changes the reference station and the observation station as necessary. Note that the change program also includes a program for the other station side that receives a reception signal broadcast from the selected reference station.

  The received signal memory unit 2122a stores a received signal received by the own station. The positioning result memory unit 2123a temporarily stores the result of the RTK positioning process. The satellite selection list memory unit 2124a stores a list of satellites that are recommended in terms of positioning accuracy.

  The control unit 21a functions as a reception signal processing unit 2101a, an RTK positioning calculation unit 2102a, an averaging processing unit 2103a provided as necessary, and a communication processing unit 2104a by executing a processing program.

  The reception signal processing unit 2101a performs a process of receiving a positioning signal for each broadcast and a process of temporarily storing the reception signal in the reception signal memory unit 2122a. The RTK positioning calculation unit 2102a functions when the own station is other than the selected reference station (another station). The received signal of each GPS satellite Sat transmitted from the selected reference station 10 and each GPS satellite Sat at the own station. RTK positioning processing for performing kinematic baseline analysis using the received signal is executed, and the positioning result is stored in the positioning result memory unit 2123a. The averaging processing unit 2103a is adopted as necessary, and executes the averaging processing of positioning results for a plurality of times as described in the above embodiment. When the local station becomes the selection reference station, the communication processing unit 2104a monitors the received signal stored in the received signal memory unit 2122a at the same time for each epoch, and the positioning result received from each other station. Processing to be transmitted to the unit 3 is performed. In addition, when the own station is an observation station (another station), the communication processing unit 2104a performs a process of receiving a reception signal simultaneously transmitted from the selection reference station or returning a calculated positioning result.

  The reference station selection unit 2105a is used according to the embodiment, and is a functional unit in the case where a part of processing performed by the reference station selection unit 314 of the monitoring unit 3 described below is executed on each station side.

  FIG. 14 is a flowchart illustrating an example of a reference station selection process performed by the reference station selection unit 314 of the monitoring unit 3. This process is performed at the time of initialization, and is preferably performed at predetermined intervals or at other timings. The selection reference station may be a combination of a plurality of (two or more) selection stations, and will be described below in the case of two for convenience of explanation. The two combinations of the reference selection stations are stored in advance in a storage unit such as the positioning result storage unit 312 as a candidate list or as a combination arithmetic expression, and the first combination candidate is set in step S101. .

  Next, in steps S103 and S105, a positioning process is performed on the first candidate reference station and the second candidate reference station of the first selected set. That is, in step S103, the first candidate reference station receives the positioning result obtained in the other station, and in step S105, the second candidate reference station obtains the positioning result obtained in the other station. Is received.

  Next, from the positioning results obtained in steps S103 and S105, matching of positioning results between corresponding observation stations, that is, corresponding position information matching / mismatching processing is performed (step S107). Note that the threshold value for determining the coincidence / non-coincidence is set within a certain range from the viewpoint of reliability. For example, when the L1 wave is used, 1/4 of the wavelength (19 cm) (about 5 cm). ).

  If it is determined that the corresponding positioning results match (step S109), the first candidate reference station and the second candidate reference station at this time are registered as the first and second selection reference stations (step S111). The registered content is transmitted to each station (# 0 to #n) via the communication processing unit 311. On the other hand, if it is determined in step S109 that they do not match, the combination is changed to another combination candidate (step S113), and the process returns to step S103 to execute the same processing.

  FIG. 15 is a flowchart illustrating an example of processing for determining a reference station executed by the reference station selection unit 314 of the monitoring unit 3. Of the selected reference stations, it is necessary to determine which of the selected reference stations is the reference station for each epoch. In step S121, it is determined which of the selected reference stations is set as the reference station for each epoch. When there are two selection reference stations as in the present embodiment, for example, a process of switching alternately every preset number of epochs may be used. The switching period may be set as a time width, for example, 10 minutes, or may not be fixed. When the reference station is determined, for example, station number information is transmitted to each station (step S123). As a result, each station can recognize whether its own station is a reference station or another station in this epoch.

  Note that only the information of the selected reference station may be notified and transmitted from the reference station selection unit 314 of the monitoring unit 3, and in this case, a determination process for determining the reference station for each epoch from the selected reference station stored in advance in each station Using the (determination program), the reference station may be determined by the reference station selection unit 2105a of each station. As a result, each station can identify whether its own station is a reference station or an observation station (another station).

  FIG. 16 is a time chart showing an example of the simultaneous transmission timing of the received signal of the selected reference station. FIG. 16A shows a state in which the station (# 0) and the station (# 1) are selected as the selection reference stations, and function as reference stations alternately for a preset time, for example, 10 minutes each. Yes. That is, the station (# 0) functions as a reference station during the period from the past time point 0 seconds before to the first second, and broadcasts the received signal, and the station (# 1) is the reference station for the next 10 minutes from the first second It shows a state in which the received signal is transmitted all at once and then switched to the station (# 0). Note that the time from the reception of the positioning signal to the simultaneous transmission may be higher than the first half (T1) of 500 ms as described above, for example, 250 ms for a short time in the first half.

  In FIG. 16B, the original reference station (# 0) is fixed as one of the selected reference stations, and the remaining one selected reference station is selected from the stations (# 1) to (#n). This is the case of the embodiment. In FIG. 16B, the station (# 0) and the station (# 1) are selected as the selection reference stations. Further, the time width of simultaneous transmission is 250 ms as in FIG.

  In FIG. 16B, the station (# 0) performs simultaneous transmission of the received signal as the reference station at a short time of 250 ms in the first half. On the other hand, during the period (for example, 10 minutes) when the station (# 1) becomes the reference station, simultaneous transmission of the received signal from the station (# 1) is performed in the second half (T2) of one epoch, for example, 250 ms. Yes. Thereby, the station (# 1) alternately switches the functions of the reference station and the other stations at intervals of 10 minutes. In this way, although the station (# 0) is fixed as the reference station, the station (# 0) is not required to perform the process of periodically switching the simultaneous transmission operation at the station (# 0) (at intervals of 10 minutes). ) Of the operation control is reduced. In the case of FIG. 16B, the other station serving as the observation station receives and recognizes that the station (# 0) is the reference station when the simultaneous transmission is performed only in the first half. Is performed in both the first half and the second half, the other selected reference station (in this example, the station (# 1)) different from the station (# 0) is recognized as the reference station, and the second half received signal , It is possible to distinguish and capture signals simultaneously transmitted from the reference station for each epoch. In this case, the transmission of the positioning result from the observation station may be performed between 750 ms and 1000 ms in the second half (T2).

  FIG. 17 is a flowchart illustrating an example of RTK positioning calculation processing in the observation station with respect to the determined reference station. First, a process of identifying which station is the reference station in the current epoch is executed (step S131). Next, the positioning signal at the current epoch is captured at the own station (step S133), and further, the received signal simultaneously transmitted from the identified reference station is captured (step S135). When one packet is captured (step S137), RTK positioning calculation is executed from the received signals at the reference station and the local station (step S139). When one packet is not captured, the calculation of the positioning result is passed.

  FIG. 18 is a flowchart illustrating another example of reference station selection processing performed in each station. In the above example, the number of selection reference stations is two. However, in FIG. 18, the reference station is determined for each predetermined period from an arbitrary number of selection reference stations in order to provide versatility. Note that the number of selected reference stations is represented by n (> = 2).

First, the conversion calculation for the current time is performed (step S141). For example, the current time is converted into, for example, (minutes) based on midnight every day. Next, in the current epoch among the selected reference stations, which are information received from the monitoring unit 3, a determination process is performed to determine which is the reference station every predetermined time, for example, every 10 minutes (step S143). The calculation of the determination process is performed by Expression (1) that employs the operator mod. That is,
Output value = mod {(current time (minutes) / 10), n} Expression (1)
The operator mod in the expression (1) outputs the first digit value of the remainder obtained by dividing the value of the first term in parentheses by the value n of the second term. For example, when n = 5, the output value = 0 when the current time (minutes) is from 0 minutes to 9 minutes. When the current time (minute) is from 10 minutes to 19 minutes, the output value = 1. Furthermore, the output value = 4 when the current time (minutes) is 40 minutes to 49 minutes. Then, when the current time (minute) is from 50 minutes to 59 minutes, the output value returns to 0. Accordingly, the output value cyclically repeats 0, 1, 2, 3, and 4 every 10 minutes. Therefore, if five selected reference stations are associated with the output value in advance according to a common rule, for example, in order from the smallest station number, the reference station is cyclically selected every 10 minutes from the selected reference station. Can be determined.

  Next, it is determined whether or not the associated number is its own station number (step S145). If the numbers match, the own station broadcasts the received signal as the current reference station (step S147). On the other hand, if it does not match the station number of the own station, it is determined that it is another station (observation station) and the process (step S147) is passed through to perform the process as the observation station.

  Since the selected reference station is dynamically changed, the determined reference station is replaced with a fixed mode in which the positioning result obtained at each station is returned to the monitoring unit 3 via the original reference station # 0. It is good also as a mode which returns to the monitoring part 3 via. Further, FIG. 18 illustrates an aspect in which processing is performed by the reference station selection unit 314 of the monitoring unit 3 instead of the processing in each station, the corresponding reference station is determined using the result of step S143, and the determination result is notified to each station. It is good.

  In addition, the selection process of the selected reference station may cause a decrease in reliability, such as fluctuations in the positioning results when using at least one of the reference stations as a reference station periodically or in displacement monitoring using the current selected reference station It is preferable to be performed. For example, as shown in FIG. 14, instead of the displacement monitoring operation, a selection reference station is selected from a plurality of stations (# 0 to #n) while sequentially changing the combination, by the determination program described above. Process.

  Also, each station (# 0 to #n) is a fixed type, but the restricted area is equipped with a moving body including a vehicle such as a plurality of traveling tractors, and their positional displacement is monitored. It is also applicable to the system.

10 reference station 11 control unit 1102 communication processing unit (reference side communication means)
113 Communication unit (reference side communication means)
20 observation station 21 control unit 2102 RTK positioning calculation unit (positioning calculation means, satellite selection means)
2103 Averaging processing unit (average processing means)
2104 Communication processing unit (observation side communication means)
213 Communication Department (observation side communication means)
3 Monitoring unit 314, 2105a Reference station selection unit (reference station selection means)
321 Monitoring information generation unit (difference calculation means)
322 Data distribution unit (monitoring means)

Claims (13)

A reference station installed at a predetermined position and receiving a positioning signal broadcast from each satellite, a plurality of observation stations installed within a monitoring target range and receiving a positioning signal from the satellite, and a positional displacement of the observation station And a monitoring unit for monitoring the reference station, selecting a plurality of the reference stations as a selection reference station, comprising a reference station selection means for determining the reference station one by one from the selected reference stations,
The reference station includes reference side communication means for transmitting the positioning signal received by the own station to the plurality of observation stations,
The observation station receives a positioning calculation means for obtaining a positioning result of the own station by kinematic baseline analysis from a positioning signal received by the own station and a positioning signal received by the reference station, and a positioning signal of the reference station And an observation side communication means for transmitting the positioning result of the own station to the monitoring unit,
The displacement monitoring system, wherein the reference station selection means changes the determination of the reference station from the selected reference stations every predetermined period. 2. The displacement monitoring system according to claim 1, wherein the positioning calculation unit includes an averaging processing unit that averages a plurality of previous positioning results obtained in a time series direction and uses the result as the positioning result. The displacement monitoring system according to claim 1, wherein the reference station and the observation station include satellite selection means for selecting a satellite to be used. 4. The displacement monitoring system according to claim 2, wherein the monitoring unit includes a difference calculating unit that obtains at least one of a time-series difference in time-series positioning results and a relative difference between stations. . The displacement monitoring system according to claim 4, wherein the monitoring unit includes a monitoring unit that outputs an alarm when the difference exceeds a threshold value. The observation side communication means receives a positioning result from an upstream observation station, and transmits its own positioning result together with the received positioning result of the upstream observation station to a downstream observation station,
The observation side communication means of the most downstream observation station transmits its own positioning result to the monitoring unit together with the received positioning results of all the upstream observation stations. The displacement monitoring system described in 1. A reference station installed at a predetermined position and receiving a positioning signal broadcast from each satellite, a plurality of observation stations installed within a monitoring target range and receiving a positioning signal from the satellite, and a positional displacement of the observation station And a monitoring unit for monitoring the reference station, selecting a plurality of the reference stations as a selection reference station, comprising a reference station selection means for determining the reference station one by one from the selected reference stations,
And as factories for transmitting the positioning signal received by the reference station to the plurality of observation stations,
Wherein from positioning signal transmitted from a positioning signal and the reference station received at each observation station, as engineering seeking positioning result of the each observation station by kinematic baseline analysis at the observation station,
And as factories for transmitting the positioning results of the observation stations in the monitoring unit,
Every predetermined period, displacement monitoring method and a degree Engineering change the determination of the reference station from among said selected reference station by said base station selecting means. The positioning result as engineering seeking, when averaged positioning information of a plurality min immediately before obtained series direction, displacement monitoring method of claim 7, the average result as the positioning result. The reference station and observation station, displacement monitoring method according to claim 7 or 8 including more factory to select a satellite to be used. Displacement according to any one of claims 7-9, characterized in that it comprises as at least one of determining Engineering relative difference between the differential and each station of the time-series positioning result for temporal direction from the observation station Monitoring method. The reference station selection means, the displacement of any one of claims 1 to 6, characterized in that performs positioning accuracy evaluation with the respective combinations of the plurality of reference stations, selects the selected reference station from the evaluation results Monitoring system. The displacement monitoring system according to claim 11, wherein the reference station selecting unit performs the positioning accuracy evaluation at every predetermined time and at a predetermined timing. The displacement monitoring system according to claim 11 or 12, wherein the selected reference station is two reference stations.