A method and system for monitoring GNSS using a single BeiDou multi-level base station combination

Abstract

This invention provides a high-precision GNSS monitoring method and system using a single BeiDou multi-level base station combination, suitable for environments with obstructions. A multi-level base station is set up on-site, utilizing communication technology. Lower-level base stations continuously receive information from higher-level base stations, continuously update their own positions, and broadcast this information to the server / monitoring station. The monitoring station calculates its relative position and absolute coordinates, and reports these to the server for further processing. In this way, the system can continuously and dynamically react to changes in the position of any one or even multiple lower-level base stations, correcting the station displacement in real time to ensure that the monitoring results are always accurate and reliable.

Description

Technical Field

[0001] This invention relates to the field of satellite positioning technology, and in particular to a method and system for monitoring GNSS using a single BeiDou multi-level base station combination. Background Technology

[0002] Current GNSS surface displacement monitoring is simple to set up, low in cost, stable in performance, and can run automatically 24 hours a day. It generally adopts the method of one point and one base station, using a single base station to support multiple stations at each monitoring point and building a measurement baseline for each station. This method is simple, flexible and efficient to set up, but it cannot effectively handle situations where the base station moves along with the stations.

[0003] It is often difficult to find a rock foundation for a base station, so the only way to reinforce it is by pouring concrete piles. These simple concrete piles may slide along with the soft foundation.

[0004] For measurement stations, the on-site observation environment often cannot fully meet the monitoring standards, such as the requirement for the minimum satellite observation elevation angle;

[0005] There are also situations where base stations are obstructed at the site, such as by mature trees and forests around the area, or by slopes.

[0006] The existing measurement method, which establishes a measurement baseline for each station, is also difficult to support the construction of multiple temporary field base stations and the temporary change of base station locations, because this will change the original measurement baseline. If a control network is introduced, it will introduce additional workload and bring a large workload to subsequent data processing, making it difficult to compare and refer to the data before and after, and to assist in decision-making. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-precision GNSS monitoring method and system for single BeiDou multi-level base station combination suitable for obstructed environments.

[0008] To achieve the above objectives, the present invention provides a method for monitoring GNSS using a single BeiDou multi-level base station combination, comprising the following steps:

[0009] S1. Construct multiple base stations B1, B2 and field station R1, and connect the field base stations B1 and B2 to the Cors station C1. The base stations form a cascaded combination relationship.

[0010] S2. R1 receives RTCM information from B1 and B2, calculates its own absolute coordinates cord11, and calculates its own relative coordinates enu11 and enu12 relative to B1 and B2; B1 and B2 receive RTCM information from C1, calculate their own precise positions in real time, and correct their own coordinates cord01 and cord02 as base stations;

[0011] S3. Base stations B1 and B2 use coordinates cord01 and cord02 to broadcast RTCM information;

[0012] S4. R1 reports absolute coordinates cord11 and relative coordinates enu11 to the server, while enu12, B1, and B2 report cord01 and cord02 to the server.

[0013] S5. R1 reports the raw observations to the server, and B1 and B2 also report the raw observations to the server;

[0014] S6. The server processes the measurement results;

[0015] In S1, each level of field base station is in a parallel network relationship, and the upper and lower level base stations are in a master-slave network relationship, forming a multi-level base station; the roles of the base station and the measuring station can be interchanged without affecting the observation results; in S6, multiple base stations, measuring stations, and CORS stations at the measurement site report their respective single BeiDou information to the server; the server performs simple filtering and merging based on the signal-to-noise ratio of the base station information, processes the observation information broadcast by the upper-level base station such as RTCM1124, selects the missing satellite frequency information of the field base stations, merges it into the above message to obtain a complete local single BeiDou message; and then broadcasts it to each measuring station for edge computing. The key feature is that the server integrates the information of multiple base stations at the field, virtualizes a base station, and pushes the virtual base station to the measuring station. The virtualization steps are as follows:

[0016] The original observations of each constellation at the on-site base station were reported to the server;

[0017] The server simultaneously receives raw observations broadcast by the upstream base station;

[0018] For on-site base stations, the server filters and merges data based on the signal-to-noise ratio information;

[0019] For the raw observations broadcast by the superior base station, the server selects the missing star frequency information from the on-site base station and merges it into the above message;

[0020] A unified coordinate system is established, and the location is determined by a virtual reference station on-site.

[0021] The server performs the calculation, or broadcasts the message to the station receiver for edge calculation.

[0022] Furthermore, the base station supports soft soil slopes and sliding surfaces, allowing the base station to slide throughout its measurement lifecycle.

[0023] Furthermore, when there are obstructions at the measurement site, any number of base stations can be set up in different directions of the obstruction to improve accuracy.

[0024] Furthermore, all the multi-level base stations adopt a single BeiDou configuration, and the base stations at each level communicate with each other using RTCM1124 format messages, which cover multi-frequency information emitted by BeiDou satellites operating in MEO, GEO, IGSO, and LEO orbits. When the number of satellites or frequency bands exceeds the message capacity limit, multiple RTCM1124 messages are used for information transmission.

[0025] Furthermore, in the S6 measurement site, multiple base stations, measurement stations, and CORS stations report their respective single BeiDou information to the server. The server performs simple filtering and merging based on the signal-to-noise ratio of the base station information. For the original observations broadcast by the superior base station and CORS station, such as RTCM1124, the server selects the missing star frequency information of the on-site base station and merges it into the above message to obtain a complete local single BeiDou message. Then, it is broadcast to each measurement station for edge calculation.

[0026] The beneficial effects of this invention are as follows: By establishing a multi-level base station on-site and utilizing communication technology, lower-level base stations continuously receive information from higher-level Cors base stations. This allows lower-level base stations to continuously update their own positions and broadcast their positions to the monitoring station. The monitoring station calculates its relative position and its absolute coordinates, which are then reported to the server for further processing. Thus, any change in the position of any base station, or even multiple base stations, can be dynamically and continuously corrected by adjusting the station displacement in real time, ensuring that the station displacement monitoring results are always accurate and reliable. Attached Figure Description

[0027] For ease of explanation, the present invention will be described in detail below with reference to the preferred embodiments and accompanying drawings.

[0028] Figure 1 This is a flowchart of a single Beidou multi-level base station combined GNSS monitoring method and system described in this invention;

[0029] Figure 2 This is a measurement flowchart of a single Beidou multi-level base station combined GNSS monitoring method and system described in this invention. Detailed Implementation

[0030] The following description, with reference to the accompanying drawings, further illustrates the GNSS monitoring method and system based on a single BeiDou multi-level base station combination according to the present invention:

[0031] Example 1, Figure 1 System setup process:

[0032] Base stations B1 and B2 were set up at the measurement site;

[0033] Set up station R1 at the measurement site;

[0034] Assuming that the upstream base station C1 already exists and is a Cors site, then connect B1 and B2 to C1 to receive the differential correction information broadcast by C1;

[0035] Continuous measurement, Figure 2 As shown, the measurement process is as follows:

[0036] Base stations B1 and B2 receive differential correction information from C1, such as RTCM1124 format messages, which contain the following information:

[0037] The pseudorange P(s,r) is defined as follows: s and r represent the satellite and base station receiver numbers, respectively.

[0038] Phase L(s,r);

[0039] Signal-to-noise ratio (SNR) (s,r);

[0040] Its observation equation based on non-difference can be expressed as:

[0041]

[0042] In the formula: ρ represents the geometric distance between the base station and the satellite; I(r) represents the ionospheric delay of the satellite; T(r) represents the tropospheric delay; dt(r) and dt(s) represent the clock bias of the satellite and the base station receiver, respectively; λ represents the carrier wavelength; N(s,r) represents the carrier phase integer ambiguity parameter; d(s), d(r), b(s), and b(r) represent the pseudorange and carrier phase hardware delays of the satellite and the receiver, respectively; dm(s,r) is the pseudorange multipath error; δm(s,r) is the carrier phase multipath error; e(s,r) and ε(s,r) are the observation noise of the pseudorange and carrier phase; and c is the speed of light.

[0043] Based on the aforementioned information base stations B1 and B2, calculate its own real-time precise location, including latitude, longitude, and altitude;

[0044] When a nearby base station broadcasts its ECEF coordinates (x0, y0, z0) and the pseudoranges (P01, P02, P03, P04) and carrier phase values ​​(L01, L02, L03, L04) of the four received satellites, this data is used to correct the coordinates of the base station receiver. The following are the steps for correcting the base station receiver coordinates:

[0045] Calculate the geometric range between each satellite and the base station:

[0046] R01 = c * (P01 - d01) (where c is the speed of light and d01 is the clock difference between the base station and satellite 1).

[0047] R02 = c * (P02 - d02);

[0048] R03 = c * (P03 - d03);

[0049] R04 = c * (P04 - d04);

[0050] Convert geometric distance into pseudorange observation:

[0051] P01' = R01 + d01;

[0052] P02' = R02 + d02;

[0053] P03' = R03 + d03;

[0054] P04' = R04 + d04;

[0055] Calculate the difference between carrier phase measurement measurements:

[0056] ΔL01 = L01 - λ1 * N01 (where λ1 is the wavelength of L1 and N01 is the integer ambiguity).

[0057] ΔL02 = L02 - λ2 * N02;

[0058] ΔL03 = L03 - λ3 * N03;

[0059] ΔL04 = L04 - λ4 * N04;

[0060] Calculate the corrected ECEF coordinates (X, Y, Z) of the receiver: Construct matrix A and vector b:

[0061] A = [2 * (X1 - x0), 2 * (Y1 - y0), 2 * (Z1 - z0)]

[0062] [2 * (X2 - x0), 2 * (Y2 - y0), 2 * (Z2 - z0)]

[0063] [2 * (X3 - x0), 2 * (Y3 - y0), 2 * (Z3 - z0)]

[0064] [2 * (X4 - x0), 2 * (Y4 - y0), 2 * (Z4 - z0)]

[0065] b = [c * (P01' - P01) - ΔL01]

[0066] [c * (P02' - P02) - ΔL02]

[0067] [c * (P03' - P03) - ΔL03]

[0068] Solve the linear system of equations Ax = b, where x = [X, Y, Z] are the corrected ECEF coordinates of the receiver; convert the ECEF coordinates to latitude, longitude and altitude coordinates [lat, lon, alt].

[0069] Based on observations over a period of time, base stations B1 and B2 correct their coordinates as base stations: cord01[lat01, lon01, alt01], cord02[lat02, lon02, alt02].

[0070] The observation period was set to 100 epochs. During this period, B1 accumulated 100 coordinate points cord01-00 cord0199, and B2 accumulated 100 coordinate points cord02-00 cord02-99. When the error distribution conforms to a Gaussian distribution, the standard deviation of a single measurement is 5 cm, which is also the standard service level currently provided by the Cors station.

[0071] The above measurements were performed 100 times, and the error follows a normal distribution.

[0072] Calculate the error of a single measurement:

[0073] SE_single = σ = 5 cm;

[0074] SE_avg100 = σ / sqrt(n) = 5 cm / sqrt(100) = 0.5 cm;

[0075] Compared to a single measurement, the error was reduced:

[0076] (5 cm - 0.5 cm) / 5 cm = 90%;

[0077] Compared to a single measurement, 100 measurements can reduce the error by 90%. Using this method, the coordinates of base stations B1 and B2 can be corrected to 5mm to meet monitoring requirements.

[0078] If 10,000 epochs are used, and combined with filtering methods such as IGG3, the B1 and B2 coordinates can be corrected to a smaller error range, such as 0.5mm.

[0079] In the subsequent differential information broadcast, base stations B1 and B2 adjust the broadcast content according to the corrected coordinates cord01 and cord02, such as RTCM1005;

[0080] The base station reports cord01 and cord02 to the server via the communication network;

[0081] Example 2: The base station's original observations can also be reported to the server;

[0082] Station R1 receives the differential correction information broadcast by base stations B1 and B2 as described above;

[0083] Station R1 calculates its own absolute position coordinates cord11 and cord12 based on the base station information;

[0084] Based on the base station information, station R1 calculates its own coordinates enu11 relative to the northeast sky of B1 and enu12 relative to the northeast sky of B2.

[0085] The original observations from the station can be reported to the server;

[0086] Typically, more than four stars are observed. In this case, adjustment is performed at each step. In this embodiment, the least squares method is used to fit the best observation value.

[0087] R1 reports the measurement results to the server, which then performs coordinate fusion positioning by integrating information from the base station and the measurement station.

[0088] The server further performs post-calculation based on the raw satellite observation information reported by the base station and the monitoring station;

[0089] The server can integrate information from multiple base stations on-site, virtualize a base station, and push the virtual base station to the test station. The virtualization method is as follows:

[0090] The original observations of each constellation at the on-site base station were reported to the server;

[0091] The server simultaneously receives raw observations broadcast by the upstream CORS base station;

[0092] For on-site base stations, the server performs simple filtering and merging based on the signal-to-noise ratio;

[0093] For the raw observations broadcast by the upper-level base station CORS station, the server selects the missing star frequency information of the on-site base station and merges it into the above message;

[0094] Establish a unified coordinate system and locate a virtual reference point on-site.

[0095] The server performs the calculation, or broadcasts the message to the station receiver for edge calculation.

[0096] Because of the introduction and real-time updating of the absolute coordinates of the base station, existing CORS sites can be fully utilized to set up two or even more levels of base stations. Any number of base stations of the same level can be introduced within each level of base station, which can improve the accuracy and reliability of the measurement results. The relative displacement of the station can be easily obtained by subtracting the absolute coordinates of the virtual base station from the absolute coordinates of the station, without having to worry about the actual changes in the location and number of base stations.

[0097] Example 3: Establishment of a Virtual Base Station

[0098] Based on Example 2, the server can integrate the raw observations from multiple base stations (such as B1, B2, B3) and CORS stations on site and process them uniformly as follows;

[0099] Each base station reports raw observations (such as pseudorange, carrier phase, signal-to-noise ratio, etc.) to the server;

[0100] The server receives observation data from all base stations and CORS stations, filters and merges the observations based on parameters such as signal-to-noise ratio, and completes the missing satellite frequency information for the on-site base stations.

[0101] The server unifies the coordinate systems of each base station to a virtual reference point on site, merges the observation messages of local base stations and CORS stations, and generates virtual base station messages.

[0102] The server pushes the virtual base station observation message to each station. The stations combine their own observations to perform edge calculations, obtain high-precision coordinates, and realize real-time monitoring of displacement.

[0103] This invention supports dynamic access and large-scale fusion of multiple base stations, innovatively introduces a signal-to-noise ratio (SNR) based filtering mechanism, and achieves intelligent completion of satellite frequency information observed by base stations, ensuring data integrity and high reliability of virtual base station messages. Compared with traditional virtual base station technology, this invention breaks through the limitations of the number and deployment method of base stations, not only improving the integrity of virtual base stations but also achieving high-precision edge computing at the station end, significantly expanding the system's applicability and engineering application value. Overall, this solution achieves higher precision, higher reliability, and stronger adaptability in GNSS monitoring, representing a significant improvement and breakthrough over existing virtual base station technology.

[0104] In Examples 1, 2, and 3, after the server aggregates the data, it fills multiple RTCM1124 messages into multiple frequency bands (such as B1I, B1C, B2a, and B3I) of multiple BeiDou satellites (e.g., 22 satellites) according to different frequency band combinations, such as L1+L2 and L1+L5. The server then sends the RTCM1124 messages to each measurement station. Similarly, the BeiDou base station can also directly send multiple RTCM1124 messages to the measurement station.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A single-BeiDou multi-level base station combined GNSS monitoring method, characterized in that: It comprises the following steps: S1. Build multiple field base stations B1, B2 and field stations R1, connect the field base stations B1, B2 to the CORS station C1, and form a cascading combination relationship between the base stations; S2. The R1 receives the RTCM information of B1 and B2, calculates the absolute coordinate cord11 of itself, and calculates the relative coordinates enu11 and enu12 of R1 relative to B1 and B2; the B1 and B2 receive the RTCM information of C1, and real-time calculate the accurate position of themselves, and correct the coordinates cord01 and cord02 of B1 and B2 as base stations; S3. The base stations B1 and B2 broadcast RTCM information using coordinates cord01 and cord02; S4. R1 reports absolute coordinates cord11 and relative coordinates enu11 and enu12 to the server; B1 and B2 report cord01 and cord02 to the server; S5. R1 reports the original observation to the server, and B1 and B2 report the original observation to the server; S6. The server processes the measurement results; In S1, each level of field base station is in parallel networking relationship, wherein C1 is the upper base station, B1 and B2 are the lower base stations, and the upper and lower base stations are in master-slave networking relationship, forming a multi-level base station; the multi-level base station adopts single Beidou configuration, the base stations at all levels communicate with each other by using RTCM1124 format message, and covers the multi-frequency band information transmitted by the Beidou satellites running on MEO, GEO, IGSO and LEO orbits; when the number of satellites or frequency bands exceeds the message capacity limit, multiple RTCM1124 messages are used for information transmission; The roles of the field base station and the station can be interchanged without affecting the measurement results and without the need to correct historical data; in S6, the single Beidou information of each base station is reported to the server; The server performs simple filtering and merging according to the signal-to-noise ratio of the base station information, processes the observation information such as RTCM1124 broadcast by the upper base station, selects the missing satellite frequency information of the field base station, and combines it into the above message to obtain a complete local single Beidou message; Then broadcast it to each station for edge calculation; the server integrates the information of multiple field base stations, virtually generates a base station, and pushes the virtual base station to the station; the virtual step is as follows: Report the original observation of each constellation of the field base station to the server; The server simultaneously receives the original observation broadcast by the upper base station; For the field base station, the server filters and merges according to the signal-to-noise ratio information; For the original observation broadcast by the upper base station, the server selects the missing satellite frequency information of the field base station and combines it into the above message; Unified coordinate system to a certain virtual reference station site in the field; The server calculates, or broadcasts the message to the station receiver for edge calculation; the base station supports soft slope surface and sliding surface, and allows the base station to slide in the whole measurement life cycle; When there is shielding in the measurement field, multiple base stations are built in different directions to improve the accuracy, and this networking method does not affect the previous observation data and does not need to adjust the observation data.

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