A method and system for extracting co-seismic displacement by using a Beidou short message

Abstract

The application belongs to the field of satellite navigation and positioning technology, and discloses a method and system for realizing coseismic displacement extraction by using Beidou short message, wherein a monitoring center receives RTS correction numbers broadcast by IGS through a network and saves the RTS correction numbers, calculates RTS real-time precise ephemeris orbit and clock error correction numbers, calculates equivalent distance correction numbers and change rate correction numbers of visible satellites, removes redundant satellites according to a predefined GNSS constellation order and precision attenuation factor, encodes a message header part composed of minute count, satellite number mask per minute and IODSSR, and broadcasts the message header part to an earthquake monitoring station by using a Beidou short message communication terminal, each earthquake monitoring station decodes received short message information to obtain equivalent distance correction numbers, and the precise coseismic displacement sequence is obtained by substituting the equivalent distance correction numbers into a TPP method. The application realizes broadcasting of correction numbers calculated and encoded by IGS RTS, and reduces transmission cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of satellite navigation and positioning technology, and particularly relates to a method and system for extracting co-seismic displacement by using BeiDou short message. BACKGROUND

[0002] In recent years, with the continuous development of the global navigation satellite system (GNSS), the improvement of real-time data transmission capability and the enhancement of data processing efficiency, GNSS has been widely applied in the field of earthquake monitoring. The GNSS co-seismic displacement extraction method is derived from the GNSS positioning technology. According to the different positioning methods, the GNSS co-seismic displacement extraction method can be divided into two ways: relative positioning and absolute positioning. The relative positioning technology needs reference station information, and it is difficult to recover the earthquake signal in a major earthquake. The precise point positioning method can obtain centimeter-level absolute co-seismic displacement, but it needs more than ten minutes of convergence time. The real-time single-station velocity-displacement solution method does not need convergence, but there is a drift when integrating to displacement. The time-domain point positioning (TPP) method obtains displacement without integration and does not have a drift trend, and the solution accuracy is high, but the premise is to need accurate satellite orbit and clock error information. Since 2013, the International GNSS Service (IGS) has been providing RTS (real-time streaming) services through the Internet, which includes satellite orbit, clock and other corrections. However, IGS RTS will not be able to continue broadcasting after network interruption, and monitoring stations will have difficulty in obtaining real-time satellite orbit and clock information. Currently, commercial companies use communication satellites to broadcast correction numbers. But ordinary users cannot afford the high cost.

[0003] With the continuous development and improvement of the BeiDou satellite navigation system, its unique BeiDou short message communication (BDS SMC) service can still send IGS RTS real-time ephemeris to the monitoring station in the form of short message communication to complete the co-seismic displacement extraction work even if the ground rupture causes the base station to be damaged and the network is interrupted. And the service price is low, which can be used as an effective communication means in a strong earthquake. However, the BeiDou short message has two shortcomings: low bandwidth, ordinary users can only send 78 bytes of information each time; and low transmission frequency, ordinary users can only send information once a minute. To realize the transmission of real-time satellite orbit and clock information, the two shortcomings need to be overcome. SUMMARY

[0004] In view of the problems in the prior art, the application provides a method and system for extracting co-seismic displacement by using BeiDou short message.

[0005] The application is achieved by a method for extracting coseismic displacement by using Beidou short message, which encodes and broadcasts the correction number provided by RTS by using Beidou short message, and provides a more stable and reliable means for real-time displacement extraction, and the method comprises the following steps:

[0006] S1: the monitoring center receives the RTS correction number broadcast by IGS through the network and saves it, and calculates the RTS real-time precise ephemeris orbit and clock error correction number by using broadcast ephemeris;

[0007] S2: the monitoring center calculates the satellite cut-off elevation angle at each whole minute by using the pre-stored monitoring station coordinates, so as to determine the visible satellites, and the monitoring center calculates the equivalent distance correction number and the change rate correction number of the visible satellites; if the number of visible satellites is greater than the maximum number limited by the Beidou short message communication, the redundant satellites are removed according to the pre-defined GNSS constellation order and accuracy attenuation factor;

[0008] S3: the monitoring center forms a message header part by combining the minute count, the satellite number mask of each minute and the data period number (IODSSR) of SSR information, forms a message body part by combining the issue of data of navigation data (IODN) and the RTS equivalent distance correction number and the distance change rate correction number of the visible satellites meeting the short message communication bandwidth, and encodes and broadcasts to the Beidou short message communication terminal of the earthquake monitoring station by the Beidou short message communication terminal;

[0009] S4: each earthquake monitoring station decodes the received short message information to obtain the equivalent distance correction number, and further restores it to the time domain differential equivalent distance correction number corresponding to the observation epoch, and substitutes it into the TPP method to obtain the accurate coseismic displacement sequence.

[0010] Further, in the S3, the encoding method is specifically as follows:

[0011] 1) encoding of the information header part: 6-bit binary ASCII code represents the minute count, corresponding to the 10-bit number 0 to 63, and the maximum number actually used is 59; 134-bit data represents the satellite number mask of 134 satellites, wherein: the number corresponding to the GPS satellite is 1 to 37, the number corresponding to the GLONASS satellite is 38 to 61, the number corresponding to the Galileo satellite is 62 to 97, and the number corresponding to the BDS satellite is 98 to 134; 4-bit binary ASCII code represents IODSSR, corresponding to 10-bit number 0 to 15.

[0012] 2) the encoding of the information body part: 10-bit binary ASCII code represents IODN, corresponding to the decimal number is 0 to 1023; 11-bit binary ASCII code represents the distance correction number with the resolution of 1cm, corresponding to the decimal number is -1023 to 1023, representing -10.23m to 10.23m; 11-bit binary ASCII code represents the distance change rate correction number with the resolution of 0.01cm / s, corresponding to the decimal number is -1023 to 1023, representing 0.1023m / s to 0.1023m / s; the main function of IODN is to provide the user with the corresponding broadcast ephemeris, so as to calculate the distance correction number.

[0013] Further, the method is verified by using two application scenarios of static experiment and earthquake instance.

[0014] Further, the static experiment specifically includes:

[0015] Eight IGS stations in China and surrounding areas are selected for solution, and the sampling time of data is 05:45:01 to 05:59:59 (GPST) on January 1, 2020, a total of 15 minutes, and '0' is used as a reference value. The accuracy of the displacement obtained by the TPP method based on the Beidou short message communication is evaluated.

[0016] Further, the earthquake instance specifically includes:

[0017] The AVLN station of the 2016 Mw 7.8 Kaikoura earthquake is used to solve the coseismic displacement. Four displacement solving schemes are designed to compare their solving accuracy.

[0018] Further, the four displacement solving schemes are: TPP+RTS, TPP+BDS SMC G, TPP+BDS SMCG, TPP+BDS SMC G+R.

[0019] Another purpose of the present application is to provide a system for extracting coseismic displacement using Beidou short message, which implements the method for extracting coseismic displacement using Beidou short message.

[0020] Earthquake monitoring center and earthquake monitoring station;

[0021] The earthquake monitoring center includes a server, a Beidou short message communication terminal 1;

[0022] The server is used for receiving and saving the RTS correction number broadcasted by the IGS through the network, and calculating the RTS real-time precise ephemeris orbit and clock error correction number by using broadcast ephemeris; a message header part is composed of minute count, satellite number mask per minute and IODSSR, a message body part is composed of IODN and visible satellite RTS equivalent distance correction number and distance change rate correction number satisfying short message communication bandwidth, and encoding is carried out;

[0023] The Beidou short message communication terminal 1 is connected with the server, and is used for broadcasting the encoded short message information of the monitoring center to the Beidou short message communication terminal 2.

[0024] The earthquake monitoring station comprises the Beidou short message communication terminal 2 and the user GNSS receiver.

[0025] The Beidou short message communication terminal 2 communicates with the Beidou short message communication terminal 1 through the Beidou GEO satellite, and is used for receiving the short message information sent by the Beidou short message communication terminal 1.

[0026] The user GNSS receiver calculates the satellite cut-off elevation angle at each whole minute by using the pre-stored earthquake monitoring station coordinates, so as to determine the visible satellites, and calculates the equivalent distance correction number and the change rate correction number of the visible satellites; if the number of the visible satellites is greater than the maximum number limited by the Beidou short message communication, the redundant satellites are removed according to the pre-defined GNSS constellation order and the precision attenuation factor.

[0027] The received short message information is decoded to obtain the equivalent distance correction number, which is further restored to the time domain difference equivalent distance correction number corresponding to the observation epoch, and is substituted into the TPP method to obtain the accurate coseismic displacement sequence.

[0028] Another purpose of the present application is to provide a computer device, characterized in that the computer device comprises a memory and a processor, the memory stores a computer program, and the computer program is executed by the processor to make the processor execute the steps of the method for extracting coseismic displacement by using Beidou short message.

[0029] Another purpose of the present application is to provide a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to make the processor execute the steps of the method for extracting coseismic displacement by using Beidou short message.

[0030] Another purpose of the present application is to provide an information data processing terminal for realizing the system for extracting coseismic displacement by using Beidou short message.

[0031] In combination with the above technical solutions and the technical problems solved, the technical solutions to be protected by the application have the following advantages and positive effects:

[0032] First, the method for extracting co-seismic displacement by using Beidou short message can break through the limitation of network interruption during strong earthquakes, and provide a stable and reliable extraction means for the monitoring center.

[0033] In the method for extracting co-seismic displacement by using Beidou short message, the distance correction number and the distance change rate correction number are calculated and coded based on the free IGS RTS correction number, and the service cost of Beidou short message is low, thereby reducing the burden of ordinary users.

[0034] In the method for extracting co-seismic displacement by using Beidou short message, the information to be sent is coded by using ASCII code, thereby reducing the amount of data to be sent.

[0035] Second, the technical solutions are regarded as a whole or from the perspective of products, the technical effects and advantages of the technical solutions to be protected by the application are described as follows:

[0036] The encoding and broadcasting of the correction number calculated by IGS RTS are realized by using Beidou short message, thereby reducing the transmission cost.

[0037] The Beidou short message communication provides a stable and reliable real-time positioning means for the extraction of real-time co-seismic displacement, can more accurately estimate the magnitude, and avoid unnecessary personnel casualties and economic losses caused by underestimating the magnitude.

[0038] Third, the creativity of the claims of the application is also reflected in the following important aspects:

[0039] (1) The expected income and commercial value of the technical solutions of the application after transformation are as follows:

[0040] The method for extracting co-seismic displacement based on Beidou short message communication can realize effective broadcasting of IGS RTS correction number and high-precision displacement calculation function when the network is interrupted during strong earthquakes, and the low-cost Beidou short message service can replace the mature and expensive commercial satellite communication service abroad, thereby greatly reducing the communication transmission cost of earthquake monitoring and early warning.

[0041] (2) The technical solutions of the application fill the technical gap in the industry at home and abroad:

[0042] Although the current TPP method has high displacement extraction accuracy, it is limited by network interruption during strong earthquakes, and the application provides a new communication means, which can communicate through Beidou short message service when the network is interrupted, is more stable and reliable, and fills the technical gap at home and abroad.

[0043] (3) The technical scheme of the application solves the technical problems that people have been eager to solve but have failed to obtain success:

[0044] The frequency and bandwidth of Beidou No.2 civil short message communication are limited, and cannot meet the needs of coseismic displacement monitoring, the application innovatively converts IGS RTS into equivalent distance correction and applies it to coseismic displacement extraction, solving the problem of IGS RTS broadcast interruption and coseismic displacement cannot be solved caused by network interruption during strong earthquakes. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a method flowchart for realizing coseismic displacement extraction by using Beidou short message provided by the embodiment of the application;

[0046] Figure 2 is a system structure diagram for realizing coseismic displacement extraction by using Beidou short message provided by the embodiment of the application;

[0047] Figure 3 is a TPP+BDS SMC G scheme schematic diagram provided by the embodiment of the application;

[0048] Figure 4 is a statistical schematic diagram of displacement deviation and STD value in north, east and sky directions obtained by four schemes provided by the embodiment of the application;

[0049] Figure 5 is an RMSE box plot of four schemes provided by the embodiment of the application;

[0050] Figure 6 is a coseismic displacement result schematic diagram of AVLN station calculation under four schemes provided by the embodiment of the application;

[0051] Figure 7 is a statistical schematic diagram of displacement deviation and STD value in north, east and sky directions obtained by four schemes provided by the embodiment of the application;

[0052] Figure 8 is an RMSE box plot of four schemes provided by the embodiment of the application. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical scheme and advantages of the application more clear and explicit, the application will be further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the application, and are not used to limit the application.

[0054] In order to enable those skilled in the art to fully understand how the application is specifically implemented, this part is an explanatory embodiment for explaining and describing the technical scheme of the claims.

[0055] Embodiment 1

[0056] As Figure 1 shown, the application utilizes Beidou short message to realize the method for coseismic displacement extraction, which comprises the process of coseismic displacement extraction.

[0057] The steps of realizing the process of coseismic displacement extraction

[0058] The first step, the monitoring center receives the RTS correction number broadcasted by IGS through network and saves it, and calculates the RTS real-time precise ephemeris orbit and clock error correction number by using broadcast ephemeris.

[0059] The second step, the monitoring center calculates the satellite cut-off elevation angle at every whole minute by using the pre-stored monitoring station coordinates, so as to determine the visible satellites, and the monitoring center calculates the equivalent distance correction number and its change rate correction number of the visible satellites; if the number of visible satellites is greater than the maximum number limited by Beidou short message communication, the redundant satellites are removed according to the pre-defined GNSS constellation order and dilution of precision (DOP).

[0060] The third step, the monitoring center composes the message header part by the minute count, the satellite number mask of every minute and IODSSR, composes the message body part by IODN and the RTS equivalent distance correction number and distance change rate correction number of the visible satellites satisfying the short message communication bandwidth, and encodes them, and then broadcasts them to the Beidou short message communication terminal of the earthquake monitoring station by the Beidou short message communication terminal. The encoding method is specifically as follows:

[0061] 1) The encoding of the information header part: 6-bit binary ASCII code represents the minute count, corresponding to the 10-digit number from 0 to 63, and the maximum number actually used is 59; 134-bit data represents the satellite number mask of 134 satellites, wherein: the number corresponding to GPS satellite is from 1 to 37, the number corresponding to GLONASS satellite is from 38 to 61, the number corresponding to Galileo satellite is from 62 to 97, and the number corresponding to BDS satellite is from 98 to 134; 4-bit binary ASCII code represents IODSSR, corresponding to the 10-digit number from 0 to 15.

[0062] 2) The encoding of the information body part: 10-bit binary ASCII code represents IODN, corresponding to the decimal number is 0 to 1023; 11-bit binary ASCII code represents the distance correction number with resolution of 1cm, corresponding to the decimal number is -1023 to 1023, representing -10.23m to 10.23m; 11-bit binary ASCII code represents the distance rate correction number with resolution of 0.01cm / s, corresponding to the decimal number is -1023 to 1023, representing 0.1023m / s to 0.1023m / s; the main function of IODN is to provide the user with the corresponding broadcast ephemeris, so as to calculate the distance correction number.

[0063] The fourth step is that each seismic monitoring station decodes the received short message information to obtain the equivalent distance correction number, and further restores it to the time domain differential equivalent distance correction number corresponding to the observation epoch, and substitutes it into the TPP method to obtain the accurate coseismic displacement sequence.

[0064] Embodiment 2

[0065] The application scenarios of the method for extracting coseismic displacement by using Beidou short message are illustrated as follows:

[0066] Based on the Beidou short message communication service, an equivalent distance correction number calculation and encoding method is designed, and is applied to the TPP method for extracting coseismic displacement, and static experiment and earthquake example two application scenarios are verified.

[0067] 1) Static experiment

[0068] In order to evaluate the precision of the coseismic displacement extracted by the TPP method based on the Beidou short message equivalent distance correction number, eight IGS stations in China and surrounding areas are selected for calculation. The sampling time of the data is from 05:45:01 to 05:59:59 (GPST) on January 1, 2020, for a total of 15 minutes. Taking "0" as the reference value, the precision of the displacement obtained by the TPP method based on the Beidou short message communication is evaluated.

[0069] The LHAZ, WUH2, MIZU and ULAB stations can continuously track more than 15 GPS and GLONASS satellites with an elevation angle greater than 10 degrees within the observation period. Figure 3In general, the displacement time series calculated by TPP+BDS SMC G+R is more stable than that of TPP+BDS SMC G, and the short-period jitter trend in the north, east and vertical directions is further weakened compared with the single GPS system, which is more consistent with the displacement time series calculated by TPP+RTS. However, the displacement time series calculated by TPP+BRDC shows a large drift value at the end of the displacement time series in the north, east and vertical directions, with an average value of 7.5 cm in the horizontal direction and 15 cm in the vertical direction. The short-period jitter of the displacement time series in the three directions is strong, which is due to the weak constraint of the additional precise coordinates in the TPP method on the displacement results calculated by broadcast ephemeris, and the small part of uncompensated atmospheric and ephemeris errors cannot be eliminated.

[0070] To quantitatively describe the precision of the displacement extracted by the TPP method, the displacement bias and STD value in the north, east and vertical directions calculated by the four schemes are counted, as shown in Table 1. Figure 4 In general, within the calculation range of fifteen minutes, the precision of the co-seismic displacement extracted by TPP+BDS SMC G, TPP+BDS SMC G+R and TPP+RTS is relatively close, and the displacement bias in the north, east and vertical directions of almost all stations is within 5 cm. The STD value of the displacement in the north and east directions is significantly lower than that in the vertical direction. The displacement results calculated by TPP+BRDC are inferior to the other three schemes, with a displacement bias of less than 10 cm in the north and east directions and less than 20 cm in the vertical direction. The STD value also shows the same change rule.

[0071] Figure 5 Table 1 further shows the RMSE box plot and precision statistical results of the four schemes. For the TPP+RTS scheme, the horizontal direction RMSE is 1.79 cm, and the vertical direction RMSE is 2.11 cm. For the TPP+BDS SMC G scheme, the horizontal direction RMSE is 2.11 cm, and the vertical direction RMSE is 2.65 cm. After adding the GLONASS system, the horizontal direction RMSE of the static displacement is 1.89 cm, and the average value of each station is 2.54 cm. Compared with the single GPS system, the precision in the horizontal direction is improved by 10.32%, and the precision in the vertical direction is improved by 4.04%. The precision of the TPP+BRDC scheme is relatively low compared with the previous two schemes, with a horizontal direction RMSE of 5.23 cm and a vertical direction RMSE of 9.40 cm.

[0072] Table 1 Average displacement precision of eight IGS stations extracted by four schemes (unit: cm)

[0073]

[0074] It should be noted that in static experiments, the displacement extraction effect of the TPP+BDS SMC scheme is weaker than that of the TPP+RTS scheme, because the equivalent distance correction number reduces the RTS orbit and clock correction number of high sampling rate (5s) to 1min, and uses a first-order polynomial fitting method to predict the equivalent distance correction number of each observation epoch in 1min. Generally speaking, the extrapolated BDS SMC equivalent distance correction number is slightly inferior to the RTS orbit and clock accuracy obtained by Lagrange interpolation, so the displacement accuracy of its solution is lower than that of the RTS product solution.

[0075] 2) 2016 New Zealand Mw 7.8 Kaikoura earthquake

[0076] In order to further prove the feasibility of the proposed method in earthquake examples, the AVLN station of the 2016 Mw 7.8 Kaikoura earthquake was used to solve the coseismic displacement. Four displacement solving schemes were designed to compare their solving accuracy. Figure 6 The coseismic displacement results of AVLN station under four schemes are given, the displacement results of TPP+RTS and TPP+BDS SMC G schemes in the horizontal direction are not much different, and are better than the displacement results of TPP+BRDC. In the vertical direction, the short-period jitter of TPP+BDS SMC G scheme is obviously weakened; after adding GLONASS system, the overall solution result of TPP+BDS SMC G+R scheme is close to the displacement solution result of TPP+RTS, and the difference with the reference value is small. Compared with the solution result of TPP+BRDC, the displacement results extracted by TPP+BDS SMC G and TPP+BDS+SMC G+R schemes are more robust, and there is almost no obvious drift trend.

[0077] As Figure 7The displacement bias and STD values of north, east and sky directions obtained by the four schemes are counted. In general, in the 5 minutes containing the main shock period, the TPP+BDS SMC G scheme has larger displacement bias value in the north direction compared with the TPP+RTS scheme, and the displacement bias of the remaining two directions is relatively small. After adding the GLONASS system, the extracted displacement bias and STD value of the TPP+BDS SMC G+R scheme are obviously reduced compared with the results of the single GPS system. The north and east displacement biases of almost all stations are within 2 cm, the sky direction bias is within 5 cm, and the STD values of the north and east directions are obviously better than those of the sky direction, which are more close to the results of the TPP+RTS scheme. The TPP+BRDC scheme has larger displacement bias and STD value in the east direction, which is within 3 cm, and the displacement bias and STD value of the remaining two directions are relatively consistent.

[0078] Figure 8 The RMSE box plot and overall accuracy index of the four schemes are further given in Table 2. In the TPP+BRDC scheme, the horizontal direction RMSE of each station is 3.42 cm, and the horizontal direction accuracy of the TPP+RTS scheme is 1.22 cm. The horizontal direction accuracy of the TPP+BDS SMC G scheme and the TPP+BDS SMC G+R scheme is 2.47 cm and 1.59 cm, respectively. The vertical direction RMSE values of the single system and the double system are 2.15 cm and 1.40 cm, respectively, which are greatly improved compared with the broadcast ephemeris solution, and are relatively consistent with the results of the TPP+RTS scheme. In summary, the TPP+BDS SMC and the TPP+RTS have the same co-seismic displacement extraction capability. Compared with the results of the TPP+BRDC scheme, the TPP+BDS SMC scheme significantly eliminates the short-period jitter effect in the co-seismic displacement sequence and the drift value at the end of the time sequence. After adding the GLONASS system, the number of visible satellites is increased and the satellite spatial structure is optimized. The extraction accuracy of the co-seismic displacement is improved by 35.57% in the horizontal direction and by 34.88% in the vertical direction compared with the GPS system.

[0079] Table 2 Average co-seismic displacement accuracy of each station obtained by the four schemes (unit: cm)

[0080]

[0081]

[0082] Compared with the static experiment, the displacement calculation accuracy difference between the TPP+BDS SMC scheme and the TPP+RTS scheme in the earthquake instance is further increased, because the influence of surface rupture causes the change of the environment around the station, and the influence of the constantly changing multipath effect and troposphere error. On the one hand, the observation noise level of the receiver is higher than that in the static state, and on the other hand, the time domain point difference method cannot effectively eliminate the residual error, thereby causing the difference in the displacement calculation of the two.

[0083] In order to prove the creativity and technical value of the technical scheme of the application, this part is the application embodiment of the technical scheme of the claim on the specific product or related technology.

[0084] As shown in Figure 2 The application embodiment provides a system for extracting coseismic displacement by using Beidou short message, which implements the method for extracting coseismic displacement by using Beidou short message, and the system comprises:

[0085] a seismic monitoring center and a seismic monitoring station;

[0086] The seismic monitoring center comprises a server and a Beidou short message communication terminal 1.

[0087] The server is used for receiving and saving the RTS correction number broadcast by IGS through a network, and calculating the RTS real-time precise ephemeris orbit and clock error correction number by using broadcast ephemeris; composing a message header part by using a minute count, a satellite number mask per minute and IODSSR, composing a message body part by using IODN and the RTS equivalent distance correction number and distance change rate correction number of visible satellites that meet the short message communication bandwidth, and performing encoding;

[0088] The Beidou short message communication terminal 1 is connected with the server, and is used for broadcasting the encoded short message information of the monitoring center to a Beidou short message communication terminal 2.

[0089] The seismic monitoring station comprises the Beidou short message communication terminal 2 and a user GNSS receiver.

[0090] The Beidou short message communication terminal 2 communicates with the Beidou short message communication terminal 1 through a Beidou GEO satellite, and is used for receiving the short message information sent by the Beidou short message communication terminal 1.

[0091] The user GNSS receiver calculates the satellite cut-off elevation angle at each whole minute by using the pre-stored coordinates of the seismic monitoring station, thereby determining the visible satellites, calculating the equivalent distance correction number and the change rate correction number of the visible satellites, and eliminating the redundant satellites according to a pre-defined GNSS constellation order and an accuracy attenuation factor if the number of visible satellites is greater than the maximum number limited by the Beidou short message communication.

[0092] The received short message information is decoded to obtain an equivalent distance correction number, which is further restored to a time domain difference equivalent distance correction number corresponding to an observation epoch, and substituted into a TPP method to obtain an accurate coseismic displacement sequence.

[0093] The embodiment of the present application provides a computer device, which comprises a memory and a processor, the memory stores a computer program, and the computer program is executed by the processor to enable the processor to execute the steps of the method for extracting coseismic displacement by using a Beidou short message.

[0094] The embodiment of the present application provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to enable the processor to execute the steps of the method for extracting coseismic displacement by using a Beidou short message.

[0095] The embodiment of the present application provides an information data processing terminal, which is used for implementing the system for extracting coseismic displacement by using a Beidou short message.

[0096] It should be noted that the embodiments of the present application can be realized by hardware, software or the combination of software and hardware. The hardware part can be realized by special logic; the software part can be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or a specially designed hardware. Those skilled in the art can understand that the above-mentioned device and method can be realized by computer executable instructions and / or included in processor control code, for example, such code is provided on a carrier medium, such as a magnetic disk, a CD or a DVD-ROM, a programmable memory, such as a read-only memory (firmware) or a data carrier, such as an optical or electronic signal carrier. The device of the present application and its modules can be realized by a hardware circuit, such as a very large scale integrated circuit or a gate array, a semiconductor, such as a logic chip, a transistor, or a programmable hardware device, such as a field programmable gate array, a programmable logic device, or the like, can also be realized by software executed by various types of processors, and can also be realized by the combination of the above-mentioned hardware circuit and software, such as firmware.

[0097] In the simulation experiment of the 2016 New Zealand Mw 7.8 Kaikoura earthquake, the extraction accuracy of co-seismic displacement of the four schemes is as follows: the horizontal direction accuracy of the TPP+RTS scheme is 1.22 cm. The horizontal direction accuracy of the TPP+BDS SMC G scheme and the TPP+BDS SMC G+R scheme is 2.47 cm and 1.59 cm, respectively. The vertical direction RMSE values of the single system and the double system are 2.15 cm and 1.40 cm, respectively, which is greatly improved compared with the broadcast ephemeris solution result and is consistent with the result of the TPP+RTS scheme. In summary, the TPP+BDS SMC and the TPP+RTS have the same co-seismic displacement acquisition capability. Compared with the calculation result of the TPP+BRDC, the TPP+BDS SMC scheme obviously eliminates the short-period jitter effect in the co-seismic displacement sequence and the drift value at the end of the time sequence. After adding the GLONASS system, the number of visible satellites is increased and the satellite spatial structure is optimized. The extraction accuracy of the co-seismic displacement of the GPS system is improved by 35.57% in the horizontal direction and by 34.88% in the vertical direction. The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any modification, equivalent replacement and improvement within the technical range disclosed in the present application, which is within the spirit and principles of the present application, should be covered within the protection scope of the present application.

Claims

1. A method for coseismic displacement extraction using BeiDou short message service, characterized in that, The method includes: S1: The monitoring center receives and saves the RTS correction data broadcast by IGS over the network, and uses the broadcast ephemeris to calculate the real-time precise ephemeris orbit and clock error correction data of RTS. S2: The monitoring center uses the pre-stored coordinates of the monitoring stations to calculate the satellite cutoff elevation angle at every whole minute to determine the visible satellites. The monitoring center calculates the equivalent distance correction and its rate of change correction for the visible satellites. If the number of visible satellites exceeds the maximum number of BeiDou short message communication limits, the redundant satellites are removed according to the predefined GNSS constellation order and accuracy attenuation factor. S3: The monitoring center will form the message header by combining the minute count, the satellite number mask per minute, and the IODSSR, and the message body by combining the IODN, the RTS equivalent distance correction, and the distance change rate correction of the visible satellites that meet the short message communication bandwidth. The message body will be encoded and broadcast by the Beidou short message communication terminal to the Beidou short message communication terminal of the earthquake monitoring station. S4: Each earthquake monitoring station decodes the received short message information to obtain the equivalent distance correction, and further restores it to the time-domain difference equivalent distance correction of the corresponding observation epoch. Substitutes it into the time-domain point positioning TPP method to obtain the accurate coseismic displacement sequence.

2. The method for coseismic displacement extraction using BeiDou short messages as described in claim 1, characterized in that, In S3, the encoding method is specifically as follows: 1) Regarding the encoding of the header section: 6 bits of binary ASCII code represent the minute count, corresponding to decimal numbers 0 to 63, with the maximum number actually used being 59; 134 bits of data represent the satellite number mask for 134 satellites, where: GPS satellites correspond to numbers 1 to 37, GLONASS satellites to numbers 38 to 61, Galileo satellites to numbers 62 to 97, and BDS satellites to numbers 98 to 134; 4 bits of binary ASCII code represent IODSSR, corresponding to decimal numbers 0 to 15; 2) Encoding of the information body: 10-bit binary ASCII code represents the IODN, corresponding to decimal numbers 0 to 1023; 11-bit binary ASCII code represents the distance correction with a resolution of 1cm, corresponding to decimal numbers -1023 to 1023, representing -10.23m to 10.23m; 11-bit binary ASCII code represents the distance change rate correction with a resolution of 0.01cm / s, corresponding to decimal numbers -1023 to 1023, representing 0.1023m / s to 0.1023m / s; the main function of the IODN is to allow users to look up the corresponding broadcast ephemeris to calculate the distance correction.

3. The method for coseismic displacement extraction using BeiDou short messages as described in claim 1, characterized in that, This method is validated using two application scenarios: static experiments and earthquake examples.

4. The method for coseismic displacement extraction using BeiDou short messages as described in claim 3, characterized in that, The static experiment specifically includes: Eight IGS stations in China and surrounding areas were selected for analysis. Using GPS time as the standard, the data sampling time was from 05:45:01 to 05:59:59 on January 1, 2020, a total of 15 minutes. "0" was used as the reference value to evaluate the accuracy of the displacement obtained by the TPP method based on Beidou short message communication.

5. The method for coseismic displacement extraction using BeiDou short messages as described in claim 3, characterized in that, The earthquake examples specifically include: The coseismic displacement was calculated using the AVLN station based on the 2016 Mw 7.8 Kaikoura earthquake. Four displacement calculation schemes were designed and their calculation accuracy was compared.

6. The method for coseismic displacement extraction using BeiDou short messages as described in claim 5, characterized in that, The four displacement calculation schemes are: TPP+RTS, TPP+BDS SMC G, TPP+BRDC, and TPP+BDS SMC G+R.

7. A system for coseismic displacement extraction using BeiDou short messages, implementing the method for coseismic displacement extraction using BeiDou short messages as described in any one of claims 1-6, characterized in that, The system includes: Earthquake monitoring centers and earthquake monitoring stations; The earthquake monitoring center includes a server and a Beidou short message communication terminal 1. The server is used to receive and store the RTS corrections broadcast by IGS over the network, and to calculate the RTS real-time precise ephemeris orbit and clock error corrections using the broadcast ephemeris; the message header is composed of minute counts, satellite number masks per minute and IODSSR, and the message body is composed of IODN and the RTS equivalent distance corrections and distance change rate corrections of visible satellites that meet the short message communication bandwidth, and then encoded. The Beidou short message communication terminal 1 is connected to the server and is used to broadcast the short message information encoded by the monitoring center to the Beidou short message communication terminal 2. The earthquake monitoring station includes a Beidou short message communication terminal 2 and a user GNSS receiver; The Beidou short message communication terminal 2 is connected to the Beidou short message communication terminal 1 and is used to receive short message information sent by the Beidou short message communication terminal 1. The user GNSS receiver uses pre-stored earthquake monitoring station coordinates to calculate the satellite cutoff elevation angle at every whole minute, thereby determining visible satellites and calculating the equivalent distance correction and its rate of change correction for visible satellites; if the number of visible satellites exceeds the maximum number limited by BeiDou short message communication, the redundant satellites are removed according to the predefined GNSS constellation order and accuracy attenuation factor. The received short message information is decoded to obtain the equivalent distance correction, which is then restored to the time-domain difference equivalent distance correction for the corresponding observation epoch. This correction is then substituted into the TPP method to obtain the accurate coseismic displacement sequence.

8. A computer device, characterized in that, The computer device includes a memory and a processor. The memory stores a computer program. When the computer program is executed by the processor, the processor performs the steps of the method for coseismic displacement extraction using BeiDou short messages as described in any one of claims 1-6.

9. A computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method for coseismic displacement extraction using BeiDou short messages as described in any one of claims 1-6.

10. An information data processing terminal, characterized in that, The information data processing terminal is used to implement the coseismic displacement extraction system using BeiDou short messages as described in claim 7.

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