A spoofing detection method based on low-orbit GNSS observation data

Abstract

This application discloses a deception detection method based on low-orbit GNSS observation data, involving satellite data processing technology, including: receiving GNSS satellite navigation signals and performing positioning calculations using observation files and ephemeris files in the GNSS satellite navigation signals; performing position determination based on the position information output by processing the GNSS satellite navigation signals; when the position determination is normal, calculating the power attenuation result based on the transmission power of the GNSS satellite navigation signals and the distance information between the satellite and the onboard GNSS receiver and converting it into a carrier-to-noise ratio; completing a carrier-to-noise ratio determination based on the carrier-to-noise ratio converted from the power attenuation result and the carrier-to-noise ratio information output by receiving and processing the GNSS satellite navigation signals; and issuing an alarm when the carrier-to-noise ratio is abnormal. This application can fully utilize the original output value of the receiver as a deception detection variable, effectively reducing costs.

Description

Technical Field

[0001] The present application relates to the field of satellite data processing technology, and in particular to a deception detection method based on low-orbit GNSS observation data. Background Art

[0002] Satellite-borne GNSS receivers use navigation satellites as spatial reference points to measure the satellite's orbital status information. For satellite orbit determination, the ground-based layer uses a combination of ground-based multi-station and angle measurement. The distance, azimuth, and pitch angle information measured by the ground-based measurement are batch-processed to obtain the initial orbital status for orbit prediction. Compared with space-based measurements, the coverage of satellite orbits by ground-based measurements is severely affected by the insufficient deployment of ground measurement and control networks. When applied to satellite orbit determination, the orbit determination accuracy is not high. This shortcoming can be overcome by configuring GNSS receivers on satellites. Satellite-borne GNSS receivers are at risk of spoofing attacks when receiving GNSS navigation signals. In recent years, GNSS spoofing attacks have occurred frequently, posing a major challenge to the security of signal reception by satellite-borne GNSS receivers.

[0003] In the existing technical solutions for low-orbit satellite-borne GNSS receiver deception detection, the invention provides a "Fusion Processing Method for Low-orbit Aircraft GNSS Receiver Anti-deception Interference". First, the judgment is made based on the clock error information. When the clock error information is normal, the geometric distance and laser ranging results between the low-orbit aircraft and nearby aircraft are judged. When the comparison results are normal, the comparison results of the aircraft theoretical coordinates and the receiver output coordinates are judged. When it is determined that a deception signal exists, the same medium and high-orbit satellite numbers and different low-orbit aircraft are grouped together, and the original pseudo-range observations are subtracted to obtain pseudo-range differences. The pseudo-range differences are sorted and adjacent observations are subtracted to calculate the detection amount of the deception interference signal. The deception signal is judged based on the detection amount, isolated, re-positioned and solved, and the deception signal is eliminated. However, this solution requires the addition of other equipment such as laser ranging equipment. Summary of the Invention

[0004] The embodiment of the present application provides a deception detection method based on low-orbit GNSS observation data, which does not require the addition of other equipment such as laser ranging equipment, fully utilizes the original output value of the receiver as the deception detection value, and effectively reduces costs.

[0005] This embodiment of the present application provides a spoofing detection method based on low-orbit GNSS observation data, including:

[0006] Receive GNSS satellite navigation signals and use the observation files and ephemeris files in the GNSS satellite navigation signals to perform positioning solutions;

[0007] Determine the position based on the position information output by processing the GNSS satellite navigation signal;

[0008] When there is no abnormality in the position judgment, the power attenuation result is calculated based on the transmission power of the GNSS satellite navigation signal and the distance information between the satellite and the onboard GNSS receiver, and converted into the carrier-to-noise ratio;

[0009] The carrier-to-noise ratio is determined based on the carrier-to-noise ratio converted from the power attenuation result and the carrier-to-noise ratio information output by the GNSS satellite navigation signal reception and processing.

[0010] In case of abnormal carrier-to-noise ratio, an alarm is issued.

[0011] Optionally, receiving the GNSS satellite navigation signal includes dividing the received data into a GNSS observation file, a satellite ephemeris file, and a satellite ICD file; wherein,

[0012] Use the GNSS observation file, satellite ephemeris file and satellite ICD file to extrapolate the theoretical coordinates of the current epoch from the position coordinates of the previous epoch and compare them with the coordinates of the positioning solution;

[0013] Use GNSS observation files for carrier-to-noise ratio determination.

[0014] Optionally, positioning solution using observation files and ephemeris files in GNSS satellite navigation signals includes:

[0015] Extract pseudorange observation value ρ from GNSS observation file i ;

[0016] According to the satellite ephemeris file, calculate the visible satellite coordinates (x i ,y i , z i );

[0017] After performing pseudorange corrections for satellite clock error, ionospheric delay, and tropospheric delay errors, the observation model is established:

[0018]

[0019] Where c represents the speed of light, t u represents the clock error of the receiver to be solved, and x, y, and z represent the position coordinates of the receiver to be solved;

[0020] The receiver position coordinates (x m ,y m ,z m );

[0021] The receiver velocity and acceleration are calculated as (v x,m ,v y,m ,v z,m )、(a x,m ,a y,m ,az,m );

[0022] Specify the receiver position coordinates of the previous epoch as (x m-1 ,y m-1 ,z m-1 ), then the theoretical coordinates of the current epoch position are:

[0023]

[0024] Where, v x,m-1 、v y,m-1 、v z,m-1 are the three-dimensional speed of the receiver at time m-1; a x,m-1 、a y,m-1 、a z,m-1 They represent the three-dimensional acceleration of the receiver at time m-1.

[0025] Optionally, determining the position based on the position information output by processing the GNSS satellite navigation signal includes:

[0026] Determine the difference between the current position coordinates and the theoretical coordinates. If it exceeds the set threshold, an alarm will be issued.

[0027] When there is no abnormality in the position judgment, the power attenuation result is calculated based on the transmission power of the GNSS satellite navigation signal and the distance information between the satellite and the onboard GNSS receiver and converted into the carrier-to-noise ratio, including:

[0028] Calculate the geometric distance between the satellite and the onboard GNSS receiver at the current epoch:

[0029]

[0030] According to the satellite ICD file, obtain the satellite transmission power information to Calculate the null attenuation power result and convert it into carrier-to-noise ratio information.

[0031] Optional, according to Calculate the null attenuation power result and convert it into carrier-to-noise ratio information including:

[0032] Thermal noise is generated by the thermal motion of charged particles in the GPS receiver antenna and circuits. The power temperature and noise bandwidth of thermal noise satisfy the following function:

[0033] N=kTB

[0034] Where k is the Boltzmann constant, T is the absolute temperature in Kelvin, and B is the signal bandwidth in Hz.

[0035] It is defined as the ratio of signal power Ps to noise signal power N:

[0036]

[0037] Then the carrier-to-noise power spectral density ratio C / N0 satisfies:

[0038]

[0039] According to the satellite signal power P received by the receiving antenna at point R R , converted into a carrier-to-noise ratio that satisfies:

[0040]

[0041] Optionally, according to the satellite signal power P received by the receiving antenna at point R R , converted into carrier-to-noise ratio specifically includes:

[0042] Let the effective receiving area of ​​the receiving antenna in a specified direction be A R , then the corresponding gain of the antenna is G R for:

[0043]

[0044] Where λ is the signal wavelength;

[0045] At the signal transmitting end, the effective area of ​​the satellite transmitting antenna is A T , the corresponding gain G T for:

[0046]

[0047] The satellite signal power P received by the receiving antenna at point R R for:

[0048]

[0049] Where d is the distance between the satellite antenna and the receiving point R of the satellite S in the specified direction.

[0050] Optionally, the carrier-to-noise ratio determination is completed based on the carrier-to-noise ratio converted from the power attenuation result and the carrier-to-noise ratio information output by receiving and processing the GNSS satellite navigation signal, including:

[0051] Calculate the difference between the carrier-to-noise ratio of the satellite signal power attenuation result of the corresponding epoch and the carrier-to-noise ratio of the satellite signal recorded in the GNSS observation file. If the difference is greater than the threshold, an alarm is issued.

[0052] The embodiment of the present application only needs to determine whether the receiver output position is abnormal. Under normal circumstances, the theoretical value of the satellite signal power reaching the receiver is calculated and converted into a carrier-to-noise ratio. It is compared with the carrier-to-noise ratio of the receiver's own output to determine whether the satellite signal arrival power is abnormal, thereby determining whether there is a deception signal. The original output value of the receiver is fully utilized as a deception detection quantity, effectively reducing costs.

[0053] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0055] Figure 1 This is a flowchart of a fraud detection method according to an embodiment of the present application;

[0056] Figure 2 This is a schematic diagram of the GNSS observation data collection architecture of the deception detection method according to an embodiment of the present application;

[0057] Figure 3 This is a schematic diagram of the position anomaly judgment and the conversion of the null-attenuation carrier-to-noise ratio result into the carrier-to-noise ratio calculation process of the deception detection method according to an embodiment of the present application;

[0058] Figure 4 This is a schematic diagram of the abnormal carrier-to-noise ratio judgment architecture of the deception detection method according to an embodiment of the present application;

[0059] Figure 5 This is a schematic diagram of the architecture of the fraud detection system according to an embodiment of the present application;

[0060] Figure 6 The following is a schematic diagram of the detection process of the fraud detection system according to an embodiment of the present application. DETAILED DESCRIPTION

[0061] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0062] To achieve the objectives of the present invention, a spoofing detection method based on low-orbit GNSS observation files is provided. The receiving-end spoofing detection and processing hardware platform is a space-based GNSS receiver. Compared to traditional space-based GNSS receiver signal reception and processing, this application adds spoofing detection capabilities. Based on the space-based receiver's reception and processing of observation files, position anomalies and carrier-to-noise ratio anomalies are determined, and warning information is output based on the results of these determinations.

[0063] Specifically, the present invention provides a method for detecting spoofing based on low-orbit GNSS observation data. Figure 1 As shown, the following steps are included:

[0064] In step S101, GNSS satellite navigation signals are received and positioning is performed using the observation files and ephemeris files in the GNSS satellite navigation signals. The received data includes the satellite interface control document (ICD) file, the GNSS signal observation file and the GNSS ephemeris file. Figure 2 As shown, in some embodiments, receiving a GNSS satellite navigation signal includes dividing the received data into a GNSS observation file, a satellite ephemeris file, and a satellite ICD file; wherein,

[0065] The GNSS observation file, satellite ephemeris file and satellite ICD file are used to extrapolate the theoretical coordinates of the current epoch from the position coordinates of the previous epoch, and then compared with the positioning solution coordinates;

[0066] Use GNSS observation files for carrier-to-noise ratio determination.

[0067] In a specific example, the navigation satellite signal transmission power is obtained according to the satellite ICD file; the pseudorange observation value, navigation satellite signal carrier-to-noise ratio information, and epoch information are extracted according to the GNSS signal observation file; and the navigation satellite ephemeris information, clock correction parameters, and ionospheric delay parameter information are extracted according to the GNSS ephemeris file.

[0068] In step S102, position determination is performed based on the position information output from processing the GNSS satellite navigation signal. Specifically, the GNSS observation file and the ephemeris file are received, the coordinates of each epoch are calculated, and then position determination is performed.

[0069] In step S103, when there is no abnormality in the position determination, the power attenuation result is calculated based on the transmission power of the GNSS satellite navigation signal and the distance information between the satellite and the onboard GNSS receiver and converted into a carrier-to-noise ratio.

[0070] In step S104, the carrier-to-noise ratio is determined based on the carrier-to-noise ratio converted from the power attenuation result and the carrier-to-noise ratio information output by receiving and processing the GNSS satellite navigation signal.

[0071] In step S105 , if the carrier-to-noise ratio is abnormal, an alarm is issued.

[0072] The embodiment of the present application only needs to determine whether the receiver output position is abnormal. Under normal circumstances, the theoretical value of the satellite signal power reaching the receiver is calculated and converted into a carrier-to-noise ratio. It is compared with the carrier-to-noise ratio of the receiver's own output to determine whether the satellite signal arrival power is abnormal, thereby determining whether there is a deception signal. The original output value of the receiver is fully utilized as a deception detection quantity, effectively reducing costs.

[0073] In some embodiments, as Figure 3 As shown in the figure, positioning solution using observation files and ephemeris files in GNSS satellite navigation signals includes:

[0074] Extract pseudorange observation value ρ from GNSS observation file i ;

[0075] According to the satellite ephemeris file, calculate the visible satellite coordinates (x i ,y i , z i );

[0076] After performing pseudorange corrections for satellite clock error, ionospheric delay, and tropospheric delay errors, the observation model is established:

[0077]

[0078] Where c represents the speed of light, t u represents the clock error of the receiver to be solved, and x, y, and z represent the position coordinates of the receiver to be solved;

[0079] The receiver position coordinates (x m ,y m ,z m );

[0080] The receiver position coordinates (x m ,y m ,z m );

[0081] The receiver velocity and acceleration are calculated as (v x,m ,v y,m ,v z,m )、(a x,m ,a y,m ,a z,m );

[0082] Specify the receiver position coordinates of the previous epoch as (x m-1 ,y m-1 ,z m-1 ), then the theoretical coordinates of the current epoch position are:

[0083]

[0084] Where, v x,m-1 、v y,m-1 、v z,m-1 are the three-dimensional speed of the receiver at time m-1; a x,m-1 、a y,m-1 、a z,m-1 They represent the three-dimensional acceleration of the receiver at time m-1.

[0085] In some embodiments, determining a position based on position information output from processing a GNSS satellite navigation signal includes:

[0086] Determine the difference between the current position coordinates and the theoretical coordinates. If it exceeds the set threshold, an alarm is issued. If it does not exceed the set threshold, proceed to the next step.

[0087] When there is no abnormality in the position judgment, the power attenuation result is calculated based on the transmission power of the GNSS satellite navigation signal and the distance information between the satellite and the onboard GNSS receiver and converted into the carrier-to-noise ratio, including:

[0088] Calculate the geometric distance between the satellite and the onboard GNSS receiver at the current epoch:

[0089]

[0090] According to the satellite ICD file, obtain the satellite transmission power information to Calculate the null attenuation power result and convert it into carrier-to-noise ratio information.

[0091] In some embodiments, according to Calculate the null attenuation power result and convert it into carrier-to-noise ratio information including:

[0092] Thermal noise is generated by the thermal motion of charged particles in the GPS receiver antenna and circuits. The power temperature and noise bandwidth of thermal noise satisfy the following function:

[0093] N=kTB

[0094] Where k is the Boltzmann constant, T is the absolute temperature in Kelvin, and B is the signal bandwidth in Hz. For ease of calculation, the room temperature is set to 16.85°C, so that T = 290°K. In the case of a 1Hz bandwidth, the noise power is calculated as:

[0095] N (dBW) =10×lg(1.38×10 -23 ×290×1)=-204dBW

[0096] Since the noise power N is related to the value of the noise bandwidth B, the noise bandwidth must be defined to be constant each time the noise power is given. Therefore, the power spectral density (dBm / Hz) is often used to describe noise of different bandwidths:

[0097]

[0098] The thermal noise power of the GPS L1 C / A signal calculated with a 2MHz bandwidth is -111dBm.

[0099] The strength of the signal received by a GPS receiver cannot fully reflect the quality of the signal. The signal-to-noise ratio (SNR) is often used to measure signal quality. It is defined as the ratio of the signal power Ps to the noise signal power N, expressed in dB, and satisfies:

[0100]

[0101] Then the carrier-to-noise power spectral density ratio C / N0 (Carrier to Noise density ratio), in dB·Hz, satisfies:

[0102]

[0103] If the transmission power of a satellite signal is P T , the gain of the satellite antenna in a certain direction is G T At the receiving point R at a distance d from the satellite S in this direction, the satellite signal power intercepted by the receiving antenna per unit area is equal to the transmitting power P T Divide by the area of ​​the sphere 4πd 2 Multiply by the gain G T ,Right now

[0104]

[0105] The received power per unit area ψ shown in the above formula is also called power flow density.

[0106] In some embodiments, the power P of the satellite signal received by the receiving antenna at point R is R , converted into carrier-to-noise ratio specifically includes:

[0107] Let the effective receiving area of ​​the receiving antenna in a specified direction be A R , then the corresponding gain of the antenna is G R for:

[0108]

[0109] Where λ is the signal wavelength; at the signal transmitting end, the effective area of ​​the satellite transmitting antenna is A T , the corresponding gain G T for:

[0110]

[0111] The satellite signal power P received by the receiving antenna at point R R for:

[0112]

[0113] According to the satellite signal power P received by the receiving antenna at point R R , converted into a carrier-to-noise ratio that satisfies:

[0114]

[0115] In some embodiments, as Figure 4 As shown, based on the carrier-to-noise ratio converted from the power attenuation result and the carrier-to-noise ratio information output by the GNSS satellite navigation signal reception and processing, the carrier-to-noise ratio judgment is completed, including:

[0116] Calculate the corresponding epoch satellite signal power attenuation result to convert the carrier-to-noise ratio Satellite signal carrier-to-noise ratio recorded in GNSS observation files The difference between If the difference is greater than the threshold, an alarm is generated and an alarm is output. For example, if the alarm threshold is set to 2dB, if it is greater than the alarm threshold, an alarm message is output.

[0117] The method of the present application first compares the pseudo-range single-point positioning result calculated based on the pseudo-range observation value output by the receiver with the theoretical position of the receiver to determine whether the receiver position coordinates have deviated significantly due to a deceptive interference signal. If the deviation is large, it is directly considered to be the presence of a deceptive signal. Otherwise, the geometric distance between the satellite and the receiver is calculated, and the power forwarding carrier-to-noise ratio after free space propagation loss is calculated based on the transmission power of each satellite. The power forwarding carrier-to-noise ratio is compared with the receiver output carrier-to-noise ratio observation value. When the difference is less than a set threshold, it is judged to be a real signal. Otherwise, the satellite signal is a deceptive signal. If some satellite signals are deceptive signals, this method can also identify the satellite numbers with deceptive signals. The present invention fully utilizes the original output observation value of the receiver, does not require additional equipment, has low computational cost, and can effectively classify and identify real signals and deceptive signals.

[0118] The embodiment of the present application also proposes an architectural example of a deception detection method based on low-orbit GNSS observation data, in which an onboard GNSS receiver receives GNSS satellite navigation signals and uses the observation files and ephemeris files in the GNSS signals for positioning and solution. Compared with the traditional GNSS user receivers that have GNSS signal reception and processing functions, the present application adds a deception detection function. Position judgment is performed based on the position information output by GNSS signal reception and processing; on the premise that there is no abnormality in the position judgment, the power attenuation result is obtained based on the GNSS satellite navigation signal transmission power and the distance information between the satellite and the onboard GNSS receiver and converted into a carrier-to-noise ratio; and then the carrier-to-noise ratio is converted based on the power attenuation result and the carrier-to-noise ratio information output by GNSS signal reception and processing to realize carrier-to-noise ratio judgment. Specifically, if Figure 5 、 Figure 6 As shown, the architecture of this application includes:

[0119] The data collection module is used to divide the received data into GNSS observation files, satellite ephemeris files and satellite ICD files; wherein the GNSS observation files, satellite ephemeris files and satellite ICD files are sent to the position determination module; and the GNSS observation files are sent to the carrier-to-noise ratio determination module;

[0120] A position determination module is used to determine the position based on the position information output by processing the GNSS satellite navigation signal;

[0121] The carrier-to-noise ratio judgment module is used to calculate the power attenuation result based on the transmission power of the GNSS satellite navigation signal and the distance information between the satellite and the onboard GNSS receiver, and convert it into a carrier-to-noise ratio, and complete the carrier-to-noise ratio judgment based on the carrier-to-noise ratio converted from the power attenuation result and the carrier-to-noise ratio information output by the GNSS satellite navigation signal reception and processing;

[0122] The system alarm module is used to issue an alarm when the carrier-to-noise ratio is abnormal.

[0123] Specifically, the position judgment module includes three sub-modules: pseudo-range positioning, satellite and receiver distance calculation, and power attenuation result conversion to carrier-to-noise ratio. The pseudo-range positioning sub-module receives the GNSS observation file and the ephemeris file, calculates the position coordinates of the previous epoch and the current epoch, extrapolates the theoretical position coordinates of the current epoch through the previous epoch position coordinates, and then performs position judgment, and then sends the judgment result to the sub-module for calculating the distance between the GNSS satellite and the receiver. The sub-module for calculating the distance between the receiver and the satellite receives the position judgment and pseudo-range positioning solution information, and then sends the calculation result of the distance between the satellite and the receiver to the power attenuation result conversion to carrier-to-noise ratio sub-module. The power attenuation result conversion to carrier-to-noise ratio sub-module receives the satellite and receiver distance information and the satellite transmission power obtained from the satellite ICD file, and sends the carrier-to-noise ratio result.

[0124] This application utilizes a spoofing detection and processing hardware platform on a satellite-based GNSS receiver. Compared to traditional satellite-based GNSS receiver signal reception and processing, this application adds spoofing detection capabilities. Compared to existing technologies, spoofing detection is primarily targeted at future developments in satellite-based GNSS receiver anomaly detection. It does not require changes to the satellite-based GNSS receiver hardware; instead, it adds a spoofing detection module. By determining the correctness of the receiver's received signal power, this improves the security of the receiver's received signal and enhances the user terminal's ability to resist spoofing attacks.

[0125] It should be noted that, in the various embodiments of the present application, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0126] The serial numbers of the above embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0127] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus the necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes a number of instructions for enabling a terminal (which can be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in each embodiment of the present application.

[0128] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are protected by this application.

Claims

1. A spoofing detection method based on low-orbit GNSS observation data, characterized in that: include: Receive GNSS satellite navigation signals and use the observation files and ephemeris files in the GNSS satellite navigation signals to perform positioning solutions; Determine the position based on the position information output by processing the GNSS satellite navigation signal; When there is no abnormality in the position judgment, the power attenuation result is calculated based on the transmission power of the GNSS satellite navigation signal and the distance information between the satellite and the onboard GNSS receiver, and converted into the carrier-to-noise ratio; The carrier-to-noise ratio is determined based on the carrier-to-noise ratio converted from the power attenuation result and the carrier-to-noise ratio information output by the GNSS satellite navigation signal reception and processing. In case of abnormal carrier-to-noise ratio, an alarm is issued.

2. The spoofing detection method based on low-orbit GNSS observation data according to claim 1, characterized in that: Receiving GNSS satellite navigation signals includes dividing the received data into GNSS observation files, satellite ephemeris files and satellite ICD files; wherein, Use the GNSS observation file, satellite ephemeris file and satellite ICD file to extrapolate the theoretical coordinates of the current epoch from the position coordinates of the previous epoch and compare them with the coordinates of the positioning solution; Use GNSS observation files for carrier-to-noise ratio determination.

3. The spoofing detection method based on low-orbit GNSS observation data according to claim 2, characterized in that: Positioning solutions using observation files and ephemeris files in GNSS satellite navigation signals include: Extract pseudorange observation value ρ from GNSS observation file i ; According to the satellite ephemeris file, calculate the visible satellite coordinates (x i ,y i , z i ); After performing pseudorange corrections for satellite clock error, ionospheric delay, and tropospheric delay errors, the observation model is established: Where c represents the speed of light, t u represents the receiver clock error to be solved, and x, y, and z represent the receiver position coordinates to be solved; The receiver position coordinates (x m ,y m ,z m ); The receiver velocity and acceleration are calculated as (v x,m ,v y,m ,v z,m )、(a x,m ,a y,m ,a z,m ); Specify the receiver position coordinates of the previous epoch as (x m-1 ,y m-1 ,z m-1 ), then the theoretical coordinates of the current epoch position are: Where, v x,m-1 、v y,m-1 、v z,m-1 are the three-dimensional speed of the receiver at time m-1; a x,m-1 、a y,m-1 、a z,m-1 They represent the three-dimensional acceleration of the receiver at time m-1.

4. The method for detecting spoofing based on low-orbit GNSS observation data according to claim 3, wherein: Position determination based on the position information output by processing the GNSS satellite navigation signal includes: Determine the difference between the current position coordinates and the theoretical coordinates. If it exceeds the set threshold, an alarm will be issued. When there is no abnormality in the position judgment, the power attenuation result is calculated based on the transmission power of the GNSS satellite navigation signal and the distance information between the satellite and the onboard GNSS receiver and converted into the carrier-to-noise ratio, including: Calculate the geometric distance between the satellite and the onboard GNSS receiver at the current epoch: According to the satellite ICD file, obtain the satellite transmission power information to Calculate the null attenuation power result and convert it into carrier-to-noise ratio information.

5. The method for detecting spoofing based on low-orbit GNSS observation data according to claim 4, wherein: according to Calculate the null attenuation power result and convert it into carrier-to-noise ratio information including: Thermal noise is generated by the thermal motion of charged particles in the GPS receiver antenna and circuits. The power temperature and noise bandwidth of thermal noise satisfy the following function: N=kTB Where k is the Boltzmann constant, T is the absolute temperature in Kelvin, and B is the signal bandwidth in Hz. Define the ratio of signal power Ps to noise signal power N to satisfy: Then the carrier-to-noise power spectral density ratio C / N0 satisfies: According to the satellite signal power P received by the receiving antenna at point R R , converted into a carrier-to-noise ratio that satisfies:

6. The method for detecting spoofing based on low-orbit GNSS observation data according to claim 5, wherein: According to the satellite signal power P received by the receiving antenna at point R R , converted into carrier-to-noise ratio specifically includes: Let the effective receiving area of ​​the receiving antenna in a specified direction be A R , then the corresponding gain of the antenna is G R for: Where λ is the signal wavelength; At the signal transmitting end, the effective area of ​​the satellite transmitting antenna is A T , the corresponding gain G T for: The satellite signal power P received by the receiving antenna at point R R for: Where d is the distance between the satellite antenna and the receiving point R of the satellite S in the specified direction.

7. The method for detecting spoofing based on low-orbit GNSS observation data according to claim 6, wherein: Based on the carrier-to-noise ratio converted from the power attenuation result and the carrier-to-noise ratio information output by the GNSS satellite navigation signal reception and processing, the carrier-to-noise ratio judgment is completed, including: Calculate the difference between the carrier-to-noise ratio of the satellite signal power attenuation result of the corresponding epoch and the carrier-to-noise ratio of the satellite signal recorded in the GNSS observation file. If the difference is greater than the threshold, an alarm is issued.

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