Vehicle status determination method and GPS drift compensation method

Abstract

This invention relates to a vehicle state determination method and a GPS drift compensation method, belonging to the field of vehicle positioning technology. The method includes: acquiring the vehicle's ACC status, vehicle speed, GPS speed, and acceleration; if ACC is on and the vehicle speed is greater than zero for a first set time, the vehicle is in a pre-moving state; if ACC is off, or if ACC is on and the vehicle speed is zero for a first set time, the vehicle is in a pre-stationary state; in the pre-moving state, if the vehicle is stationary, the vehicle is stationary; if the vehicle is moving, the GPS speed is determined: if the GPS speed is less than or equal to a GPS speed threshold for a second set time, the vehicle is stationary; otherwise, the vehicle is moving; in the pre-stationary state, if the vehicle is moving, the vehicle is moving; if the vehicle is stationary, the vehicle is stationary. This invention adds GPS speed and acceleration to the ACC status and vehicle speed, thus determining the vehicle's state more accurately.

Description

Technical Field

[0001] This invention relates to a method for determining vehicle status and a GPS drift compensation method, belonging to the field of vehicle positioning technology. Background Technology

[0002] GPS (Global Positioning System) positioning is a widely used positioning technology, applied in fields such as navigation, exploration, transportation, and fieldwork. GPS positioning technology calculates the location of a target GPS receiver by using the known positions of three satellites in space and the relative distances between the target GPS receiver and these satellites. Specifically, satellites orbit precisely according to ephemeris data, and their positions at any given time are known. The specific radio waves (GPS signals) emitted by the satellites propagate through space and can be received by the target GPS receiver. Since the speed of radio wave propagation is known, the distance between the target GPS receiver and the satellite can be calculated by using the time difference between the received radio wave and the emitted radio wave.

[0003] In GPS positioning technology applications, due to satellite orbit position deviations, ephemeris and clock errors, and fluctuations in the propagation speed of radio waves (the propagation speed of radio waves varies slightly in different environments; for example, the propagation speed changes when radio waves pass through the atmosphere or ionosphere), there will be a certain deviation between the calculated location of the target GPS receiver and the actual location of the target GPS receiver. Furthermore, during the movement, a continuous trajectory with a certain interval from the actual route will appear, which is known as GPS positioning drifting.

[0004] GPS positioning drift is categorized into static drift and dynamic drift. Static drift refers to the drift that occurs when the GPS receiver's position at the test point remains unchanged relative to its surroundings during the positioning process. Dynamic drift refers to the drift that occurs when the GPS receiver is in motion during the positioning process. Generally, different drift compensation methods are required for different GPS receiver states. Therefore, it is necessary to determine whether the GPS receiver is stationary or in motion before performing drift compensation.

[0005] Current technologies typically determine vehicle status based on ACC status and vehicle speed. When ACC is active and the vehicle speed is zero, or when ACC is off, the vehicle is considered stationary; when ACC is active and the vehicle speed is greater than zero, the vehicle is considered moving. This method of determining vehicle status is inaccurate. For example, when ACC is off, the vehicle is considered moving even when it is rolling backwards or being towed, leading to reduced accuracy in GPS drift compensation. Therefore, a more accurate technical solution for determining vehicle status is needed to achieve more precise GPS drift compensation. Summary of the Invention

[0006] The purpose of this application is to provide a technical solution for a vehicle state determination method to solve the problem of inaccurate vehicle state determination in existing methods, and also to provide a technical solution for a GPS drift compensation method to solve the problem of inaccurate drift compensation in existing methods.

[0007] To achieve the above objectives, this application proposes a technical solution for a vehicle state determination method, comprising the following steps:

[0008] 1) Obtain the vehicle's ACC status, vehicle speed, GPS speed, and acceleration; and determine the vehicle's attitude based on the acceleration; ACC status includes ACC off and ACC on; the GPS speed is the speed output by the GPS positioning device;

[0009] 2) Determine the vehicle's pre-state based on ACC status and vehicle speed: If ACC is on and the vehicle speed is greater than zero for a first set time, the vehicle is in a pre-moving state, proceed to step 3); If ACC is off, or if ACC is on and the vehicle speed is zero for a first set time, the vehicle is in a pre-stationary state, proceed to step 4).

[0010] 3) In the pre-motion state, if the vehicle's attitude is determined to be stationary based on acceleration, then the vehicle is stationary; if the vehicle's attitude is determined to be moving based on acceleration, then the magnitude of the GPS speed is determined: if the GPS speed is less than or equal to the GPS speed threshold for a second set time, then the vehicle is stationary; otherwise, the vehicle is moving.

[0011] 4) In the pre-stationary state, if the vehicle's attitude is determined to be in motion based on acceleration, then the vehicle is in motion; if the vehicle's attitude is determined to be in a stationary state based on acceleration, then the vehicle is in a stationary state.

[0012] The beneficial effects of the vehicle state determination method of the present invention are as follows: The present invention adds GPS speed and acceleration to the ACC state and vehicle speed. The pre-state of the vehicle is determined by the ACC state and vehicle speed. In the pre-stationary state, the vehicle state is determined directly by the vehicle attitude obtained from the acceleration. In the pre-moving state, in addition to the vehicle attitude obtained from the acceleration, the vehicle state is also determined by combining the GPS speed. The present invention determines the vehicle state more accurately.

[0013] Furthermore, the acceleration is acquired by a triaxial accelerometer.

[0014] Furthermore, the process of determining the vehicle's attitude based on acceleration is as follows:

[0015] Take N sets of acceleration data. Each set of acceleration data includes several sampling data. Each sampling data includes acceleration values ​​on the X-axis, Y-axis, and Z-axis.

[0016] Calculate the standard deviation of acceleration along the X-axis (stdX), Y-axis (stdY), and Z-axis (stdZ) for each set of acceleration data.

[0017] If stdX>stdMX, or stdY>stdMY, or stdZ>stdMZ in a certain group, then the vehicle is in a pre-moving posture; otherwise, the vehicle is in a pre-stationary posture. Where stdMX is the acceleration threshold of the X-axis, stdMY is the acceleration threshold of the Y-axis, and stdMZ is the acceleration threshold of the Z-axis.

[0018] If all acceleration data in group M are in a pre-motion posture, then the vehicle is in a moving posture; otherwise, the vehicle is in a stationary posture, and M < N.

[0019] Furthermore, in step 2), if the vehicle speed is an invalid speed, the vehicle state is determined by using a pre-motion state or a pre-stationary state.

[0020] Furthermore, in step 3), if the acceleration is ineffective in the pre-motion state, the previous state of the vehicle is output as the current state of the vehicle.

[0021] Furthermore, in step 4), if the acceleration is ineffective in the pre-stationary state, the vehicle is determined to be stationary.

[0022] In addition, this application also proposes a technical solution for a GPS drift compensation method, including the following steps:

[0023] 1) Obtain the vehicle's ACC status, vehicle speed, GPS speed, and acceleration; and determine the vehicle's attitude based on the acceleration; ACC status includes ACC off and ACC on; the GPS speed is the speed output by the GPS positioning device;

[0024] 2) Determine the vehicle's pre-state based on ACC status and vehicle speed: If ACC is on and the vehicle speed is greater than zero for a first set time, the vehicle is in a pre-moving state, proceed to step 3); If ACC is off, or if ACC is on and the vehicle speed is zero for a first set time, the vehicle is in a pre-stationary state, proceed to step 4).

[0025] 3) In the pre-motion state, if the vehicle's attitude is determined to be stationary based on the acceleration, then the vehicle is stationary and proceeds to step 6); if the vehicle's attitude is determined to be in motion based on the acceleration, then the magnitude of the GPS speed is determined: if the GPS speed is less than or equal to the GPS speed threshold for a second set time, then the vehicle is stationary and proceeds to step 6); otherwise, the vehicle is in motion and proceeds to step 5.

[0026] 4) In the pre-stationary state, if the vehicle's attitude is determined to be in motion based on the acceleration, then the vehicle is in motion and proceed to step 5); if the vehicle's attitude is determined to be in a stationary state based on the acceleration, then the vehicle is in a stationary state and proceed to step 6).

[0027] 5) In motion, determine whether a large-distance drift has occurred based on the original latitude and longitude information of the current and previous moments: if a large-distance drift has occurred, calculate the azimuth angle and output the latitude and longitude of the current moment by calculating the historical trajectory;

[0028] 6) In a stationary state, compare the HDOP value at the current moment with the HDOP value at the previous moment. If the HDOP value at the current moment is greater than the HDOP value at the previous moment, output the original latitude and longitude information of the previous moment as the compensated latitude and longitude information of the current moment. If the HDOP value at the current moment is less than or equal to the HDOP value at a historical moment, output the original latitude and longitude information of the current moment.

[0029] The beneficial effects of the GPS drift compensation method of the present invention are as follows: The present invention adds GPS speed and acceleration to the ACC state and vehicle speed. The pre-state of the vehicle is determined by the ACC state and vehicle speed. In the pre-stationary state, the vehicle state is determined directly based on the vehicle attitude obtained from the acceleration. In the pre-moving state, in addition to the vehicle attitude obtained from the acceleration, the vehicle state is also determined by combining the GPS speed. The present invention determines the vehicle state more accurately, and thus performs drift compensation more accurately.

[0030] Furthermore, in step 5), if d is greater than dm, it is determined that a large-distance drift has occurred. d is the displacement at the current moment, which is calculated based on the original latitude and longitude information of the current moment and the previous moment. dm is the maximum displacement at the current moment, which is calculated based on the vehicle speed at the current moment.

[0031] Furthermore, the formula for calculating the maximum displacement dm at the current moment is: dm=(speed / 3.6)(t-t1)+x, where speed is the vehicle speed at the current moment; x is the positioning error; t is the time at the current moment; and t1 is the time at the previous moment.

[0032] Furthermore, the acceleration is acquired by a triaxial accelerometer. Attached Figure Description

[0033] Figure 1 This is a flowchart of the vehicle state determination method of the present invention;

[0034] Figure 2 This is a flowchart of the vehicle attitude determination process of the present invention;

[0035] Figure 3 This is a flowchart of GPS drift compensation when the vehicle is in motion according to the present invention.

[0036] Figure 4 This is a flowchart of GPS drift compensation when the vehicle is stationary. Detailed Implementation

[0037] Example of GPS drift compensation method:

[0038] The main concept of this invention is that, based on the existing technology, judging the vehicle status solely by ACC status and vehicle speed is inaccurate, leading to inaccurate GPS drift compensation. This invention also combines the status of a three-axis accelerometer to judge the vehicle status. By comprehensively judging the vehicle status using data collected by the three-axis accelerometer, the accuracy of vehicle status judgment is improved, thereby improving the accuracy of GPS drift compensation.

[0039] The GPS drift compensation method is based on a GPS drift compensation system, which includes a positioning module, a three-axis accelerometer, and a controller. The positioning module is communicatively connected to the controller, and the three-axis accelerometer is connected to the controller's input.

[0040] The three-axis accelerometer is used to collect acceleration information of the vehicle's X, Y, and Z axes and send the collected information to the controller. The controller calculates the vehicle's attitude based on the information collected by the three-axis accelerometer.

[0041] The positioning module includes a GPS positioning device, a vehicle speed acquisition device (which can be a device that acquires pulse speed or acquires vehicle speed through the vehicle's CAN bus), and an ACC status acquisition device. The GPS positioning device is used to acquire the vehicle's original positioning information and GPS speed, the vehicle speed sensor is used to acquire the vehicle's speed, and the ACC status acquisition device is used to acquire the ACC status of the ignition switch (ACC is the accessory power position, one of the positions of the car ignition switch, which connects the power supply to some of the car's equipment).

[0042] The controller receives raw positioning information, GPS speed, vehicle speed, and ACC status from the positioning module in real time. Based on the received information and the vehicle's attitude, it determines the vehicle's state, calculates drift compensation according to the vehicle's state, and returns the compensated positioning information to the GPS positioning module for display. Specifically, the controller includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the vehicle state determination method and the GPS drift compensation method.

[0043] Vehicle status determination methods, such as Figure 1 As shown, it includes the following steps:

[0044] 1) Obtain ACC status, GPS speed, vehicle speed, and vehicle attitude.

[0045] In this step, the ACC status, GPS speed, and vehicle speed are collected by the corresponding data acquisition devices. The ACC status includes two types: ACCOFF (power off, ACC off) and ACC ON (power on, ACC on).

[0046] like Figure 2 As shown, the vehicle's attitude is calculated based on the acceleration information collected by the triaxial accelerometer. The calculation process is as follows:

[0047] a. With the triaxial accelerometer active, buffer 5 consecutive sets of acceleration values ​​for the X, Y, and Z axes; each set includes 60 sampling data points;

[0048] b. Based on the 60 sampling data in each group, calculate the standard deviation of acceleration stdX, stdY, and stdZ of acceleration for each group;

[0049] c. Compare the standard deviation of acceleration on the X-axis (stdX), Y-axis (stdY), and Z-axis (stdZ) of a given group with their respective thresholds. If stdX > stdMX, or stdY > stdMY, or stdZ > stdMZ, the vehicle is in a pre-motion posture; otherwise, the vehicle is in a pre-stationary posture. Where stdMX is the acceleration threshold on the X-axis, stdMY is the acceleration threshold on the Y-axis, and stdMZ is the acceleration threshold on the Z-axis.

[0050] d. If at least 4 out of the 5 sets of data are in a pre-motion posture, then the vehicle is in a motion posture; otherwise, the vehicle is in a stationary posture.

[0051] 2) Determine whether the vehicle is in a pre-stationary state, a pre-moving state, or an unknown state based on the ACC status and vehicle speed.

[0052] If the ACC status is ACC OFF, the vehicle is determined to be in a pre-stationary state, and proceed to step 4);

[0053] If the ACC status is ACC ON, then the vehicle speed is determined: if the vehicle speed is valid and remains zero for 3 seconds (the first set time, which can be set as needed), the vehicle is determined to be in a pre-stationary state and proceeds to step 4); if the vehicle speed is valid and remains greater than zero for 3 seconds, the vehicle is determined to be in a pre-moving state and proceeds to step 3); if the vehicle speed is invalid (e.g., the vehicle speed is negative, indicating an abnormal speed and unusable), the vehicle is determined to be in an unknown state and proceeds to step 5).

[0054] 3) In the pre-motion state, if the three-axis accelerometer is effective and the vehicle is in motion, the vehicle state is determined based on the GPS speed: if the GPS speed Vg is less than or equal to 5 km / h (GPS speed threshold) for 3 seconds (the second set time, which can be set as needed), the vehicle is stationary; otherwise, the vehicle is in motion. If the three-axis accelerometer is effective and the vehicle is in a stationary state, the vehicle is stationary. If the three-axis accelerometer is ineffective (no data output from the three-axis accelerometer indicates that the three-axis accelerometer is ineffective), the previous vehicle state is output as the current vehicle state.

[0055] 4) In the pre-stationary state, if the three-axis accelerometer is effective and the vehicle is in a moving posture, then the vehicle is in a moving state; if the three-axis accelerometer is effective and the vehicle is in a stationary posture, then the vehicle is in a stationary state; if the three-axis accelerometer is ineffective, then the vehicle is determined to be in a stationary state.

[0056] 5) In an unknown state, the vehicle's state can be determined by referring to either the pre-movement state or the pre-stationary state.

[0057] Based on the above vehicle state determination method, the vehicle state can be determined, and then the positioning information can be compensated according to the vehicle state and the corresponding compensation algorithm: when the vehicle is in motion, large-distance drift is determined and compensated to achieve dynamic drift compensation; when the vehicle is stationary, latitude and longitude are dynamically optimized according to HDOP (Horizontal Dilution Of Precision) to achieve static drift compensation.

[0058] Specifically, in motion, such as Figure 3 As shown, GPS drift compensation includes the following steps:

[0059] 1) Cache 8 seconds of continuous raw location information, including the raw latitude and longitude information and HDOP value corresponding to each UTC time (Coordinated Universal Time, also known as World Standard Time or Coordinated International Time).

[0060] 2) Calculate the displacement d at the current time based on the longitude lon and latitude lat at the current time t and the longitude lon1 and latitude lat1 at the previous time t1. Determine the magnitude of the displacement d at the current time and the maximum displacement dm at the current time. If d is greater than dm, it is determined that a large-distance drift has occurred, and proceed to step 3) to perform drift compensation.

[0061] In this step, the Earth is considered a perfect sphere, and the displacement d and the maximum displacement dm at the current moment are calculated using the Earth's average radius Re:

[0062] dm = (speed / 3.6)(t-t1) + x;

[0063] Where speed is the current vehicle speed in km / h; however, in cases of abnormal speed, the maximum speed will be used, which depends on the vehicle's performance. x represents the positioning error in meters (m). The current displacement d can be calculated using the Haversine formula.

[0064] 3) Calculate the azimuth angle based on the longitude lon1 and latitude lat1 at the previous time t1 and the longitude lon2 and latitude lat2 at the time two before that t2. Then, without any sudden change in azimuth angle and vehicle speed, calculate the longitude and latitude of the current time through the historical trajectory, and output the calculated longitude and latitude of the current time as the compensated longitude and latitude.

[0065] The azimuth angle and the longitude lon and latitude lat at the current time t can be calculated using the inverse solution method in the Vincenty formula.

[0066] In the above drift compensation process, if the compensation time is too long, the trajectory will be significantly distorted. Therefore, generally, the maximum compensation time is 3 s. At the 4th second, it is determined whether drift continues to occur based on the HDOP value h at the current moment and the displacement d at the current moment. If h < hm (hm is the HDOP threshold) and d < sm (sm is the maximum displacement calculated based on the maximum vehicle speed), no dynamic drift occurs, and the original latitude and longitude information can be output. Otherwise, drift continues to occur. However, at this time, continuing compensation is meaningless, and the original latitude and longitude information is directly output. Of course, the maximum compensation duration can be adjusted as needed, and this invention does not limit it.

[0067] In the stationary state, as Figure 4 shown, the GPS drift compensation includes the following steps:

[0068] 1) Collect the original latitude and longitude information and HDOP value corresponding to each UTC time, that is, the original positioning information;

[0069] 2) Compare the magnitude relationship between the HDOP value at the current moment and the HDOP value at the previous moment. If the HDOP value at the current moment is greater than the HDOP value at the previous moment, the original latitude and longitude information at the previous moment is output as the compensated latitude and longitude information at the current moment. If the HDOP value at the current moment is less than or equal to the HDOP value at the historical moment, the original latitude and longitude information at the current moment is output.

[0070] Method for determining the validity of latitude and longitude information: The longitude range is [-180°, 180°], and the latitude range is [-90°, 90°]. Data beyond this range is discarded and not used.

[0071] In the above embodiments, in order to improve the accuracy of vehicle attitude determination, the vehicle attitude is determined by multiple groups of acceleration data. As other implementation manners, the vehicle attitude can also be determined by a group of data, and this invention does not limit this.

[0072] Regarding when the acceleration is invalid, due to the invalidity of the data, the vehicle state can also be directly determined through the pre-state, and this invention does not limit this.

[0073] This invention adds GPS speed and acceleration on the basis of the ACC state and vehicle speed. The pre-state of the vehicle is judged through the ACC state and vehicle speed. In the pre-stationary state, the vehicle state is determined directly according to the vehicle attitude obtained from the acceleration. In the pre-moving state, in addition to the vehicle attitude obtained from the acceleration, the GPS speed needs to be combined to finally determine the vehicle state. This invention more accurately determines the vehicle state and further more accurately performs drift compensation.

[0074] Embodiment of the vehicle state determination method:

[0075] The specific implementation process and effects of the vehicle status determination method have been described in the above-mentioned GPS drift compensation method embodiments, and will not be repeated here.

Claims

1. A vehicle state determination method characterized by, The method comprises the following steps: 1) obtaining an ACC state, a vehicle speed, a GPS speed and an acceleration of the vehicle, and determining a posture of the vehicle according to the acceleration; the ACC state comprises ACC off and ACC on; the GPS speed is a speed output by a GPS positioning device; 2) determining a pre-state of the vehicle according to the ACC state and the vehicle speed: if the ACC is on and the vehicle speed is greater than zero for a first set time, the vehicle is in a pre-motion state, and step 3) is entered; if the ACC is off or the ACC is on and the vehicle speed is zero for the first set time, the vehicle is in a pre-still state, and step 4) is entered; 3) in the pre-motion state, if the posture of the vehicle determined according to the acceleration is a still posture, the vehicle is in a still state; if the posture of the vehicle determined according to the acceleration is a motion posture, the size of the GPS speed is judged: when the GPS speed is less than or equal to a GPS speed threshold for a second set time, the vehicle is in the still state, otherwise the vehicle is in the motion state; 4) in the pre-still state, if the posture of the vehicle determined according to the acceleration is a motion posture, the vehicle is in the motion state; if the posture of the vehicle determined according to the acceleration is a still posture, the vehicle is in the still state.

2. The vehicle state determination method according to claim 1, characterized by, The acceleration is obtained by a three-axis acceleration sensor.

3. The vehicle state determination method according to claim 2, characterized by, The process of determining the posture of the vehicle according to the acceleration is as follows: N groups of acceleration data are taken, each group of acceleration data comprises a plurality of sampling data, and each sampling data comprises acceleration values of X-axis, Y-axis and Z-axis; X-axis acceleration standard deviation stdX, Y-axis acceleration standard deviation stdY and Z-axis acceleration standard deviation stdZ corresponding to each group of acceleration data are calculated; if stdX of a group is greater than stdMX, or stdY is greater than stdMY, or stdZ is greater than stdMZ, the vehicle is in a pre-motion posture, otherwise the vehicle is in a pre-still posture; wherein stdMX is an X-axis acceleration threshold; stdMY is a Y-axis acceleration threshold; and stdMZ is a Z-axis acceleration threshold; if M groups of acceleration data are all in the pre-motion posture, the vehicle is in the motion state, otherwise the vehicle is in the still state, and M < N.

4. The vehicle state determination method according to claim 1, characterized by, In step 2), if the vehicle speed is an invalid vehicle speed, the pre-motion state or the pre-still state is used to determine the state of the vehicle.

5. The vehicle state determination method according to claim 1, characterized by, In step 3), in the pre-motion state, if the acceleration is invalid, the state of the vehicle in the last time is output as the state of the vehicle in the current time.

6. The vehicle state determination method according to claim 1, characterized by, In step 4), in the pre-still state, if the acceleration is invalid, the vehicle is determined to be in the still state.

7. A GPS drift compensation method, characterized by, The method comprises the following steps: 1) obtaining an ACC state, a vehicle speed, a GPS speed and an acceleration of the vehicle, and determining a posture of the vehicle according to the acceleration; the ACC state comprises ACC off and ACC on; the GPS speed is a speed output by a GPS positioning device; 2) determining a pre-state of the vehicle according to the ACC state and the vehicle speed: if the ACC is on and the vehicle speed is greater than zero for a first set time, the vehicle is in a pre-motion state, and step 3) is entered; if the ACC is off or the ACC is on and the vehicle speed is zero for the first set time, the vehicle is in a pre-still state, and step 4) is entered; 3) in the pre-motion state, if the vehicle posture is determined to be a static posture according to the acceleration, the vehicle is in a static state, and step 6) is entered; if the vehicle posture is determined to be a motion posture according to the acceleration, the size of the GPS speed is judged: when the GPS speed is less than or equal to the GPS speed threshold for a second set time, the vehicle is in a static state, and step 6) is entered, otherwise the vehicle is in a motion state, and step 5) is entered; 4) in the pre-static state, if the vehicle posture is determined to be a motion posture according to the acceleration, the vehicle is in a motion state, and step 5) is entered; if the vehicle posture is determined to be a static posture according to the acceleration, the vehicle is in a static state, and step 6) is entered; 5) in the motion state, whether a large distance drift occurs is judged according to the original longitude and latitude information at the current time and the last time: if a large distance drift occurs, the azimuth angle is calculated, the longitude and latitude at the current time are calculated through the historical trajectory, and output is performed; 6) in the static state, the HDOP value at the current time is compared with the HDOP value at the last time: if the HDOP value at the current time is greater than the HDOP value at the last time, the original longitude and latitude information at the last time is taken as the compensated longitude and latitude information at the current time, and output is performed; if the HDOP value at the current time is less than or equal to the HDOP value at the last time, the original longitude and latitude information at the current time is output.

8. The GPS drift compensation method of claim 7, wherein, In step 5), if d is greater than dm, it is determined that a large distance drift occurs, d is the displacement at the current time, which is calculated according to the original longitude and latitude information at the current time and the last time, and dm is the maximum displacement at the current time, which is calculated according to the vehicle speed at the current time.

9. The GPS drift compensation method of claim 8, wherein, The calculation formula of the maximum displacement dm at the current time is: dm=(speed / 3.6)(t-t1)+x, wherein speed is the vehicle speed at the current time; x is the positioning error; t is the time at the current time; t1 is the time at the last time.

10. The GPS drift compensation method of claim 7, wherein, The acceleration is collected by a three-axis acceleration sensor.

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