Real-time Correction System for Low Earth Orbit Satellite Positioning Error in Dynamic Environment

Abstract

The present invention discloses a real-time correction system for positioning errors of low-orbit satellites in a dynamic environment, which relates to the technical field of satellite positioning, and includes: obtaining a characteristic coordinate system; calculating the first real-time position coordinates of a target satellite; obtaining real-time environmental characteristics; determining whether the signal of the target satellite can be directly transmitted to a user receiver. If so, calculating the second real-time position coordinates of the user receiver; if not, identifying the reflection path of the signal of the target satellite and the user receiver; obtaining a characteristic angle; obtaining a target time difference, and calculating the third real-time position coordinates of the user receiver. By obtaining real-time environmental characteristics, determining whether the signal of the target satellite can be directly transmitted to the user receiver, and identifying the reflection path of the signal of the target satellite and the user receiver, the deflection angle from the direct path can be estimated through the reflection transmission path, and the time when transmission is carried out along the direct path can be estimated.

Description

Technical Field

[0001] The present invention relates to the technical field of satellite positioning, and specifically relates to a real-time correction system for low-orbit satellite positioning errors in a dynamic environment. Background Art

[0002] A satellite positioning system is a technology that uses satellites to accurately locate an object. It has developed from the initial low positioning accuracy, inability to perform real-time positioning, and difficulty in providing timely navigation services to the current high-precision GPS global positioning system. Satellite positioning can be used to guide airplanes, ships, vehicles, and individuals to reach their destinations safely, accurately, along the selected routes, and on time.

[0003] When a satellite performs positioning, since the user may move between high-rise buildings or in mountains and forests, the satellite signal cannot directly reach the user and needs to reach the user through reflection. During reflection, the angle of the satellite signal will deviate. Due to the long distance between the satellite and the user, a small deviation angle causes a large distance error, resulting in a longer received signal time measured at the user's location, a large error in calculating the distance between the satellite and the user, and a large error in the final positioning accuracy, affecting the user experience. Summary of the Invention

[0004] To solve the above technical problems, a real-time correction system for low-orbit satellite positioning errors in a dynamic environment is provided, and this technical solution solves the problems raised in the above background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A real-time correction system for low-orbit satellite positioning errors in a dynamic environment, comprising:

[0007] A satellite screening module, which selects three satellites for positioning from a group of satellites and respectively serves as target satellites. The satellites complete positioning through the signal reception of a user receiver carried by the user;

[0008] A coordinate establishment module, which selects three base points on the earth to establish coordinates and obtains a characteristic coordinate system;

[0009] A position calculation module, which calculates the first real-time position coordinates of the target satellite based on the operating orbit, operating speed, and initial position coordinates in the characteristic coordinate system of the target satellite;

[0010] A time acquisition module, which acquires the time difference between the signal of the target satellite reaching the user receiver at the positioning location as a preliminary time difference;

[0011] An environment recognition module, which recognizes the surrounding environment at the user receiver to obtain real-time environmental characteristics;

[0012] A judgment module, which, based on the real-time environmental characteristics, judges whether the signal of the target satellite can be directly transmitted to the user receiver. If so, the second real-time position coordinates of the user receiver are calculated using the prepared time difference. If not, the occluder that obstructs the signal of the target satellite and the reflector that enables indirect transmission of the signal of the target satellite are identified. The path of directly transmitting the signal of the target satellite through the occluder to the user receiver is used as the direct path, and based on the reflector, the reflection path of the signal of the target satellite to the user receiver is identified;

[0013] An angle acquisition module, which intercepts the part of the reflection path between the occluder and the target satellite to obtain a characteristic path, and identifies the deflection angle of the characteristic path relative to the direct transmission of the signal of the target satellite to the user receiver to obtain a characteristic angle;

[0014] A position correction module, which corrects the prepared time difference based on the characteristic angle and the direct path to obtain a target time difference, and uses the target time difference to calculate the third real-time position coordinates of the user receiver.

[0015] Preferably, the steps of selecting three base points on the earth to establish a coordinate system to obtain a characteristic coordinate system are as follows:

[0016] Select three base points on the earth as the first base point, the second base point, and the third base point respectively, satisfying that the lines connecting the three base points to the center of the earth are perpendicular to each other;

[0017] Use the center of the earth as the origin, use the line connecting the first base point to the center of the earth as the x-axis, use the line connecting the second base point to the center of the earth as the y-axis, and use the line connecting the third base point to the center of the earth as the z-axis to form a characteristic coordinate system.

[0018] Preferably, the steps of calculating the first real-time position coordinates of the target satellite are as follows:

[0019] Pre-obtain the equation of the operating orbit of the target satellite, and obtain the time difference between the current moment and the moment corresponding to the initial position coordinates of the target satellite as the characteristic time difference;

[0020] Multiply the characteristic time difference by the operating speed of the target satellite to obtain a calibrated distance;

[0021] Use the characteristic equivalent relationship to solve for the first real-time position coordinates. The characteristic equivalent relationship is that the calibrated distance is equal to the length of the part of the operating orbit between the first real-time position coordinates and the initial position coordinates.

[0022] Preferably, the step of identifying the surrounding environment at the user receiver to obtain real-time environmental features comprises the following steps:

[0023] Taking the location of the user receiver as the center, at least one ray is emitted along the surface of the earth, and the angle between adjacent rays is a preset angle, which is based on empirical data and is set according to the recognition accuracy;

[0024] The highest object in the direction of the ray extending from the user receiver location is taken as the feature object, and the feature object is a building or a mountain;

[0025] Pre-acquire the coordinates of the top of the feature object in the feature coordinate system as the feature coordinates;

[0026] Feature objects are paired with feature coordinates and summarized as real-time environment features.

[0027] Preferably, the step of determining whether the target satellite signal and the user receiver can be directly transmitted comprises the following steps:

[0028] Obtaining an equation of a characteristic straight line passing through the characteristic coordinates and the first real-time position coordinates as a characteristic equation;

[0029] By combining the characteristic equation and the spherical equation of the earth, the coordinates of the intersection of the characteristic straight line and the earth's surface are calculated as the node coordinates, and the distance between the node coordinates and the characteristic coordinates is calculated as the characteristic distance;

[0030] The user receiver uses laser ranging to determine the point corresponding to the node coordinates on the ray where the characteristic object is located, and the distance from the point corresponding to the node coordinates to the characteristic coordinates of the characteristic object is equal to the characteristic distance;

[0031] Connect the points corresponding to the coordinates of the adjacent nodes with line segments, and the area enclosed by at least one line segment is a feature area;

[0032] When the characteristic area contains the user receiver, direct transmission can be performed, otherwise, direct transmission cannot be performed.

[0033] Preferably, the identifying of the obstruction that blocks the signal of the target satellite and the reflector that blocks the indirect transmission of the signal of the target satellite comprises the following steps:

[0034] Use laser ranging to determine the point corresponding to the coordinates of the node closest to the user receiver as the feature point;

[0035] The feature objects on the two rays collinear with the feature points are regarded as target feature objects, the target feature objects with a larger distance from the feature coordinates to the first real-time position coordinates are regarded as reflectors, and the target feature objects with a smaller distance from the feature coordinates to the first real-time position coordinates are regarded as obstructions.

[0036] Preferably, the identification of the signal of the target satellite and the reflection path of the user receiver based on the reflector includes the following steps:

[0037] Pre-acquire the coordinates of the reflector on the ground surface as plane coordinates, divide the result of subtracting the plane coordinates from the characteristic coordinates by n to obtain a reference vector;

[0038] Uniformly set at least one sampling point in the vertical direction on the reflector, number the sampling points from top to bottom, the total number of sampling points is n + 1, and the coordinate of the i-th sampling point is the sum of the characteristic coordinates and (i - 1) times the reference vector, where the value range of i is from 1 to n + 1;

[0039] Calculate the modulus of the reference vector, and the height of the i-th sampling point is (n + 1 - i) times the modulus of the reference vector;

[0040] The user receiver uses the method of laser ranging to obtain the distance from the user receiver to the reflector;

[0041] Obtain the tangent plane equation of the reflector on the ground surface, subtract the coordinate of the i-th sampling point from the first real-time position coordinate to obtain an i vector, calculate the included angle between the i vector and the tangent plane equation to obtain a first included angle;

[0042] The ratio of the height of the i-th sampling point to the distance from the user receiver to the reflector gives a characteristic tangent value, substitute the characteristic tangent value into the arctangent function to obtain a second included angle;

[0043] Take the sampling point where the first included angle is equal to the second included angle as the reflection point;

[0044] Take the connection line between the reflection point and the target satellite and the connection line between the reflection point and the user receiver as the reflection path.

[0045] Preferably, the obtaining of the characteristic path by intercepting the part of the reflection path between the occluder and the target satellite includes the following steps:

[0046] Extend the occluder upward to divide the reflection path into two characteristic parts, and take the characteristic part closer to the target satellite as the characteristic path.

[0047] Preferably, the obtaining of the characteristic angle by identifying the deflection angle of the characteristic path relative to the signal of the target satellite and the direct transmission of the user receiver includes the following steps:

[0048] Calculate the distance from the coordinate of the reflection point to the first real-time position coordinate to obtain a first distance;

[0049] The user receiver obtains the distance from the user receiver to the reflection point by laser ranging as the second distance;

[0050] Superimpose the first included angle and the second included angle of the reflection point to obtain the target angle;

[0051] Using the cosine theorem, calculate the distance from the user receiver to the target satellite as the actual distance;

[0052] Using the sine theorem and the actual distance, calculate the characteristic angle.

[0053] Preferably, the step of correcting the preliminary time difference based on the characteristic angle and the direct path to obtain the target time difference includes the following steps:

[0054] Take the cosine value of the characteristic angle as the ratio of the target time difference to the preliminary time difference, and solve for the target time difference by inversion.

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0056] By obtaining the real-time environmental characteristics, determining whether the signal of the target satellite can be directly transmitted to the user receiver, and identifying the reflection path of the signal of the target satellite to the user receiver, it is possible to estimate the reflection transmission path of the signal when the satellite cannot directly transmit the signal. Thus, the deflection angle from the direct path can be estimated through the reflection transmission path, and then the time for direct path transmission can be estimated through the reflection transmission time. Furthermore, the time for straight-line transmission can be estimated more accurately, and the distance between the user and the satellite can be calculated through the estimated time. Finally, positioning is completed through the distance relationship of multiple satellites. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a schematic flow chart of the real-time correction system for low-earth orbit satellite positioning error in the dynamic environment of the present invention;

[0058] Figure 2 It is a schematic flow chart of establishing a coordinate system by selecting three base points on the earth to obtain a characteristic coordinate system in the present invention;

[0059] Figure 3 It is a schematic flow chart of calculating the first real-time position coordinates of the target satellite in the present invention;

[0060] Figure 4 It is a schematic flow chart of identifying the surrounding environment at the user receiver to obtain real-time environmental characteristics in the present invention;

[0061] Figure 5 It is a schematic flow chart of determining whether the signal of the target satellite can be directly transmitted to the user receiver in the present invention;

[0062] Figure 6Schematic flow chart of identifying an object blocking the signal of a target satellite and a reflector indirectly transmitting the signal of the target satellite according to the present invention;

[0063] Figure 7 Schematic flow chart of identifying the reflection path between the signal of a target satellite and a user receiver based on a reflector according to the present invention;

[0064] Figure 8 Schematic flow chart of identifying the deflection angle of a characteristic path relative to the direct transmission of the signal of a target satellite to a user receiver according to the present invention to obtain a characteristic angle. Detailed implementation manners

[0065] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments in the following description are only examples, and those skilled in the art can think of other obvious variations.

[0066] Referring to Figure 1 as shown, a real-time correction system for low-orbit satellite positioning errors in a dynamic environment includes:

[0067] A satellite screening module, which selects three satellites for positioning from a group of satellites as target satellites respectively, and the satellites complete positioning through signal reception by a user receiver carried by the user;

[0068] A coordinate establishment module, which selects three base points on the earth to establish coordinates to obtain a characteristic coordinate system;

[0069] A position calculation module, which calculates the first real-time position coordinate of the target satellite based on the running orbit, running speed and initial position coordinate of the target satellite in the characteristic coordinate system;

[0070] A time acquisition module, which acquires the time difference between the signal of the target satellite reaching the user receiver at the positioning location as a preliminary time difference;

[0071] An environment recognition module, which recognizes the surrounding environment at the user receiver to obtain real-time environment characteristics;

[0072] A judgment module, which judges whether the signal of the target satellite and the user receiver can be directly transmitted based on the real-time environment characteristics. If so, it uses the preliminary time difference to calculate the second real-time position coordinate of the user receiver. If not, it identifies an object blocking the signal of the target satellite and a reflector indirectly transmitting the signal of the target satellite, takes the path of directly transmitting the signal of the target satellite through the object blocking the user receiver as the direct path, and identifies the reflection path between the signal of the target satellite and the user receiver based on the reflector;

[0073] An angle acquisition module, which intercepts the part of the reflection path between the obstacle and the target satellite to obtain a characteristic path, identifies the deflection angle of the signal of the characteristic path relative to the target satellite from the direct transmission to the user receiver, and obtains a characteristic angle.

[0074] A position correction module, which corrects the preliminary time difference based on the characteristic angle and the direct path to obtain a target time difference, and uses the target time difference to calculate the third real-time position coordinates of the user receiver.

[0075] When positioning, usually four satellites are used for positioning, three satellites are used to determine the position, and one satellite is used to eliminate the influence of time synchronization error. The satellite transmits signals to the user receiver. There are clocks on both the satellite and the user receiver. Therefore, the distance between the satellite and the user receiver can be obtained by multiplying the time difference of signal reception and transmission by the speed of light. Then, through the distance relationship with the three satellites, the positioning of the user receiver can be carried out. However, when the user is in a high-rise building, the satellite may not be able to directly receive and transmit signals with it, and the signal will reach the user receiver through secondary reflection. That is, the preliminary time difference at this time is longer than the direct transmission time, and the error cannot be ignored. Therefore, the calculated distance deviates from the straight-line distance between the satellite and the user receiver, which will affect the positioning. Therefore, it is necessary to reduce the error.

[0076] The reason for the selection of the target satellite is as follows: The signal of the satellite can be transmitted to the user receiver, which needs to meet the following conditions: The satellite is above the tangent plane of the earth position where the user receiver is located. However, the satellite will orbit the earth and may run below the tangent plane of the earth position where the user receiver is located. Therefore, at this time, it is necessary to reselect the satellite to ensure that all the satellites used for positioning are above the tangent plane of the earth position where the user receiver is located.

[0077] When the distances between the user receiver and the three target satellites are determined, assuming the coordinates of the user receiver are (x, y, z), then through the coordinates of the user receiver and the first real-time position coordinates of the target satellite, the equations of the distances between the user receiver and the target satellite can be obtained. Since there are three target satellites, there are three such equations. Therefore, the coordinates of the user receiver can be obtained by solving the three equations simultaneously.

[0078] Refer to Figure 2 As shown, the steps to establish a characteristic coordinate system by selecting three base points on the earth are as follows:

[0079] Select three base points on the earth, namely the first base point, the second base point, and the third base point, satisfying that the connecting lines between the three base points and the center of the earth are perpendicular to each other.

[0080] Using the center of the Earth as the origin, the line connecting the first base point and the center of the Earth as the x-axis, the line connecting the second base point and the center of the Earth as the y-axis, and the line connecting the third base point and the center of the Earth as the z-axis, a characteristic coordinate system is formed.

[0081] Using a fixed characteristic coordinate system can perform unified standard position positioning for all positions, so that data can be processed according to the coordinates in the subsequent process.

[0082] Refer to Figure 3 As shown, calculating the first real-time position coordinates of the target satellite includes the following steps:

[0083] Pre-obtain the equation of the operating orbit of the target satellite, and obtain the time difference between the current moment and the moment corresponding to the initial position coordinates of the target satellite as the characteristic time difference;

[0084] Multiply the characteristic time difference by the operating speed of the target satellite to obtain the calibrated distance;

[0085] Using the characteristic equivalent relationship, solve to obtain the first real-time position coordinates. The characteristic equivalent relationship is that the calibrated distance is equal to the length of the part of the operating orbit between the first real-time position coordinates and the initial position coordinates.

[0086] Since the equation of the operating orbit of the target satellite is determined and the speed of the target satellite is also determined, therefore, the distance it travels at each moment is determined. When the initial position coordinates are determined, the equation of the first real-time position coordinates of the target satellite can be obtained through path integration, and the first real-time position coordinates can be calculated through this equation. Path integration is existing knowledge in advanced mathematics.

[0087] Refer to Figure 4 As shown, identifying the surrounding environment at the user receiver to obtain real-time environment characteristics includes the following steps:

[0088] Taking the position where the user receiver is located as the center, emitting at least one ray along the ground surface. The included angle between adjacent rays is a preset angle, and the preset angle is based on empirical data and set according to the recognition accuracy;

[0089] Taking the highest object in the direction of the ray from the position where the user receiver is located as the characteristic object, and the characteristic object is a building or a mountain;

[0090] Pre-obtain the coordinates of the top of the characteristic object in the characteristic coordinate system as the characteristic coordinates;

[0091] Pair and summarize the characteristic object and the characteristic coordinates as the real-time environment characteristics.

[0092] The characteristic object is a fixed object. Therefore, all the required data can be pre-obtained for subsequent data calculations;

[0093] The purpose of environmental recognition is to identify characteristic objects. When the user is surrounded by characteristic objects, signal blockage is likely to occur. The signal cannot be transmitted directly and must be raised to a certain angle and transmitted through reflection. Therefore, in order to identify this situation, the environment needs to be identified.

[0094] At least one ray is emitted along the surface. When the recognition accuracy requirement is higher, more rays can be set. A characteristic object is set on each ray, that is, the highest object on this ray. Because if signal obstruction occurs, it must be caused by the highest object.

[0095] Reference Figure 5 As shown, judging whether the signal of the target satellite and the user receiver can be directly transmitted includes the following steps:

[0096] Obtaining an equation of a characteristic straight line passing through the characteristic coordinates and the first real-time position coordinates as a characteristic equation;

[0097] By combining the characteristic equation and the spherical equation of the earth, the coordinates of the intersection of the characteristic straight line and the earth's surface are calculated as the node coordinates, and the distance between the node coordinates and the characteristic coordinates is calculated as the characteristic distance;

[0098] The user receiver uses laser ranging to determine the point corresponding to the node coordinates on the ray where the characteristic object is located, and the distance from the point corresponding to the node coordinates to the characteristic coordinates of the characteristic object is equal to the characteristic distance;

[0099] Connect the points corresponding to the coordinates of the adjacent nodes with line segments, and the area surrounded by at least one line segment is a feature area;

[0100] When the characteristic area contains the user receiver, direct transmission can be performed, otherwise, direct transmission cannot be performed.

[0101] The signal of the target satellite is transmitted in all directions. The line connecting the signal of the target satellite and the top of the characteristic object and extending to the surface forms a node. There are multiple such nodes, which will form an area, namely the characteristic area. Through geometric relationships, the user receiver, characteristic objects and nodes are made. It can be known that the intersection of the characteristic area and the area surrounded by all characteristic objects is the part that the signal of the target satellite can directly reach, and the difference between the area surrounded by all characteristic objects and the characteristic area is the part that the signal of the target satellite cannot directly reach. The user receiver must be in the area surrounded by all characteristic objects. At this time, due to the generation of the characteristic objects, it is only necessary to determine whether the user receiver is in the characteristic area.

[0102] Since the distances of the objects around the user receiver are all very close, the distance between the user receiver and these objects can be determined by laser ranging.

[0103] Referring to Figure 6 As shown, the steps for identifying the obstacles that block the signal of the target satellite and the reflectors that indirectly transmit the signal of the target satellite include the following:

[0104] Use laser ranging to determine the point corresponding to the node coordinates closest to the user receiver as the feature point;

[0105] Take the feature objects on the two rays collinear with the feature point as the target feature objects. Take the target feature object with a larger distance from the feature coordinates to the first real-time position coordinates as the reflector, and take the target feature object with a smaller distance from the feature coordinates to the first real-time position coordinates as the obstacle.

[0106] When determining the obstacle and the reflector, it is easy to know that the obstacle and the reflector must be coplanar with the user receiver and the target satellite. Otherwise, the signal reflection and reception cannot be completed. Since the feature region is formed by the intersection of the lines connecting the tops of all feature objects and the target satellite with the ground surface, and it is a convex figure. When there is an occlusion, the part of the user receiver outside the feature region. Therefore, the position on the feature region closest to the user receiver, that is, the feature point, can be approximately regarded as the feature point, the user receiver, and the target satellite being coplanar. Therefore, the feature objects collinear with the feature point must also be coplanar with the user receiver and the target satellite. These two target feature objects respectively play the roles of occlusion and reflection. Then, according to the geometric relationship, the obstacle and the reflector can be determined. The signal of the target satellite cannot be directly transmitted to the user receiver because it is blocked by the obstacle and can only reach the user receiver through the secondary reflection of the reflector. In the following, it is necessary to determine the reflection point on the reflector and thus determine the reflection path.

[0107] Referring to Figure 7 As shown, the steps for identifying the reflection path of the signal of the target satellite and the user receiver based on the reflector include the following:

[0108] Pre-acquire the coordinates of the reflector on the ground surface as the plane coordinates. Divide the result of subtracting the plane coordinates from the feature coordinates by n to obtain the reference vector;

[0109] Uniformly set at least one sampling point on the reflector in the vertical direction. Number the sampling points from top to bottom. The total number of sampling points is n + 1. The coordinates of the i-th sampling point are the sum of the feature coordinates and (i - 1) times the reference vector, where the value range of i is from 1 to n + 1;

[0110] Calculate the modulus of the reference vector. The height of the i-th sampling point is (n + 1 - i) times the modulus of the reference vector;

[0111] The user receiver obtains the distance from the user receiver to the reflector by means of laser ranging;

[0112] Obtain the tangent plane equation of the reflector at the ground surface. Subtract the coordinates of the first real-time position from the coordinates of the i-th sampling point to obtain the i-vector, and calculate the angle between the i-vector and the tangent plane equation to obtain the first angle;

[0113] The height of the i-th sampling point divided by the distance from the user receiver to the reflector gives the characteristic tangent value. Substitute the characteristic tangent value into the arctangent function to obtain the second angle;

[0114] Take the sampling points where the first angle is equal to the second angle as the reflection points;

[0115] Take the line connecting the reflection point and the target satellite and the line connecting the reflection point and the user receiver as the reflection path.

[0116] The determination of the reflection point is based on the equality of the reflection angle and the incident angle. Therefore, it is calculated through the angles formed by the lines connecting the user receiver and the target satellite at each sampling point, and then the angles are compared to screen out the reflection points from the sampling points, and then the reflection path is determined.

[0117] Intercept the part of the reflection path between the obstacle and the target satellite to obtain the characteristic path, which includes the following steps:

[0118] Extend the obstacle upward to divide the reflection path into two characteristic parts, and take the characteristic part closer to the target satellite as the characteristic path.

[0119] Refer to Figure 8 As shown, identifying the deflection angle of the signal of the characteristic path relative to the target satellite for direct transmission to the user receiver to obtain the characteristic angle includes the following steps:

[0120] Calculate the distance from the coordinates of the reflection point to the coordinates of the first real-time position to obtain the first distance;

[0121] The user receiver obtains the distance from the user receiver to the reflection point by means of laser ranging as the second distance;

[0122] Superimpose the first angle and the second angle of the reflection point to obtain the target angle;

[0123] Using the cosine theorem, calculate the distance from the user receiver to the target satellite as the actual distance;

[0124] Using the sine theorem and the actual distance, calculate the characteristic angle.

[0125] The cosine theorem is as follows: ,

[0126] Wherein, c is the actual distance, a is the first distance, b is the second distance, and A is the target angle;

[0127] The sine theorem is as follows: ,

[0128] Wherein, B is the characteristic angle.

[0129] Based on the characteristic angle and the direct path, correcting the preliminary time difference to obtain the target time difference includes the following steps:

[0130] Taking the cosine value of the characteristic angle as the ratio of the target time difference to the preliminary time difference, and inversely solving for the target time difference.

[0131] Taking the connection line between the user receiver and the target satellite as the first characteristic connection line, taking the connection line between the reflection point and the target satellite as the second characteristic connection line, making a perpendicular line to the characteristic connection line at the user receiver, intersecting the second characteristic connection line at a secondary point, taking the part between the secondary point and the target satellite as the third characteristic connection line, and taking the part of the reflection path other than the third characteristic connection line as the fourth characteristic connection line;

[0132] Then the ratio of the first characteristic connection line to the third characteristic connection line is the cosine value of the characteristic angle. According to the geometric relationship, the length of the fourth characteristic connection line part usually does not exceed 1 kilometer. Therefore, its time under the calculation of the speed of light is very small and can almost be ignored. The target time difference corresponds to the first characteristic connection line, and the preliminary time difference corresponds to the third characteristic connection line and the fourth characteristic connection line. However, since the fourth characteristic connection line can be ignored from the time perspective, the preliminary time difference corresponds to the third characteristic connection line. Therefore, the ratio of the target time difference to the preliminary time difference can be taken as the cosine value of the characteristic angle, and the target time difference can be obtained accordingly.

[0133] Furthermore, this solution also proposes a storage medium, on which a computer-readable program is stored. When the computer-readable program is called, it executes the above-mentioned real-time correction system for low-earth orbit satellite positioning errors in a dynamic environment.

[0134] It can be understood that the storage medium can be a magnetic medium, such as a floppy disk, a hard disk, or a magnetic tape; an optical medium such as a DVD; or a semiconductor medium such as a solid-state drive (SSD).

[0135] In summary, the advantages of the present invention are as follows: by obtaining real-time environmental characteristics, determining whether the signal of the target satellite can be directly transmitted to the user receiver, and identifying the reflection path of the signal between the target satellite and the user receiver, it is possible to estimate the reflection transmission path of the signal when the satellite cannot directly transmit the signal, thereby estimating the deflection angle from the direct path based on the reflection transmission path, and then estimating the time for direct path transmission based on the reflection transmission time, so as to more accurately estimate the time for straight-line transmission, and calculating the distance between the user and the satellite based on the estimated time, and finally completing the positioning through the distance relationships of multiple satellites.

[0136] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and all these changes and improvements fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A real-time correction system for positioning errors of low-orbit satellites in a dynamic environment, characterized in that, Including: A satellite screening module, which selects three satellites for positioning from a group of satellites as target satellites respectively. The satellites complete positioning through signal reception by a user receiver carried by the user; A coordinate establishment module, which selects three base points on the earth to establish coordinates and obtains a characteristic coordinate system; A position calculation module, which calculates the first real-time position coordinates of the target satellite based on the operating orbit, operating speed and initial position coordinates of the target satellite in the characteristic coordinate system; A time acquisition module, which acquires the time difference between the signal of the target satellite reaching the user receiver at the positioning location as the preliminary time difference; An environment recognition module, which recognizes the surrounding environment at the user receiver to obtain real-time environment characteristics; A judgment module, which judges whether the signal of the target satellite and the user receiver can be directly transmitted based on the real-time environment characteristics. If so, it uses the preliminary time difference to calculate the second real-time position coordinates of the user receiver. If not, it identifies the occluder that obstructs the signal of the target satellite and the reflector that obstructs the indirect transmission of the signal of the target satellite, and takes the path of directly transmitting the signal of the target satellite through the occluder to the user receiver as the direct path, and based on the reflector, identifies the reflection path of the signal of the target satellite and the user receiver; An angle acquisition module, which intercepts the part between the occluder and the target satellite in the reflection path to obtain a characteristic path, and identifies the deflection angle of the characteristic path relative to the direct transmission of the signal of the target satellite and the user receiver to obtain a characteristic angle; A position correction module, which corrects the preliminary time difference based on the characteristic angle and the direct path to obtain a target time difference, and uses the target time difference to calculate the third real-time position coordinates of the user receiver; The step of selecting three base points on the earth to establish coordinates and obtaining a characteristic coordinate system includes the following steps: Select three base points on the earth as the first base point, the second base point and the third base point respectively, satisfying that the connecting lines of the three base points and the center of the earth are perpendicular to each other; Using the center of the earth as the origin, using the connecting line between the first base point and the center of the earth as the x-axis, using the connecting line between the second base point and the center of the earth as the y-axis, and using the connecting line between the third base point and the center of the earth as the z-axis to form a characteristic coordinate system; The step of calculating the first real-time position coordinates of the target satellite includes the following steps: Pre-acquire the equation of the operating orbit of the target satellite, and obtain the time difference between the current moment and the moment corresponding to the initial position coordinates of the target satellite as the characteristic time difference; Multiply the characteristic time difference by the operating speed of the target satellite to obtain a calibrated distance; Use the characteristic equivalent relationship to solve for the first real-time position coordinates. The characteristic equivalent relationship is that the calibrated distance is equal to the length of the part of the operating orbit between the first real-time position coordinates and the initial position coordinates; The step of recognizing the surrounding environment at the user receiver to obtain real-time environment characteristics includes the following steps: Taking the location of the user receiver as the center, at least one ray is emitted along the surface of the earth, and the angle between adjacent rays is a preset angle, which is based on empirical data and is set according to the accuracy of recognition; The highest object in the direction of the ray extending from the user receiver location is taken as the feature object, and the feature object is a building or a mountain; Pre-acquire the coordinates of the top of the feature object in the feature coordinate system as the feature coordinates; Pair and summarize feature objects and feature coordinates as real-time environmental features; Determining whether the signal of the target satellite and the user receiver can be directly transmitted comprises the following steps: Obtaining an equation of a characteristic straight line passing through the characteristic coordinates and the first real-time position coordinates as a characteristic equation; By combining the characteristic equation and the spherical equation of the earth, the coordinates of the intersection of the characteristic straight line and the earth's surface are calculated as the node coordinates, and the distance between the node coordinates and the characteristic coordinates is calculated as the characteristic distance; The user receiver uses laser ranging to determine the point corresponding to the node coordinates on the ray where the characteristic object is located, and the distance from the point corresponding to the node coordinates to the characteristic coordinates of the characteristic object is equal to the characteristic distance; Connect the points corresponding to the coordinates of the adjacent nodes with line segments, and the area surrounded by at least one line segment is a feature area; When the characteristic area contains the user receiver, direct transmission can be performed, otherwise, direct transmission cannot be performed.

2. The real-time correction system for low-earth orbit satellite positioning errors in a dynamic environment according to claim 1, wherein, The identifying of the obstruction that blocks the signal of the target satellite and the reflector that blocks the indirect transmission of the signal of the target satellite comprises the following steps: Use laser ranging to determine the point corresponding to the coordinates of the node closest to the user receiver as the feature point; The feature objects on the two rays collinear with the feature points are regarded as target feature objects, the target feature objects with a larger distance from the feature coordinates to the first real-time position coordinates are regarded as reflectors, and the target feature objects with a smaller distance from the feature coordinates to the first real-time position coordinates are regarded as obstructions.

3. The real-time correction system for low-earth orbit satellite positioning error in a dynamic environment according to claim 2, wherein The method of identifying the reflection path of the target satellite signal and the user receiver based on the reflector comprises the following steps: The coordinates of the reflector on the ground surface are obtained in advance as the plane coordinates. The difference between the plane coordinates and the characteristic coordinates is divided by n to obtain the reference vector. At least one sampling point is evenly set on the reflector in the vertical direction, and the sampling points are numbered from top to bottom. The total number of sampling points is n+1. The coordinate of the i-th sampling point is the sum of the characteristic coordinate and i-1 times the reference vector, and the value range of i is 1 to n+1. Find the modulus of the reference vector. The height of the i-th sampling point is n+1-i times the modulus of the reference vector. The user receiver uses laser ranging to obtain the distance between the user receiver and the reflector; Obtain the tangent plane equation of the reflector on the surface, subtract the first real-time position coordinates from the coordinates of the i-th sampling point to obtain the i-vector, calculate the angle between the i-vector and the tangent plane equation to obtain the first angle; The height of the i-th sampling point is divided by the distance from the user receiver to the reflector to obtain the characteristic tangent value, and the characteristic tangent value is substituted into the inverse tangent function to obtain the second angle; The sampling points where the first angle and the second angle are equal are taken as reflection points; The line connecting the reflection point and the target satellite and the line connecting the reflection point and the user receiver are used as the reflection path.

4. The real-time correction system for low-earth orbit satellite positioning error in a dynamic environment according to claim 3, characterized in that, The steps for obtaining the characteristic path by intercepting the part of the reflection path between the obstacle and the target satellite include the following: Extend the obstacle upward to divide the reflection path into two characteristic parts, and take the characteristic part closer to the target satellite as the characteristic path.

5. The real-time correction system for low-orbit satellite positioning error in a dynamic environment according to claim 4, characterized in that, The steps for obtaining the characteristic angle by identifying the deflection angle of the signal of the characteristic path relative to the target satellite for direct transmission to the user receiver include the following: Calculate the distance from the coordinates of the reflection point to the first real-time position coordinates to obtain the first distance; The user receiver obtains the distance from the user receiver to the reflection point by means of laser ranging as the second distance; Superimpose the first included angle and the second included angle of the reflection point to obtain the target angle; Use the cosine theorem to calculate the distance from the user receiver to the target satellite as the actual distance; Use the sine theorem and the actual distance to calculate the characteristic angle.

6. The real-time correction system for the positioning error of low-earth orbit satellites in a dynamic environment according to claim 5, wherein The steps for correcting the preliminary time difference based on the characteristic angle and the direct path to obtain the target time difference include the following: Take the cosine value of the characteristic angle as the ratio of the target time difference to the preliminary time difference, and solve for the target time difference inversely.

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