A high-precision on-orbit target positioning method and system based on space-ground collaboration

Abstract

The present invention discloses a method and system for high-precision positioning of on-orbit targets based on space-ground collaboration, belonging to the technical field of space remote sensing monitoring. It includes real-time on-orbit target recognition, imaging ray calculation, camera calibration, and ground coordinate calculation. The remote sensing image data and attitude auxiliary information collected on the satellite complete the recognition and extraction of the target through target recognition respectively. The imaging ray calculation completes the calculation of the imaging ray vector, and then is transmitted to the satellite ground processing system through the space-ground transmission link. The precise coordinates of the target are calculated according to the digital elevation, and then compared with the control point library to determine whether this target is a control point with known three-dimensional coordinates. If it is a control point, it is input into the camera calibration module of the on-orbit system to calculate the camera calibration parameters. This method can make full use of the respective advantages of the on-orbit system and the ground system, optimize the real-time on-orbit target recognition process, and improve the acquisition efficiency and real-time performance of on-orbit targets.

Description

Technical Field

[0001] The present invention relates to the technical field of space remote sensing monitoring, and particularly to a method and system for high-precision positioning of on-orbit targets based on space-ground collaboration. Background Art

[0002] With the rapid development of satellite payload technologies such as remote sensing and radar, the capacity and rate of on-orbit payload data have increased rapidly. The on-orbit data transmission technology and storage technology are constantly progressing. Just downlinking the original data cannot meet the growing demand for payload data, severely restricting the utilization efficiency of the payload. At the same time, the real-time application demand for satellite payload data is getting stronger. Under the existing system, remote sensing data is downlinked to the ground station, preprocessed, and then distributed to users. This process will cause long delays, which is the main bottleneck for the real-time application of remote sensing data. Users cannot directly obtain the targets of interest and their precise coordinates from the satellite, making it difficult to meet the timeliness requirements of applications such as reconnaissance and monitoring. Summary of the Invention

[0003] The purpose of the present invention is to provide a method and system for high-precision positioning of on-orbit targets based on space-ground collaboration to solve the technical problem of real-time high-precision positioning of targets in traditional space remote sensing monitoring. The present invention makes full use of the satellite transit time window and limited transmission bandwidth, and establishes a collaborative joint processing mode between the on-orbit system and the ground system, that is, the on-orbit system performs on-orbit real-time detection on the original data to directly extract and downlink the target-related information, and then after the ground system receives the target information, it directly performs type discrimination and high-precision coordinate calculation in combination with auxiliary data to meet the real-time requirements of users. The content of the present invention is as follows:

[0004] In a first aspect of the present invention, there is provided a method for high-precision positioning of on-orbit targets based on space-ground collaboration, the technical points of which include the following steps:

[0005] Target recognition step: perform target recognition on the image data to obtain target ground object data;

[0006] Imaging ray calculation step: select the pixel coordinates of the target center from the target ground object data in the target recognition step, and perform imaging ray calculation on the pixel coordinates of the target center and the attitude data to obtain the vector of the imaging ray corresponding to the target center in three-dimensional space;

[0007] Coordinate calculation step: perform the first data compression on the target ground object data and the vector of the imaging ray in three-dimensional space, and then calculate the precise coordinates of the target using the digital elevation model;

[0008] Control point discrimination step: Compare the precise coordinates of the target with all control points in the control point library to determine whether the target is a control point. If it is a control point, perform second - stage data compression and then enter the camera calibration step. The control point library stores control point pictures and control point picture coordinate values.

[0009] Camera calibration step: Calculate camera calibration parameters based on the control point picture coordinate values in the control point library and the attitude data in the on - satellite system, and upload the camera calibration parameters to the on - satellite system to correct the vector of the imaging light in three - dimensional space.

[0010] In some embodiments of the present invention, in the method for high - precision on - satellite target positioning based on space - ground cooperation, the camera calibration parameters include the correction numbers of the camera interior orientation elements and the correction numbers of the camera mounting matrix.

[0011] In some embodiments of the present invention, in the method for high - precision on - satellite target positioning based on space - ground cooperation, the target recognition step is completed on multiple frames of image data stored in short - term on the satellite.

[0012] In some embodiments of the present invention, in the coordinate calculation step of the method for high - precision on - satellite target positioning based on space - ground cooperation, the intersection coordinates of the vector of the imaging light in three - dimensional space and the digital elevation model are iteratively solved.

[0013] In some embodiments of the present invention, in the control point discrimination step of the method for high - precision on - satellite target positioning based on space - ground cooperation, first determine the candidate control points according to the precise coordinates of the target, and then determine whether the target is a control point by comparing with the control point pictures, and record it in a list.

[0014] In some embodiments of the present invention, in the camera calibration step of the method for high - precision on - satellite target positioning based on space - ground cooperation, all control points recorded in the list are used to complete the calculation of calibration parameters.

[0015] The second object of the present invention is to provide a high - precision on - satellite target positioning system based on space - ground cooperation. The technical point is that it includes an on - satellite system and a ground system. The on - satellite system obtains target ground object data and the vector of the imaging light in three - dimensional space according to the attitude data and image data, performs first - stage data compression, and then downloads it to the ground system. The ground system compares the compressed data downloaded from the on - satellite system with the control point library, performs second - stage data compression, and uploads the second - stage compressed data to the on - satellite system to obtain camera calibration parameters through camera calibration and then correct the vector of the imaging light in three - dimensional space.

[0016] In some embodiments of the present invention, in the on - satellite system of the method for high - precision on - satellite target positioning based on space - ground cooperation, it includes the following modules:

[0017] Target recognition module: performs target recognition on the image data to obtain target ground object data;

[0018] Imaging light ray calculation module: selects the pixel coordinates of the target center from the target ground object data in the target recognition step, and performs imaging light ray calculation on the pixel coordinates of the target center and the attitude data to obtain the vector of the imaging light ray corresponding to the target center in three-dimensional space;

[0019] Camera calibration module: calculates camera calibration parameters based on the control point image coordinate values in the control point library and the attitude data in the on-orbit system, and uploads the camera calibration parameters to the on-orbit system to correct the vector of the imaging light ray in three-dimensional space.

[0020] In some embodiments of the present invention, the ground system in the on-orbit target high-precision positioning method based on space-ground cooperation includes the following modules:

[0021] Coordinate calculation module: performs the first data compression on the target ground object data and the vector of the imaging light ray in three-dimensional space, and then calculates the target accurate coordinates using the digital elevation model;

[0022] Control point discrimination module: compares the target accurate coordinates with all control points in the control point library to determine whether the target is a control point. If it is a control point, it enters the camera calibration step after the second data compression. The control point library stores control point images and control point image coordinate values.

[0023] The on-orbit target high-precision positioning method and system based on space-ground cooperation provided by the present invention can achieve the following beneficial effects:

[0024] First, make full use of the characteristics of the on-orbit on-orbit system to obtain and process remote sensing data in real time. Since only the target-related information is downlinked, the load of the space-ground transmission link is greatly reduced.

[0025] Second, make full use of the basic geographic information data such as the digital elevation model and the control point library in the ground system to achieve high-precision positioning of the target;

[0026] Third, the on-orbit target high-precision positioning method based on space-ground cooperation of the present invention performs two data compressions in the on-orbit system and the on-orbit system, greatly reducing the data upload and download bandwidth and improving the data transmission rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0028] Figure 1Schematic flowchart of the on - satellite target high - precision positioning method based on space - ground cooperation of the present invention;

[0029] Figure 2 Schematic diagram of coordinate calculation of the present invention. Detailed implementation manners

[0030] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] The technical solutions provided by each embodiment of the present invention will be described in detail below with reference to the drawings.

[0032] As Figure 1 shown, the on - satellite target high - precision positioning method based on space - ground cooperation of the present invention includes the following steps:

[0033] Target recognition step: Perform target recognition on the image data to obtain target ground object data;

[0034] Imaging light ray calculation step: Select the pixel coordinates of the target center from the target ground object data in the target recognition step, and perform imaging light ray calculation on the pixel coordinates of the target center and the attitude data to obtain the vector of the imaging light ray corresponding to the target center in three - dimensional space. If the camera calibration parameters uploaded from the ground system are already stored in the system, first correct the internal orientation and installation matrix of the camera through the camera calibration parameters, and then calculate the target imaging light ray;

[0035] Coordinate calculation step: Perform the first data compression on the target ground object data and the vector of the imaging light ray in three - dimensional space, and then calculate the target accurate coordinates using the digital elevation model. The first data compression is divided into image data compression and coordinate data compression. Preferably, the image data compression algorithm can be selected from one of the static and dynamic Huffman coding algorithms, arithmetic coding algorithms, LZW coding and its improved algorithms, run - length coding and improved adaptive run - length coding algorithms, Fano - Shannon coding algorithms, and jpeg2000 image coding. Preferably, the coordinate data compression algorithm can be selected from one of the conventional compression methods gzip, bzip2, xz, xz - e, lz4, and zop, or the coordinate data compression can be performed according to the "Coordinate Data Compression Method" disclosed in Chinese Patent CN202010303198.6.

[0036] Control point discrimination step: Compare the accurate coordinates of the target with all control points in the control point library to determine whether the target is a control point. If it is a control point, perform second - stage data compression and then enter the camera calibration step. The control point library stores control point pictures and control point picture coordinate values. The second - stage data compression uses the same coordinate data compression method as the first - stage data compression.

[0037] Camera calibration step: Calculate camera calibration parameters based on the control point picture coordinate values in the control point library and the attitude data in the on - satellite system, and upload the camera calibration parameters to the on - satellite system to correct the vector of the imaging light in three - dimensional space.

[0038] Preferably, in the method for high - precision on - satellite target positioning based on space - ground collaboration of the present invention, the calculation formula for imaging light resolution is as follows:

[0039] (1)

[0040] where is the vector of the imaging light in three - dimensional space, is the scale factor, is the transformation matrix from the satellite body reference frame to the Earth - fixed ground reference frame, is the transformation matrix composed of the satellite attitude information , is the installation matrix composed of the camera installation information ; is the image point coordinate, is the camera interior orientation elements, is the correction number of the camera installation matrix, is the correction number of the camera interior orientation elements.

[0041] Preferably, in the method for high - precision on - satellite target positioning based on space - ground collaboration of the present invention, the camera calibration parameters include the correction number of the camera interior orientation elements and the correction number of the camera installation matrix.

[0042] Preferably, in the method for high - precision on - satellite target positioning based on space - ground collaboration of the present invention, the target recognition step is completed on multiple frames of image data stored in short - term on the satellite.

[0043] Preferably, in the method for high - precision on - satellite target positioning based on space - ground collaboration of the present invention, in the coordinate resolution step, the intersection coordinates of the vector of the imaging light in three - dimensional space and the digital elevation model are iteratively solved, as Figure 2 shown in the figure. In the figure, is the initial elevation value, generally the average altitude value or 0, are the elevation values gradually optimized during the iteration process, and They are all plane coordinates. The specific steps for calculating the accurate coordinates of the target based on the digital elevation model near the coordinates and the imaging rays of the target are as follows:

[0044] 1) Let the elevation of the object point at the -th iteration be , and its initial value be ;

[0045] 2) Obtain the coordinates of the imaging ray vector on the elevation plane ;

[0046] 3) Obtain the elevation value of the digital elevation model at ;

[0047] 4) Repeat steps 2) and 3) until the difference between the elevation value calculated at the -th time and the elevation value calculated at the -th time is less than a given threshold, then is the accurate coordinate value of the target.

[0048] Preferably, in the control point discrimination step of the on-orbit target high-precision positioning method based on space-ground collaboration of the present invention, first determine the candidate control points according to the accurate coordinates of the target, and then compare them one by one with the control point pictures to find all the control points with a distance less than a given threshold between the two as candidate control points. If there are no candidate control points, directly return "no". Otherwise, calculate the correlation between the target picture and each candidate control point picture, and select the candidate control point with the highest correlation. If its correlation is less than the given threshold, return "no", otherwise return "yes" and package and record the target information and this control point information in a list.

[0049] Preferably, in the camera calibration step of the on-orbit target high-precision positioning method based on space-ground collaboration of the present invention, use all the target and control point information in the list as observation values and substitute them into formula 1 to solve for the correction of the camera interior orientation elements and the correction of the camera installation matrix, and transmit them to the on-orbit system through space-ground transmission.

[0050] An on-orbit target high-precision positioning system based on space-ground collaboration includes an on-orbit system and a ground system. The on-orbit system obtains the target ground object data and the vector of the imaging ray in three-dimensional space according to the attitude data and the image data, and performs the first data compression and then downloads it to the ground system; the ground system compares the compressed data downloaded from the on-orbit system with the control point library, performs the second data compression, and uploads the second compressed data to the on-orbit system for camera calibration to obtain the camera calibration parameters and then correct the vector of the imaging ray in three-dimensional space.

[0051] Further, the on - satellite system in the high - precision on - satellite target positioning method based on space - ground cooperation of the present invention includes the following modules:

[0052] Target recognition module: performing target recognition on the image data to obtain target ground object data;

[0053] Imaging ray resolution module: selecting the pixel coordinates of the target center from the target ground object data in the target recognition step, and performing imaging ray resolution on the pixel coordinates of the target center and the attitude data to obtain the vector of the imaging ray corresponding to the target center in three - dimensional space;

[0054] Camera calibration module: calculating camera calibration parameters according to the control point picture coordinate values in the control point library and the attitude data in the on - satellite system, and uploading the camera calibration parameters to the on - satellite system to correct the vector of the imaging ray in three - dimensional space.

[0055] Further, the ground system in the high - precision on - satellite target positioning method based on space - ground cooperation of the present invention includes the following modules:

[0056] Coordinate resolution module: performing the first data compression on the target ground object data and the vector of the imaging ray in three - dimensional space, and then calculating the target precise coordinates using the digital elevation model;

[0057] Control point discrimination module: comparing the target precise coordinates with all control points in the control point library to determine whether the target is a control point. If it is a control point, perform the second data compression and then enter the camera calibration step. The control point library stores control point pictures and control point picture coordinate values.

[0058] The above are only embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A high-precision on-orbit target positioning method based on space-ground collaboration, characterized in that, It includes the following steps: Target recognition step: performing target recognition on the image data to obtain target ground object data; this step is completed on multiple frames of image data in on-board short-term storage; Imaging ray calculation step: selecting the pixel coordinates of the target center from the target ground object data in the target recognition step, performing imaging ray calculation on the pixel coordinates of the target center and the attitude data to obtain the vector of the imaging ray corresponding to the target center in three-dimensional space; performing the first data compression on the target ground object data and the vector of the imaging ray in three-dimensional space; Coordinate calculation step: calculating the accurate target coordinates from the data after the first data compression using a digital elevation model; this step iteratively solves the intersection coordinates of the two by the vector of the imaging ray in three-dimensional space and the digital elevation model; Control point discrimination step: comparing the accurate target coordinates with all control points in the control point library to determine whether the target is a control point; if it is a control point, perform the second data compression and then enter the camera calibration step, and the control point library stores control point pictures and control point picture coordinate values; Camera calibration step: calculating camera calibration parameters according to the control point picture coordinate values in the control point library and the attitude data in the on-board system, and uploading the camera calibration parameters to the on-board system to correct the vector of the imaging ray in three-dimensional space; The target recognition step, imaging ray calculation step, and camera calibration step are completed on-board; the coordinate calculation step and control point discrimination step are completed on the ground.

2. The high-precision on-orbit target positioning method based on space-ground collaboration according to claim 1, wherein, The camera calibration parameters include the correction number of the camera interior orientation elements and the correction number of the camera mounting matrix.

3. A high-precision on-orbit target positioning method based on space-ground collaboration according to claim 1, characterized in that In the control point discrimination step, first determine the candidate control points according to the accurate target coordinates, then determine whether the target is a control point by comparing with the control point pictures, and record it in a list.

4. The high-precision on-orbit target positioning method based on space-ground collaboration according to claim 3, wherein, In the camera calibration step, all control points recorded in the list are used to complete the calculation of the calibration parameters.

5. A high-precision on-orbit target positioning system based on space-ground collaboration, characterized in that, It includes an on-board system and a ground system. The on-board system obtains the target ground object data and the vector of the imaging ray in three-dimensional space according to the attitude data and image data, performs the first data compression, and then downloads it to the ground system; the ground system compares the compressed data downloaded by the on-board system with the control point library, performs the second data compression, and uploads the second compressed data to the on-board system to perform camera calibration to obtain camera calibration parameters and then correct the vector of the imaging ray in three-dimensional space; the on-board system includes the following modules: Target recognition module: performing target recognition on the image data to obtain target ground object data; Imaging ray calculation module: selecting the pixel coordinates of the target center from the target ground object data in the target recognition step, performing imaging ray calculation on the pixel coordinates of the target center and the attitude data to obtain the vector of the imaging ray corresponding to the target center in three-dimensional space; performing the first data compression on the target ground object data and the vector of the imaging ray in three-dimensional space; Camera calibration module: calculating camera calibration parameters according to the control point picture coordinate values in the control point library and the attitude data in the on-board system, and uploading the camera calibration parameters to the on-board system to correct the vector of the imaging ray in three-dimensional space; The ground system includes the following modules: Coordinate calculation module: Calculating the accurate coordinates of the target from the data after the first data compression using a digital elevation model; Control point discrimination module: Comparing the accurate coordinates of the target with all the control points in the control point library to determine whether the target is a control point. If it is a control point, it will enter the camera calibration step after the second data compression. The control point library stores control point pictures and control point picture coordinate values.

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