Camera parameter correction method based on optical imaging and AIS information

Abstract

The present invention discloses a camera parameter correction method based on optical imaging and AIS information, comprising: using a satellite-borne camera to shoot an optical imaging image of a preset area where a ship is located, using a satellite-borne AIS receiver to receive and analyze the ship's AIS information; preprocessing the optical imaging image and the AIS information respectively; performing target detection on the preprocessed optical imaging image to obtain the coordinates of the ship target in the optical imaging image; performing time matching on the AIS information to extrapolate the AIS information at the imaging moment; performing target association on the ship target in the optical imaging image and the AIS information at the imaging moment to determine the AIS information corresponding to the ship target in the optical imaging image and obtain characteristic information of the ship target; constructing an imaging geometry model, and using the characteristic information of the ship target and the imaging geometry model to solve the satellite-borne camera parameters. The present invention can realize rapid on-orbit calibration of camera parameters, reduce the cost of on-orbit calibration of camera parameters, and improve the efficiency and timeliness of on-orbit calibration.

Description

Technical Field

[0001] The present invention relates to the technical field of on-orbit camera parameter calibration, and in particular to a camera parameter correction method based on optical imaging and AIS information. Background Art

[0002] With the rapid development of space technology, the ground resolution of optical satellite images has continued to improve, making acquisition more convenient and the cost gradually decreasing. They have become a vital component of high-resolution Earth observation systems. With this continuous improvement in spatial resolution, the clarity and resolution of optical satellite images have continued to increase, and their detailed information has become richer. For optical satellites, the focal position and imaging parameters of their onboard cameras are preset before launch. However, due to the influence of various factors during launch, as well as changes in environmental factors such as atmospheric pressure, temperature, and humidity, the camera state may change after the satellite enters orbit, causing the camera's geometric parameters to deviate from the original laboratory calibration values. These deviations can lead to errors in the actual object-image relationship, directly affecting the satellite's geometric positioning accuracy. Therefore, after launch, the camera must undergo rigorous on-orbit geometric calibration to correct the camera parameters.

[0003] The traditional on-orbit camera calibration method forms a ground calibration field by deploying a large number of control points on the ground. It uses the control point data in the ground calibration field and the image, orbit and attitude data obtained when the satellite passes overhead, and adopts the rear intersection method to achieve high-precision solution of internal and external system error parameters.

[0004] However, traditional on-orbit geometric calibration methods for cameras require the use of ground calibration field data. However, different satellites and sensors generally require different ground calibration fields. The construction of a ground calibration field requires comprehensive consideration of factors such as terrain, area, weather, and cost, making it a time-consuming and labor-intensive process. Furthermore, using a ground calibration field for on-orbit geometric calibration of cameras requires obtaining satellite imagery data from the ground calibration field. Due to factors such as weather, orbit, and time scheduling, calibration time for satellites using the calibration field is typically measured in months, resulting in poor timeliness and severely hindering the rapid application of the satellite after it is placed in orbit. Summary of the Invention

[0005] In order to solve some or all of the technical problems existing in the above-mentioned prior art, the present invention provides a camera parameter correction method based on optical imaging and AIS information.

[0006] The technical solutions of the present invention are as follows:

[0007] A camera parameter correction method based on optical imaging and AIS information is provided, the method comprising:

[0008] Use the satellite-borne camera to capture optical images of the preset ship area, and use the satellite-borne AIS receiver to receive and analyze the ship's AIS information;

[0009] Preprocess the optical imaging images and AIS information respectively;

[0010] Perform target detection on the pre-processed optical imaging image to obtain the coordinates of the ship target in the optical imaging image;

[0011] Time-match the AIS information and extrapolate the AIS information at the imaging moment;

[0012] Performing target association between the ship target in the optical imaging image and the AIS information at the imaging moment, determining the AIS information corresponding to the ship target in the optical imaging image, and obtaining characteristic information of the ship target, wherein the characteristic information includes at least: the position, size, and direction of the ship target;

[0013] An imaging geometry model is constructed, and the characteristic information of the ship target and the imaging geometry model are used to solve the parameters of the spaceborne camera.

[0014] In some possible implementations, the pre-processing of the optical imaging image includes:

[0015] Perform geometric correction and target enhancement processing on optical imaging images.

[0016] In some possible implementations, preprocessing the AIS information includes:

[0017] Perform data cleaning and data denoising on AIS information to remove erroneous data;

[0018] The erroneous data includes data that does not comply with the AIS standard and repeated data with the same Chinese field content in the AIS data.

[0019] In some possible implementations, performing time matching on the AIS information and extrapolating the AIS information at the imaging time includes:

[0020] Determining the imaging moment of the optical imaging image;

[0021] The first preset time before the imaging moment to the second preset time after the imaging moment is used as the preset time range, and the AIS information received within the preset time range is determined. Based on the AIS information received within the preset time range, the position information and motion information of the ship at the imaging moment are extrapolated to obtain the AIS information at the imaging moment, wherein the motion information includes the speed and heading of the ship.

[0022] In some possible implementations, extrapolating the position information and motion information of the ship at the imaging moment based on the AIS information received within a preset time range includes:

[0023] The ship's motion equation is constructed based on the position, heading and speed of the ship in the AIS information received at different receiving times within a preset time range, and the ship's position and motion information at the extrapolated imaging moment are calculated using the ship's motion equation.

[0024] In some possible implementations, extrapolating the position information and motion information of the ship at the imaging moment based on the AIS information received within a preset time range includes:

[0025] According to the position, heading and speed of the ship in the AIS information received at different receiving times within the preset time range, the interpolation method is used to extrapolate the position and motion information of the ship at the imaging moment.

[0026] In some possible implementations, the performing target association on the ship target in the optical imaging image and the AIS information at the imaging moment to determine the AIS information corresponding to the ship target in the optical imaging image includes:

[0027] Constructing a template point set and a target point set, wherein the template point set includes each ship target in the AIS information at the imaging moment, and the target point set includes each ship target in the optical imaging image;

[0028] The template point set is fitted to the target point set through geometric transformation, and the ship target points in the template point set corresponding to each ship target point in the target point set are determined;

[0029] According to the ship target points in the template point set corresponding to the ship target points in the target point set, the AIS information corresponding to each ship target in the optical imaging image is determined.

[0030] In some possible implementations, it is assumed that the exterior orientation element of the image is X S ,Y S ,Z S , ω,κ, the internal orientation elements of the image are x0,y0,f, [X S Y S Z S ] T Indicates the coordinates of the projection center in the national geodetic coordinate system. ω,κ represent the pitch angle, roll angle and yaw angle of the film in the photographic space, [x0 y0] T represents the coordinates of the principal point in the frame coordinate system, and f represents the principal distance of the camera;

[0031] The imaging geometry model is:

[0032]

[0033] Among them, [xy -f] T Indicates the coordinates of the image point in the camera coordinate system, [XYZ] T Indicates the coordinates of the ground point in the national geodetic coordinate system, a i ,b i ,c i (i=1,2,3) represents the exterior orientation element The 9 coefficients of the rotation matrix R composed of ω,κ,

[0034] In some possible implementations, calculating the parameters of the spaceborne camera using the characteristic information of the ship target and the imaging geometry model includes:

[0035] The image point coordinates and ground point coordinates corresponding to the ship target are brought into the imaging geometric model to obtain the imaging geometric model corresponding to the ship target;

[0036] The exterior and interior orientation elements of the image are regarded as unknowns, and the imaging geometric models corresponding to multiple ship targets are jointly established to solve the exterior and interior orientation elements of the image.

[0037] In some possible implementations, the method further includes:

[0038] Before using the characteristic information of the ship target and the imaging geometry model to solve the parameters of the satellite-borne camera, the distance between the ship's centroid and the positioning point on the ship used to report the ship's position is calculated according to the size of the ship, and the position of the ship target in the characteristic information of the ship target is corrected according to the calculated distance.

[0039] The main advantages of the technical solution of the present invention are as follows:

[0040] The camera parameter correction method based on optical imaging and AIS information of the present invention associates the optical image and the AIS positioning results of the same ship target, takes the ship target as a calibration source with a known position, and uses multiple ship targets with known position information to perform on-orbit calibration of camera parameters. This can achieve rapid on-orbit calibration of camera parameters, reduce the cost of on-orbit calibration of camera parameters by satellites, and improve the efficiency and timeliness of on-orbit calibration of camera parameters by satellites. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings described herein are used to provide a further understanding of the embodiments of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0042] Figure 1 Flowchart of a camera parameter correction method based on optical imaging and AIS information according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] The technical solutions provided by the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0045] See also Figure 1 An embodiment of the present invention provides a camera parameter correction method based on optical imaging and AIS information, the method comprising the following steps:

[0046] Step S1: Using a satellite-borne camera to capture an optical image of a preset area where a ship is located, and using a satellite-borne AIS receiver to receive and analyze the ship's AIS information;

[0047] Step S2, pre-processing the optical imaging image and AIS information respectively;

[0048] Step S3, performing target detection on the pre-processed optical imaging image to obtain the coordinates of the ship target in the optical imaging image;

[0049] Step S4, performing time matching on the AIS information and extrapolating the AIS information at the imaging moment;

[0050] Step S5: performing target association between the ship target in the optical imaging image and the AIS information at the imaging moment, determining the AIS information corresponding to the ship target in the optical imaging image, and obtaining characteristic information of the ship target, wherein the characteristic information includes at least: the position, size, and direction of the ship target;

[0051] Step S6: construct an imaging geometry model, and use the characteristic information of the ship target and the imaging geometry model to calculate the parameters of the satellite-borne camera.

[0052] A camera parameter correction method based on optical imaging and AIS information provided by an embodiment of the present invention associates the optical image and AIS positioning results of the same ship target, uses the ship target as a calibration source with a known position, and uses multiple ship targets with known position information to perform on-orbit calibration of camera parameters. This can achieve rapid on-orbit calibration of camera parameters, reduce the cost of on-orbit calibration of camera parameters by satellites, and improve the efficiency and timeliness of on-orbit calibration of camera parameters by satellites.

[0053] The following describes in detail the steps and principles of a camera parameter correction method based on optical imaging and AIS information provided by an embodiment of the present invention:

[0054] Step S1: Use a satellite-borne camera to capture an optical image of a preset area where a ship is located, and use a satellite-borne AIS receiver to receive and analyze the AIS information of the ship.

[0055] The area where the ships are photographed by the spaceborne camera can be pre-selected. In order to ensure that the spaceborne camera parameters can be accurately calculated, a sufficient number of ships must be in the area photographed by the spaceborne camera.

[0056] In one embodiment of the present invention, the area captured by the spaceborne camera contains at least four ships. Furthermore, considering potential issues such as missed detection and incorrect association during target detection and data association, the area captured by the spaceborne camera preferably contains at least ten ships.

[0057] The Automatic Identification System (AIS) is a navigation aid required by the International Maritime Organization (IMO) to be installed on ships. It utilizes GPS, Very High Frequency (VHF), and Self-Organizing Time Division Multiple Access (SOTDMA) technologies, offering 24 / 7 operation and widespread global distribution. The AIS system utilizes open broadcast technology to periodically broadcast a wide range of vessel information, including static, dynamic, voyage, and safety information. Static information includes the vessel's name, size, and type; dynamic information includes the vessel's position, speed, and heading; and voyage information includes draft and destination.

[0058] In one embodiment of the present invention, a satellite-borne AIS receiver is mounted on a satellite to receive AIS information broadcast by a ship. By parsing the received AIS information, the static information, dynamic information, voyage information, safety information, etc. of the ship can be obtained.

[0059] Step S2: Pre-process the optical imaging image and AIS information respectively.

[0060] In one embodiment of the present invention, pre-processing the optical imaging image includes:

[0061] Perform geometric correction and target enhancement processing on optical imaging images.

[0062] When a space-borne camera performs optical imaging, geometric distortion occurs due to different attitude angles, which can lead to inaccurate matching of ship targets. In one embodiment of the present invention, geometric correction of the optical image can eliminate geometric distortion and ensure accurate matching of the ship target. Furthermore, target enhancement of the optical image can improve image quality and ensure the efficiency and accuracy of target detection and recognition.

[0063] Optionally, target enhancement processing can be achieved by suppressing highlight areas, filtering and noise reduction, and downsampling.

[0064] Furthermore, in one embodiment of the present invention, pre-processing the AIS information includes:

[0065] Perform data cleaning and data denoising on AIS information to remove erroneous data;

[0066] The erroneous data includes data that does not comply with the AIS standard and duplicate data with the same Chinese field content in the AIS data.

[0067] AIS data may be erroneous or missing due to human factors, equipment failure, or signal transmission errors. In one embodiment of the present invention, data cleaning and data denoising are performed on the ship's AIS information to remove erroneous data in the AIS information, thereby ensuring the reliability of the AIS information used and improving the accuracy of the camera parameters ultimately obtained.

[0068] Optionally, in one embodiment of the present invention, the reliability of the AIS information may be verified based on the ship registration information to further improve the reliability of the acquired AIS information.

[0069] Step S3: performing target detection on the pre-processed optical imaging image to obtain the coordinates of the ship target in the optical imaging image.

[0070] Specifically, the existing deep learning neural network (such as Yolo, RCNN, etc.) image target detection method can be used to perform ship target detection on optical imaging images to obtain the area of ​​interest of the ship target in the optical imaging image as the position area of ​​the ship target, and calculate and determine the ship target coordinates based on the position area of ​​the ship target.

[0071] The coordinates of the center point of the position area of ​​the ship target can be calculated as the ship target coordinates, and the specific coordinates can be the image plane coordinates of the optical imaging image.

[0072] Step S4: Time matching is performed on the AIS information to extrapolate the AIS information at the imaging moment.

[0073] Optical imaging has a fixed imaging time, while AIS information is received by satellite-borne AIS receivers at fixed intervals. Satellite-borne AIS receivers often receive AIS information within a certain time range of the optical imaging moment. Therefore, there is no guarantee that AIS information transmitted by a ship target within the optical imaging moment will be received at the imaging moment. For moving ship targets, the difference in data acquisition time will lead to a difference between the imaging position and the position in the AIS information, which in turn affects the accuracy of subsequent correlation and the final camera parameters.

[0074] In order to ensure that the optical imaging image and the AIS information can be correctly associated and obtain more accurate position information of the ship target, in one embodiment of the present invention, the AIS information is time-matched and the AIS information at the imaging time is extrapolated.

[0075] Specifically, time matching is performed on the AIS information to extrapolate the AIS information at the imaging moment, including the following steps:

[0076] Determining the imaging moment of the optical imaging image;

[0077] The first preset time before the imaging moment to the second preset time after the imaging moment is used as the preset time range, and the AIS information received within the preset time range is determined. Based on the AIS information received within the preset time range, the position information and motion information of the ship at the imaging moment are extrapolated to obtain the AIS information at the imaging moment, wherein the motion information includes the speed and heading of the ship.

[0078] Since the static information in AIS information is fixed, and the voyage information and safety information are usually fixed as well, it is only necessary to extrapolate the dynamic information at the time of imaging, that is, the position, speed and heading of the ship, to obtain the AIS information at the time of imaging.

[0079] Optionally, in one embodiment of the present invention, extrapolating the position information and motion information of the ship at the imaging moment based on the AIS information received within a preset time range includes:

[0080] The ship's motion equation is constructed based on the position, heading and speed of the ship in the AIS information received at different receiving times within a preset time range, and the ship's position and motion information at the extrapolated imaging moment are calculated using the ship's motion equation.

[0081] As another embodiment, extrapolating the position information and motion information of the ship at the imaging moment based on the AIS information received within a preset time range may also include:

[0082] According to the position, heading and speed of the ship in the AIS information received at different receiving times within the preset time range, the interpolation method is used to extrapolate the position and motion information of the ship at the imaging moment.

[0083] Since the received AIS information is sent within a time slot in the time division multiple access (TDMA) protocol, it is necessary to fit the ship's motion equation based on the ship's position, heading, and speed in the AIS message. The ship's position, heading, and speed at the time of imaging can then be extrapolated based on the fitted motion equation. Alternatively, the ship's position, heading, and speed at the time of imaging can be directly extrapolated using interpolation based on the ship's position, heading, and speed at different times.

[0084] The specific values ​​of the first preset time and the second preset time can be determined based on the reception interval of the satellite-borne AIS receiver, the actual required matching efficiency, and the extrapolation accuracy. Generally, when the reception interval is fixed, when the first preset time and the second preset time are short, the less AIS data used to extrapolate the ship's position and motion information, the higher the matching efficiency, but the accuracy of the extrapolation result is relatively low. When the first preset time and the second preset time are long, the more AIS data used to extrapolate the ship's position and motion information, the lower the matching efficiency, but the accuracy of the extrapolation result is relatively high.

[0085] Taking the time slot division of the AIS receiver as 2 minutes as an example, the first preset time and the second preset time can both be 2 minutes, 4 minutes, or 6 minutes.

[0086] Furthermore, because AIS receivers have a very wide detection range, the number of targets contained in the received AIS information is relatively large, while the range of optical cameras is smaller and contains fewer targets. Directly time-matching all AIS data received by the AIS receiver with the optical imagery would result in low matching efficiency. Furthermore, when correlating the AIS data with the optical imagery, correlation efficiency would also be low.

[0087] In one embodiment of the present invention, in order to improve matching efficiency and data association efficiency, before performing temporal matching on the optical imaging image and the AIS information, spatial matching may also be performed on the optical imaging image and the AIS information.

[0088] Specifically, spatial matching of optical imaging images and AIS information includes the following steps:

[0089] The airspace range contained in the optical imaging image is determined, the airspace range contained in the optical imaging image is used as the reference airspace range, and AIS information from all AIS information within the reference airspace range is selected as the AIS information for time matching.

[0090] Step S5: performing target association between the ship target in the optical imaging image and the AIS information at the imaging moment, determining the AIS information corresponding to the ship target in the optical imaging image, and obtaining feature information of the ship target.

[0091] Specifically, in one embodiment of the present invention, target association is performed between a ship target in an optical imaging image and AIS information at the imaging moment to determine the AIS information corresponding to the ship target in the optical imaging image, including the following steps:

[0092] Constructing a template point set and a target point set, wherein the template point set includes each ship target in the AIS information at the imaging moment, and the target point set includes each ship target in the optical imaging image;

[0093] The template point set is fitted to the target point set through geometric transformation, and the ship target points in the template point set corresponding to each ship target point in the target point set are determined;

[0094] According to the ship target points in the template point set corresponding to the ship target points in the target point set, the AIS information corresponding to each ship target in the optical imaging image is determined.

[0095] In one embodiment of the present invention, by treating each ship target as a point, the entire ship target formation constitutes a point set, the ship target feature information from the AIS data is unified into the same feature space, and the feature relationship between each point in the point set is used to perform association matching processing to achieve ship target association, and then the ship target feature information including the position, size and direction of the ship target is obtained from the AIS information associated with the ship target in the optical imaging image.

[0096] At the same time, since the number of target points and the number of reference points obtained in practice are generally different, and the relationship between the topological structures of the two point sets is often not a simple translation and scaling, the above-mentioned data association method can effectively overcome this problem and improve the association accuracy.

[0097] Step S6: construct an imaging geometry model, and use the characteristic information of the ship target and the imaging geometry model to calculate the parameters of the satellite-borne camera.

[0098] The camera's imaging geometry model is an equation that relates the coordinates of image points to the coordinates of corresponding ground points through a series of coordinate transformations based on the camera's geometric structure. When constructing a rigorous camera imaging geometry model, establishing a rotation matrix is ​​crucial. The essence of constructing a rotation matrix is ​​to establish a series of coordinate systems and the transformation relationships between them.

[0099] Generally, the imaging process establishes a spatial transformation relationship between image point coordinates and ground point coordinates, involving a series of coordinate systems such as the image coordinate system, camera coordinate system, satellite body coordinate system, orbit coordinate system, and ground rectangular coordinate system. The imaging geometry model from object space to image space can be expressed as:

[0100]

[0101] in, Represents the transformation matrix between the J2000 coordinate system and the WGS-84 coordinate system. PN(t) represents the precession and nutation matrix, R(t) represents the Earth rotation matrix, and W(t) represents the polar motion matrix. Represents the transformation matrix from the satellite body coordinate system to the J2000 coordinate system, represents the transformation matrix from the camera coordinate system to the satellite body coordinate system, λ represents the imaging scale coefficient, [XYZ] T and [X S Y S Z S ] T Respectively represent the coordinates of the ground point and the projection center in the national geodetic coordinate system, [D x D y D z ] T and [d x d y d z ] T are the spatial offsets of the phase center of the GPS antenna and the camera lens center relative to the satellite body, [xy -f] T represents the coordinates of the image point in the camera coordinate system, and f represents the camera principal distance.

[0102] Because [D x D y D z ] T and [d x d y d z ] TThe error caused is small. In one embodiment of the present invention, in the subsequent calculation process, [D x D y D z ] T and [d x d y d z ] T Ignore.

[0103] Since the projection rays of the camera can be obtained by connecting the ground points and image points of the same target, different projection rays intersect at the projection center. Therefore, according to the relationship that the ground points and image points of the same target are on a straight line with the projection center of the camera, the exterior orientation element of the image is set as X S ,Y S ,Z S , ω,κ, the internal orientation elements of the image are x0, y0, f, and the imaging geometry model of the camera can be transformed into:

[0104]

[0105] Among them, [X S Y S Z S ] T Indicates the coordinates of the projection center in the national geodetic coordinate system. ω,κ represent the pitch angle, roll angle and yaw angle of the film in the photographic space, [x0 y0] T represents the coordinates of the principal point in the frame coordinate system, f represents the camera principal distance, [xy -f] T Indicates the coordinates of the image point in the camera coordinate system, [XYZ] T Indicates the coordinates of the ground point in the national geodetic coordinate system, a i ,b i ,c i (i=1,2,3) represents the exterior orientation element The 9 coefficients of the rotation matrix R composed of ω,κ,

[0106] Among them, a i ,b i ,c i (i=1,2,3) by external orientation elements ω,κ are determined as follows:

[0107]

[0108]

[0109]

[0110] b1=cosωsinκ

[0111] b2=cosωcosκ

[0112] b3=-sinω

[0113]

[0114]

[0115]

[0116] Furthermore, after the optical imaging image is associated with the AIS information, the image point coordinates and ground point coordinates of the ship targets that have completed data association in the optical imaging image are known. Therefore, based on the characteristic information of multiple ship targets and the above-mentioned imaging geometric model, the exterior orientation elements and interior orientation elements of the camera can be calculated, thereby realizing the correction of the camera parameters.

[0117] Specifically, the characteristic information of the ship target and the imaging geometry model are used to solve the parameters of the spaceborne camera, including the following steps:

[0118] The image point coordinates and ground point coordinates corresponding to the ship target are brought into the imaging geometric model to obtain the imaging geometric model corresponding to the ship target;

[0119] The exterior and interior orientation elements of the image are regarded as unknowns, and the imaging geometric models corresponding to multiple ship targets are jointly established to solve the exterior and interior orientation elements of the image.

[0120] According to the obtained exterior and interior orientation elements of the image, the camera's shooting position and posture can be determined to achieve the correction of the camera parameters.

[0121] Furthermore, considering that the ship position information broadcast by the AIS on the ship is derived from the positioning information of the GPS on the ship, the positioning point in the positioning information is actually the position of the GPS antenna on the ship. This position has a certain deviation from the center point position of the ship extracted from the optical imaging image, that is, the centroid position of the ship.

[0122] To this end, in one embodiment of the present invention, the method may further include: before using the characteristic information of the ship target and the imaging geometry model to solve the satellite camera parameters, calculating the distance between the ship's centroid and the positioning point on the ship used to report the ship's position based on the size of the ship, and correcting the position of the ship target in the characteristic information of the ship target based on the calculated distance.

[0123] By calculating the distance between the ship's centroid and the positioning point on the ship used to report the ship's position, and correcting the position of the ship target given in the AIS information according to the calculated distance, the position deviation can be eliminated and the accuracy of the calculated camera parameters can be improved.

[0124] Since the static information in the AIS information provides the relative position information of the GPS antenna used by AIS installed on the ship, including the distance between the position of the GPS antenna and the bow, stern, port and starboard of the ship, that is, the distance between the positioning point used to report the ship's position and the bow, stern, port and starboard of the ship, the length and width of the ship can be calculated based on the distance between the position of the GPS antenna and the bow, stern, port and starboard of the ship. The centroid position of the ship can be determined based on the length and width, and then the distance between the position of the GPS antenna and the centroid position can be calculated.

[0125] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A camera parameter correction method based on optical imaging and AIS information, characterized in that: include: Use the satellite-borne camera to capture optical images of the preset ship area, and use the satellite-borne AIS receiver to receive and analyze the ship's AIS information; Preprocess the optical imaging images and AIS information respectively; Perform target detection on the pre-processed optical imaging image to obtain the coordinates of the ship target in the optical imaging image; Time-match the AIS information and extrapolate the AIS information at the imaging moment; Performing target association between the ship target in the optical imaging image and the AIS information at the imaging moment, determining the AIS information corresponding to the ship target in the optical imaging image, and obtaining characteristic information of the ship target, wherein the characteristic information includes at least: the position, size, and direction of the ship target; Construct an imaging geometry model and use the characteristic information of the ship target and the imaging geometry model to calculate the parameters of the satellite-borne camera; Setting: The exterior orientation elements of the image are , the internal orientation elements of the image are , Indicates the coordinates of the projection center in the national geodetic coordinate system. They represent the pitch angle, roll angle and yaw angle of the film in the photographic space, Represents the coordinates of the principal point in the frame coordinate system, Indicates the camera principal distance; The imaging geometry model is: ； in, Represents the coordinates of the image point in the camera coordinate system, Indicates the coordinates of the ground point in the national geodetic coordinate system. Represents exterior orientation elements The rotation matrix The 9 coefficients of .

2. The camera parameter correction method based on optical imaging and AIS information according to claim 1, characterized in that: The pre-processing of the optical imaging image includes: Perform geometric correction and target enhancement processing on optical imaging images.

3. The camera parameter correction method based on optical imaging and AIS information according to claim 1, characterized in that: The pre-processing of the AIS information includes: Perform data cleaning and data denoising on AIS information to remove erroneous data; The erroneous data includes data that does not comply with the AIS standard and repeated data with the same Chinese field content in the AIS data.

4. The camera parameter correction method based on optical imaging and AIS information according to any one of claims 1 to 3, characterized in that: The time matching of the AIS information and the extrapolation of the AIS information at the imaging time include: Determining the imaging moment of the optical imaging image; The first preset time before the imaging moment to the second preset time after the imaging moment is used as the preset time range, and the AIS information received within the preset time range is determined. Based on the AIS information received within the preset time range, the position information and motion information of the ship at the imaging moment are extrapolated to obtain the AIS information at the imaging moment, wherein the motion information includes the speed and heading of the ship.

5. The camera parameter correction method based on optical imaging and AIS information according to claim 4, characterized in that: The extrapolating the position information and motion information of the ship at the imaging moment based on the AIS information received within the preset time range includes: The ship's motion equation is constructed based on the position, heading and speed of the ship in the AIS information received at different receiving times within a preset time range, and the ship's position and motion information at the extrapolated imaging moment are calculated using the ship's motion equation.

6. The camera parameter correction method based on optical imaging and AIS information according to claim 4, characterized in that: The extrapolating the position information and motion information of the ship at the imaging moment based on the AIS information received within the preset time range includes: According to the position, heading and speed of the ship in the AIS information received at different receiving times within the preset time range, the interpolation method is used to extrapolate the position and motion information of the ship at the imaging moment.

7. The camera parameter correction method based on optical imaging and AIS information according to claim 1, characterized in that: The step of performing target association between the ship target in the optical imaging image and the AIS information at the imaging moment to determine the AIS information corresponding to the ship target in the optical imaging image includes: Constructing a template point set and a target point set, wherein the template point set includes each ship target in the AIS information at the imaging moment, and the target point set includes each ship target in the optical imaging image; The template point set is fitted to the target point set through geometric transformation, and the ship target points in the template point set corresponding to each ship target point in the target point set are determined; According to the ship target points in the template point set corresponding to the ship target points in the target point set, the AIS information corresponding to each ship target in the optical imaging image is determined.

8. The camera parameter correction method based on optical imaging and AIS information according to claim 1, characterized in that: The method of calculating the parameters of the satellite-borne camera by using the characteristic information of the ship target and the imaging geometric model includes: The image point coordinates and ground point coordinates corresponding to the ship target are brought into the imaging geometric model to obtain the imaging geometric model corresponding to the ship target; The exterior and interior orientation elements of the image are regarded as unknowns, and the imaging geometric models corresponding to multiple ship targets are jointly established to solve the exterior and interior orientation elements of the image.

9. The camera parameter correction method based on optical imaging and AIS information according to claim 1, characterized in that: The method further comprises: Before using the characteristic information of the ship target and the imaging geometry model to solve the parameters of the satellite-borne camera, the distance between the ship's centroid and the positioning point on the ship used to report the ship's position is calculated according to the size of the ship, and the position of the ship target in the characteristic information of the ship target is corrected according to the calculated distance.

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