A method for calculating the orbit period of a spaceborne remote sensing camera

Abstract

The application discloses a kind of satellite-borne remote sensing camera line period calculation method, comprising: obtaining the corresponding shooting of first row of image elements in the coordinates of geocentric geodetic coordinate system at T0 Moment point P coordinate;Obtain the coordinates of object point O and the coordinates of object point N that first row of image elements and last row of image elements respectively shoot at T1 Moment, calculate the coordinates of object point M that object point N is on the line segment OP when object point O, object point P and object point N three points are collinear;According to object point P coordinate, object point O coordinate, object point M coordinate, the time difference of T1 time and T0 time and the number K of detector image elements, calculate the camera line period.The method provided by the application is based on satellite positioning, only uses the current position, ground speed and satellite attitude of satellite, to calculate the line period, simplify the existing calculation method, and the ground speed calculated by the method has universal adaptability, and can be iterated to the accuracy requirement according to specific use scene.

Description

Technical Field

[0001] This invention relates to the field of remote sensing camera imaging technology, and in particular to a method for calculating the period of a spaceborne remote sensing camera. Background Technology

[0002] The most common imaging method for existing spaceborne remote sensing cameras is the pushbroom imaging mode of multi-stage TDI (Time Delay Integration) linear detectors. According to its principle, during the imaging process of a multi-stage TDI linear detector, it is necessary to ensure that the direction of the image velocity of the image point on the camera's image plane is perpendicular to the direction of the linear detector. Based on the image velocity, the time taken for the image point to translate through a single row of pixels must be calculated, which is the imaging row period of the remote sensing camera. This allows for the matching of a suitable row period to the multi-stage TDI linear detector, ensuring that the image velocity matches the charge transfer velocity. Furthermore, the attitude zero position of a remote sensing satellite is generally a stable attitude state with zero values ​​across all three axes of the orbital system. During remote sensing camera imaging, the remote sensing satellite platform needs to dynamically calculate the vector angle between the image velocity and the linear detector relative to the attitude zero state through direct attitude adjustment or other indirect methods, and then adjust this angle back to zero. This process is the compensation for the remote sensing camera's drift angle. While adjusting the deflection angle, the row period of the remote sensing camera is also adjusted to ensure that the multi-stage TDI linear detector can complete energy integration and energy superposition normally, and achieve correct imaging data acquisition.

[0003] However, a complete analytical expression for image velocity is high-order and complex, depending not only on satellite position and velocity and satellite attitude, but also on higher-order variables such as satellite attitude angular velocity and angular acceleration. In engineering derivations, simplified analytical solutions are often derived for specific application scenarios, meaning that a general image velocity expression may not represent all special cases.

[0004] If a complete analytical model is used, new requirements are placed on the onboard processing and computing capabilities. In general, on satellite platforms, velocity calculations are performed by onboard computers or camera functional units, which limits computing resources. Summary of the Invention

[0005] To address the problems of poor universality and computational complexity in existing methods for calculating the line period of remote sensing cameras, this invention provides a method for calculating the line period of spaceborne remote sensing cameras.

[0006] The first aspect of this invention provides a method for calculating the period of a spaceborne remote sensing camera, comprising:

[0007] S1: Set the camera line-of-sight vector of the first row pixel e of the multi-level TDI linear array detector at time T0 to coincide with the +Z axis vector of the satellite body coordinate system, and obtain the coordinates of the object point P corresponding to the first row pixel e in the geocentric geofixed coordinate system at time T0.

[0008] S2: Select time T1 and set the satellite attitude yaw angle to zero at time T1. Obtain the coordinates of the object point O corresponding to the first row pixel e in the geocentric-ground-fixed coordinate system and the coordinates of the object point N corresponding to the last row pixel n of the multi-level TDI linear array detector in the geocentric-ground-fixed coordinate system at time T1.

[0009] S3: Based on the coordinates of object point P, object point O and object point N, calculate the coordinates of object point M on the line segment OP formed by object point O and object point P when object point O, object point P and object point N are collinear;

[0010] S4: Calculate the ground velocity V of the multi-stage TDI linear array detector based on the coordinates of object point P, object point O, and the time difference between time T1 and time T0.

[0011] S5: Calculate the row period of the multi-level TDI linear detector based on the coordinates of object point M, object point O, ground velocity V, and the number of pixel rows K of the multi-level TDI linear detector.

[0012] Furthermore, prior to S1, the transformation relationship between the image plane coordinate system and the geocentric coordinate system of the multi-level TDI linear array detector is obtained.

[0013] Furthermore, the difference between T1 and T0 is greater than the preset time threshold.

[0014] Furthermore, the preset time threshold is less than or equal to 100 seconds.

[0015] Further, S4 specifically includes: calculating the length of the line segment OP formed by object point P and object point O based on the coordinates of object point P and object point O, and calculating the ground velocity V of the multi-stage TDI line array detector based on the length of line segment OP and the time difference between time T1 and time T0.

[0016] Further, S5 specifically includes: calculating the length of the line segment OM formed by object point M and object point O based on the coordinates of object point M and object point O; and calculating the row period of the multi-level TDI line detector based on the length of line segment OM, ground velocity V, and the number of pixel rows K of the multi-level TDI line detector.

[0017] A second aspect of the present invention also provides an electronic device, including a processor and a memory, the memory storing a plurality of instructions, the processor being configured to read the instructions and execute the calculation method as described in the first aspect.

[0018] A third aspect of the present invention also provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores a plurality of instructions, which can be read by a processor and executed as the calculation method described in the first aspect.

[0019] The beneficial effects of this invention are:

[0020] The method for calculating the orbital period of a spaceborne remote sensing camera provided by this invention no longer focuses on higher-order physical quantities such as satellite attitude angular velocity and angular acceleration. Based on satellite positioning, it only uses the current position of the satellite, ground velocity, and satellite attitude quantities to calculate the orbital period of the spaceborne remote sensing camera, which simplifies the existing calculation methods. At the same time, the method provided by this invention has universal adaptability, and the calculated ground velocity can be iterated to the required accuracy according to the specific application scenario. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the calculation method for the orbital period of a spaceborne remote sensing camera provided by the present invention.

[0022] Figure 2 A schematic diagram illustrating the transformation process between the image plane coordinate system and the geocentric-solid coordinate system of the multi-level TDI linear detector provided by the present invention;

[0023] Figure 3 This is a schematic diagram illustrating the principle of solving the orbital period of a spaceborne remote sensing camera provided by the present invention. Detailed Implementation

[0024] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0025] This embodiment provides a method for calculating the period of a spaceborne remote sensing camera, including:

[0026] S1: Set the camera line-of-sight vector of the first row pixel e of the multi-level TDI linear array detector at time T0 to coincide with the +Z axis vector of the satellite body coordinate system, and obtain the coordinates of the object point P corresponding to the first row pixel e in the geocentric geofixed coordinate system at time T0.

[0027] S2: Select time T1 and set the satellite attitude yaw angle to zero at time T1. Obtain the coordinates of the object point O corresponding to the first row pixel e in the geocentric-ground-fixed coordinate system and the coordinates of the object point N corresponding to the last row pixel n of the multi-level TDI linear array detector in the geocentric-ground-fixed coordinate system at time T1.

[0028] S3: Based on the coordinates of object point P, object point O, and object point N, calculate the coordinates of object point M on the line segment OP formed by object points O and P when object points O, P, and N are collinear:

[0029] S4: Calculate the ground velocity V of the multi-stage TDI linear array detector based on the coordinates of object point P, object point O, and the time difference between time T1 and time T0; specifically, calculate the length of the line segment OP formed by object point P and object point O based on the coordinates of object point P and object point O, and calculate the ground velocity V of the multi-stage TDI linear array detector based on the length of line segment OP and the time difference between time T1 and time T0.

[0030] S5: Calculate the line period of the multi-level TDI linear detector based on the coordinates of object point M, object point O, ground velocity V, and the number of pixel rows K of the multi-level TDI linear detector; specifically, calculate the length of the line segment OM formed by object point M and object point O based on the coordinates of object point M and object point O, and calculate the line period of the multi-level TDI linear detector based on the length of line segment OM, ground velocity V, and the number of pixel rows K of the multi-level TDI linear detector.

[0031] It should be noted that before proceeding to step S1, it is necessary to first obtain the transformation relationship between the image plane coordinate system and the geocentric-ground-fixed coordinate system of the multi-stage TDI linear detector. Based on the transformation relationship, the coordinates of the corresponding object point P of the first row pixel e of the multi-stage TDI linear detector in the geocentric-ground-fixed coordinate system at time T0 are obtained. The image plane coordinate system is determined by the ROWS axis and the COLOMNS axis, which are parallel to the integration direction and the linear direction of the multi-stage TDI linear detector, respectively. At time T0, the camera line-of-sight vector derived from the first row pixel e is set to coincide with the +Z axis vector of the satellite body coordinate system. Since the change in the +Z axis yaw attitude angle of the satellite body coordinate system does not change the coordinates of the corresponding object point of the first row pixel e in the geocentric-ground-fixed coordinate system, the yaw attitude angle at time T0 is not set.

[0032] In steps S1-S2, the coordinates of the object points captured by each pixel of the multi-stage TDI linear detector are transformed from the image plane coordinate system to the geocentric-fixed coordinate system according to the photogrammetry principle of the spaceborne camera before the camera's period is calculated. The transformation process between the image plane coordinate system and the geocentric-fixed coordinate system of the multi-stage TDI linear detector is as follows: Figure 2As shown, for example, if the coordinates of a certain pixel of a multi-level TDI linear detector in the image plane coordinate system are set as (row, col), firstly, based on the orientation of the pixel in the camera, the coordinates of the object point captured by the pixel in the image plane coordinate system are transformed to the camera coordinate system, and then transformed from the camera coordinate system to the satellite coordinate system (Xs, Ys, Zs). Secondly, considering factors such as satellite attitude angle, it is further transformed to the orbital coordinate system (Xorb, Yorb, Zorb). Then, based on the principles of photogrammetry, the geocentric inertial coordinate system (Xi, Yi, Zi) of the ground object is calculated. Considering the effects of precession, nutation, polar motion, etc., the corresponding object point coordinates (Xo, Yo, Zo) in the geocentric geofixed coordinate system (Xr, Yr, Zr) are finally obtained. The satellite is in a high-speed flight state around its orbit, and the transformation relationship between the image plane coordinate system and the geocentric coordinate system is constantly changing. In this embodiment, the camera period is calculated based on the coordinates of the object point captured by each pixel in the geocentric coordinate system at different times. It can be seen that the entire calculation process does not involve high-order solutions such as attitude angular velocity and angular acceleration.

[0033] Obtain the number of pixel rows K of the multi-level TDI linear detector. The first row of pixels in the K rows is labeled e, and the last row of pixels is labeled n. Based on the pushbroom imaging principle of the multi-stage TDI linear array detector, the first row of pixels e and the last row of pixels n should scan the same object point in chronological order. For example, at a certain time T0, the coordinates P of the object point corresponding to the first row of pixels e can be calculated according to the remote sensing photogrammetry principle of the spaceborne camera. Here, the coordinates P of the object point are coordinates in the geocentric-ground-fixed coordinate system. Time T1 is selected, and the satellite attitude yaw angle is set to zero at time T1. The coordinates O of the object point corresponding to the first row of pixels e in the geocentric-ground-fixed coordinate system and the coordinates N of the object point corresponding to the last row of pixels n in the geocentric-ground-fixed coordinate system are obtained at time T1. Here, the coordinates O and N of the object point are coordinates in the geocentric-ground-fixed coordinate system. The difference between T1 and T0 is greater than a preset time threshold. To ensure the accuracy and correctness of the calculation, the preset time threshold is less than or equal to 100 seconds. Figure 3As shown, only when object point N is on line segment OP, that is, when object points O, P and N are collinear, can the first row pixel e and the last row pixel n scan through object point P in sequence, thus avoiding distortion and blurring of the image obtained by the multi-level TDI linear detector. When object points O, P, and N are collinear, the coordinates of object point M corresponding to object point N on line segment OP can be calculated based on the coordinates of object points O, P, and N. Specifically, when line segment ON rotates by an angle Δα to coincide with line segment OP, the point where object point N falls on line segment OP is object point M. Based on the coordinates of object point P and object point O, the length of line segment OP is calculated. Based on the length of line segment OP and the time difference between time T1 and T0, the ground velocity V of the multi-stage TDI linear array detector is calculated. Assuming that the time taken for an image point on the image plane of the multi-stage TDI linear array detector to translate through a single row of pixels is ΔT, that is, the imaging row period of the remote sensing camera is ΔT, and since the time corresponding to the distance 0M is K×ΔT, the length of line segment OM can be calculated based on the coordinates of object point M and object point O. Based on the length of line segment OM, ground velocity V, and the number of pixel rows K of the multi-stage TDI linear array detector, the row period ΔT of the multi-stage TDI linear array detector is calculated.

[0034] The present invention also provides an electronic device, including a processor and a memory, wherein the memory stores multiple instructions, and the processor is used to read the instructions and execute a method for calculating the line period of a spaceborne remote sensing camera provided in the embodiments.

[0035] The present invention also provides a computer-readable storage medium storing a plurality of instructions, which can be read and executed by a processor, according to an embodiment of a method for calculating the line period of a spaceborne remote sensing camera.

[0036] The method for calculating the orbital period of a spaceborne remote sensing camera provided by this invention no longer focuses on higher-order physical quantities such as attitude angular velocity and angular acceleration, but only uses the current position, velocity and attitude of the satellite, thus simplifying the calculation method; moreover, the method has universal adaptability, and the calculated ground velocity can be iterated to the required accuracy according to the specific application scenario.

[0037] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A method for calculating the orbital period of a spaceborne remote sensing camera, characterized in that, include: S1: Set the camera line-of-sight vector of the first row pixel e of the multi-level TDI linear array detector at time T0 to coincide with the +Z axis vector of the satellite body coordinate system, and obtain the coordinates of the object point P corresponding to the first row pixel e in the geocentric geofixed coordinate system at time T0. S2: Select time T1 and set the satellite attitude yaw angle to zero at time T1. Obtain the coordinates of the object point O corresponding to the first row pixel e in the geocentric-ground-fixed coordinate system and the coordinates of the object point N corresponding to the last row pixel n of the multi-level TDI linear array detector in the geocentric-ground-fixed coordinate system at time T1. S3: Based on the coordinates of object point P, object point O and object point N, calculate the coordinates of object point M on the line segment OP formed by object point O and object point P when object point O, object point P and object point N are collinear; S4: Calculate the ground velocity V of the multi-stage TDI linear detector based on the coordinates of object point P, object point O, and the time difference between time T1 and time T0. S5: Calculate the row period of the multi-level TDI linear detector based on the coordinates of object point M, object point O, ground velocity V, and the number of pixel rows K of the multi-level TDI linear detector.

2. The method for calculating the period of a spaceborne remote sensing camera as described in claim 1, characterized in that, Before step S1, the transformation relationship between the image plane coordinate system and the geocentric coordinate system of the multi-level TDI linear array detector is obtained.

3. The method for calculating the period of a spaceborne remote sensing camera as described in claim 2, characterized in that, The difference between T1 and T0 is greater than the preset time threshold.

4. The method for calculating the period of a spaceborne remote sensing camera as described in claim 3, characterized in that, The preset time threshold is less than or equal to 100 seconds.

5. The method for calculating the period of a spaceborne remote sensing camera as described in claim 4, characterized in that, S4 specifically includes: calculating the length of the line segment OP formed by object point P and object point O based on the coordinates of object point P and object point O, and calculating the ground velocity V of the multi-stage TDI line array detector based on the length of line segment OP and the time difference between time T1 and time T0.

6. The method for calculating the period of a spaceborne remote sensing camera as described in claim 5, characterized in that, S5 specifically includes: calculating the length of the line segment OM formed by object point M and object point O based on the coordinates of object point M and object point O; and calculating the line period of the multi-level TDI line detector based on the length of line segment OM, ground velocity V, and the number of pixel rows K of the multi-level TDI line detector.

7. An electronic device, characterized in that, It includes a processor and a memory, the memory storing multiple instructions, and the processor being used to read the instructions and execute a method for calculating the line period of a spaceborne remote sensing camera as described in any one of claims 1-6.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores multiple instructions, which can be read and executed by a processor as described in any one of claims 1-6, for a method of calculating the line period of a spaceborne remote sensing camera.

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