CN116503269A - SAR image correction method and device - Google Patents
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Abstract
The invention discloses a correction method and device of SAR images, wherein the method comprises the following steps: after obtaining initial DEM data, adding the initial DEM data with a plurality of position offsets respectively to obtain a plurality of offset DEM data; calculating an offset average gray value of the SAR image to be corrected by adopting each offset DEM data to obtain a plurality of offset average gray values; and carrying out offset correction on the SAR image to be corrected by utilizing the offset average gray values and the preset initial average gray value. According to the method, after DEM data corresponding to the SAR image to be corrected are obtained, the horizontal offset is added into the DEM data, then the average gray level of the DEM data added with the horizontal offset and the average gray level of the DEM data not added with the horizontal offset are calculated respectively, the horizontal offset meeting the actual requirements is screened out through comparison of the two gray values, and image correction is carried out, so that the influence caused by relative position deviation is reduced, and the effect of image correction is improved.
Description
Technical Field
The invention relates to the technical field of image correction, in particular to a SAR image correction method and device.
Background
The SAR (Synthetic Aperture Radar, SAR) image is an image acquired by earth observation with a synthetic aperture radar mounted on a flight platform such as an airplane, satellite, spacecraft, or the like. Because the SAR image has a certain geometrical distortion compared with the common optical image, such as perspective shrinkage, overlay masking, top-bottom inversion and the like, the SAR image is not beneficial to interpretation and understanding of the image by a common user. Geometric correction is required before application to generate an orthographic image which better reflects the real terrain.
The current commonly used image correction method comprises a forward method and a backward method. The forward method finds out the corresponding three-dimensional space coordinates of each pixel point of the image by accurately positioning the pixel points of the image, and resamples the original image into an orthographic image according to the positioning result. The backward method is to precisely position each element in auxiliary DEM data through digital elevation model (Digital Elevation Model, DEM) data, find SAR image coordinates corresponding to each element, and endow pixel gray values of the SAR image coordinates to DEM data elements at corresponding positions, and the generated equidistant images are the geometrically corrected orthographic images.
However, the current common correction method has the following technical problems: the forward method requires mapping a two-dimensional plane to a three-dimensional space, and an elevation of a ground point to be assumed, which may introduce error data, thereby affecting positioning accuracy and final geometric correction results. And then, the relative position of the actual terrain represented by the DEM data used by the forward method may deviate from the relative position of the actual terrain, and the coordinates of the pixel points positioned by using the DEM data may be wrong, so that the generated orthographic image position deviates from the actual geographic position, and the subsequent correction is wrong.
Disclosure of Invention
The invention provides a correction method and a correction device for SAR images, wherein a plurality of offset values can be added in DEM data to compensate relative position errors, and the SAR images are corrected by combining the offset values so as to reduce the influence caused by the relative position errors and improve the image correction effect.
A first aspect of an embodiment of the present invention provides a method for correcting a SAR image, including:
after initial DEM data are obtained, the initial DEM data are respectively added with a plurality of position offset values to obtain a plurality of offset DEM data, wherein the initial DEM data are DEM data of a region corresponding to an SAR image to be corrected;
calculating an offset average gray value of the SAR image to be corrected by adopting each offset DEM data to obtain a plurality of offset average gray values;
and carrying out offset correction on the SAR image to be corrected by utilizing the offset average gray values and a preset initial average gray value, wherein the preset initial average gray value is the average gray value of the SAR image to be corrected calculated by adopting initial DEM data.
In a possible implementation manner of the first aspect, the performing offset correction on the SAR image to be corrected by using the plurality of offset average gray values and a preset initial average gray value includes:
selecting a gray value with the largest value from a plurality of offset average gray values and preset initial average gray values;
obtaining the offset of DEM data corresponding to the gray value with the maximum value to obtain a target offset;
and generating a corrected SAR orthographic image by adopting the target offset.
In a possible implementation manner of the first aspect, the calculating, using each of the offset DEM data, an offset average gray value of the SAR image to be corrected includes:
acquiring first parameters of an SAR image to be corrected, wherein the first parameters comprise: radar imaging parameters and radar orbit operating parameters;
positioning each element in the offset DEM data according to the first parameter to obtain an offset coordinate, wherein the offset coordinate is a pixel coordinate of each element of the offset DEM data on an SAR image to be corrected;
assigning the pixel gray values of the offset coordinates to the data elements of the corresponding offset DEM data to form an offset orthographic image;
and counting the average gray level of the offset orthophoto to obtain an offset average gray level value.
In a possible implementation manner of the first aspect, the average gray value of the SAR image to be corrected calculated using the initial DEM data includes:
acquiring a second parameter of the SAR image to be corrected, wherein the second parameter comprises: radar imaging parameters and radar orbit operating parameters;
positioning each element in the initial DEM data according to the second parameter to obtain an initial coordinate, wherein the initial coordinate is a pixel coordinate of each element of the initial DEM data on an SAR image to be corrected;
assigning the pixel gray values of the initial coordinates to the data elements of the corresponding initial DEM data to form an initial orthographic image;
and counting the average gray level of the initial orthophoto to obtain an initial average gray level value.
A second aspect of an embodiment of the present invention provides a correction apparatus for a SAR image, including:
the offset adding module is used for adding the initial DEM data with a plurality of position offsets respectively after acquiring the initial DEM data, so as to obtain a plurality of offset DEM data, wherein the initial DEM data are DEM data of a region corresponding to an SAR image to be corrected;
the gray value calculating module is used for calculating an offset average gray value of the SAR image to be corrected by adopting each offset DEM data to obtain a plurality of offset average gray values;
the image correction module is used for carrying out offset correction on the SAR image to be corrected by utilizing the offset average gray values and a preset initial average gray value, wherein the preset initial average gray value is the average gray value of the SAR image to be corrected calculated by adopting initial DEM data.
In a possible implementation manner of the second aspect, the image correction module is further configured to:
selecting a gray value with the largest value from a plurality of offset average gray values and preset initial average gray values;
obtaining the offset of DEM data corresponding to the gray value with the maximum value to obtain a target offset;
and generating a corrected SAR orthographic image by adopting the target offset.
In a possible implementation manner of the second aspect, the gray value calculating module is further configured to:
acquiring first parameters of an SAR image to be corrected, wherein the first parameters comprise: radar imaging parameters and radar orbit operating parameters;
positioning each element in the offset DEM data according to the first parameter to obtain an offset coordinate, wherein the offset coordinate is a pixel coordinate of each element of the offset DEM data on an SAR image to be corrected;
assigning the pixel gray values of the offset coordinates to the data elements of the corresponding offset DEM data to form an offset orthographic image;
and counting the average gray level of the offset orthophoto to obtain an offset average gray level value.
In a possible implementation manner of the second aspect, the average gray value of the SAR image to be corrected calculated using the initial DEM data is specifically:
acquiring a second parameter of the SAR image to be corrected, wherein the second parameter comprises: radar imaging parameters and radar orbit operating parameters;
positioning each element in the initial DEM data according to the second parameter to obtain an initial coordinate, wherein the initial coordinate is a pixel coordinate of each element of the initial DEM data on an SAR image to be corrected;
assigning the pixel gray values of the initial coordinates to the data elements of the corresponding initial DEM data to form an initial orthographic image;
and counting the average gray level of the initial orthophoto to obtain an initial average gray level value.
Compared with the prior art, the SAR image correction method and device provided by the embodiment of the invention have the beneficial effects that: according to the method, after DEM data corresponding to the SAR image to be corrected are obtained, the horizontal offset is added into the DEM data, then the average gray level of the DEM data added with the horizontal offset and the average gray level of the DEM data not added with the horizontal offset are calculated respectively, the horizontal offset meeting the actual requirements is screened out through comparison of the two gray values, and image correction is carried out, so that the influence caused by relative position deviation is reduced, and the effect of image correction is improved.
Drawings
Fig. 1 is a flowchart of a method for correcting a SAR image according to an embodiment of the present invention;
fig. 2 is an operation flowchart of a method for correcting a SAR image according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a device for correcting SAR images according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In order to solve the above-mentioned problems, a method for correcting a SAR image provided in the present embodiment will be described and explained in detail by the following specific embodiments.
Referring to fig. 1, a flowchart of a method for correcting a SAR image according to an embodiment of the present invention is shown.
As an example, the method for correcting the SAR image may include:
s11, after initial DEM data are obtained, the initial DEM data are respectively added with a plurality of position offset amounts to obtain a plurality of offset DEM data, and the initial DEM data are DEM data of a region corresponding to an SAR image to be corrected.
In an embodiment, image data of the SAR image to be corrected and a series of imaging parameters corresponding to the SAR image to be corrected may be read. The series of imaging parameters may include radar pulse repetition time interval, radar signal wavelength, image proximity, image distance sampling interval, image azimuth sampling interval, image width, image height, longitude and latitude coordinates corresponding to four corner points of the image, and the like.
The radar orbit operation parameters corresponding to the SAR image to be corrected can be read, wherein the radar orbit operation parameters can comprise position information in the radar operation process, speed information in the radar operation process, starting time and ending time of radar observation and the like.
Taking SAR image data of a third high-resolution satellite as an example, during actual operation, the operation steps of reading the radar orbit operation parameters corresponding to the image may include: one piece of SAR image data of the high-resolution satellite No. three comprises an image file and a parameter file corresponding to the image. The parameter file contains imaging parameters of the image, the starting time and the ending time of radar observation, the position vector and the speed vector of each time point of the radar platform in the running process. The imaging parameters of the image, the starting time and the ending time of radar observation, the position vector and the speed vector of each time point in the running process of the radar platform can be directly read from the parameter file.
Then, DEM data of an actual area corresponding to the SAR image to be corrected can be acquired. The operation mode of obtaining DEM data of the actual area may be as follows: if the radar imaging data contains longitude and latitude coordinates corresponding to four corner points of the image, the actual geographic area corresponding to the image can be directly determined according to the longitude and latitude coordinates of the four corner points, and then the data of the area is intercepted from the existing DEM data; if the radar imaging data does not contain the longitude and latitude coordinates of the corner points, the four corner points of the image are required to be positioned based on the distance-Doppler model by a forward method so as to determine the longitude and latitude coordinates corresponding to the four corner points, and then the actual geographic area corresponding to the image is intercepted from the DEM data according to the longitude and latitude coordinates of the corner points obtained by positioning.
After the initial DEM data is acquired, a different positional offset, which may be a horizontal offset, may be added to the initial DEM data. For example, there are 10 different positional offsets, and 10 different positional offsets may be added to the initial DEM data, respectively, to obtain 10 offset DEM data.
Each position offset may be within a suitable range, where the suitable range may be determined based on the predicted data error magnitude.
Optionally, the range of the added offset may also be adjusted according to the size of errors that may exist in the SAR data and the DEM data. The spacing between the different offsets added determines the accuracy of the error compensation. The interval between each position offset can be adjusted according to actual needs.
When the offset interval is set smaller, the compensation of the final error will be more accurate, but the offset that needs to be added will be more, and thus the time will be longer.
For example, when the error of the SAR data and the DEM data is approximately in the order of ten meters, the added DEM data horizontal offset may be taken as: the longitude offset ranges from-0.001 ° to 0.001 ° with 0.00001 ° spacing; the latitude offset ranges from-0.001 ° to 0.001 ° with 0.00001 ° spacing, and there are 201×201=40401 offsets to be added in total.
When the estimated SAR image data and DEM data have errors of several tens of meters, the latitude and longitude 1 ° is empirically equal to about 100km. At this time, the addition range of the offset may be-0.001 ° to 0.001 °, so as to ensure that a certain offset in the range can exactly compensate for the existing data error.
The key point of adding the offset is to find the offset which makes the average gray level of the corrected image highest. Thus, the appropriate range may be defined in advance mainly to improve the efficiency of the method so as to find the offset more quickly. If the error of the data cannot be estimated, the addition range of the offset can take a larger value as far as possible, and the offset in the range is only required to be ensured to be capable of compensating possible data errors.
S12, calculating an offset average gray value of the SAR image to be corrected by adopting each offset DEM data to obtain a plurality of offset average gray values.
After a plurality of offset DEM data are obtained, gray values corresponding to the SAR image to be corrected under the offset DEM data can be calculated respectively, so that offset average gray values corresponding to each offset DEM data are obtained.
Because the SAR image or the region with serious geometric distortion in the SAR image is often a region with large actual topography fluctuation, the gray scale difference of the orthophoto image generated by the region with large topography fluctuation under the condition of adding different offsets is also larger.
The offset which enables the average gray level to reach the highest can be found more easily through the gray level value, so that the SAR image or SAR image can be corrected by utilizing the offset.
In an alternative embodiment, step S12 may comprise the sub-steps of:
s121, acquiring first parameters of an SAR image to be corrected, wherein the first parameters comprise: radar imaging parameters and radar orbit operating parameters.
S122, positioning each element in the offset DEM data according to the first parameter to obtain an offset coordinate, wherein the offset coordinate is a pixel coordinate of each element of the offset DEM data on the SAR image to be corrected.
S123, assigning the pixel gray values of the offset coordinates to the data elements of the corresponding offset DEM data to form an offset orthographic image.
S124, counting the average gray level of the offset orthophoto image to obtain an offset average gray level value.
Specifically, each element in the offset DEM data may be located according to the first parameter (including the radar imaging parameter and the radar orbit operation parameter) of the to-be-corrected SAR image obtained as described above, so as to obtain the pixel coordinate of each element in the offset DEM data corresponding to the to-be-corrected SAR image.
It should be noted that, during positioning, the RPC model may be used to quickly position the offset DEM data element, so as to improve positioning efficiency.
Then, according to the pixel coordinates of the SAR image to be corrected corresponding to each element of the obtained offset DEM data, the pixel gray value of each coordinate can be given to the element of the corresponding offset DEM data.
When the coordinates obtained by the positioning are not integers, the pixel gray values at the coordinates are obtained by bilinear interpolation of the pixel gray values of the adjacent four integer coordinates. For example, the pixel coordinates are (x, y), and the coordinates of each pixel of the SAR image to be corrected are integers, but the coordinates obtained by the positioning calculation are not necessarily integers, and when any one of the calculated values of x and y is not an integer, in order to obtain the gray value of the SAR image to be corrected under the non-integer coordinates, the gray values of surrounding pixel points may be interpolated to obtain the gray value under the non-integer coordinates.
For example, in one implementation, if the corresponding pixel coordinate obtained by the positioning solution of a certain DEM data element is (1.2,1.6), four pixels closest to the non-integer coordinate, that is, four pixels with coordinates of (1, 1), (1, 2), (2, 1), (2, 2), are found, and the gray value corresponding to the coordinate (1.2,1.6) is obtained by bilinear interpolation of the gray values of the four integer coordinate pixels, and the gray value is assigned to the corresponding DEM data element.
After assignment is completed, the offset DEM data after assignment of the corresponding gray values can be used as a pair of SAR orthographic images to obtain offset orthographic images. The average gray level of the orthophoto image can be counted and recorded, thus completing the preliminary geometric correction.
In an alternative embodiment, the number of offsets to be added may be larger, and if the offset average gray values corresponding to the plurality of offset DEM data are calculated at the same time, the calculation pressure may be increased.
In order to relieve the calculation pressure, an offset may be added to the initial DEM data to obtain first offset DEM data, and then an offset average gray value corresponding to the offset DEM data is calculated. Then, adding the next offset to the initial DEM data to obtain second offset DEM data, and repeating the steps of S121-S124 again to obtain an offset average gray value corresponding to the second offset DEM data, and so on.
And S13, carrying out offset correction on the SAR image to be corrected by utilizing the offset average gray values and a preset initial average gray value, wherein the preset initial average gray value is the average gray value of the SAR image to be corrected calculated by adopting initial DEM data.
In an embodiment, the offset average gray value and the preset initial average gray value may be used to find the offset of the most suitable or closest DEM data, so that the offset of the DEM data may be used to correct the SAR image to be corrected, and the corrected SAR image is output.
In one embodiment, the obtaining the preset initial average gray value by using the average gray value of the SAR image to be corrected calculated by using the initial DEM data may include the following substeps:
s21, acquiring second parameters of the SAR image to be corrected, wherein the second parameters comprise: radar imaging parameters and radar orbit operating parameters.
S22, positioning each element in the initial DEM data according to the second parameter to obtain an initial coordinate, wherein the initial coordinate is a pixel coordinate of each element of the initial DEM data on the SAR image to be corrected.
S23, assigning the pixel gray values of the initial coordinates to the data elements of the corresponding initial DEM data to form an initial orthographic image.
S24, counting the average gray level of the initial orthophoto to obtain an initial average gray level value.
In an embodiment, the operation of steps S21-S24 is the same as that of steps S121-S124, and for avoiding repetition, reference is made to the above description for details.
In one embodiment, step S13 may include the sub-steps of:
s131, selecting the gray value with the largest value from a plurality of offset average gray values and preset initial average gray values.
S132, obtaining the offset of the DEM data corresponding to the gray value with the maximum value, and obtaining a target offset.
S133, generating a corrected SAR orthographic image by adopting the target offset.
Specifically, the average gray scale of the normal image generated under different offset amounts and the preset initial average gray scale value can be compared to find the average gray scale value with the largest value. And then searching the offset of the DEM data corresponding to the maximum gray value. And then using the horizontal offset as the compensation amount of the relative position error of the radar and the DEM data, and taking the SAR orthographic image generated under the offset as the final output.
Referring to fig. 2, an operation flowchart of a method for correcting a SAR image according to an embodiment of the present invention is shown.
In an optional operation manner, the specific operation of the SAR image correction method may include the following procedures:
the SAR image data to be corrected, a series of imaging parameters corresponding to the image and the DEM data of an actual area corresponding to the SAR image can be read first. And correcting the DEM data corresponding to the SAR image according to a backward method to generate an orthographic image, and counting the average gray level of the orthographic image. Meanwhile, after DEM data corresponding to the SAR image is obtained, a horizontal offset is added to the DEM data, then correction can be performed by adopting the DEM data added with the horizontal offset according to a backward method to generate an orthographic image, and the average gray value of the orthographic image is counted.
Comparing the average gray value of the orthophoto image without the addition of the offset with the average gray value of the orthophoto image with the addition of the offset, screening out the maximum average gray value from the average gray values, and obtaining the horizontal offset of the DEM data corresponding to the average gray value with the maximum value. The SAR orthophotos generated at the horizontal offset are taken as final outputs.
In the invention, the geometrical distortion characteristics of short slope and long back slope often exist in mountain areas in SAR images in consideration of imaging modes of oblique projection and observation directions of downward side viewing when the synthetic aperture radar works. Meanwhile, the slope is closer to specular reflection than radar in imaging, and has stronger scattering intensity, so that the slope appears as a higher gray value in the image.
Meanwhile, in the geometric correction process, the slope-facing area and the slope-backing area are restored to the normal widths. The brighter facing slopes are widened, the darker back slopes are compressed, and the proportion of pixels with higher gray scales in the image is improved, so that the integral gray scale of the orthographic image is also improved.
When the relative position between the radar and the DEM data has deviation, the backward geometric correction cannot accurately match and correspond each element of the DEM data with each pixel of the original SAR image, so that the generated orthographic image still has partial geometric distortion, and the average gray level of the image is deficient. The invention can take the average gray level of the orthophoto as the evaluation standard for the correction result. The proportion of the pixels with higher gray scale in the image can be used as an evaluation standard, so that the accuracy of the image can be improved.
Because the existing SAR orthographic image generation process ignores the influence caused by radar imaging parameters, radar orbit operation parameters and DEM data errors, the quality of the geometric correction result is completely dependent on the measurement accuracy of each parameter.
According to the technical scheme, the step of self-correcting the orthographic image is added on the basis of the existing geometric correction flow, and geometric distortion still existing in the orthographic image can be further reduced or even eliminated. The geometrical distortion which cannot be eliminated by adopting the traditional geometrical correction method mainly comes from radar parameter errors and auxiliary DEM data errors, and the method can compensate relative position errors by adding horizontal offset into the DEM data, is simple to operate and easy to understand. The correction of the relative positional relationship is effective in facing different data regardless of whether the error is derived from radar parameters or DEM data.
Meanwhile, the invention establishes an evaluation mechanism taking the average gray level of the orthophoto as an index, the index is clear, simple and easy to obtain, and the high efficiency of self-correction is ensured.
In addition, the invention can correct and eliminate the geometric distortion still existing in the orthographic image without additional more accurate measuring equipment or imaging models, and has higher feasibility and stronger applicability.
Because the area with serious geometric distortion in the SAR image is often an area with large actual topography fluctuation, the gray scale difference of the orthographic image generated by the area with large topography fluctuation under the condition of adding different offsets is also large, so that the offset which enables the average gray scale to reach the highest is easier to find, which shows that the invention has better performance when being applied to the area.
In this embodiment, the embodiment of the present invention provides a method for correcting an SAR image, which has the following beneficial effects: according to the method, after the DEM data corresponding to the SAR image to be corrected are obtained, the horizontal offset is added into the DEM data, then the average gray level of the DEM data added with the horizontal offset and the average gray level of the DEM data not added with the horizontal offset are calculated respectively, the horizontal offset meeting the actual requirement is screened out through comparison of a plurality of gray values, and the image correction is carried out, so that the influence caused by relative position deviation is reduced, and the effect of the image correction is improved.
The embodiment of the invention also provides a correction device for the SAR image, and referring to fig. 3, a schematic structural diagram of the correction device for the SAR image provided by the embodiment of the invention is shown.
As an example, the correction device of the SAR image may include:
the offset adding module 301 is configured to obtain initial DEM data, and then add the initial DEM data with a plurality of position offsets to obtain a plurality of offset DEM data, where the initial DEM data is DEM data of a region corresponding to the SAR image to be corrected;
the gray value calculating module 302 is configured to calculate an offset average gray value of the SAR image to be corrected using each of the offset DEM data, so as to obtain a plurality of offset average gray values;
the image correction module 303 is configured to perform offset correction on the SAR image to be corrected by using the plurality of offset average gray values and a preset initial average gray value, where the preset initial average gray value is an average gray value of the SAR image to be corrected calculated by using initial DEM data.
Optionally, the image correction module is further configured to:
selecting a gray value with the largest value from a plurality of offset average gray values and preset initial average gray values;
obtaining the offset of DEM data corresponding to the gray value with the maximum value to obtain a target offset;
and generating a corrected SAR orthographic image by adopting the target offset.
Optionally, the gray value calculating module is further configured to:
acquiring first parameters of an SAR image to be corrected, wherein the first parameters comprise: radar imaging parameters and radar orbit operating parameters;
positioning each element in the offset DEM data according to the first parameter to obtain an offset coordinate, wherein the offset coordinate is a pixel coordinate of each element of the offset DEM data on an SAR image to be corrected;
assigning the pixel gray values of the offset coordinates to the data elements of the corresponding offset DEM data to form an offset orthographic image;
and counting the average gray level of the offset orthophoto to obtain an offset average gray level value.
Optionally, the average gray value of the SAR image to be corrected calculated by using the initial DEM data is specifically:
acquiring a second parameter of the SAR image to be corrected, wherein the second parameter comprises: radar imaging parameters and radar orbit operating parameters;
positioning each element in the initial DEM data according to the second parameter to obtain an initial coordinate, wherein the initial coordinate is a pixel coordinate of each element of the initial DEM data on an SAR image to be corrected;
assigning the pixel gray values of the initial coordinates to the data elements of the corresponding initial DEM data to form an initial orthographic image;
and counting the average gray level of the initial orthophoto to obtain an initial average gray level value.
It will be clearly understood by those skilled in the art that, for convenience and brevity, the specific working process of the apparatus described above may refer to the corresponding process in the foregoing method embodiment, which is not described herein again.
Further, an embodiment of the present application further provides an electronic device, including: the SAR image correction method comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, wherein the processor realizes the SAR image correction method according to the embodiment when executing the program.
Further, the embodiment of the present application also provides a computer-readable storage medium storing a computer-executable program for causing a computer to execute the method for correcting a SAR image according to the above embodiment.
While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that changes and modifications may be made without departing from the principles of the invention, such changes and modifications are also intended to be within the scope of the invention.
Claims (10)
1. A method of correcting a SAR image, comprising:
after initial DEM data are obtained, the initial DEM data are respectively added with a plurality of position offset values to obtain a plurality of offset DEM data, wherein the initial DEM data are DEM data of a region corresponding to an SAR image to be corrected;
calculating an offset average gray value of the SAR image to be corrected by adopting each offset DEM data to obtain a plurality of offset average gray values;
and carrying out offset correction on the SAR image to be corrected by utilizing the offset average gray values and a preset initial average gray value, wherein the preset initial average gray value is the average gray value of the SAR image to be corrected calculated by adopting initial DEM data.
2. The SAR image correction method according to claim 1, wherein the offset correction of the SAR image to be corrected using the plurality of offset average gray values and a preset initial average gray value comprises:
selecting a gray value with the largest value from a plurality of offset average gray values and preset initial average gray values;
obtaining the offset of DEM data corresponding to the gray value with the maximum value to obtain a target offset;
and generating a corrected SAR orthographic image by adopting the target offset.
3. The SAR image correction method according to claim 1, wherein said calculating an offset average gray value of the SAR image to be corrected using each of the offset DEM data comprises:
acquiring first parameters of an SAR image to be corrected, wherein the first parameters comprise: radar imaging parameters and radar orbit operating parameters;
positioning each element in the offset DEM data according to the first parameter to obtain an offset coordinate, wherein the offset coordinate is a pixel coordinate of each element of the offset DEM data on an SAR image to be corrected;
assigning the pixel gray values of the offset coordinates to the data elements of the corresponding offset DEM data to form an offset orthographic image;
and counting the average gray level of the offset orthophoto to obtain an offset average gray level value.
4. The SAR image correction method according to claim 1, wherein the average gray value of the SAR image to be corrected calculated using the initial DEM data comprises:
acquiring a second parameter of the SAR image to be corrected, wherein the second parameter comprises: radar imaging parameters and radar orbit operating parameters;
positioning each element in the initial DEM data according to the second parameter to obtain an initial coordinate, wherein the initial coordinate is a pixel coordinate of each element of the initial DEM data on an SAR image to be corrected;
assigning the pixel gray values of the initial coordinates to the data elements of the corresponding initial DEM data to form an initial orthographic image;
and counting the average gray level of the initial orthophoto to obtain an initial average gray level value.
5. A correction device for SAR images, comprising:
the offset adding module is used for adding the initial DEM data with a plurality of position offsets respectively after acquiring the initial DEM data, so as to obtain a plurality of offset DEM data, wherein the initial DEM data are DEM data of a region corresponding to an SAR image to be corrected;
the gray value calculating module is used for calculating an offset average gray value of the SAR image to be corrected by adopting each offset DEM data to obtain a plurality of offset average gray values;
the image correction module is used for carrying out offset correction on the SAR image to be corrected by utilizing the offset average gray values and a preset initial average gray value, wherein the preset initial average gray value is the average gray value of the SAR image to be corrected calculated by adopting initial DEM data.
6. The SAR image correction device of claim 5, wherein the image correction module is further configured to:
selecting a gray value with the largest value from a plurality of offset average gray values and preset initial average gray values;
obtaining the offset of DEM data corresponding to the gray value with the maximum value to obtain a target offset;
and generating a corrected SAR orthographic image by adopting the target offset.
7. The SAR image correction device of claim 5, wherein the calculated gray value module is further configured to:
acquiring first parameters of an SAR image to be corrected, wherein the first parameters comprise: radar imaging parameters and radar orbit operating parameters;
positioning each element in the offset DEM data according to the first parameter to obtain an offset coordinate, wherein the offset coordinate is a pixel coordinate of each element of the offset DEM data on an SAR image to be corrected;
assigning the pixel gray values of the offset coordinates to the data elements of the corresponding offset DEM data to form an offset orthographic image;
and counting the average gray level of the offset orthophoto to obtain an offset average gray level value.
8. The SAR image correction apparatus according to claim 5, wherein the average gray value of the SAR image to be corrected calculated using the initial DEM data is specifically:
acquiring a second parameter of the SAR image to be corrected, wherein the second parameter comprises: radar imaging parameters and radar orbit operating parameters;
positioning each element in the initial DEM data according to the second parameter to obtain an initial coordinate, wherein the initial coordinate is a pixel coordinate of each element of the initial DEM data on an SAR image to be corrected;
assigning the pixel gray values of the initial coordinates to the data elements of the corresponding initial DEM data to form an initial orthographic image;
and counting the average gray level of the initial orthophoto to obtain an initial average gray level value.
9. An electronic device, comprising: memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor implements the SAR image correction method according to any one of claims 1-4 when executing the program.
10. A computer-readable storage medium storing a computer-executable program for causing a computer to execute the SAR image correction method according to any one of claims 1 to 4.
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