CN116184341B - SAR load cross radiation calibration method in constellation - Google Patents
SAR load cross radiation calibration method in constellation Download PDFInfo
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- CN116184341B CN116184341B CN202310469540.3A CN202310469540A CN116184341B CN 116184341 B CN116184341 B CN 116184341B CN 202310469540 A CN202310469540 A CN 202310469540A CN 116184341 B CN116184341 B CN 116184341B
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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Abstract
The invention discloses a method for calibrating SAR load cross radiation in a constellation, which comprises the steps of utilizing a calibration constant K of a calibrated SAR satellite in the constellation Reference to The method comprises the steps of carrying out a first treatment on the surface of the By correcting the two satellites to detect imaging data and registering the regional position, the cross calibration region of the two satellites to be calculated is determined, and the SAR satellite calibration constant K to be calibrated is calculated according to the cross calibration region Calibrating The method comprises the steps of carrying out a first treatment on the surface of the According to the SAR satellite radiometric calibration method, the requirements of the ground field are not increased, the radiometric calibration process is simplified, the time consumed by radiometric calibration is reduced, and the SAR satellite radiometric calibration efficiency is improved; the two-star imaging data are sequentially processed by correction processing, regional position configuration, determination of cross calibration regions and other modes, the obtained radiation brightness average value is stable and reliable, and the obtained calibration constant K is improved Calibrating Is a precision of (a).
Description
Technical Field
The invention relates to the technical field of SAR satellite radiometric calibration, in particular to a method for calibrating SAR load cross radiometric calibration in a constellation.
Background
In-orbit SAR satellites are affected by a plurality of factors such as emission vibration, space environment change, electronic component aging, component movement and the like, the imaging quality of the SAR satellites generally changes, but in use, when a plurality of SAR satellites are used for synchronous detection imaging, the average value of the radiation brightness, the earth surface reflectivity and the radiation quality of a standard geometric product which are expected to be acquired can be kept at a higher consistent level, and therefore, the SAR load satellites in a constellation are required to be subjected to radiometric calibration.
Along with the development of the remote sensing industry in China, the SAR satellite remote sensing technology plays an increasingly important role in national defense construction and national economy construction in China, the application requirements of SAR satellite remote sensing are gradually changed from qualitative to quantitative, radiometric calibration is the basis of SAR satellite quantitative remote sensing, so that the acquisition of the radiometric calibration constant of SAR satellites becomes increasingly urgent, but the traditional SAR satellite radiometric calibration field investment is high, the calibration process is complex to realize, the calibration frequency is always maintained only once a year, and people are urgent to develop other alternative calibration methods.
The inventor does not find a method for cross radiation calibration in a SAR load satellite constellation at present through retrieval, and the patent document with the document number of CN113920203A relates to an optical remote sensing satellite radiation cross calibration method based on a stable radiation source, but mainly realizes the stable correction of an optical remote sensing satellite on-orbit absolute radiation reference, and the radiation cross calibration reference area and calibration method and process cannot be applied to the SAR load satellite, so that the SAR load satellite radiation calibration method is needed in reality, the SAR load satellite is rapidly and accurately calibrated, and the SAR satellite radiation calibration efficiency is improved.
Disclosure of Invention
The invention aims to provide a constellation inner SAR load cross radiation calibration method, which ensures radiation calibration precision and solves the problems of high field investment, complex implementation of the radiation calibration process, long time consumption and low radiation calibration efficiency of the traditional radiation calibration.
The aim of the invention can be achieved by the following technical scheme: a method for intra-constellation SAR loading cross-radiation scaling, comprising the steps of:
s1, acquiring a calibration constant K of a calibrated SAR satellite in a constellation Reference to ;
S2, detecting and imaging the same selected area by the calibrated SAR satellite and the SAR satellite to be calibrated according to the same imaging parameters;
s3, correcting the two satellite detection imaging data to obtain corrected standard geometric products imaged by the two satellites;
s4, carrying out regional position registration on the two satellite standard geometric products;
s5, determining a cross calibration area to be calculated by the two satellites according to the area position registration data;
s6, according to the intersectionCalculating SAR satellite calibration constant K to be calibrated in fork calibration area Calibrating 。
Further: in the step S2, the same selected area is a tropical rain forest zone.
Further: the content of the correction processing of the probe imaging data in the step S3 includes frame format analysis processing, BAQ decompression processing, pulse compression processing, and imaging processing.
Further: in the step S4, the region position registration of the two satellite standard geometric products includes the following steps:
s41, extracting geographic position information of two satellite standard geometric products;
s42, converting the geographic position information into the position of the image pixel point;
s43, performing coarse registration on the imaging data area positions according to the pixel point positions of the two satellite images;
s44, searching respective maximum radiance image coordinates in the imaging data range of the two satellites after coarse registration;
s45, comparing the maximum radiance image coordinate positions of the two satellites;
s46, performing further region position fine registration on the standard geometric product according to the maximum radiance image coordinate position.
Further: the step of determining the cross calibration area in the step S5 is as follows:
s51, registering the regional position, namely, the initial regional range of the calibrated SAR satellite geometric product;
s52, gradually expanding the initial fixed area range on the basis of the initial fixed area range, and synchronously calculating the change of the average value of the radiation brightness in the area range;
and S53, when the change of the mean value of the radiation brightness does not change significantly along with the expansion of the area range, determining two stars to be used for calculating the range of the cross calibration area.
Further, in the step S6, calculating the SAR satellite calibration constant Kcalibration to be calibrated according to the cross calibration area comprises the following steps:
s61, calculating the average value of the radiation brightness of two stars in a cross calibration area;
s62, calculating the ratio of the two-star radiation brightness mean value in the cross calibration area to obtain the two-star radiation brightness cross ratio;
s63, utilizing the calibration constant K of the calibrated SAR satellite Reference to And cross-over ratio to determine the calibration constant K of SAR satellite to be calibrated Calibrating 。
The invention has the beneficial effects that:
1. the invention utilizes the calibration constant K of the existing calibrated SAR satellite Reference to Scaling constant K for other SAR satellites of constellation Calibrating The requirements of ground sites are not increased, the radiometric calibration process is simplified, the time consumed by radiometric calibration is reduced, and the radiometric calibration efficiency of the SAR satellites is improved.
2. The two-star imaging data are sequentially processed by correction processing, regional position configuration, determination of cross calibration regions and other modes, the obtained radiation brightness average value is stable and reliable, and the obtained calibration constant K is improved Calibrating Is a precision of (a).
3. The area detection imaging area is selected as a tropical rain forest area, so that the reflectivity of an imaging product for radiation calibration is ensured to be uniform and stable, the specific better radiation brightness average value is ensured, and the calibration constant K after the radiation calibration is improved Calibrating Is a precision of (a).
4. The standard geometric products of the two satellites are subjected to two-time region position registration, so that the accuracy of the crossed calibration region is improved, and the calibration constant K obtained after the region position registration is relied on Calibrating Has higher precision.
5. The method of gradually expanding the range of the initial fixed area is adopted to obtain the cross calibration area with stable radiation brightness mean value, thereby reducing the calibration constant K of satellite standard geometric products in different areas Calibrating The influence of (2) further improves the obtained scaling constant K Calibrating Is a precision of (a).
Drawings
Fig. 1 is a schematic flow chart of a method for calibrating SAR load cross radiation in a constellation according to the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar symbols indicate like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only for explaining the present invention and are not to be construed as limiting the present invention.
As shown in fig. 1, the invention discloses a method for calibrating SAR load cross radiation in a constellation, which comprises the following steps:
s1, acquiring a calibration constant K of a calibrated SAR satellite in a constellation Reference to ;
S2, detecting and imaging the same selected area by the calibrated SAR satellite and the SAR satellite to be calibrated according to the same imaging parameters;
s3, correcting the two satellite detection imaging data to obtain corrected standard geometric products imaged by the two satellites;
s4, carrying out regional position registration on the two satellite standard geometric products;
s5, determining a cross calibration area to be calculated by the two satellites according to the area position registration data;
s6, calculating a SAR satellite calibration constant K to be calibrated according to the cross calibration area Calibrating 。
For convenience of description, the two satellites refer to a calibrated SAR satellite and a SAR satellite to be calibrated.
The cross radiometric calibration method of the invention is to radiometric calibrate another SAR satellite to be calibrated by taking one calibrated SAR satellite as a reference on the basis of synchronous imaging of two satellites, correct the calibration constant of the calibrated SAR satellite, and ensure the accuracy of cross radiometric elevation due to higher consistency of satellite design in a networking constellation under the background that SAR satellite constellation networking becomes the main direction of SAR earth observation development along with the increasing miniaturization of SAR satellite platforms and the increasing cost.
The invention is described by taking two satellites as an example, and the method can also be used for cross radiometric calibration of other SAR satellites in SAR satellite constellation.
Calibration constant K of calibrated SAR satellite Reference to Calibration method by traditional SAR satelliteThe calibration constant K can be ensured to be obtained by using the traditional SAR satellite calibration method Reference to But the traditional SAR satellite calibration method has the defects of high investment of the used calibration field, complex realization, low calibration frequency and common calibration frequency once a year.
The SAR satellite has great influence on the average value of the radiation brightness due to different reflectivities of different areas, so that the selection of a proper unified imaging area is an important aspect for realizing high-precision cross radiation calibration, the selected imaging area is required to meet the characteristics of medium and high reflectivity, good spatial uniformity, large area and relatively flat ground surface, and weather conditions of low influence by cloud layers, clean atmosphere and clear weather, and is repeatedly compared and selected, and the tropical rain forest, particularly the Amazon tropical rain forest area, is uniform and stable in reflectivity for the SAR satellite radar, and the imaging specific better average value of the radiation brightness can be used as a cross radiation fixed reference area.
The method is characterized in that detection imaging is preferably carried out on the calibrated SAR satellite and the SAR satellite to be calibrated by using the same imaging parameters, the same time and the same region, but in practical application, the imaging on the same region is difficult when the calibrated SAR satellite and the SAR satellite to be calibrated are accurate, the imaging data at different time points can be different due to the influence of brightness, weather and the like, and the contrast is poor, so that when cross radiometric calibration is carried out, the time deviation of the imaging of two satellites is controlled to be minimum, for example, a few minutes, the detection imaging data of the two satellites are close, the influence of brightness and weather reasons can be basically ignored, and the calibration constant K after the cross radiometric calibration is improved Calibrating Is a precision of (a).
The two satellites detection imaging data comprise a large amount of detection information, such as longitude and latitude information, space geographic information and the like, and have larger information quantity, geometric correction processing is needed to be carried out on the detection imaging data, the geometric correction processing means comprise a plurality of modes such as frame format analysis processing, BAQ decompression processing, pulse compression processing, imaging processing and the like, geometric correction is carried out on the space information corresponding to the two satellites imaging data, space registration is carried out, a projection relation is constructed, and the corrected two satellite standard geometric products are obtained.
The cross radiation calibration is realized, and the region position registration of the standard geometric products of two stars is needed; so that the areas of the two-star standard geometric products for cross radiation calibration are the same, firstly, geographic position information of the two-star standard geometric products is extracted, image registration of the two-star standard geometric products is carried out by utilizing the geographic position information, and the geographic position information is converted into image pixel positions; therefore, the two-star standard geometric products realize basic rough registration by means of geographic position information, but the two-star standard geometric products can have pixel position deviation after registration by means of the geographic position information, which is caused by two-star positioning errors and cannot be completely avoided, on the basis of rough registration, the coordinates of the maximum radiance images of the two-satellite standard geometric products are further searched, the coordinates of the maximum radiance images in the two-satellite standard geometric products have relativity, the standard geometric products are further and precisely registered by utilizing the coordinates of the maximum radiance images, the accuracy of the regional position registration of the two-star standard geometric products is improved, the two-star standard geometric products are correspondingly related to each other, the regional position registration is more accurate, the cross radiation calibration comparability is provided, and the calibration postcalibration constant K is improved Calibrating Is a precision of (a).
On the basis of the completion of the regional position registration, the cross calibration regional scope of two stars needs to be further determined, the cross calibration regional scope needs to meet the stability of the radiation brightness mean value in the regional scope, and the calibrated SAR satellite calculates a calibration constant K Calibrating Is favorable for improving the calibration constant K by selecting the cross calibration area according to the standard geometric product of the calibrated SAR satellite Calibrating Accuracy of (3).
Firstly, a preliminary region range is carried out on a calibrated SAR satellite standard geometric product after registration, 50 x 50 pixels, 100 x 100 pixels, 200 x 200 pixels or 400 x 400 pixels and the like can be selected as the preliminary region range, 50 x 50 pixels are selected as an example, the radiation brightness average value in 50 x 50 pixels is calculated and then is expanded to 100 x 100 pixels, the radiation brightness average value in 100 x 100 pixels is calculated, the radiation brightness average value of 50 x 50 pixels and the radiation brightness average value of 100 x 100 pixels are compared, if the radiation brightness average value of the two is very close, the change of the radiation brightness average value is not changed obviously along with the expansion of the region range, the 100 x 100 pixels region range is selected as the cross calibration region range, otherwise, the method is adopted to continue to expand the 100 x 100 pixels region range until the change of the radiation brightness average value is not changed obviously along with the expansion of the region range.
The average value of the radiation brightness of the SAR satellite to be calibrated is different from that of the calibrated SAR satellite in the same area, so that the average value of the radiation brightness is the main basis of the difference of calibration constants among satellites, and after the different SAR satellites perform radiation calibration, the average value of the radiation brightness of standard geometric products in the same area at the same time is very close or the same, and the calibrated SAR satellite calibration constant K is utilized Reference to And the cross ratio of the two-star radiation brightness mean value, the uncalibrated SAR satellite scaling constant K can be carried out Measurement Is calculated by the computer.
After the cross calibration area is selected, calculating in the selected cross calibration area, respectively obtaining the radiation brightness average value of the calibrated SAR satellite standard geometric product in the cross calibration area and the radiation brightness average value of the SAR satellite standard geometric product to be calibrated in the cross calibration area, and calculating the two-star radiation brightness average value cross ratio according to the two-star radiation brightness average value; according to the cross ratio of the two-star radiation brightness mean value, the calibrated SAR satellite calibration constant K can be known Reference to And SAR satellite constant K to be calibrated Measurement The SAR satellite constant to be calibrated is adjusted according to the discrimination degree and the calibration constant of the calibrated SAR satellite, and the calibration constant K after the calibration of the SAR satellite to be calibrated is obtained Measurement 。
Compared with the traditional site-specific calibration, the method for carrying out SAR satellite radiometric calibration has the advantages that the investment cost is low, the radiometric calibration efficiency is high, the precision is guaranteed, the cross radiometric calibration does not need to depend on an observation station to directly observe ground actual data, and the requirements for measuring and researching sites and calibrating time are small.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (4)
1. A constellation internal SAR load cross radiation scaling method is characterized in that: the method comprises the following steps:
s1, acquiring a calibration constant K of a calibrated SAR satellite in a constellation Reference to ;
S2, detecting and imaging the same selected area by the calibrated SAR satellite and the SAR satellite to be calibrated according to the same imaging parameters;
s3, correcting the two satellite detection imaging data to obtain corrected standard geometric products imaged by the two satellites;
s4, carrying out regional position registration on the two satellite standard geometric products;
s5, determining a cross calibration area to be calculated by the two satellites according to the area position registration data;
s6, calculating a SAR satellite calibration constant K to be calibrated according to the cross calibration area Calibrating ;
The cross scaling area determining step in step S5 is:
s51, registering the regional position, namely, the initial regional range of the calibrated SAR satellite geometric product;
s52, gradually expanding the initial fixed area range on the basis of the initial fixed area range, and synchronously calculating the change of the average value of the radiation brightness in the area range;
s53, when the change of the radiation brightness mean value does not change obviously along with the expansion of the area range, determining two stars to be used for calculating the range of the cross calibration area;
in step S6, calculating SAR satellite calibration constant K to be calibrated according to the cross calibration area Calibrating The method comprises the following steps:
s61, calculating the average value of the radiation brightness of two stars in a cross calibration area;
s62, calculating the ratio of the two-star radiation brightness mean value in the cross calibration area to obtain the two-star radiation brightness cross ratio;
s63, utilizing the calibration constant K of the calibrated SAR satellite Reference to And cross-over ratio to determine the calibration constant K of SAR satellite to be calibrated Calibrating 。
2. An intra-constellation SAR load cross-radiation scaling method according to claim 1, wherein: in step S2, the same selected area is a tropical rain forest zone.
3. A method of intra-constellation SAR loading cross-radiation scaling according to claim 1, wherein: the content of the correction processing for the probe imaging data in step S3 includes frame format analysis processing, BAQ decompression processing, pulse compression processing, and imaging processing.
4. An intra-constellation SAR load cross-radiation scaling method according to claim 1, wherein: in step S4, performing regional position registration on two satellite standard geometric products includes the following steps:
s41, extracting geographic position information of two satellite standard geometric products;
s42, converting the geographic position information into the position of the image pixel point;
s43, performing coarse registration on the imaging data area positions according to the pixel point positions of the two satellite images;
s44, searching respective maximum radiance image coordinates in the imaging data range of the two satellites after coarse registration;
s45, comparing the maximum radiance image coordinate positions of the two satellites;
s46, performing further region position fine registration on the standard geometric product according to the maximum radiance image coordinate position.
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EP2065731A1 (en) * | 2007-11-27 | 2009-06-03 | Politecnico di Milano | Method for radiometric calibration of SAR sensors |
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CN113406584A (en) * | 2021-06-22 | 2021-09-17 | 北京化工大学 | Cross calibration method for synthetic aperture radar |
CN113702933A (en) * | 2021-06-17 | 2021-11-26 | 中国科学院空天信息创新研究院 | Synthetic aperture radar radiation calibration method and device |
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KR101751020B1 (en) * | 2015-12-08 | 2017-07-11 | 한국해양과학기술원 | Method and apparatus for detecting hns using images from multiple satellites |
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EP2065731A1 (en) * | 2007-11-27 | 2009-06-03 | Politecnico di Milano | Method for radiometric calibration of SAR sensors |
CN108562882A (en) * | 2018-06-21 | 2018-09-21 | 武汉大学 | A kind of satellite-borne SAR image geometry intersects calibrating method and system |
CN113702933A (en) * | 2021-06-17 | 2021-11-26 | 中国科学院空天信息创新研究院 | Synthetic aperture radar radiation calibration method and device |
CN113406584A (en) * | 2021-06-22 | 2021-09-17 | 北京化工大学 | Cross calibration method for synthetic aperture radar |
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