CN111487621B - Sea surface flow field inversion method based on radar image and electronic equipment - Google Patents
Sea surface flow field inversion method based on radar image and electronic equipment Download PDFInfo
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- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/9021—SAR image post-processing techniques
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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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- G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
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Abstract
The invention discloses a sea-surface flow field inversion method based on radar images and electronic equipment, wherein the radar images are acquired through a preset radar in a first time range, and echo frequency f corresponding to a preset area and representing the center of an imaging wave beam is obtained Dc After which the first Doppler frequency f is removed Dp Removing the third Doppler frequency f D1 Thereby obtaining Doppler frequency shift f which is closer to the radar view direction corresponding to the ocean current motion g Based on the Doppler shift f g Determining the radial velocity V of the corresponding sea surface flow field D The method comprises the steps of carrying out a first treatment on the surface of the And further obtaining the sea surface radial flow field which corresponds to the preset area and is in the first time range. The calculation process in the technical scheme in the embodiment of the application can reject the traditional implementation mode, and the actual radar imaging beam pointing angle is adopted for calculation, so that the sea surface radial flow field result obtained by final calculation is more accurate, and the technical effects of improving sea surface flow field inversion realization efficiency and result precision are achieved.
Description
Technical Field
The invention relates to the technical field of electronic information, in particular to a sea surface flow field inversion method based on radar images and electronic equipment.
Background
The sea surface flow field is an important motion form of sea water, and reflects the transportation state of the sea water in various scales under the quasi-steady state. The research of the ocean surface flow field has very important scientific significance for deeply understanding the interaction among the ocean, the land and the atmosphere and the ocean disaster early warning.
Synthetic aperture radar (Synthetic Aperture Radar, SAR for short) is a radar which is independent of solar radiation, can penetrate cloud layers and rain, has multiple polarization modes, multiple imaging modes and multiple spatial resolutions of different scales, and can realize all-day and all-weather observation of the ocean.
In practical application, the SAR image can capture the spatial distribution of sea surface micro-scale waves caused by the sea surface flow field, and then the radar apparent Doppler frequency shift based on SAR detection is proportional to the operation relation of the relative speed of sea surface motion and a radar platform, so that the sea surface flow field information with high resolution can be obtained through inversion.
However, in the inversion calculation process, the most critical calculation of the original radar apparent Doppler frequency shiftOften by calculating the "measured Doppler frequency f Dc And predicted Doppler frequency f Dp "difference of (a), wherein f Dc Is the echo frequency of the radar imaging beam center, f Dp Is the doppler frequency caused by the relative motion between the earth and the satellite. f (f) Dp Most of the calculation of the SAR is realized by adopting a precompiled C language library CFI of Envisat, and accurate SAR orbit time, position, sensor attitude parameters and the like are required to be obtained during calculation; on the other hand, f Dp The calculation of (a) using theoretical rather than actual radar imaging beam pointing angles can lead to errors in the inversion of the sea-surface flow field. In addition, radar apparent doppler shift of SAR detection is not caused by a single factor, but also includes doppler shift caused by sea surface flow field, sea surface wind field, bragg scattering and orbital velocity.
Therefore, in the prior art, the sea surface flow field inversion method based on radar images is often caused by key parameters: the Doppler frequency caused by the relative motion between the earth and the satellite is doped with various noise Doppler frequency shift data, so that the technical problem of low precision of the sea surface radial flow field data obtained by final inversion calculation is caused.
Disclosure of Invention
The application provides a sea surface flow field inversion method based on radar images and electronic equipment, which are used for solving the problem that the sea surface flow field inversion method based on radar images in the prior art is often caused by key parameters: the Doppler frequency caused by the relative motion between the earth and the satellite is doped with various noise Doppler frequency shift data, so that the technical problem of low precision of the sea surface radial flow field data obtained by final inversion calculation is caused.
The first aspect of the application provides an inversion method for acquiring a high-precision sea surface flow field based on a satellite-borne radar, which comprises the following steps:
when radar images are acquired through a preset radar in a first time range, acquiring echo frequency f corresponding to a preset area and representing the center of an imaging beam radiated by the preset radar Dc Wherein the echo frequency f Dc In order to take the time interval as the scale, the distance and the direction are respectively the preset two-dimensional sitting of the x axis and the y axisParameters represented in the label system;
for the echo frequency f Dc Performing removal of the first Doppler frequency f Dp Processing to obtain a second Doppler frequency f Dca Wherein the first Doppler frequency f Dp Comprising Doppler frequency f generated in azimuth direction by the relative motion of the satellite and the earth carried by the preset radar DpAZ And a Doppler frequency f generated in the range direction DpR ；
For the second Doppler frequency f Dca Performing removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to sea current motion g Wherein the third Doppler frequency f D1 Comprising Doppler shift f caused by sea-surface wind fields w And Doppler shift f caused by Bragg scattering B ；
Based on the Doppler shift f g Determining the radial velocity V of the sea surface flow field corresponding to the preset area in the first time range D ；
Determining a first sea surface radial flow field corresponding to the preset area in the first time range according to a preset mode, wherein the first sea surface radial flow field comprises sea surface flow field radial velocity V corresponding to each time scale in the preset two-dimensional coordinate system D Sea surface flow field direction.
Optionally, the pair of echo frequencies f Dc Performing removal of the first Doppler frequency f Dp Processing to obtain a second Doppler frequency f Dca Comprising:
in the preset two-dimensional coordinate system, calculating an azimuth average value of the first frequency chart in each unit of inclined distance time scale along the distance direction to obtain an average value f of the first frequency chart in the azimuth direction AZm ；
Based on the calculation formula: f (f) Dc -f AZm ＝f Dc-AZm Calculating in the preset two-dimensional coordinate system to obtain a representation f Dc-AZm A second frequency plot of values of (2);
construct in the preset two-dimensional coordinate system by adopting a linear fitting methodBuilding a linear function relation F (t) to obtain a corresponding correlation coefficient R 2 Wherein the linear function relation F (t) takes each slope distance time scale in the azimuth direction in the preset two-dimensional coordinate system as an independent variable t, and F is respectively in one-to-one correspondence with each slope distance time scale in the distance direction Dc-AZm Is a dependent variable;
based on maximum correlation coefficient R 2 F (t) corresponding to each inclined distance time scale in the azimuth direction is obtained through calculation Dc-AZm To obtain f (Dc-AZm) ’；
The f is set to (Dc-AZm) The value of' is taken as the Doppler frequency f generated in azimuth by the relative motion of the satellite and the earth DpAZ 。
Optionally, the pair of echo frequencies f Dc Performing removal of the first Doppler frequency f Dp Processing to obtain a second Doppler frequency f Dca Comprising:
in the preset two-dimensional coordinate system, f corresponding to each unit of inclined distance time scale is carried out on the first frequency chart along the azimuth direction Dc -f DpAZ Is calculated to obtain Doppler frequency f generated by the relative motion of the earth and the satellite DpR ；
Based on the calculation formula: f (f) Dca ＝f Dc -f DpAZ -f DpR Calculating to obtain the second Doppler frequency f Dca 。
Optionally, the pair of second Doppler frequencies f Dca Performing removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to sea current motion g Comprising:
acquiring a monitoring parameter set, wherein the monitoring parameter set comprises a sea surface wind direction parameter, a sea surface wind speed parameter, a radiation beam incidence angle parameter of the preset radar and a polarization mode parameter of the preset radar in the view direction of the preset radar, which are respectively in one-to-one correspondence with each time scale in the preset two-dimensional coordinate system;
based on the monitoring parameter set and the geophysical experience model CDOP, the method is calculated and obtainedDoppler frequency shift f generated by sea surface wind field corresponding to each time scale in preset two-dimensional coordinate system w 。
Optionally, the pair of second Doppler frequencies f Dca Performing removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to sea current motion g Comprising:
obtaining Doppler frequency shift f generated by Bragg scattering Bragg corresponding to each time scale in the preset two-dimensional coordinate system based on a double-scale irradiance scattering model B 。
Optionally, the Doppler frequency shift f generated by the Bragg scattering Bragg corresponding to each time scale in the preset two-dimensional coordinate system is obtained based on the dual-scale irradiance model B Comprising:
based on the calculation formula:
Wherein g is gravity acceleration, k e The wave number of the incident electromagnetic wave at the center of the imaging beam, theta is the incident angle, f B The positive and negative values of (a) correspond to the ocean current movement direction in the preset area.
Optionally, after the determining, in a preset manner, the sea surface radial flow field corresponding to the preset area within the first time range, the method further includes:
and converting the first sea surface radial flow field in the preset two-dimensional coordinate system into a second sea surface radial flow field characterized in a longitude and latitude coordinate system based on the geolocation grid annotation data set in the SAR product header file.
A second aspect of the present application provides an electronic device, comprising:
the signal receiving device is used for acquiring radar image data;
the processor is connected with the signal receiving device and is used for acquiring radar images through a preset radar in a first time rangeObtaining an echo frequency f corresponding to a preset area and representing the center of an imaging beam radiated by the preset radar Dc For the echo frequency f Dc Performing removal of the first Doppler frequency f Dp Processing to obtain a second Doppler frequency f Dca For the second Doppler frequency f Dca Performing removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to sea current motion g Based on the Doppler shift f g Determining the radial velocity V of the sea surface flow field corresponding to the preset area in the first time range D The method comprises the steps of carrying out a first treatment on the surface of the Based on the radial velocity V D Determining a sea surface radial flow field corresponding to the preset area in the first time range, wherein the echo frequency f Dc The distance and the direction are parameters represented in a preset two-dimensional coordinate system with the time interval as a scale and the x axis and the y axis respectively; the first Doppler frequency f Dp Comprising Doppler frequency f generated in azimuth direction by the relative motion of the satellite and the earth carried by the preset radar DpAZ And a Doppler frequency f generated in the range direction DpR The method comprises the steps of carrying out a first treatment on the surface of the The third Doppler frequency f D1 Comprising Doppler shift f caused by sea-surface wind fields w And Doppler shift f caused by Bragg scattering B The first sea surface radial flow field comprises sea surface flow field radial velocity V corresponding to each time scale in the preset two-dimensional coordinate system D Sea surface flow field direction.
Optionally, the processor is configured to calculate, in the preset two-dimensional coordinate system, an azimuth average value of the first frequency chart in the azimuth direction per unit time scale of the slant distance along the distance direction, and obtain an average value f of the first frequency chart in the azimuth direction AZm The method comprises the steps of carrying out a first treatment on the surface of the Based on the calculation formula: f (f) Dc -f AZm ＝f Dc-AZm Calculating in the preset two-dimensional coordinate system to obtain a representation f Dc-AZm A second frequency plot of values of (2); constructing a linear function relation F (t) in the preset two-dimensional coordinate system by adopting a linear fitting method to obtain a corresponding correlation coefficient R 2 Based on the maximum correlation coefficient R 2 Corresponding F (t), calculationObtaining f corresponding to each inclined distance time scale in the azimuth direction Dc-AZm To obtain f (Dc-AZm) 'A'; the f is set to (Dc-AZm) The value of' is taken as the Doppler frequency f generated in azimuth by the relative motion of the satellite and the earth DpAZ Wherein the linear function relation F (t) takes each slope distance time scale in the azimuth direction in the preset two-dimensional coordinate system as an independent variable t, and F is respectively in one-to-one correspondence with each slope distance time scale in the distance direction Dc-AZm Is a dependent variable.
Optionally, the processor is configured to perform f corresponding to each unit of skew time scale on the first frequency chart along the azimuth direction in the preset two-dimensional coordinate system Dc -f DpAZ Is calculated to obtain Doppler frequency f generated by the relative motion of the earth and the satellite DpR The method comprises the steps of carrying out a first treatment on the surface of the Based on the calculation formula: f (f) Dca ＝f Dc -f DpAZ -f DpR Calculating to obtain the second Doppler frequency f Dca 。
One or more technical solutions provided in the embodiments of the present application at least have the following technical effects or advantages:
according to the technical scheme, the radar image is acquired through the preset radar in the first time range, so that the echo frequency f corresponding to the preset area and representing the center of the imaging beam can be obtained Dc After which the echo frequencies f are respectively compared with the first frequency pattern of Dc Performing removal of the first Doppler frequency f Dp Processing and removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to ocean current motion of the preset area and closer to the original radar view direction g Based on the Doppler shift f g Determining the radial velocity V of the sea surface flow field corresponding to the preset area in the first time range D The method comprises the steps of carrying out a first treatment on the surface of the And further obtaining the sea surface radial flow field which corresponds to the preset area and is in the first time range. The calculation process in the technical scheme in the embodiment of the application can reject the traditional implementation mode, and adopts the actual radar imaging beam pointing angle to perform the calculationThe calculation is carried out, so that the sea surface radial flow field result obtained by final calculation is more accurate, and the technical effects of improving the sea surface flow field inversion realization efficiency and result accuracy are achieved.
Drawings
FIG. 1 is a flow chart of an inversion method for acquiring a high-precision sea surface flow field based on a satellite-borne radar according to an embodiment of the invention;
fig. 2 is a block diagram of an electronic device according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a calculation process of a method for obtaining a high-precision sea-surface flow field inversion based on a satellite-borne radar according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a sea surface flow field obtained by calculation based on a satellite-borne radar obtaining high-precision sea surface flow field inversion method according to an embodiment of the present invention.
Detailed Description
The application provides a sea surface flow field inversion method based on radar images and electronic equipment, which are used for solving the problem that the sea surface flow field inversion method based on radar images in the prior art is often caused by key parameters: the Doppler frequency caused by the relative motion between the earth and the satellite is doped with various noise Doppler frequency shift data, so that the technical problem of low precision of the sea surface radial flow field data obtained by final inversion calculation is caused.
The technical scheme in the embodiment of the application aims to solve the technical problems, and the overall thought is as follows:
according to the technical scheme, the radar image is acquired through the preset radar in the first time range, so that the echo frequency f corresponding to the preset area and representing the center of the imaging beam can be obtained Dc After which the echo frequencies f are respectively compared with the first frequency pattern of Dc Performing removal of the first Doppler frequency f Dp Processing and removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to ocean current motion of the preset area and closer to the original radar view direction g Based on the Doppler shift f g Determining the diameter of the sea surface flow field corresponding to the preset area in the first time rangeRate of direction V D The method comprises the steps of carrying out a first treatment on the surface of the And further obtaining the sea surface radial flow field which corresponds to the preset area and is in the first time range. The calculation process in the technical scheme in the embodiment of the application can reject the traditional implementation mode, and the actual radar imaging beam pointing angle is adopted for calculation, so that the sea surface radial flow field result obtained by final calculation is more accurate, and the technical effects of improving sea surface flow field inversion realization efficiency and result precision are achieved.
The following detailed description of the technical solutions of the present application will be made with reference to the accompanying drawings and specific embodiments, and it should be understood that the specific features of the embodiments and embodiments of the present application are detailed descriptions of the technical solutions of the present application, and not limiting the technical solutions of the present application, and the technical features of the embodiments and embodiments of the present application may be combined with each other without conflict.
The term "and/or" is herein merely an association relationship describing an associated object, meaning that there may be three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.
Example 1
Referring to fig. 1, fig. 2, fig. 3, and fig. 4, a first embodiment of the present application provides an inversion method for obtaining a high-precision sea surface flow field based on a satellite-borne radar, including:
step 101: when radar images are acquired through a preset radar in a first time range, acquiring echo frequency f corresponding to a preset area and representing the center of an imaging beam radiated by the preset radar Dc Wherein the echo frequency f Dc The distance and the direction are parameters represented in a preset two-dimensional coordinate system with the time interval as a scale and the x axis and the y axis respectively;
in the embodiment of the present application, the preset radar specifically refers to a synthetic aperture radar SAR.
The time interval may be a scale with a unit time interval as a coordinate axis in the preset two-dimensional coordinate system, or a scale with different time intervals as coordinate axes.
Fig. 3 and 4 show ASAR images of the C-band (wavelength 5.6 cm) of the ENVISAT satellite at 7 months and 26 days in 2007, the swath width of the images being about 420km, the spatial resolution being 150m, the vv polarization mode, the track lifting images, the number of doppler meshes being 115 in azimuth and the distance being 100.
As shown in fig. 3, in the implementation, the corresponding echo frequency f can be obtained from the center measurement of the imaging beam of the radar image Dc Further determine the sum f Dc A corresponding first frequency map. Since in actual operation, the user often needs to measure and obtain the sea level radial flow field data within a time range (i.e. the first time range), the time range may be 30 minutes, 1 hour, 3 hours, 1 day, 2 days, etc., and the satellite may only obtain the corresponding radar image when passing over the preset area, and the time period of the satellite passing may be less than the first time range or greater than the first time range.
Therefore, the following working modes can be adopted in the actual operation: when the first time range belongs to a time range of the satellite carried by the preset radar passing through the upper portion of the preset area, the preset radar can continuously acquire corresponding required radar image parameters in the first time range, and further re-measure to acquire f Dc And a corresponding first frequency map; when the first time range exceeds the time range of the satellite carried by the preset radar passing through the preset area, the preset radar can acquire a corresponding required radar image when the satellite passes through the preset area, so that multiple pieces of radar image data of discontinuous time ranges corresponding to the preset area can be acquired, the multiple pieces of radar image data are extracted and combined during calculation, the multiple pieces of radar image data are taken as the radar image data corresponding to the preset area in the preset first time range, and the echo frequency f of the corresponding imaging beam center is further acquired Dc And a first frequency plot.
Step (a)102: for the echo frequency f Dc Performing removal of the first Doppler frequency f Dp Processing to obtain a second Doppler frequency f Dca Wherein the first Doppler frequency f Dp Comprising Doppler frequency f generated in azimuth direction by the relative motion of the satellite and the earth carried by the preset radar DpAZ And a Doppler frequency f generated in the range direction DpR ；
That is, in the technical solution in the embodiment of the present application, the first doppler frequency f may be Dp As the doppler frequency generated by the relative motion of the satellite and earth. And the first Doppler frequency f Dp Including azimuth Doppler frequency f DpAZ Range-to-doppler frequency f DpR . In particular, the azimuthal Doppler frequency f DpAZ May refer to the Doppler frequency generated by the relative motion of the satellite and the earth in a direction opposite to a preset direction, and the maximum value, the minimum value or the average value or the predicted value of a plurality of Doppler frequencies generated by the relative motion in azimuth can be taken on a corresponding time scale in actual operation; whereas range-to-doppler frequency f DpR The method can refer to Doppler frequency generated by relative motion of a satellite and the earth on a relative moving distance, and the maximum value, the minimum value or the average value or the predicted value of a plurality of Doppler frequencies generated by the relative motion on the distance can be taken on a corresponding time scale in actual operation; in summary, the azimuthal Doppler frequency f DpAZ Range-to-doppler frequency f DpR The user can set the calculation mode or the value mode according to the needs.
Step 103: for the second Doppler frequency f Dca Performing removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to sea current motion g Wherein the third Doppler frequency f D1 Comprising Doppler shift f caused by sea-surface wind fields w And Doppler shift f caused by Bragg scattering B ；
That is, in the technical solution in the embodiment of the present application, the third doppler frequency f D1 Comprising the induction of sea surface wind fieldsIs of Doppler shift f w And Doppler shift f caused by Bragg scattering B . Specifically, the Doppler shift f w The maximum value, the minimum value, or the average value, or the predicted value of the plurality of Doppler frequencies caused by the sea surface wind field on the corresponding time scale can be taken; the Doppler shift f B The maximum, minimum, or average value, or predicted value of the plurality of Doppler frequencies caused by Bragg scattering on the corresponding time scale may be taken; also, the Doppler shift f w Said Doppler shift f B The user can set the calculation mode or the value mode according to the needs.
Step 104: based on the Doppler shift f g Determining the radial velocity V of the sea surface flow field corresponding to the preset area in the first time range D 。
Due to the Doppler shift f g Is to remove Doppler frequency f generated by the relative motion of satellite and earth Dp Doppler shift f caused by sea surface wind field w And Doppler shift f caused by Bragg scattering B The echo frequency of the imaging beam center of (2), and thus the Doppler shift f g The value of the radar apparent Doppler frequency shift corresponding to the sea-surface flow field is more similar to that of the radar apparent Doppler frequency shift, and the radial velocity V of the sea-surface flow field can be calculated and obtained very accurately based on the operation relation that the radar apparent Doppler frequency shift is proportional to the relative velocity of sea-surface motion and a radar platform in the step D 。
Step 105: determining a first sea surface radial flow field corresponding to the preset area in the first time range according to a preset mode, wherein the first sea surface radial flow field comprises sea surface flow field radial velocity V corresponding to each time scale in the preset two-dimensional coordinate system D Sea surface flow field direction.
In the technical solution of the embodiment of the present application, the direction of the sea surface radial flow field depends on the sign of the radial sea current, for example, the positive speed value may represent that the direction of the sea surface radial sea current is far from the radar antenna, and the negative speed value may represent that the direction of the sea surface radial sea current is towards the radar antenna; of course, vice versa.
While determining the radial velocity V of the sea surface flow field D And after the direction of the sea surface flow field, determining a corresponding sea surface radial flow field in the preset two-dimensional coordinate system.
Further, the pair of echo frequencies f Dc Performing removal of the first Doppler frequency f Dp Processing to obtain a second Doppler frequency f Dca Comprising:
in the preset two-dimensional coordinate system, calculating an azimuth average value of the first frequency chart in each unit of inclined distance time scale along the distance direction to obtain an average value f of the first frequency chart in the azimuth direction AZm The method comprises the steps of carrying out a first treatment on the surface of the Based on the calculation formula: f (f) Dc -f AZm ＝f Dc-AZm Calculating in the preset two-dimensional coordinate system to obtain a representation f Dc-AZm A second frequency plot of values of (2); constructing a linear function relation F (t) in the preset two-dimensional coordinate system by adopting a linear fitting method to obtain a corresponding correlation coefficient R 2 Wherein the linear function relation F (t) takes each slope distance time scale in the azimuth direction in the preset two-dimensional coordinate system as an independent variable t, and F is respectively in one-to-one correspondence with each slope distance time scale in the distance direction Dc-AZm Is a dependent variable; based on maximum correlation coefficient R 2 F (t) corresponding to each inclined distance time scale in the azimuth direction is obtained through calculation Dc-AZm To obtain f (Dc-AZm) 'A'; the f is set to (Dc-AZm) The value of' is taken as the Doppler frequency f generated in azimuth by the relative motion of the satellite and the earth DpAZ 。
As shown in fig. 3, in actual operation, the azimuth average value of each unit of the slant distance time scale is calculated for the first frequency chart along the distance direction, which may be specifically as follows: in the preset two-dimensional coordinate system, the values in the azimuth direction (or y-axis) on a certain time interval scale may be the average value of the values in all the distance directions corresponding to the time scale to the reference point, namely: and (5) adopting an average filtering method to obtain a value in the distance direction.
For example, the preset two-dimensional coordinate system is 100 scales in the distance direction (x axis), 115 scales in the azimuth direction (y axis), the scales in the x axis and the y axis are all divided at time intervals, and the calculated value of each scale is calculated by averaging 115 azimuth values in each distance direction corresponding to the time scale (i.e. the average value of 115 azimuth values in each distance direction).
As shown in FIG. 3, after the mean value filtering process is completed, f is obtained AZm Then, based on the calculation formula: f (f) Dc -f AZm ＝f Dc-AZm Calculating in the preset two-dimensional coordinate system to obtain a representation f Dc-AZm A second frequency plot of values of (2); then constructing a linear function relation F (t) in the preset two-dimensional coordinate system by adopting a linear fitting method to obtain a corresponding correlation coefficient R 2 In the calculation process, the correlation coefficient R may take a plurality of values, in this embodiment, the F (t) is determined by taking the largest R value, and then the corresponding F is calculated (Dc-AZm) ' and bringing f (Dc-AZm) The value of' is taken as the Doppler frequency f generated in azimuth by the relative motion of the satellite and the earth DpAZ 。
Further, the pair of echo frequencies f Dc Performing removal of the first Doppler frequency f Dp Processing to obtain a second Doppler frequency f Dca Comprising:
in the preset two-dimensional coordinate system, f corresponding to each unit of inclined distance time scale is carried out on the first frequency chart along the distance direction Dc -f DpAZ Is calculated to obtain Doppler frequency f generated by the relative motion of the earth and the satellite DpR The method comprises the steps of carrying out a first treatment on the surface of the Based on the calculation formula: f (f) Dca ＝f Dc -f DpAZ -f DpR Calculating to obtain the second Doppler frequency f Dca 。
Similarly, the technical scheme in the embodiment of the application also adopts a mean filtering mode to calculate and obtain the Doppler frequency f generated by the relative motion of the satellite and the earth in the distance direction DpR 。
The calculation process adopts linear fitting to calculate Doppler frequency f generated by satellite and earth relative motion in azimuth DpAZ Calculation by mean value filteringIts Doppler frequency f generated in the distance direction DpR The calculation process can not only lead f Dp The conventional implementation manner is abandoned, and the actual radar imaging beam pointing angle is adopted to calculate, so that the calculation result is more accurate, and the finally obtained second Doppler frequency f can be further obtained Dca A frequency image characterized as very accurate and containing only the sea-surface doppler frequency anomalies.
Still further, the pair of second Doppler frequencies f Dca Performing removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to sea current motion g Comprising:
acquiring a monitoring parameter set, wherein the monitoring parameter set comprises a sea surface wind direction parameter, a sea surface wind speed parameter, a radiation beam incidence angle parameter of the preset radar and a polarization mode parameter of the preset radar in the view direction of the preset radar, which are respectively in one-to-one correspondence with each time scale in the preset two-dimensional coordinate system; calculating and obtaining Doppler frequency shift f generated by the sea surface wind field corresponding to each time scale in the preset two-dimensional coordinate system based on the monitoring parameter set and the geophysical experience model CDOP w 。
At the same time, the pair of second Doppler frequencies f Dca Performing removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to sea current motion g Further comprising:
obtaining Doppler frequency shift f generated by Bragg scattering Bragg corresponding to each time scale in the preset two-dimensional coordinate system based on a double-scale irradiance scattering model B 。
The Doppler frequency abnormality also comprises Doppler frequency shift f caused by the sea surface wind field w And a Doppler shift f generated by Bragg scattering Bragg B Therefore, the technical solution in the embodiment of the present application further depends on the geophysical empirical model CDOP, and inputs the corresponding monitoring data set to obtain the doppler shift f generated by the corresponding sea-surface wind field w The method comprises the steps of carrying out a first treatment on the surface of the Obtaining the multiscale radiation scattering modelThe Doppler shift f B 。
Specifically, the Doppler frequency shift f generated by the Bragg scattering Bragg corresponding to each time scale in the preset two-dimensional coordinate system is obtained based on the double-scale irradiance model B Comprising:
based on the calculation formula:
calculating to obtain Doppler shift f B The method comprises the steps of carrying out a first treatment on the surface of the Wherein g is gravity acceleration, k e The wave number of the incident electromagnetic wave at the center of the imaging beam, theta is the incident angle, f B The positive and negative values of (a) correspond to the ocean current movement direction in the preset area.
Still further, after the determining, in a preset manner, a first sea level radial flow field within the first time range corresponding to the preset area, the method further includes:
and converting the first sea surface radial flow field in the preset two-dimensional coordinate system into a second sea surface radial flow field characterized in a longitude and latitude coordinate system based on the geolocation grid annotation data set in the SAR product header file.
The first sea surface radial flow field is characterized by adopting a coordinate system of a time Doppler grid (namely the preset two-dimensional coordinate system), namely, a coordinate system taking a time interval as a unit is formed by taking the backward receiving time of the azimuth direction and the distance direction of the SAR image as a coordinate.
The preset two-dimensional coordinate system depends on f g The data set can be annotated by means of the geographical positioning grid in the SAR product header file during actual operation, so that the time grid coordinate system can be converted into a universal longitude and latitude coordinate system, and further the international universal SAR radial flow field taking longitude and latitude as the coordinate system, namely the second sea surface radial flow field, is obtained. Through the second sea surface radial flow field, a user can more intuitively observe and know the sea surface radial flow field movement direction of the preset area in the first time range. In particular in the figures, the sea surface radial flow direction can be characterized by image depth.
It can be seen that the technical solution in the embodiment of the present application acquires a radar image through a preset radar within a first time range, so that an echo frequency f corresponding to a preset area and representing the center of an imaging beam can be obtained Dc After which the echo frequencies f are respectively compared with the first frequency pattern of Dc Performing removal of the first Doppler frequency f Dp Processing and removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f of radar view direction closer to real ocean current movement corresponding to preset region g Based on the Doppler shift f g Determining the radial velocity V of the sea surface flow field corresponding to the preset area in the first time range D The method comprises the steps of carrying out a first treatment on the surface of the And further obtaining the sea surface radial flow field which corresponds to the preset area and is in the first time range. The calculation process in the technical scheme in the embodiment of the application can reject the traditional implementation mode, and the actual radar imaging beam pointing angle is adopted for calculation, so that the sea surface radial flow field result obtained by final calculation is more accurate, and the technical effects of improving sea surface flow field inversion realization efficiency and result precision are achieved.
Example two
Referring to fig. 2 and 3, a second embodiment of the present application provides an electronic device, including:
a signal receiving device 201 for acquiring radar image data;
a processor 202, coupled to the signal receiving device, for obtaining an echo frequency f corresponding to a preset area and representing a center of an imaging beam emitted by the preset radar when a radar image is obtained by the preset radar in a first time range Dc For the echo frequency f Dc Performing removal of the first Doppler frequency f Dp Processing to obtain a second Doppler frequency f Dca For the second Doppler frequency f Dca Performing removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to sea current motion g Based on the Doppler shift f g Determining the radial direction of the sea surface flow field corresponding to the preset area in the first time rangeRate V D The method comprises the steps of carrying out a first treatment on the surface of the Based on the radial velocity V D Determining a first sea level radial flow field corresponding to the preset area within the first time range, wherein the echo frequency f Dc The distance and the direction are parameters represented in a preset two-dimensional coordinate system with the time interval as a scale and the x axis and the y axis respectively; the first Doppler frequency f Dp Comprising Doppler frequency f generated in azimuth direction by the relative motion of the satellite and the earth carried by the preset radar DpAZ And a Doppler frequency f generated in the range direction DpR The method comprises the steps of carrying out a first treatment on the surface of the The third Doppler frequency f D1 Comprising Doppler shift f caused by sea-surface wind fields w And Doppler shift f caused by Bragg scattering B The first sea surface radial flow field comprises sea surface flow field radial velocity V corresponding to each time scale in the preset two-dimensional coordinate system D Sea surface flow field direction.
Specifically, the processor 202 may be a general purpose Central Processing Unit (CPU), an application specific integrated circuit (english: application Specific Integrated Circuit, abbreviated as ASIC), or one or more integrated circuits for controlling program execution.
Further, the electronic device may further include a memory, and the number of memories may be one or more. The Memory may include a Read Only Memory (ROM), a random access Memory (Random Access Memory, RAM), and a disk Memory.
Optionally, the processor 202 is configured to calculate, in the preset two-dimensional coordinate system, an azimuth average value of the first frequency chart in the azimuth direction per unit time scale of the slant distance along the distance direction, and obtain an average value f of the first frequency chart in the azimuth direction AZm The method comprises the steps of carrying out a first treatment on the surface of the Based on the calculation formula: f (f) Dc -f AZm ＝f Dc-AZm Calculating in the preset two-dimensional coordinate system to obtain a representation f Dc-AZm A second frequency plot of values of (2); constructing a linear function relation F (t) in the preset two-dimensional coordinate system by adopting a linear fitting method to obtain a corresponding correlation coefficient R 2 Based on maximum correlationCoefficient R 2 F (t) corresponding to each inclined distance time scale in the azimuth direction is obtained through calculation Dc-AZm To obtain f (Dc-AZm) 'A'; the f is set to (Dc-AZm) The value of' is taken as the Doppler frequency f generated in azimuth by the relative motion of the satellite and the earth DpAZ Wherein the linear function relation F (t) takes each slope distance time scale in the azimuth direction in the preset two-dimensional coordinate system as an independent variable t, and F is respectively in one-to-one correspondence with each slope distance time scale in the distance direction Dc-AZm Is a dependent variable.
Optionally, the processor 202 is configured to perform f corresponding to each unit of skew time scale on the first frequency chart along the azimuth direction in the preset two-dimensional coordinate system Dc -f DpAZ Is calculated to obtain Doppler frequency f generated by the relative motion of the earth and the satellite DpR The method comprises the steps of carrying out a first treatment on the surface of the Based on the calculation formula: f (f) Dca ＝f Dc -f DpAZ -f DpR Calculating to obtain the second Doppler frequency f Dca 。
Of course, in actual operation, the electronic device may further include a display for displaying the parameters or graphics; the instruction input device is used for inputting various parameters or operation instructions, and the like, and can be set by a user according to the needs.
While preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the spirit or scope of the application. Further, the steps of the methods in the technical solutions of the present application may be reversed, and the sequence may be changed while still falling within the scope of the invention covered by the present application. Thus, if such modifications and variations of the present application fall within the scope of the claims and the equivalents thereof, the present application is intended to cover such modifications and variations.
Claims (8)
1. An inversion method for acquiring a high-precision sea surface flow field based on a spaceborne radar is characterized by comprising the following steps:
when radar images are acquired through a preset radar in a first time range, acquiring echo frequency f corresponding to a preset area and representing the center of an imaging beam radiated by the preset radar Dc Wherein the echo frequency f Dc The distance and the direction are parameters represented in a preset two-dimensional coordinate system with the time interval as a scale and the x axis and the y axis respectively;
for the echo frequency f Dc Performing removal of the first Doppler frequency f Dp Processing to obtain a second Doppler frequency f Dca Wherein the first Doppler frequency f Dp Comprising Doppler frequency f generated in azimuth direction by the relative motion of the satellite and the earth carried by the preset radar DpAZ And a Doppler frequency f generated in the range direction DpR The method comprises the following steps: in the preset two-dimensional coordinate system, calculating an azimuth average value of the first frequency chart in each unit of inclined distance time scale along the distance direction to obtain an average value f of the first frequency chart in the azimuth direction AZm The method comprises the steps of carrying out a first treatment on the surface of the Based on the calculation formula: f (f) Dc -f AZm ＝f Dc-AZm Calculating in the preset two-dimensional coordinate system to obtain a representation f Dc-AZm A second frequency plot of values of (2); constructing a linear function relation F (t) in the preset two-dimensional coordinate system by adopting a linear fitting method to obtain a corresponding correlation coefficient R 2 Wherein the linear function relation F (t) takes each slope distance time scale in the azimuth direction in the preset two-dimensional coordinate system as an independent variable t, and F is respectively in one-to-one correspondence with each slope distance time scale in the distance direction Dc-AZm Is a dependent variable; based on maximum correlation coefficient R 2 F (t) corresponding to each inclined distance time scale in the azimuth direction is obtained through calculation Dc-AZm To obtain f (Dc-AZm) 'A'; the f is set to (Dc-AZm) The 'value' is azimuthal as the relative motion of the satellite and earthUpward generated Doppler frequency f DpAZ ；
For the second Doppler frequency f Dca Performing removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to sea current motion g Wherein the third Doppler frequency f D1 Comprising Doppler shift f caused by sea-surface wind fields w And doppler shift f caused by Bragg scattering B ；
Based on the Doppler shift f g Determining the radial velocity V of the sea surface flow field corresponding to the preset area in the first time range D ；
Determining a first sea surface radial flow field corresponding to the preset area in the first time range according to a preset mode, wherein the first sea surface radial flow field comprises sea surface flow field radial velocity V corresponding to each time scale in the preset two-dimensional coordinate system D Sea surface flow field direction.
2. The method of claim 1 wherein said pair of echo frequencies f Dc Performing removal of the first Doppler frequency f Dp Processing to obtain a second Doppler frequency f Dca Comprising:
in the preset two-dimensional coordinate system, f corresponding to each unit of inclined distance time scale is carried out on the first frequency chart along the azimuth direction Dc -f DpAZ Is calculated to obtain Doppler frequency f generated by the relative motion of the earth and the satellite DpR ；
Based on the calculation formula: f (f) Dca ＝f Dc -f DpAZ -f DpR Calculating to obtain the second Doppler frequency f Dca 。
3. The method of claim 1 wherein said pair of said second doppler frequencies f Dca Performing removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to sea current motion g Comprising:
acquiring a monitoring parameter set, wherein the monitoring parameter set comprises a sea surface wind direction parameter, a sea surface wind speed parameter, a radiation beam incidence angle parameter of the preset radar and a polarization mode parameter of the preset radar in the view direction of the preset radar, which are respectively in one-to-one correspondence with each time scale in the preset two-dimensional coordinate system;
calculating and obtaining Doppler frequency shift f generated by the sea surface wind field corresponding to each time scale in the preset two-dimensional coordinate system based on the monitoring parameter set and the geophysical experience model CDOP w 。
4. A method according to claim 3, wherein said pair of said second doppler frequencies f Dca Performing removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to sea current motion g Comprising:
obtaining Doppler frequency shift f generated by Bragg scattering Bragg corresponding to each time scale in the preset two-dimensional coordinate system based on a double-scale irradiance scattering model B 。
5. The method of claim 4, wherein said obtaining, based on a dual-scale irradiance model, a doppler shift f generated by said Bragg-scatter Bragg corresponding to each time scale in said preset two-dimensional coordinate system B Comprising:
based on the calculation formula:
Wherein g is gravity acceleration, k e The wave number of the incident electromagnetic wave at the center of the imaging beam, theta is the incident angle, f B The positive and negative values of (a) correspond to the ocean current movement direction in the preset area.
6. The method of claim 1, wherein after said determining a first sea-surface radial flow field within said first time frame corresponding to said predetermined area in a predetermined manner, the method further comprises:
and converting the sea surface radial flow field in the preset two-dimensional coordinate system into a second sea surface radial flow field characterized in the longitude and latitude coordinate system based on the geolocation grid annotation data set in the SAR product header file.
7. An electronic device, comprising:
the signal receiving device is used for acquiring radar image data;
the processor is connected with the signal receiving device and is used for obtaining the echo frequency f corresponding to a preset area and representing the center of an imaging wave beam radiated by the preset radar when the radar image is obtained by the preset radar in a first time range Dc For the echo frequency f Dc Performing removal of the first Doppler frequency f Dp Processing to obtain a second Doppler frequency f Dca For the second Doppler frequency f Dca Performing removal of the third Doppler frequency f D1 Processing to obtain Doppler shift f corresponding to sea current motion g Based on the Doppler shift f g Determining the radial velocity V of the sea surface flow field corresponding to the preset area in the first time range D The method comprises the steps of carrying out a first treatment on the surface of the Based on the radial velocity V D Determining a first sea level radial flow field corresponding to the preset area within the first time range, wherein the echo frequency f Dc The distance and the direction are parameters represented in a preset two-dimensional coordinate system with the time interval as a scale and the x axis and the y axis respectively; the first Doppler frequency f Dp Comprising Doppler frequency f generated in azimuth direction by the relative motion of the satellite and the earth carried by the preset radar DpAZ And a Doppler frequency f generated in the range direction DpR The method comprises the steps of carrying out a first treatment on the surface of the The third Doppler frequency f D1 Comprising Doppler shift f caused by sea-surface wind fields w And Doppler shift f caused by Bragg scattering B The first sea surface radial flow field is included in the preset two-dimensional coordinate system and eachSea surface flow field radial velocity V corresponding to time scale D A sea surface flow field direction; the processor is further configured to calculate an azimuth average value of the first frequency chart per unit of skew time scale along a distance direction in the preset two-dimensional coordinate system, to obtain an average value f of the first frequency chart in the azimuth direction AZm The method comprises the steps of carrying out a first treatment on the surface of the Based on the calculation formula: f (f) Dc -f AZm ＝f Dc-AZm Calculating in the preset two-dimensional coordinate system to obtain a representation f Dc-AZm A second frequency plot of values of (2); constructing a linear function relation F (t) in the preset two-dimensional coordinate system by adopting a linear fitting method to obtain a corresponding correlation coefficient R 2 Based on the maximum correlation coefficient R 2 F (t) corresponding to each inclined distance time scale in the azimuth direction is obtained through calculation Dc-AZm To obtain f (Dc-AZm) 'A'; the f is set to (Dc-AZm) The value of' is taken as the Doppler frequency f generated in azimuth by the relative motion of the satellite and the earth DpAZ Wherein the linear function relation F (t) takes each slope distance time scale in the azimuth direction in the preset two-dimensional coordinate system as an independent variable t, and F is respectively in one-to-one correspondence with each slope distance time scale in the distance direction Dc-AZm Is a dependent variable.
8. The electronic device of claim 7, wherein the processor is configured to perform f corresponding to a time scale per unit of skew for the first frequency map along the azimuth direction in the preset two-dimensional coordinate system Dc -f DpAZ Is calculated to obtain Doppler frequency f generated by the relative motion of the earth and the satellite DpR The method comprises the steps of carrying out a first treatment on the surface of the Based on the calculation formula: f (f) Dca ＝f Dc -f DpAZ -f DpR Calculating to obtain the second Doppler frequency f Dca 。
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