CN113739788A - Geographical position correction method and device for brightness temperature data - Google Patents
Geographical position correction method and device for brightness temperature data Download PDFInfo
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Abstract
The invention belongs to the technical field of geoscience, and discloses a geographical position correction method and a geographical position correction device for brightness and temperature data, wherein the method comprises the following steps: obtaining brightness temperature data, and obtaining a coastline point set according to brightness temperature gradient change of the brightness temperature data; comparing a first coastline point and a second coastline point in the coastline point set to obtain a geographical positioning error set of the first coastline point; counting distribution characteristics of the geographic positioning errors in the geographic positioning error set in the along-track and cross-track directions; and correcting the geographical position of the brightness temperature data according to the distribution characteristics. Has the advantages that: the invention provides an image matching method taking a first coastline point as a ground control point, corrects a geographical positioning error caused by an observation angle error in a scanning coordinate system, tries to avoid conversion among different coordinate systems, realizes geographical position correction of satellite brightness temperature data by a smaller calculation amount and a simpler method, and provides effective support and guarantee for improving and promoting application of domestic satellite data.
Description
Technical Field
The invention relates to the technical field of geoscience, in particular to a geographical position correction method and a geographical position correction device for brightness and temperature data.
Background
The satellite-borne passive microwave data has the capability of carrying out earth observation all day long and all day long because the satellite-borne passive microwave data is not influenced by atmospheric conditions, and is widely applied to monitoring of variables such as sea ice density, ice cover/glacier ablation, soil humidity and the like. But the existing passive microwave data generally has geographical position deviation. If AMSR-E has a geometric geographic deviation of about 3.5 to 7km, FY-3B MWRI 89GHz data has an along-track position deviation of 3-4 km and an cross-track position deviation less than 1km, FY-3C MWRI 89GHz data has a geographic position deviation of 5-6 km, and early data of SSM/I has a geographic positioning error of up to 25 km. Accurate geographic positioning is exactly one of the basic requirements of quantitative inversion of ground and atmospheric parameters of passive microwave sensors, so that the correction of the geographic position of data is particularly important.
The brightness temperature data is one of satellite-borne passive microwave data. At present, satellite-borne passive microwave data correction methods comprise three types, namely an image correlation method, a lifting rail brightness temperature difference method and a coastline inflection point method. These methods mostly correct geometric geographical deviations by estimating the deviations of the satellite orbit and attitude parameters. The method has high correction precision, but complex conversion from an antenna coordinate system to a geographic coordinate is required in the correction process, and the calculation amount is huge. In recent years, with the continuous development of sensor technology and information acquisition technology, the remote sensing earth observation load with high resolution and high dynamic has the advantages of large number of wave bands, high spectral and spatial resolution, high data speed, short period and particularly large data volume. The method has the advantages that higher requirements are provided for satellite service processing capacity, the processing speed of remote sensing data is increased on the premise of ensuring product precision, and the problem of real-time or near-real-time remote sensing application requirements is very important.
Therefore, a new method and a device for correcting the geographical position of the brightness temperature data are needed, so that the geographical position of the brightness temperature data can be efficiently and accurately corrected, and the application requirements of the data can be met.
Disclosure of Invention
The purpose of the invention is: the geographical position correction method and device for the brightness temperature data are provided, so that the geographical position of the brightness temperature data can be efficiently and accurately corrected, and the application requirements of the data are met.
In order to achieve the above object, the present invention provides a geographical position correction method for brightness and temperature data, including:
the method comprises the steps of obtaining brightness temperature data of a first area including a sea and land boundary, and obtaining a coastline point set according to brightness temperature gradient changes of the brightness temperature data.
Comparing each first coastline point in the set of coastline points with a corresponding second coastline point in the set of real coastline points to obtain a set of geolocation errors including the geolocation error of each first coastline point.
And counting the distribution characteristics of each geographical positioning error in the geographical positioning error set in the along-track and cross-track directions.
And correcting the geographical position of the brightness temperature data according to the distribution characteristics.
Further, the obtaining of the coastline point set according to the brightness temperature gradient change of the brightness temperature data specifically includes:
acquiring bright temperature data of a first area in a scanning plane coordinate system, and marking a second coastline point according to a real coastline point set in the bright temperature data; the brightness temperature data is brightness temperature values of X rows and Y columns;
searching a plurality of brightness temperature points with the maximum brightness temperature gradient change in the X-axis direction or the Y-axis direction of each second coastline point; the brightness temperature gradient is the speed of the brightness temperature value change;
establishing a corresponding coordinate system according to the ordinate or abscissa of the plurality of bright temperature points corresponding to each second coastline point in the scanning plane coordinate system and the bright temperature values of the plurality of bright temperature points, and respectively performing function fitting;
and respectively carrying out second-order derivation on a plurality of first formulas obtained by function fitting, taking a point with a second-order derivative of zero as a first coastline point, and summarizing all the first coastline points into a coastline point set.
Further, the searching for a plurality of brightness temperature points with the largest brightness temperature gradient change specifically includes:
acquiring four brightness temperature points with the largest brightness temperature gradient change, and sequencing the four brightness temperature points according to the size of the abscissa or the ordinate of each brightness temperature point on a scanning plane;
when the extracted lighting temperatures of the four lighting temperature points are monotonically increased or decreased and the lighting temperature difference value between the first point and the fourth point of the four lighting temperature points is larger than the first threshold value, fitting a unitary cubic function to the coordinates of the four lighting temperature points in the scanning plane and taking the inflection point of the unitary cubic function as the coastline point.
Further, comparing each first coastline point in the set of coastline points with a corresponding second coastline point in the set of real coastline points to obtain a set of geolocation errors including the geolocation error of each first coastline point, specifically:
and each second coastline point corresponds to a first coastline point fitted by a function, the distance between each second coastline point and the corresponding first coastline point is obtained as a geographic positioning error, and all the geographic positioning errors are summarized into a geographic positioning error set.
Further, the counting of the distribution characteristics of each geographic positioning error in the geographic positioning error set in the along-rail and cross-rail directions specifically includes:
decomposing each geographical positioning error in the geographical positioning error set in the along track direction and the cross track direction, respectively performing function fitting on the geographical positioning errors decomposed in the along track direction and the cross track direction, and taking a second formula obtained by the function fitting as the distribution characteristics of the geographical positioning errors in the along track direction and the cross track direction.
Further, the geographic position correction of the brightness temperature data according to the distribution characteristics specifically includes:
substituting the coordinates of the first area brightness temperature data in the scanning plane coordinate system into a second formula to obtain a second geographical positioning error of the first area in the scanning plane coordinate system; and converting the scanning plane coordinate into a longitude and latitude coordinate according to a difference formula to obtain corrected brightness temperature data.
The invention also discloses a geographical position correction device of the brightness temperature data, which comprises the following components: the device comprises a first acquisition module, a first processing module, a second processing module and a third processing module.
The first obtaining module is used for obtaining brightness temperature data of a first area including a sea and land boundary, and obtaining a coastline point set according to brightness temperature gradient change of the brightness temperature data.
The first processing module is configured to compare each first coastline point in the set of coastline points with a corresponding second coastline point in the set of real coastline points to obtain a set of geographic positioning errors including a geographic positioning error of each first coastline point.
And the second processing module is used for counting the distribution characteristics of each geographical positioning error in the geographical positioning error set in the along-track and cross-track directions.
And the third processing module is used for correcting the geographical position of the brightness temperature data according to the distribution characteristics.
Further, the obtaining of the coastline point set according to the brightness temperature gradient change of the brightness temperature data specifically includes:
acquiring bright temperature data of a first area in a scanning plane coordinate system, and marking a second coastline point according to a real coastline point set in the bright temperature data; and the brightness temperature data is the brightness temperature values of X rows and Y columns.
Searching a plurality of brightness temperature points with the maximum brightness temperature gradient change in the X-axis direction or the Y-axis direction of each second coastline point; the brightness temperature gradient is the speed of the brightness temperature value change.
And establishing a corresponding coordinate system according to the ordinate or abscissa of the plurality of bright temperature points corresponding to each second coastline point in the scanning plane coordinate system and the bright temperature values of the plurality of bright temperature points, and respectively performing function fitting.
And respectively carrying out second-order derivation on a plurality of first formulas obtained by function fitting, taking a point with a second-order derivative of zero as a first coastline point, and summarizing all the first coastline points into a coastline point set.
Further, the searching for a plurality of brightness temperature points with the largest brightness temperature gradient change specifically includes:
and acquiring four brightness temperature points with the largest brightness temperature gradient change, and sequencing the four brightness temperature points according to the size of the abscissa or the ordinate of each brightness temperature point on the scanning plane.
When the extracted lighting temperatures of the four lighting temperature points are monotonically increased or decreased and the lighting temperature difference value between the first point and the fourth point of the four lighting temperature points is larger than the first threshold value, fitting a unitary cubic function to the coordinates of the four lighting temperature points in the scanning plane and taking the inflection point of the unitary cubic function as the coastline point.
Further, comparing each first coastline point in the set of coastline points with a corresponding second coastline point in the set of real coastline points to obtain a set of geolocation errors including the geolocation error of each first coastline point, specifically:
and each second coastline point corresponds to a first coastline point fitted by a function, the distance between each second coastline point and the corresponding first coastline point is obtained as a geographic positioning error, and all the geographic positioning errors are summarized into a geographic positioning error set.
Compared with the prior art, the geographic position correction method and the geographic position correction device for the brightness temperature data have the beneficial effects that: the invention provides an image matching method taking a first coastline point as a ground control point, corrects a geographical positioning error caused by an observation angle error in a scanning coordinate system, tries to avoid conversion among different coordinate systems, realizes geographical position correction of satellite brightness temperature data by a smaller calculation amount and a simpler method, and provides effective support and guarantee for improving and promoting application of domestic satellite data.
Drawings
FIG. 1 is a schematic flow chart of a geographical location correction method for brightness and temperature data according to the present invention;
FIG. 2 is a schematic diagram of a geographic position calibration apparatus for brightness and temperature data according to the present invention;
fig. 3 is a schematic reference diagram of a first coastline point acquired in the geographical location correction method of brightness and temperature data according to the present invention.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Name interpretation:
FY-3D (FengYun-3, FY-3) is the fourth satellite of the second generation polar orbit meteorological series satellite in China, and is loaded with 10 remote sensing instruments, thereby providing abundant information for land surface and atmosphere monitoring. The MWRI carried by FY-3D is an important radio sensor to monitor the earth in a cone scan with zenith angle of 53.1 ° and width of 1400 km. There are a total of 5 frequencies of 10.65GHz, 18.7GHz, 23.8GHz, 36.5GHz and 89 GHz. At 89GHz channel, the ground resolution of instantaneous field of view is 9km × 15 km.
MWRI (microwave Radiation imager) microwave imager.
Example 1:
the invention discloses a geographical position correction method of brightness temperature data, which is applied to geographical position correction of satellite brightness temperature data and mainly comprises the following steps:
and step S1, acquiring brightness temperature data of a first area including a boundary between the sea and the land, and obtaining a coastline point set according to brightness temperature gradient change of the brightness temperature data.
Step S2, comparing each first coastline point in the set of coastline points with a corresponding second coastline point in the set of real coastline points to obtain a set of geolocation errors including the geolocation error of each first coastline point.
And step S3, counting the distribution characteristics of each geographical positioning error in the geographical positioning error set in the along-track and cross-track directions.
And step S4, carrying out geographical position correction on the brightness temperature data according to the distribution characteristics.
In this embodiment, the brightness temperature data includes brightness temperature values of land and sea, and since the brightness temperature of land is higher than that of sea in the daytime, the brightness temperature gradient changes greatly in the brightness temperature transition region near the coastline. On this basis a first coastline point may be extracted.
In this embodiment, the brightness temperature data includes brightness temperature values in X rows and Y columns, and a corresponding coordinate system may be established according to rows and columns of the scanning plane coordinate system, and a corresponding coordinate system may be established by a row number and a column brightness temperature value or by a column number and a row brightness temperature value. Each light temperature value has a uniquely determined rank number. And each row number and one column number correspond to one longitude and latitude, and the longitude and latitude corresponding to each row number or column number are generated together when the brightness temperature data is generated when the satellite scans the earth surface.
In this embodiment, the method is preferably applied to the wind and cloud series satellites, and can effectively and accurately process and correct the brightness and temperature data of the wind and cloud series satellites.
In step S1, the obtaining a coastline point set according to the brightness temperature gradient change of the brightness temperature data specifically includes:
acquiring bright temperature data of a first area in a scanning plane coordinate system, and marking a second coastline point according to a real coastline point set in the bright temperature data; and the brightness temperature data is the brightness temperature values of X rows and Y columns.
Searching a plurality of brightness temperature points with the maximum brightness temperature gradient change in the X-axis direction or the Y-axis direction of each second coastline point; the brightness temperature gradient is the speed of the brightness temperature value change.
And establishing a corresponding coordinate system according to the ordinate or abscissa of the plurality of bright temperature points corresponding to each second coastline point in the scanning plane coordinate system and the bright temperature values of the plurality of bright temperature points, and respectively performing function fitting.
And respectively carrying out second-order derivation on a plurality of first formulas obtained by function fitting, taking a point with a second-order derivative of zero as a first coastline point, and summarizing all the first coastline points into a coastline point set.
In this embodiment, the searching for the plurality of brightness temperature points with the largest brightness temperature gradient change specifically includes:
acquiring four brightness temperature points with the largest brightness temperature gradient change, and sequencing the four brightness temperature points according to the size of the abscissa or the ordinate of each brightness temperature point on a scanning plane;
when the extracted lighting temperatures of the four lighting temperature points are monotonically increased or decreased and the lighting temperature difference value between the first point and the fourth point of the four lighting temperature points is larger than the first threshold value, fitting a unitary cubic function to the coordinates of the four lighting temperature points in the scanning plane and taking the inflection point of the unitary cubic function as the coastline point.
Referring to fig. 3(a), different gray scales represent different light temperature values, and the real coastline is represented by a specific gray scale. In the figure, the gray level of the rightmost black point is the area of the real coastline, and the center point of the gray level block is the real coastline point. Since the coastline in the drawing is in the column direction, four light temperature points having the largest change in luminance temperature gradient are searched in the row (X) direction of the real coastline point, such as four black points in fig. 3(a), the third point from left to right in the image is not the desired light temperature point, and the rightmost black point is the real coastline point (the second coastline point). Fig. 3(b) plots the light temperature of the four light temperature point positions and the coordinates in the scan plane coordinate system. These four bright temperature points are fitted with polynomial functions as follows:
wherein y is a brightness temperature value. x denotes the position in the scanning plane coordinate system. a, b and c are all constants. By calculating the second derivative of this function, the position in fig. 3(a) and (b) where the gradient change is the largest is obtained, and the third from the left in fig. 3(a) and (b) is the inflection point, which is the coastline inflection point and is also the first coastline point.
In step S2, the step of comparing each first coastline point in the set of coastline points with a corresponding second coastline point in the set of real coastline points to obtain a set of geographic positioning errors including a geographic positioning error of each first coastline point is specifically as follows:
and each second coastline point corresponds to a first coastline point fitted by a function, the distance between each second coastline point and the corresponding first coastline point is obtained as a geographic positioning error, and all the geographic positioning errors are summarized into a geographic positioning error set.
In step S3, the statistics of the distribution characteristics of each geolocation error in the set of geolocation errors in the along-track and cross-track directions specifically includes:
decomposing each geographical positioning error in the geographical positioning error set in the along track direction and the cross track direction, respectively performing function fitting on the geographical positioning errors decomposed in the along track direction and the cross track direction, and taking a second formula obtained by the function fitting as the distribution characteristics of the geographical positioning errors in the along track direction and the cross track direction.
In the present embodiment, for the geolocation error, fitting is performed with a constant function, a linear function, a polynomial function, and the like, in the two directions, respectively. Where y represents the geographical position error. x denotes the position in the scanning plane coordinate system. a, b, c are constants.
Respectively substituting the geographical positioning errors into the formulas to calculate the goodness of fit R2，R2The calculation formula of (a) is as follows:
wherein, yiFor the sample values, the values of the samples,
in order to predict the value of the target,
is the average of the sample values. R2The larger the fit, the better. According to R2And selecting a fitting formula with the best fitting effect from the three formulas to describe the distribution characteristics of the geographic positioning errors.
In step S4, the geographic location correction of the brightness temperature data according to the distribution characteristics specifically includes:
substituting the coordinates of the first area brightness temperature data in the scanning plane coordinate system into a second formula to obtain a second geographical positioning error of the first area in the scanning plane coordinate system; and converting the scanning plane coordinate into a longitude and latitude coordinate according to a difference formula to obtain corrected brightness temperature data.
Step S4 is to recalculate the geographic positioning error according to the distribution characteristics of the geographic positioning error, and correct the geographic positioning error. The step has the effects of reducing the geographical positioning error and improving the geographical positioning accuracy of satellite data. And substituting the coordinates of the MWRI data in the scanning plane coordinate system into the equation in the step S3 to obtain the geographical positioning error of the whole image in the scanning plane coordinate system. And then the scanning plane coordinates are converted into longitude and latitude by the following interpolation formula, and the corrected geographic position data can be obtained.
(lon′,lat′)＝f(x,y,x′,y′,lon,lat)
Where lon ', lat', x ', y' respectively represent longitude and latitude after correction, and x, y coordinates in the scanning plane coordinate system, and x, y, lon, lat respectively represent longitude and latitude before correction, and x, y coordinates in the scanning plane coordinate system. The value of the unknown function f at point P ═ x, y is solved as follows:
wherein f is in Q11＝(x1,y1)，Q12＝(x1,y2)，Q21＝(x2,y1)， Q22＝(x2,y2) The values of the four points are known quantities.
Example 2:
the invention also discloses a geographical position correction device of the brightness temperature data, which comprises the following components: a first acquisition module 101, a first processing module 102, a second processing module 103 and a third processing module 104.
The first obtaining module 101 is configured to obtain brightness temperature data of a first area including a boundary between an ocean and a land, and obtain a coastline point set according to brightness temperature gradient change of the brightness temperature data;
the first processing module 102 is configured to compare each first coastline point in the set of coastline points with a corresponding second coastline point in the set of real coastline points to obtain a set of geographic positioning errors including a geographic positioning error of each first coastline point;
the second processing module 103 is configured to count distribution characteristics of each geographic positioning error in the geographic positioning error set in along-track and cross-track directions;
the third processing module 104 is configured to perform geographic position correction on the brightness and temperature data according to the distribution characteristics.
In this embodiment, the obtaining of the coastline point set according to the brightness temperature gradient change of the brightness temperature data specifically includes:
acquiring bright temperature data of a first area in a scanning plane coordinate system, and marking a second coastline point according to a real coastline point set in the bright temperature data; and the brightness temperature data is the brightness temperature values of X rows and Y columns.
Searching a plurality of brightness temperature points with the maximum brightness temperature gradient change in the X-axis direction or the Y-axis direction of each second coastline point; the brightness temperature gradient is the speed of the brightness temperature value change.
And establishing a corresponding coordinate system according to the ordinate or abscissa of the plurality of bright temperature points corresponding to each second coastline point in the scanning plane coordinate system and the bright temperature values of the plurality of bright temperature points, and respectively performing function fitting.
And respectively carrying out second-order derivation on a plurality of first formulas obtained by function fitting, taking a point with a second-order derivative of zero as a first coastline point, and summarizing all the first coastline points into a coastline point set.
In this embodiment, the searching for the plurality of brightness temperature points with the largest brightness temperature gradient change specifically includes:
acquiring four brightness temperature points with the largest brightness temperature gradient change, and sequencing the four brightness temperature points according to the size of the abscissa or the ordinate of each brightness temperature point on a scanning plane;
when the extracted lighting temperatures of the four lighting temperature points are monotonically increased or decreased and the lighting temperature difference value between the first point and the fourth point of the four lighting temperature points is larger than the first threshold value, fitting a unitary cubic function to the coordinates of the four lighting temperature points in the scanning plane and taking the inflection point of the unitary cubic function as the coastline point.
In this embodiment, the comparing each first coastline point in the set of coastline points with a corresponding second coastline point in the set of real coastline points to obtain a set of geographic positioning errors including a geographic positioning error of each first coastline point specifically includes:
and each second coastline point corresponds to a first coastline point fitted by a function, the distance between each second coastline point and the corresponding first coastline point is obtained as a geographic positioning error, and all the geographic positioning errors are summarized into a geographic positioning error set.
In this embodiment, embodiment 2 is written based on embodiment 1, and therefore some of the same technical features are not described in detail.
To sum up, compared with the prior art, the geographic position correction method and device for brightness and temperature data provided by the embodiments of the present invention have the following beneficial effects: the invention provides an image matching method taking a first coastline point as a ground control point, corrects a geographical positioning error caused by an observation angle error in a scanning coordinate system, tries to avoid conversion among different coordinate systems, realizes geographical position correction of satellite brightness temperature data by a smaller calculation amount and a simpler method, and provides effective support and guarantee for improving and promoting application of domestic satellite data.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.
Claims (10)
1. A geographical position correction method of brightness temperature data is characterized by comprising the following steps:
obtaining brightness temperature data of a first area including a boundary between an ocean and a land, and obtaining a coastline point set according to brightness temperature gradient change of the brightness temperature data;
comparing each first coastline point in the set of coastline points with a corresponding second coastline point in the set of real coastline points to obtain a set of geographic positioning errors including the geographic positioning error of each first coastline point;
counting distribution characteristics of each geographical positioning error in the geographical positioning error set in the along-track and cross-track directions;
and correcting the geographical position of the brightness temperature data according to the distribution characteristics.
2. The geographical location correction method of brightness temperature data according to claim 1, wherein the obtaining of the coastline point set according to the brightness temperature gradient change of the brightness temperature data specifically comprises:
acquiring bright temperature data of a first area in a scanning plane coordinate system, and marking a second coastline point according to a real coastline point set in the bright temperature data; the brightness temperature data is brightness temperature values of X rows and Y columns;
searching a plurality of brightness temperature points with the maximum brightness temperature gradient change in the X-axis direction or the Y-axis direction of each second coastline point; the brightness temperature gradient is the speed of the brightness temperature value change;
establishing a corresponding coordinate system according to the ordinate or abscissa of the plurality of bright temperature points corresponding to each second coastline point in the scanning plane coordinate system and the bright temperature values of the plurality of bright temperature points, and respectively performing function fitting;
and respectively carrying out second-order derivation on a plurality of first formulas obtained by function fitting, taking a point with a second-order derivative of zero as a first coastline point, and summarizing all the first coastline points into a coastline point set.
3. The geographical location correction method of brightness temperature data according to claim 2, wherein the searching for a plurality of brightness temperature points with the largest brightness temperature gradient change specifically comprises:
acquiring four brightness temperature points with the largest brightness temperature gradient change, and sequencing the four brightness temperature points according to the size of the abscissa or the ordinate of each brightness temperature point on a scanning plane;
when the extracted lighting temperatures of the four lighting temperature points are monotonically increased or decreased and the lighting temperature difference value between the first point and the fourth point of the four lighting temperature points is larger than the first threshold value, fitting a unitary cubic function to the coordinates of the four lighting temperature points in the scanning plane and taking the inflection point of the unitary cubic function as the coastline point.
4. The method according to claim 2, wherein the step of comparing each first coastline point in the set of coastline points with a corresponding second coastline point in the set of real coastline points to obtain a set of geolocation errors including the geolocation error of each first coastline point comprises:
and each second coastline point corresponds to a first coastline point fitted by a function, the distance between each second coastline point and the corresponding first coastline point is obtained as a geographic positioning error, and all the geographic positioning errors are summarized into a geographic positioning error set.
5. The geographical location correction method of brightness temperature data according to claim 4, wherein the statistical distribution characteristics of each geographical positioning error in the geographical positioning error set in the along-track and cross-track directions are specifically:
decomposing each geographical positioning error in the geographical positioning error set in the along track direction and the cross track direction, respectively performing function fitting on the geographical positioning errors decomposed in the along track direction and the cross track direction, and taking a second formula obtained by the function fitting as the distribution characteristics of the geographical positioning errors in the along track direction and the cross track direction.
6. The geographical location correction method of brightness and temperature data according to claim 5, wherein the geographical location correction of the brightness and temperature data according to the distribution characteristics specifically includes:
substituting the coordinates of the first area brightness temperature data in the scanning plane coordinate system into a second formula to obtain a second geographical positioning error of the first area in the scanning plane coordinate system; and converting the scanning plane coordinate into a longitude and latitude coordinate according to a difference formula to obtain corrected brightness temperature data.
7. A geographical position correction device for brightness-temperature data, comprising: the device comprises a first acquisition module, a first processing module, a second processing module and a third processing module;
the first acquisition module is used for acquiring brightness temperature data of a first area including a sea and land boundary, and obtaining a coastline point set according to brightness temperature gradient change of the brightness temperature data;
the first processing module is configured to compare each first coastline point in the set of coastline points with a corresponding second coastline point in the set of real coastline points to obtain a set of geographic positioning errors including a geographic positioning error of each first coastline point;
the second processing module is used for counting distribution characteristics of each geographic positioning error in the geographic positioning error set in the along-track and cross-track directions;
and the third processing module is used for correcting the geographical position of the brightness temperature data according to the distribution characteristics.
8. The geographical location correction device of brightness temperature data according to claim 7, wherein the set of coastline points is obtained according to brightness temperature gradient changes of the brightness temperature data, and specifically comprises:
acquiring bright temperature data of a first area in a scanning plane coordinate system, and marking a second coastline point according to a real coastline point set in the bright temperature data; the brightness temperature data is brightness temperature values of X rows and Y columns;
searching a plurality of brightness temperature points with the maximum brightness temperature gradient change in the X-axis direction or the Y-axis direction of each second coastline point; the brightness temperature gradient is the speed of the brightness temperature value change;
establishing a corresponding coordinate system according to the ordinate or abscissa of the plurality of bright temperature points corresponding to each second coastline point in the scanning plane coordinate system and the bright temperature values of the plurality of bright temperature points, and respectively performing function fitting;
and respectively carrying out second-order derivation on a plurality of first formulas obtained by function fitting, taking a point with a second-order derivative of zero as a first coastline point, and summarizing all the first coastline points into a coastline point set.
9. The geographic position correction device of claim 8, wherein the searching for the plurality of brightness temperature points with the largest brightness temperature gradient change includes:
acquiring four brightness temperature points with the largest brightness temperature gradient change, and sequencing the four brightness temperature points according to the size of the abscissa or the ordinate of each brightness temperature point on a scanning plane;
when the extracted lighting temperatures of the four lighting temperature points are monotonically increased or decreased and the lighting temperature difference value between the first point and the fourth point of the four lighting temperature points is larger than the first threshold value, fitting a unitary cubic function to the coordinates of the four lighting temperature points in the scanning plane and taking the inflection point of the unitary cubic function as the coastline point.
10. The geographical location correction device of claim 8, wherein the comparing of each first coastline point in the set of coastline points with a corresponding second coastline point in the set of real coastline points results in a set of geographical positioning errors comprising a geographical positioning error of each first coastline point, specifically:
and each second coastline point corresponds to a first coastline point fitted by a function, the distance between each second coastline point and the corresponding first coastline point is obtained as a geographic positioning error, and all the geographic positioning errors are summarized into a geographic positioning error set.
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