CN115201779B - Method for acquiring imaging origin spatial position and baseline horizontal azimuth angle of radar - Google Patents
Method for acquiring imaging origin spatial position and baseline horizontal azimuth angle of radar Download PDFInfo
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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
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
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- G01S13/06—Systems determining position data of a target
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- G01S13/88—Radar or analogous systems specially adapted for specific applications
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- 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
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Abstract
The invention discloses a method for acquiring a spatial position of an imaging origin of a radar and a horizontal azimuth angle of a base line, which comprises the steps of establishing a homonymous point pair of a GB-SAR image and a DOM (document object model) and DEM/DSM (digital elevation model), combining a distance direction value of the homonymous point in the GB-SAR image with geographic data corresponding to the homonymous point, establishing a distance equation by taking a geographic coordinate of the imaging origin of the radar as an unknown number, and solving the unknown number of an equation set to obtain a three-dimensional geographic coordinate of the imaging origin of the radar; and further providing a radar baseline horizontal azimuth angle which is calculated by backward deduction by using the azimuth direction numerical value of the same-name point in the GB-SAR image and the horizontal azimuth angle from the radar imaging origin point to the same-name point based on the result of the radar imaging origin point geographic coordinate and the direction angle in the GB-SAR image. The method can solve the problems of low direction precision, excessive auxiliary measuring equipment and excessive matched hardware cost when the GPS or the total station measures the horizontal direction of the base line of the radar base station.
Description
Technical Field
The invention belongs to the technical field of GB-SAR ground synthetic aperture radars, and particularly relates to a method for acquiring the imaging origin spatial position and the baseline horizontal azimuth angle of a ground synthetic aperture radar.
Background
The ground-based synthetic aperture radar GB-SAR, namely the synthetic aperture radar SAR installed on a ground platform, acquires two-dimensional images of a distance direction and an azimuth direction through a synthetic aperture radar imaging technology. Two dimensions of the GB-SAR two-dimensional image are a distance direction and an azimuth direction respectively, the distance direction numerical value represents the distance from the center of the radar base station, and the azimuth direction numerical value represents the clockwise or anticlockwise deflection angle by taking a zero base line azimuth as a reference.
Because the two dimensional values of the GB-SAR two-dimensional image are values taking a radar synthetic aperture imaging origin and a radar synthetic aperture imaging reference direction as polar coordinate system origins, the GB-SAR two-dimensional image does not have geographic information, cannot be directly fused to a three-dimensional map, and is difficult to interpret the geographic space orientation of the image information. In order to facilitate interpretation of the geographic spatial orientation of the GB-SAR two-dimensional image information, the two-dimensional GB-SAR image needs to be mapped to a three-dimensional terrain for display, namely the two-dimensional GB-SAR image and the three-dimensional terrain data are registered and fused. A coordinate system of the two-dimensional GB-SAR image is called a radar coordinate system, and a coordinate system of the three-dimensional terrain data is called a geographic coordinate system. In order to realize the mapping registration from the two-dimensional GB-SAR image to the three-dimensional terrain data, the relation between a radar coordinate system and a geographic coordinate system needs to be found first. Assuming that a geographic coordinate system is used as a reference, the relation between the radar coordinate system and the geographic coordinate system can be obtained only by obtaining the spatial position and the direction of the radar coordinate system in the geographic coordinate system, and then the mapping registration relation between each pixel point in the two-dimensional GB-SAR image and the three-dimensional terrain is obtained by combining a GB-SAR imaging model. In the process, the space position and the direction of the radar coordinate system in the geographic coordinate system are obtained, and the space position and the baseline horizontal direction of the radar base station in the geographic coordinate reference system corresponding to the three-dimensional terrain are equivalently obtained according to the GB-SAR imaging principle model. Therefore, acquiring the spatial position (mainly the position of the logical origin coordinate) and the baseline horizontal direction of the base station of the ground-based radar is a necessary condition for realizing registration and fusion of the radar image and the three-dimensional terrain data.
In the prior art, the conventional method for acquiring the spatial position of the radar base station mainly uses a GPS with an RTK service to measure the spatial coordinates of a mark point on an equipment entity of the radar base station. The concrete method is as follows: and placing the antenna of the GPS on a mark point on the radar base station entity according to an operation manual of the GPS, standing the antenna until the GPS hand prompts that the measured coordinate value is the coordinate value measured after the fixed solution, namely the space coordinate of the radar base station to be measured. The spatial coordinates of the markers on the radar base station equipment entity can also be measured using a total station. The measuring method is different according to manufacturers of the total station, and the specific measuring details can refer to corresponding operation manuals. The method comprises the key steps that a prism of a total station is placed on a mark point on a radar base station entity, and then the prism coordinate is measured by the total station, so that the prism coordinate can be converted into a radar base station space coordinate required to be measured. In addition, the method for acquiring the baseline horizontal direction is to measure the space coordinates of two mark points used for determining the radar zero baseline horizontal direction on the radar base station entity and then calculate the space coordinates by a vector method. The specific method for measuring the coordinates of the mark points on the radar base station entity is the same as the method for acquiring the space position of the radar base station. The final value of the baseline horizontal direction can be represented by an angle of a coordinate axis clockwise rotated to the baseline horizontal direction in the horizontal plane of the geographic coordinate system, i.e., a horizontal azimuth angle.
However, the method for obtaining the spatial position (i.e. the spatial position of the imaging origin) and the baseline horizontal direction of the radar base station by measuring the mark point on the radar base station entity through hardware such as a surveying instrument in the prior art has the following disadvantages:
(1) The problems of excessive auxiliary measuring equipment and high cost of matched hardware exist, and corresponding hardware such as a GPS or a surveying instrument and the like must be provided when the spatial position of the radar base station needs to be acquired every time, so that the use cost of the radar is increased.
(2) The method has the problem of low direction accuracy when the GPS or the total station measures the horizontal direction of the base line of the radar base station, and the horizontal direction of the base line is obtained by calculating the space coordinates of two point positions with the distance not more than 2 meters, which are measured by a surveying instrument, so that the high-accuracy horizontal direction of the base line can be obtained only by measuring the high-accuracy space coordinates. High precision surveying instruments are required to measure high precision spatial coordinates. The higher the accuracy of the surveying instrument, the higher the price of the surveying instrument, so that the use cost of the GB-SAR becomes higher.
(3) The method has the problem that the coordinates and the directions of the radar base station are difficult to measure indoors during radar erection, and if the GB-SAR foundation radar is erected indoors, particularly in a high-rise building, spatial coordinate data of a corresponding mark point position on the radar base station are difficult to measure by a surveying and mapping instrument used in the existing method. The main two surveying and mapping methods in the prior art use equipment such as a GPS and a total station. Where GPS, according to its principle, cannot be used to measure the coordinates of an indoor target. The total station can measure the coordinates of an indoor target, but the total station needs to perform multiple through-sight conduction measurements, which is very complicated.
(4) The problem that the measurement cannot be performed when the logic origin and the reference azimuth of the radar imaging coordinate system deviate from the radar base station entity exists because the radar imaging origin and the baseline horizontal direction marked on the radar base station entity possibly deviate from the logic origin and the baseline horizontal direction of the radar imaging coordinate system, and the logic origin and the baseline horizontal direction cannot be directly measured.
(5) In addition, the application scenario of the GB-SAR is generally that multiple projects or multiple monitoring sites are used in turn. In the existing method, a mapping instrument is required to be reused to measure the corresponding marked point position on the radar base station after GB-SAR moves every time. Meanwhile, after the GB-SAR normally works after the measurement is finished, a surveying and mapping instrument is not needed as long as the radar does not move. Because of the need to prevent accidental movement of the GB-SAR, the surveying instrument cannot be taken off-site for other uses. This results in an ultra-low frequency of use for the surveying instrument, which in turn results in a low economic efficiency for the surveying instrument.
Therefore, based on the above problems, it is desirable to design a method for acquiring the imaging origin spatial position and the baseline horizontal azimuth angle of the radar.
Disclosure of Invention
Technical problem to be solved
Based on the method, the method can solve the problems of low direction precision, excessive auxiliary measuring equipment and excessive supporting hardware cost when a GPS or a total station measures the horizontal direction of the radar base station baseline, can adapt to the situation that the coordinates and the direction of the radar base station are difficult to measure indoors for radar erection, and indirectly realizes the measurement of the logical origin and the horizontal direction of the logical baseline of a radar imaging coordinate system in a geographic coordinate system.
(II) technical scheme
The invention discloses a method for acquiring a space position of an imaging origin and a horizontal azimuth angle of a baseline of a radar, which comprises the following steps:
step 1: reading a GB-SAR image of the ground-based synthetic aperture radar, and recording the GB-SAR image as an R image; reading the corresponding digital orthophoto map DOM and elevation topographic data map, and recording as O image and S image respectively;
step 2: searching and recording homonymy point pairs between the R image and the O image, wherein the number of the homonymy point pairs is more than or equal to 3;
and step 3: interpolating corresponding elevation data in the S image according to the geographic coordinates of each homonymous point on the O image, updating the homonymous point pairs and forming three-dimensional geographic coordinates of the homonymous points;
and 4, step 4: according to a GB-SAR imaging model formed by the R image in an O image geographic coordinate system, establishing a distance equation from the three-dimensional geographic coordinate of each identical point to the three-dimensional geographic coordinate of the radar imaging origin and integrating to form a distance equation set;
and 5: solving the three-dimensional geographic coordinates of the radar imaging origin in the distance equation set, namely the imaging origin spatial position of the ground-based synthetic aperture radar;
step 6: connecting any homonymous point and the radar imaging origin under a two-dimensional coordinate system, and calculating a clockwise azimuth angle theta from the radar imaging origin to the homonymous point n ；
And 7: according to the GB-SAR imaging model, enabling the radar imaging origin to reach a clockwise azimuth angle theta of the same-name point n Subtracting the azimuth direction value of the same-name point to obtain the horizontal azimuth angle of the radar base line;
and step 8: and outputting the three-dimensional geographic coordinates of the radar imaging origin and the horizontal azimuth angle of the radar baseline as an output result.
Preferably, the elevation terrain data map is a digital elevation model DEM or a digital surface model DSM in a remote sensing digital map.
Preferably, the homonymous points are replaced by control points which can be customized, and the control points are more than three target points with particularly obvious electromagnetic wave reflection signals searched in a scanning imaging area of the ground-based synthetic aperture radar.
Preferably, the step 2 specifically includes: finding the same-name points in the R image and the O image requires finding more than 3 pairs of same-name point pairs P { (P) 1 r , P 1 o )、(P 2 r , P 2 o )、(P 3 r , P 3 o )......(P n r , P n o ) At this point P n o The coordinates of the image are two-dimensional geographic coordinates (X) obtained by converting image space coordinates of the O image into object space coordinates n o ,Y n o ），P n r Is the horizontal azimuth value D represented by the corresponding image side position n And a distance direction value L n Is marked as (D) n ,L n ) And n is greater than or equal to 3.
Preferably, the step 3 specifically includes: interpolating P in S-pictures n o Geographic coordinates (X) n o ,Y n o ) Elevation value Z of n s To obtain P n o Corresponding three-dimensional geographic coordinates P n （X n o ，Y n o ，Z n s ) As P in the O image n （X n o ，Y n o ，Z n o ) And updating the data of the same-name point pair to be P { (P) 1 r , P 1 )、(P 2 r , P 2 )、(P 3 r , P 3 )......(P n r , P n )}。
Preferably, the step 4 specifically includes: let the logical origin coordinate of the R image in the geographic coordinate system of the O image be P 0 （X 0 ，Y 0 ，Z 0 ) And as a radar imaging origin, obtaining a distance equation according to the GB-SAR imaging model:
because n is more than or equal to 3, more than three pairs of homonymy points can obtain an equation set formed by more than three distance equations:
preferably, the step 5 specifically includes: when n =3, two solutions exist in the equation set, and the unreasonable solution is removed to obtain a true solution (X) 0 ，Y 0 ，Z 0 ) When n is equal to>3, then the unique solution (X) can be solved 0 ，Y 0 ，Z 0 ）。
Preferably, the step 6 specifically includes: connecting radar imaging origin P in digital orthophoto map DOM 0 With any one point of identity P n According to two-dimensional coordinates (X) of its coordinates 0 ，Y 0 ) And (X) n o ，Y n o ) Can obtain a vector P 0 To P n Clockwise azimuth angle theta of n 。
Preferably, the step 7 specifically includes: suppose that the desired baseline horizontal clockwise azimuth is θ 0 Due to P n r And P n Is a same name point, and can know P according to GB-SAR imaging model n r Angle of azimuth value D n Is represented by P 0 The bit origin rotates clockwise from the baseline direction to P 0 P n The angle value of the vector direction, i.e.:
D n =θ n -θ 0
the baseline horizontal azimuth can be solved:
θ 0 =θ n -D n 。
preferably, the step 8 specifically includes: by P 0 （X 0 ，Y 0 ，Z 0 ) And theta 0 And realizing the mapping registration of the two-dimensional GB-SAR image to the three-dimensional terrain data in subsequent work.
In a second aspect, the present invention also discloses a system for acquiring the imaging origin spatial position and the baseline horizontal azimuth angle of a radar, comprising:
at least one processor; and at least one memory communicatively coupled to the processor, wherein:
the memory stores program instructions executable by the processor to invoke the method of acquiring an imaging origin spatial position and a baseline azimuth angle of a radar as described in any one of the above.
In a third aspect, the invention also discloses a non-transitory computer-readable storage medium storing computer instructions that cause the computer to perform the method of acquiring an imaging origin spatial position and a baseline horizontal azimuth angle of a radar as described in any one of the above.
(III) advantageous effects
(1) The method of the invention is a software method for searching a plurality of groups of homonymous points on radar images and topographic data and calculating the logic origin and direction of a radar imaging coordinate system by a radar imaging principle model through a rear intersection method, and omits the process of using a surveying and mapping instrument, so that the application cost of the radar can be reduced, and the method has small calculated amount and is easy to realize.
(2) The method comprises the steps of firstly calculating the geographic coordinate of the origin of a radar imaging coordinate system, and then calculating the horizontal direction of a base line by using the geographic coordinate of a same-name point, the radar coordinate and the geographic coordinate of the origin. Therefore, the coordinate point used in the baseline horizontal direction calculated by the method is not limited by the physical size of the radar equipment, and long-distance direction finding can be realized. According to simple geometric theory, the farther the two base points are apart for determining the direction of the straight line, the higher the orientation precision. Increasing the base point distance for calculating the azimuth can improve the accuracy of the azimuth.
(3) The input condition of the method of the invention does not need to consider the actual position of the radar, so the method is not limited by indoor environment such as high buildings and the like.
(4) According to the method, the logical origin and the logical baseline horizontal direction of radar imaging are derived through backward extrapolation of the radar scanning imaging model through the imaging result of the radar, the homologous point of manual measurement between the orthoimage and the three-dimensional terrain data, and the measurement of the logical origin and the logical baseline horizontal direction of a radar imaging coordinate system in a geographic coordinate system is indirectly realized.
(5) The method can achieve the effect superior to that achieved by using a surveying and mapping instrument under the condition of not using the surveying and mapping instrument, can greatly save the use cost of auxiliary equipment of GB-SAR, and generates better economic benefit.
Drawings
The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:
fig. 1 is a flow chart of a method for obtaining an imaging origin spatial position and a baseline horizontal azimuth angle of a ground-based synthetic aperture radar according to the present invention.
Detailed Description
The present invention will be described more fully hereinafter with reference to the accompanying drawings and examples, in which the technical problems and advantages of the present invention are solved, wherein the described examples are only intended to facilitate the understanding of the present invention, and are not to be construed as limiting in any way.
In the prior art, two dimensions of a GB-SAR two-dimensional image are respectively numerical values that take a radar synthetic aperture imaging origin and a radar reference direction as an origin of a polar coordinate system. The distance direction realizes high resolution by a step frequency continuous wave technology; in the azimuth direction, a small number of antennas move at a constant speed on a straight line or an arc line track to form a synthetic aperture or a plurality of antennas are arranged in an array manner to form the synthetic aperture, so that high angular resolution is realized.
In the scanning imaging model of the GB-SAR ground-based synthetic aperture radar of the present invention, various coordinates of the ground-based synthetic aperture radar scanning points are generally represented in a conventional manner in the prior art, for example: p0 (X0, Y0, Z0) is expressed as the coordinate of the radar base station rotation origin, i.e., the logical origin of the radar image, in the geographic coordinate system(ii) a Pn (Xn, yn, zn) and Pn (Dn, ln) represent a pair of homonymous points, (Xn, yn, zn) represent geographical coordinates of the point, and (Dn, ln) represent radar image coordinates of the point; ln represents the linear distance from P0 to Pn, and Dn represents the angle from the baseline direction to Pn direction when the radar starts to rotate clockwise and horizontally; theta 0 The azimuth angle of the radar base line in the horizontal plane based on the X axis is expressed; theta n Expressed as the azimuth angle referenced to the X-axis in the horizontal plane after the radar has rotated to the P0-Pn direction.
Digital orthophoto Map (DOM, hereinafter referred to as orthophoto image): the digital orthographic projection image set is generated by performing digital differential correction and mosaic on an aviation (or aerospace) photo and cutting according to a certain picture range. It is an image with both map geometric accuracy and imagery features. The DOM has the advantages of high precision, rich information, intuition, vividness, quickness in obtaining and the like, can be used as map analysis background control information, can also extract historical information or latest information of natural resources and social and economic development from the map analysis background control information, and provides a reliable basis for application of disaster prevention and control, public facility construction planning and the like; and new information can be extracted and derived from the data, so that the map can be updated in a repairing and measuring way, and the accuracy, the realizability and the integrity of other data can be evaluated to be excellent.
A Digital Elevation Model (DEM), which is a solid ground Model that uses a group of ordered numerical arrays to represent ground Elevation, is a branch of a Digital Terrain Model (DTM), from which various other Terrain feature values can be derived. A Digital Surface Model (DSM) refers to a ground elevation Model that includes the height of surface buildings, bridges, trees, and the like. Compared with DEM, the DEM only contains the elevation information of terrain and does not contain other surface information, and the DSM further contains the elevation of other surface information except the ground on the basis of the DEM. Especially in some fields with high demands on the building height, the method obtains great attention.
In order to obtain the geographic spatial coordinates of the radar imaging origin and the geographic horizontal azimuth of the imaging baseline, the problem that a high-value surveying instrument such as a GPS or a total station needs to be used for measuring the reference direction and the accurate spatial coordinates of a radar base station entity in the traditional method is solved, and a plurality of technical defects discovered and proposed by an inventor in the background art are overcome. The invention firstly proposes a method for establishing a same-name point pair P of a DOM (document object model) and a DEM/DSM (digital elevation model) in a GB-SAR (synthetic aperture radar) image and a remote sensing digital map, then combining a distance direction numerical value of the same-name point in the GB-SAR image with geographic data corresponding to the same-name point, establishing a distance equation by taking a geographic coordinate of a radar imaging origin as an unknown number, and solving the unknown number through an equation set formed by a plurality of same-name points to obtain the geographic coordinate of the radar imaging origin; and further providing a radar baseline horizontal azimuth angle which is calculated by backward deduction by using the azimuth direction numerical value of the same-name point in the GB-SAR image and the horizontal azimuth angle from the radar imaging origin point to the same-name point based on the result of the previous imaging origin point geographic coordinate and the direction angle in the GB-SAR image.
Specifically, referring to fig. 1, in one embodiment, the present invention relates to a method for acquiring an imaging origin spatial position and a baseline horizontal azimuth angle of a radar, including:
step 1: reading a GB-SAR image of the ground-based synthetic aperture radar, and recording the GB-SAR image as an R image; and reading the corresponding digital orthographic image DOM and the elevation topographic data map, and respectively recording as an O image and an S image.
Further, in step 1, the elevation terrain data map is specifically a digital elevation model DEM or a digital surface model DSM in the remote sensing digital map, that is, the elevation terrain data is an image model with elevation data, which may be either the DEM or the DSM, and it is further noted that neither the DEM nor the DSM has an image representing the geometric accuracy and the image characteristics of the map.
In addition, the digital orthophoto map DOM and the elevation terrain data map DEM/DSM correspond to the same region scanned by the ground-based radar GB-SAR, so that the same name point can be searched through the overlapped part of the digital orthophoto map DOM and the elevation terrain data map DEM/DSM.
Step 2: and searching and recording homonymous point pairs between the R image and the O image, wherein the number of the homonymous point pairs is more than or equal to 3.
Further, in step 2, searching for the same-name point (i.e. the point representing the same earth surface position) in the R image and the O image, more than 3 pairs of same-name points P { (P) need to be found 1 r , P 1 o )、(P 2 r , P 2 o )、(P 3 r , P 3 o )......(P n r , P n o ) }. At this time P n o The coordinates of the coordinates are two-dimensional geographic coordinates (X) obtained by converting O image space coordinates into object space coordinates n o ,Y n o ），P n r Is the horizontal azimuth value D represented by the corresponding image side position n And a distance direction value L n Is marked as (D) n ,L n ) And n is greater than or equal to 3.
In addition, the homonymous point can be changed into a customizable control point, the control point is used for searching more than three target points with particularly obvious electromagnetic wave reflection signals in a scanning imaging area of the ground-based synthetic aperture radar, the target points can be devices capable of forming electromagnetic wave strong reflection signals such as large angle reflectors, and the like, namely more than three special devices capable of forming electromagnetic wave strong reflection signals such as angle reflectors are placed as the control points. Then, the three-dimensional geographic coordinates of the control points are obtained through technologies such as remote sensing, the coordinates of the control points are substituted into the method for replacing the original geographic coordinates of the same-name points to establish a distance equation set, and the three-dimensional geographic coordinates of the origin of the radar base station can also be solved. And further, the radar baseline horizontal azimuth can be calculated by using the geographic coordinates of the origin of the radar base station and the control point and the azimuth numerical value of the control point obtained from the radar image.
And 3, step 3: and interpolating corresponding elevation data in the S image according to the geographic coordinates of each homonymous point on the O image, updating the homonymous point pairs and forming three-dimensional geographic coordinates of the homonymous points.
Further, in step 3, P is interpolated in the S picture n o Geographic coordinates (X) n o ,Y n o ) Elevation value Z of n s To obtain P n o Corresponding three-dimensional geographic coordinates P n （X n o ，Y n o ，Z n s ) As P in the O image n （X n o ，Y n o ，Z n o ) And updating the data of the same-name point pair to be P { (P) 1 r , P 1 )、(P 2 r , P 2 )、(P 3 r , P 3 )......(P n r , P n )}。
It should be noted that the step 2 is performed prior to the step 3 because the R image and the O image belong to different coordinate expression modes, but both belong to two-dimensional coordinates, which facilitates the realization of fast and accurate matching between points of the same name by the existing geometric or image search algorithm, and then the corresponding elevation data is inserted by the step 3.
And 4, step 4: and establishing a distance equation from the three-dimensional geographic coordinate of each identical point to the three-dimensional geographic coordinate of the radar imaging origin according to a GB-SAR imaging model formed by the R image in an O image geographic coordinate system, and integrating to form a distance equation set.
Further, in step 4, let the logical origin coordinate of the R image in the geographic coordinate system of the O image be P 0 （X 0 ，Y 0 ，Z 0 ) And as a radar imaging origin, obtaining a distance equation according to a GB-SAR imaging model:
because n is more than or equal to 3, more than three pairs of homonymous points can obtain an equation set formed by more than three distance equations:
and 5: and solving the three-dimensional geographic coordinates of the radar imaging origin in the distance equation set.
Further, in step 5, since the number n of the distance equation set is greater than or equal to the number of the unknowns, the equation set has solutions, when n =3, the two solutions of the equation set exist, and a true solution (X) can be obtained by rejecting unreasonable solutions of the two solutions 0 ，Y 0 ，Z 0 ) When n is equal to>3, then the unique solution (X) can be solved 0 ，Y 0 ，Z 0 ）。
Step 6: connecting any homonymous point and a radar imaging origin under a two-dimensional coordinate system, and calculating a clockwise azimuth angle theta from the radar imaging origin to the homonymous point n 。
Further, in step 6, connecting the radar imaging origin P in the orthographic image 0 With any one point of same name P n According to two-dimensional coordinates (X) of its coordinates 0 ，Y 0 ) And (X) n o ，Y n o ) Can obtain a vector P 0 To P n Clockwise azimuth angle theta of n 。
And 7: according to a GB-SAR imaging model, enabling a radar imaging origin to reach a clockwise azimuth angle theta of the same-name point n And subtracting the azimuth value of the same-name point to obtain the horizontal azimuth of the radar baseline.
Further, in step 7, it is assumed that the required baseline horizontal clockwise azimuth angle is θ 0 Due to P n r And P n Is a same name point, and P can be known according to the GB-SAR imaging model n r Angle value D of azimuth direction n Is represented by P 0 The bit origin rotates clockwise from the baseline direction to P 0 P n The value of the angle of the vector direction, i.e.:
D n =θ n -θ 0
the baseline horizontal azimuth can be solved:
θ 0 =θ n -D n 。
and 8: and outputting the three-dimensional geographic coordinates of the radar imaging origin and the horizontal azimuth angle of the radar baseline as an output result.
Further, in step 8, outputting the coordinate of the logical origin of the R image in the geographic coordinate system of O as P by software 0 （X 0 ，Y 0 ，Z 0 ) And a base line horizontal clockwise azimuth angle theta 0 . Thereby determining the radar imaging origin spatial position and the baseline horizontal azimuth angle, and utilizing P 0 （X 0 ，Y 0 ，Z 0 ) And theta 0 And realizing the mapping registration of the two-dimensional GB-SAR image to the three-dimensional terrain data in subsequent work.
Therefore, the method can calculate and obtain the spatial position of the imaging origin of the radar and the horizontal azimuth of the baseline through the pure software operation, the DOM and the DEM/DSM are utilized to effectively pre-extract the error information of the coordinate origin and the horizontal direction of the baseline in the two-dimensional polar coordinate image of the GB-SAR, the conversion calculation under various coordinate systems is not needed through a coordinate rotation matrix, the calculation precision is high, the realization is easy, and the mapping registration of the two-dimensional GB-SAR image to the three-dimensional terrain data can be further realized after the spatial position of the imaging origin and the horizontal azimuth of the baseline of the ground-based synthetic aperture radar are obtained through the method.
The above-described method of acquiring the imaging origin spatial position and the baseline horizontal azimuth angle of the radar of the present invention may be executed as a software program or computer instructions in a non-transitory computer-readable storage medium or other system with a memory and a processor, and its calculation program is simple and fast to run. Each functional unit in each step and embodiment of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, or in a form of hardware plus a software functional unit. The integrated unit implemented in the form of a software functional unit may be stored in a computer readable storage medium. The software functional unit is stored in a storage medium and includes several instructions to enable a computer device (which may be a personal computer, a server, or a network device) or a processor (processor) to execute some steps of the methods according to the embodiments of the present invention. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
Finally, the description is as follows: the above examples are only intended to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A method for acquiring an imaging origin spatial position and a baseline horizontal azimuth angle of a radar, the method is characterized by comprising the following steps:
step 1: reading a GB-SAR image of the ground-based synthetic aperture radar, and recording the GB-SAR image as an R image; reading the corresponding digital orthophoto map DOM and elevation topographic data map, and recording as O image and S image respectively;
step 2: searching and recording homonymous point pairs between the R image and the O image, wherein the number of the homonymous point pairs is more than or equal to 3;
and step 3: interpolating corresponding elevation data in the S image according to the geographic coordinates of each homonymous point on the O image, updating the homonymous point pairs and forming three-dimensional geographic coordinates of the homonymous points;
and 4, step 4: according to a GB-SAR imaging model formed by the R image in an O image geographic coordinate system, establishing a distance equation from the three-dimensional geographic coordinate of each identical point to the three-dimensional geographic coordinate of the radar imaging origin and integrating to form a distance equation set;
and 5: solving the three-dimensional geographic coordinates of the radar imaging origin in the distance equation set, namely the imaging origin spatial position of the ground-based synthetic aperture radar;
step 6: connecting any homonymous point and the radar imaging origin under a two-dimensional geographic coordinate system, and calculating a clockwise azimuth angle theta from the radar imaging origin to the homonymous point n ；
And 7: according to the GB-SAR imaging model, enabling the radar imaging origin to reach the clockwise azimuth theta of the homonymous point n Subtracting the azimuth direction value of the same-name point to obtain the horizontal azimuth angle of the radar baseline;
and 8: and outputting the three-dimensional geographic coordinates of the radar imaging origin and the horizontal azimuth angle of the radar base line as output results.
2. The method for obtaining the spatial position of the imaging origin and the baseline horizontal azimuth angle of the radar according to claim 1, wherein the elevation topography data map is a digital elevation model DEM or a digital surface model DSM in a remote sensing digital map.
3. The method for obtaining the spatial position of the imaging origin and the horizontal azimuth of the baseline of the radar as claimed in claim 1, wherein the homologous point is replaced by a customizable control point, and the control point is used for searching more than three target points with particularly obvious electromagnetic wave reflection signals in the scanning imaging area of the ground-based synthetic aperture radar.
4. The method for obtaining the spatial position of the imaging origin and the horizontal azimuth angle of the baseline of the radar as claimed in claim 1, wherein the step 2 specifically comprises: finding the same-name points in the R image and the O image requires finding more than 3 pairs of same-name point pairs P { (P) 1 r , P 1 o )、(P 2 r , P 2 o )、(P 3 r , P 3 o ).....(P n r , P n o ) At this point P n o The coordinate of (2) is the image space coordinate of the O imageTwo-dimensional geographic coordinates (X) obtained by object space coordinate conversion n o ,Y n o ），P n r Is the horizontal azimuth value D represented by the corresponding image side position n And a distance direction value L n Is described as (D) n ,L n ) Subscript n is 3 or more.
5. The method for obtaining the spatial position of the imaging origin and the horizontal azimuth angle of the baseline of the radar as claimed in claim 4, wherein the step 3 specifically comprises: interpolating P in S picture n o Geographic coordinates (X) n o ,Y n o ) Elevation value Z of n s To obtain P n o Corresponding three-dimensional geographic coordinates P n （X n o ，Y n o ，Z n s ) To be P in O image n （X n o ，Y n o ，Z n o ) And updating the data of the same-name point pair to be P { (P) 1 r , P 1 )、(P 2 r , P 2 )、(P 3 r , P 3 )......(P n r , P n )}。
6. The method for obtaining the spatial position of the imaging origin and the horizontal azimuth angle of the baseline of the radar as claimed in claim 5, wherein the step 4 specifically comprises: let the logical origin coordinate of the R image in the geographic coordinate system of the O image be P 0 （X 0 ，Y 0 ，Z 0 ) And as a radar imaging origin, obtaining a distance equation according to the GB-SAR imaging model:
because n is more than or equal to 3, more than three pairs of homonymous points can obtain an equation set formed by more than three distance equations:
7. the method for obtaining the spatial position of the imaging origin and the horizontal azimuth angle of the baseline of the radar as claimed in claim 6, wherein the step 5 specifically comprises: when n =3, two solutions exist in the equation set, and the unreasonable solution is removed to obtain a true solution (X) 0 ，Y 0 ，Z 0 ) When n is equal to>3, then the only solution (X) can be solved 0 ，Y 0 ，Z 0 ）。
8. The method for obtaining the spatial position of the imaging origin and the horizontal azimuth angle of the baseline of the radar as claimed in claim 7, wherein the step 6 specifically comprises: connecting radar imaging origin P in digital orthophoto map DOM 0 With any one point of identity P n According to two-dimensional coordinates (X) of its coordinates 0 ，Y 0 ) And (X) n o ，Y n o ) Can obtain a vector P 0 To P n Clockwise azimuth angle theta of n 。
9. The method for obtaining the spatial position of the imaging origin and the horizontal azimuth angle of the baseline of the radar as claimed in claim 8, wherein the step 7 specifically comprises: suppose the required baseline horizontal clockwise azimuth angle is theta 0 Due to P n r And P n Is a same name point, and can know P according to the GB-SAR imaging model n r Angle value D of azimuth direction n Is represented by P 0 The bit origin rotates clockwise from the baseline direction to P 0 P n The value of the angle of the vector direction, i.e.:
D n =θ n -θ 0
the baseline horizontal azimuth can be solved:
θ 0 =θ n -D n 。
10. the method for obtaining the spatial position of the imaging origin and the horizontal azimuth angle of the baseline of the radar as claimed in claim 9, wherein the step 8 specifically comprises: by P 0 （X 0 ，Y 0 ，Z 0 ) And theta 0 And realizing the mapping registration of the two-dimensional GB-SAR image to the three-dimensional terrain data in subsequent work.
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