CN109239710B - Method and device for acquiring radar elevation information and computer-readable storage medium - Google Patents
Method and device for acquiring radar elevation information and computer-readable storage medium Download PDFInfo
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Abstract
The embodiment of the invention discloses a method and a device for acquiring radar elevation information and a computer readable storage medium, wherein the method comprises the following steps: acquiring interference phase information of a target area according to an interference radar image of the target area; acquiring initial elevation information of the target area by utilizing a radar stereo measurement technology; according to the initial elevation information, land leveling processing is carried out on the interference phase information to obtain differential phase information; and sequentially performing phase unwrapping and elevation inversion on the differential phase information, and combining the initial elevation information to obtain absolute elevation information.
Description
Technical Field
The present invention relates to data processing technologies, and in particular, to a method and an apparatus for acquiring radar elevation information, and a computer-readable storage medium.
Background
The Digital Elevation Model (DEM) is a three-dimensional Digital Model for describing the surface shape of the earth, consists of a series of data sets containing geographical plane coordinates and elevations, has important application value in the fields of scientific research, economic construction and military, and is more important in high-resolution and high-precision DEM particularly in specific scenes such as earthquake deformation detection, terrain monitoring and the like.
Generally, an Interferometric Synthetic Aperture Radar (Interferometric Synthetic Aperture Radar ) technology is adopted, which utilizes a Synthetic Aperture Radar (SAR) image pair to obtain a high-precision Interferometric phase map, and then calculates elevation information according to the Interferometric phase map, so as to reconstruct a high-precision DEM, where Interferometric phase unwrapping in the Interferometric SAR technology is a main factor affecting the accuracy of the DEM, but a flat ground phase included in the Interferometric phase map and the application of the Interferometric SAR technology to an area with large relief of terrain both result in dense Interferometric fringes and increase the difficulty of Interferometric phase unwrapping, and the removal of the flat ground phase is easily affected by satellite orbit errors or other factors, so that the removal effect of the flat ground phase is poor, the difficulty of phase unwrapping is still large, and the accuracy of the DEM is affected.
Disclosure of Invention
The invention mainly aims to provide a radar elevation reconstruction method and device and a computer readable storage medium, and aims to solve the problem that the existing elevation reconstruction method of interferometric synthetic aperture radar is poor in flat ground phase removal effect.
The technical scheme of the invention is realized as follows:
the embodiment of the invention provides a method for acquiring radar elevation information, which comprises the following steps:
acquiring interference phase information of a target area according to an interference radar image of the target area;
acquiring initial elevation information of the target area by utilizing a radar stereo measurement technology;
according to the initial elevation information, land leveling processing is carried out on the interference phase information to obtain differential phase information;
and sequentially performing phase unwrapping and elevation inversion on the differential phase information, and combining the initial elevation information to obtain absolute elevation information.
Optionally, the acquiring initial elevation information of the target area by using a radar stereo measurement technology includes:
acquiring a stereopair corresponding to the target area by utilizing the radar stereopair technology;
obtaining three-dimensional coordinates of image points with the same name in the stereoscopic image pair according to the stereoscopic image pair and the conformation model corresponding to the target area;
and performing coordinate conversion on the three-dimensional coordinates of the image points with the same name to obtain the initial elevation information.
Optionally, the performing coordinate conversion on the three-dimensional coordinates of the image points with the same name to obtain the initial elevation information includes:
converting the three-dimensional coordinates of the image points with the same name by adopting a geocoding method to obtain converted three-dimensional coordinates of the image points with the same name, wherein the converted three-dimensional coordinates are coordinates in a geodetic coordinate system;
and obtaining the initial elevation information according to the Z-axis coordinate value of the converted three-dimensional coordinate.
Optionally, the obtaining, according to the stereo pair and the conformation model corresponding to the target area, three-dimensional coordinates of image points of the same name in the stereo pair includes:
establishing the conformation model by using a distance-Doppler equation;
determining two-dimensional coordinates of image points with the same name in the stereo image pair according to the imaging geometric relation corresponding to the radar stereo measurement technology;
and obtaining a three-dimensional coordinate corresponding to the image point with the same name according to the conformation model and the two-dimensional coordinate of the image point with the same name.
Optionally, the obtaining, according to the conformation model and the two-dimensional coordinates of the image points with the same name, three-dimensional coordinates corresponding to the image points with the same name includes:
acquiring image gray information of the stereopair, and carrying out window search on the stereopair based on the image gray information to obtain the parallax of the homonymous image point;
and obtaining a three-dimensional coordinate corresponding to the image point with the same name according to the conformation model, the two-dimensional coordinate of the image point with the same name and the parallax of the image point with the same name.
Optionally, the obtaining, according to the conformation model and the two-dimensional coordinates of the image points with the same name, three-dimensional coordinates corresponding to the image points with the same name includes:
respectively carrying out horizontal coordinate subtraction and vertical coordinate subtraction on the two-dimensional coordinates of the homonymous image points to obtain the parallaxes of the homonymous image points;
and obtaining a three-dimensional coordinate corresponding to the image point with the same name according to the conformation model, the two-dimensional coordinate of the image point with the same name and the parallax of the image point with the same name.
Optionally, the land removing processing on the interference phase information according to the initial elevation information to obtain differential phase information includes:
obtaining initial phase information according to the initial elevation information and the imaging geometric relation of the interferometric synthetic aperture radar;
and carrying out land removing processing on the interference phase information by using the initial phase information to obtain differential phase information.
Optionally, sequentially performing phase unwrapping and elevation inversion on the differential phase information, and obtaining absolute elevation information by combining the initial elevation information, includes:
performing phase unwrapping on the differential phase information to obtain unwrapped differential phase information;
performing elevation inversion on the unwrapped differential phase information to obtain differential elevation information;
and obtaining absolute elevation information according to the initial elevation information and the differential elevation information.
The embodiment of the invention provides a device for acquiring radar elevation information, which is characterized by comprising the following components: a first information acquisition unit, a second information acquisition unit and an information processing unit; wherein
The first information acquisition unit is used for acquiring interference phase information of a target area according to an interference radar image of the target area;
the second information acquisition unit is used for acquiring initial elevation information of the target area by utilizing a radar stereo measurement technology;
the information processing unit is used for carrying out land leveling processing on the interference phase information according to the initial elevation information to obtain differential phase information; and sequentially performing phase unwrapping and elevation inversion on the differential phase information, and combining the initial elevation information to obtain absolute elevation information.
Optionally, the second information obtaining unit is specifically configured to obtain, by using the radar stereo measurement technology, a stereo pair corresponding to the target area; obtaining three-dimensional coordinates of image points with the same name in the stereoscopic image pair according to the stereoscopic image pair and the conformation model corresponding to the target area; and performing coordinate conversion on the three-dimensional coordinates of the image points with the same name to obtain the initial elevation information.
Optionally, the second information obtaining unit is specifically configured to convert the three-dimensional coordinates of the image points of the same name by using a geocoding method to obtain converted three-dimensional coordinates of the image points of the same name, where the converted three-dimensional coordinates are coordinates in a geodetic coordinate system; and obtaining the initial elevation information according to the Z-axis coordinate value of the converted three-dimensional coordinate.
Optionally, the second information obtaining unit is specifically configured to establish the constellation model by using a range-doppler equation; determining two-dimensional coordinates of image points with the same name in the stereo image pair according to the imaging geometric relation corresponding to the radar stereo measurement technology; and obtaining a three-dimensional coordinate corresponding to the image point with the same name according to the conformation model and the two-dimensional coordinate of the image point with the same name.
Optionally, the second information obtaining unit is specifically configured to obtain image gray scale information of the stereo pair, and perform window search on the stereo pair based on the image gray scale information to obtain a parallax of the image point of the same name; and obtaining a three-dimensional coordinate corresponding to the image point with the same name according to the conformation model, the two-dimensional coordinate of the image point with the same name and the parallax of the image point with the same name.
Optionally, the second information obtaining unit is specifically configured to perform abscissa subtraction and ordinate subtraction on the two-dimensional coordinates of the image points of the same name, so as to obtain the parallax of the image points of the same name; and obtaining a three-dimensional coordinate corresponding to the image point with the same name according to the conformation model, the two-dimensional coordinate of the image point with the same name and the parallax of the image point with the same name.
Optionally, the information processing unit is specifically configured to obtain initial phase information according to the initial elevation information and an imaging geometric relationship of the interferometric synthetic aperture radar; and carrying out land removing processing on the interference phase information by using the initial phase information to obtain differential phase information.
Optionally, the information processing unit is specifically configured to perform phase unwrapping on the differential phase information to obtain unwrapped differential phase information; performing elevation inversion on the unwrapped differential phase information to obtain differential elevation information; and obtaining absolute elevation information according to the initial elevation information and the differential elevation information.
The embodiment of the invention provides a device for acquiring radar elevation information, which comprises: the radar elevation information acquisition system comprises a processor, a memory and a communication bus, wherein the memory is communicated with the processor through the communication bus, the memory stores one or more programs executable by the processor, and when the one or more programs are executed, the processor executes the steps of any one of the radar elevation information acquisition methods.
An embodiment of the present invention provides a computer-readable storage medium, which stores one or more programs, where the one or more programs are executable by one or more processors to implement any one of the above-mentioned methods for acquiring radar elevation information.
The embodiment of the invention provides a method and a device for acquiring radar elevation information and a computer readable storage medium, by adopting the technical scheme, after initial elevation information is obtained by a radar stereo measurement technology, the initial elevation information is utilized to carry out land leveling processing on interference phase information, and the processed phase is unwrapped to acquire absolute elevation information.
Drawings
Fig. 1 is a first flowchart of a method for acquiring radar elevation information according to an embodiment of the present invention;
fig. 2 is an imaging geometry diagram of an InSAR system and a target region according to an embodiment of the present invention;
fig. 3 is a schematic diagram of an imaging geometry relationship using a StereoSAR technique according to an embodiment of the present invention;
FIG. 4 is a second flowchart of a method for acquiring radar elevation information according to an embodiment of the present invention;
fig. 5 is a schematic diagram of initial elevation information obtained by using a StereoSAR technology according to an embodiment of the present invention;
fig. 6 is an interference phase diagram obtained by using TanDEM-X/terrasaar-X bistatic data and InSAR technology according to an embodiment of the present invention;
fig. 7 is a schematic diagram of differential phase information obtained by using a StereoSAR technique and an InSAR technique according to an embodiment of the present invention;
fig. 8 is a schematic diagram of absolute elevation information in a radar image coordinate system obtained by using a StereoSAR technology and an InSAR technology according to an embodiment of the present invention;
fig. 9 is a schematic diagram of absolute elevation information in a geodetic coordinate system obtained by using a StereoSAR technology and an InSAR technology according to an embodiment of the present invention;
FIG. 10 is a schematic diagram illustrating first elevation information of a target area obtained by performing an SRTM mission for a spacecraft radar terrain mapping mission, according to an embodiment of the present invention;
fig. 11 is a first schematic structural diagram of an apparatus for acquiring radar elevation information according to an embodiment of the present invention;
fig. 12 is a schematic structural diagram of a second apparatus for acquiring radar elevation information according to an embodiment of the present invention.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
Example one
An embodiment of the present invention provides a method for acquiring radar elevation information, as shown in fig. 1, the method includes:
s101: and acquiring interference phase information of the target area according to the interference radar image of the target area.
In the embodiment of the invention, in order to obtain the elevation information of a target area, a radar measurement method has the working principle that two SAR images of the target area are obtained, a three-dimensional coordinate model is established, and the elevation information of the target area is obtained according to three-dimensional coordinates corresponding to the two SAR images, for example, a method adopting a synthetic aperture radar stereo measurement (StereoSAR) technology is adopted; another radar measurement method has the working principle that two SAR images with coherence in a target area are obtained, interference processing is carried out to obtain interference phase information, and elevation information is obtained according to the interference phase information, for example, the method of InSAR technology is adopted; the phase obtained by the InSAR technology is higher than the phase obtained by the StereoSAR technology, so that the InSAR technology is used for obtaining elevation information of a target area, however, when the elevation information is obtained according to interference phase information, because the interference phase information comprises flat ground phase information, the flat ground phase is a linear change phase generated by a flat ground surface in the interference processing process of an image, the flat ground phase increases the difficulty of phase unwrapping, and further influences the precision of the obtained elevation information, so that the interference phase information needs to be subjected to flat ground removing processing, the cleanness of removing the flat ground phase is improved as much as possible, the difficulty of phase unwrapping is reduced, and the precision of the elevation information is improved.
Alternatively, for the problem of phase unwrapping, elevation information of most regions of the world can be generated by executing a space Shuttle Radar terrain mapping Mission (SRTM) task, and phase unwrapping can be assisted by using a phase corresponding to the elevation information generated by the SRTM, but the elevation information generated by the SRTM is generated in 2000, the timeliness is poor, and the elevation error is high, and the error value is about equal to 16 m; the global high-precision elevation information can be acquired by using a satellite-borne double-satellite distributed system consisting of a TanDEM-X satellite and a Terras SAR-X satellite, but the satellite-borne double-satellite distributed system is difficult to acquire the elevation information due to the lack of external auxiliary data under the condition of lacking effective ground control points, and the problem of poor flat ground phase removal effect of InSAR cannot be solved; in order to obtain elevation information with good timeliness and small error, the elevation information obtained by the StereoSAR technology can be adopted, and the interference phase information is subjected to land leveling processing according to the phase corresponding to the elevation information of the StereoSAR, so that the phase information of a smooth horizontal plane of the earth can be removed, the phase information generated by the terrain on the surface of the earth can be removed, the difficulty of phase unwrapping is greatly reduced, and the accuracy of the unwrapped elevation information is improved.
Exemplarily, an interferometric phase map of a target region may be acquired by using an InSAR technique, which specifically includes: transmitting microwaves to a target area by using two SAR antennas with interference imaging capability, receiving echoes reflected by the target area, acquiring two single-view complex images with certain view angle difference in the same target area and having coherence, and performing interference processing on the two single-view complex images to obtain an interference phase diagram; the interference processing is carried out on the two single-view complex images, and the interference processing specifically comprises the following steps: subtracting the two single-view complex images, or carrying out conjugate multiplication on the two single-view complex images; taking any target point P in the target area as an example, the two SAR antennas and the target point P have a certain imaging geometric relationship, as shown in fig. 2, B in fig. 2 represents two SAR antennas a1And A2A baseline distance therebetween, α denotes a baseline angle between the baseline and the reference plane, β denotes a2To A1Is a straight line of1Angle between straight lines to P, theta denotes radar antenna A1R, R' respectively represent the radar antenna a1、A2The slope distance to the target point P, Δ R represents the slope distance difference between the two slope distances, H represents the height of the radar platform relative to the geodetic reference plane, and H represents the altitude of the target point P relative to the geodetic reference plane.
S102: and acquiring initial elevation information of the target area by using a radar stereo measurement technology.
In the embodiment of the invention, a stereopair corresponding to a target area can be obtained by utilizing a radar stereopair technology; obtaining two-dimensional coordinates of the same-name image points of the stereopair according to the stereopair and the three-dimensional coordinate model corresponding to the target area; obtaining three-dimensional coordinates corresponding to the image points with the same name according to the two-dimensional coordinates and the image formation model of the image points with the same name; and performing coordinate conversion on the three-dimensional coordinates to obtain initial elevation information.
Illustratively, the radar stereo measurement technique is to pair the same ground from two different positionsImaging the area to obtain a pair of images called a stereo pair, wherein the image formed by the same object point on the stereo pair is called a homonymous image point, and the image point elevation is obtained by measuring the position and coordinate value of the homonymous image point; in order to obtain initial elevation information of a target area, firstly, two SAR antennas at different positions can be adopted to respectively image the target area, or one SAR antenna is adopted to respectively image the target area at different positions to obtain a stereopair of the target area, wherein the stereopair consists of a left image and a right image; wherein, the imaging geometric relation of the StereoSAR technology is shown in figure 3, the figure 3 shows a space rectangular coordinate system which is established by taking the projection position of the SAR satellite track initial position on the ground as the origin of an X coordinate and a Y coordinate, taking the motion direction of the SAR satellite (the direction indicated by a dotted arrow in figure 3) as the positive direction of an X axis, taking a vertical line perpendicular to the ground as a Z axis and the direction of the X coordinate origin pointing to the SAR satellite track initial position as the positive direction of the Z axis, Ps in figure 3 represents the instantaneous position of the SAR antenna, Ps0Representing the starting position of the SAR antenna, V representing the flight speed of the SAR antenna, t representing the flight time of the SAR antenna, MslantRepresenting the slant-range resolution, R0Representing the shortest slope distance in SAR imaging, Rs representing the slope distance of a target point on the ground illuminated by the radar, R0The relationship with Rs is expressed as: rs ^2 ═ R0+MslantX) 2, X represents the coordinate value of the X coordinate of the target point.
Further, after obtaining the stereo pair of the target area, a rectangular coordinate system is established for the stereo pair with the X axis and the Y axis in fig. 3, that is, the position of each image point on the photo can be represented by the abscissa (X axis) value and the ordinate (Y axis) value thereof, the two-dimensional coordinates of each image point in each pair of same-name image points are obtained, and the abscissa difference and the ordinate difference, also called as the X-direction parallax and the Y-direction parallax, of each pair of same-name image points are obtained, and are collectively called as the parallax of the same-name image points; on the other hand, image gray information of the stereo pair can be acquired, and based on the image gray information, the parallax of each pair of image points with the same name is acquired, which specifically includes: selecting some control points from the left photo and the right photo, and respectively establishing a matching window and a searching window which take the control points as centers on the left photo and the right photo for registering the left photo and the right photo; the method comprises the steps that a sliding matching window is used for obtaining a correlation measure function of a window, so that an offset is obtained, in order to improve searching precision, interpolation is conducted on the maximum value of the correlation measure function, and more accurate offset is obtained; and obtaining the search offset of other pixels by using the search window according to the offset corresponding to the control point, thereby obtaining the parallax information of the image point with the same name.
Further, after obtaining the two-dimensional coordinates of the image points with the same name and the parallax of the image points with the same name, obtaining the three-dimensional coordinates of the image points with the same name according to the geometric relationship of the stereo SAR technology height measurement model, the two-dimensional coordinates of the image points with the same name and the parallax information of the image points with the same name, which specifically comprises: according to the imaging geometric relationship of the StereoSAR technology, a Range-Doppler (RD) equation can be adopted to respectively establish an image formation model of a left image point and an image formation model of a right image point, each image formation model consists of a Range condition equation and a Doppler condition equation, and the image formation model of the left image point can be expressed as follows:
wherein,
is the coordinate value of the antenna position at the moment of imaging the image point of the left picture,
is the three coordinate components of the antenna position at the instant of imaging the image point of the left slice,
doppler center frequency when imaging left image point, λ represents radar wavelength, xLCoordinate values representing an X coordinate of a left shot point in the left shot;
the constellation model for the right patch pixels can be expressed as:
wherein,
is the coordinate value of the antenna position at the moment of imaging the image point with the same name on the right picture;
three coordinate components of the antenna position at the moment of imaging the image points with the same name on the right picture;
doppler center frequency, x, when imaging a right homonymous image pointRA coordinate value of an X coordinate in the right photo representing a right photo point corresponding to the left photo point; can obtain the parallax error and SAR flight parameters of the same-name image point
And
then x of each pair of same-name image pointsLAnd xRSubstituting the three-dimensional coordinates into the formulas (1) to (4) to obtain the three-dimensional coordinates of each pair of image points with the same name.
Further, after the three-dimensional coordinates of the image points with the same name are obtained, the three-dimensional coordinates of each image point with the same name can be geocoded, that is, the three-dimensional coordinates in the geocentric space rectangular coordinate system are converted into address coordinates in a geodetic coordinate system, then the elevation of each image point with the same name is obtained according to the Z coordinate value of the converted three-dimensional coordinates, and further the initial elevation information of the target area is obtained.
S103: and carrying out land removing processing on the interference phase information according to the initial elevation information to obtain differential phase information.
In the embodiment of the invention, the absolute phase of any one target point P in the target area
Can be expressed as:
wherein the absolute phase
It may be that the phase of the interference,
for the baseline unwrapping phase, the phase,
which is the earth's surface phase, in the general case,
the method and the device for acquiring the elevation information have the advantages that the initial phase information is obtained according to the initial elevation information and the radar imaging geometric relation, the initial phase is equal to the earth surface phase
Compared with the flat ground phase obtained by other methods, the initial phase also comprises phase information generated by ground topography; and then, the initial phase information is utilized to carry out land leveling processing on the interference phase information to obtain differential phase information, so that the ground relief phase in the interference phase information is removed more cleanly, and the unwrapping difficulty of the differential phase is greatly reduced.
Illustratively, the initial elevation h of any target point P in the target area may be obtained from the imaging geometry as shown in fig. 2 as:
the pitch difference Δ R is expressed as:
wherein, the initial phase is expressed by delta phi, the relational expression about the initial elevation h and the earth surface phase delta phi can be obtained by substituting the formula (7) into the formula (6), and the initial phase delta phi, namely the earth surface phase can be obtained under the condition that the initial elevation h is known
And subtracting the initial phase from the interference phase of the target point P to obtain the differential phase of the target point P.
S104: and sequentially performing phase unwrapping and elevation inversion on the differential phase information, and combining the initial elevation information to obtain absolute elevation information.
In the embodiment of the invention, because the value range of the interference phase obtained according to the two SAR images is (-pi, pi), 2K pi phase information is lost, the interference phase is added with the correct 2K pi per se through phase unwrapping, and the real phase corresponding to each interference phase is obtained, wherein K represents the phase periodicity corresponding to each real phase, the value is 1 to N, and N is a positive integer; similarly, for the differential phase obtained according to the interference phase, phase unwrapping is also required, firstly, phase unwrapping is performed on the differential phase information, then elevation inversion is performed on the unwrapped differential phase information to obtain differential elevation information, and finally, absolute elevation information is obtained according to the initial elevation information and the differential elevation information; it should be noted that the absolute elevation information is elevation information in a radar image coordinate system, that is, a horizontal coordinate value and a vertical coordinate value corresponding to each absolute elevation information are horizontal coordinate values and vertical coordinate values in a radar image (for example, a stereo pair), geocoding is required to be performed on the absolute elevation information to obtain geocoded absolute elevation information, and the geocoded absolute elevation information is elevation information in a geodetic coordinate system, that is, a horizontal coordinate and a vertical coordinate of the geocoded absolute elevation information are coordinates expressed by geodetic longitude and latitude.
Illustratively, a method based on Chinese remainder theorem CRT, maximum likelihood estimation MLE and integral variation maximum posteriori estimation TV-MAP can be adopted to perform phase unwrapping on each differential phase information to obtain unwrapped differential phase information, perform elevation inversion on the unwrapped differential phase to obtain differential elevations, and finally add each differential elevation and the corresponding initial elevation to obtain an absolute elevation.
It should be noted that step S101 to step S104 may be implemented by a processor.
It can be understood that a Synthetic Aperture Radar (SAR) image pair is used to obtain an interference phase map with higher precision, and then elevation information is calculated according to the interference phase map, so as to reconstruct a DEM with high precision, wherein interference phase unwrapping in the InSAR technology is a main factor affecting DEM precision, while flat ground phases included in interference fringes in the interference phase map and the InSAR technology applied in an area with larger relief of terrain can cause the interference fringes to be dense, increasing difficulty of interference phase unwrapping, however, removing the flat ground phases is easily affected by satellite orbit errors or other factors, so that removing effect of the flat ground phases is poor, increasing difficulty of phase unwrapping, and further affecting the precision of the DEM.
Example two
In order to further embody the object of the present invention, the above embodiments are further illustrated.
An embodiment of the present invention provides a method for acquiring radar elevation information, as shown in fig. 4, the method includes:
s401: and acquiring interference phase information of the target area according to the interference radar image of the target area.
S402: and acquiring initial elevation information of the target area by using a radar stereo measurement technology.
In the embodiment of the invention, an Envisat satellite is used, a stereopair of a target area is shot based on a StereoSAR technology, three-dimensional coordinates of image points with the same name in the stereopair are obtained through calculation, geocoding is carried out on the three-dimensional coordinates of each image point with the same name, initial elevation information of the target area is obtained, and an initial Digital Elevation Model (DEM) corresponding to the initial elevation information is obtained, as shown in FIG. 5, a left side numerical value in FIG. 5 represents the number of pixel points in a y direction, a lower side numerical value represents the number of pixel points in an x direction, a right side numerical value represents elevation, and a unit is m.
S403: and obtaining initial phase information according to the initial elevation information and the radar imaging geometric relation.
S404: and (4) carrying out land removing processing on the interference phase information by using the initial phase information to obtain differential phase information.
In the embodiment of the invention, the interferometric phase information of the target area can be generated by adopting InSAR technology in combination with TanDEM-X/TerrasAR-X double-base data, and an interferometric phase diagram corresponding to the interferometric phase information is shown in FIG. 6; subtracting the initial phase information obtained by the StereoSAR technology from the interference phase information to obtain differential phase information, wherein a differential phase diagram corresponding to the differential phase information is shown in FIG. 7, the left numerical value in FIGS. 6 and 7 represents the number of pixels in the y direction, the lower numerical value represents the number of pixels in the x direction, the right numerical value represents the phase, and the unit is rad; it can be seen that, compared to the interference phase diagram of fig. 6, the differential phase diagram of fig. 7 has sparser fringes, i.e., the earth surface phase included in the differential phase information is less, which reduces the difficulty of phase unwrapping.
S405: and performing phase unwrapping on the differential phase information, and performing elevation inversion on the unwrapped differential phase information to obtain differential elevation information.
S406: and obtaining absolute elevation information according to the initial elevation information and the differential elevation information.
In the embodiment of the invention, the initial elevation information and the differential phase information are added to obtain absolute elevation information, the absolute elevation information is elevation information under a radar image coordinate system, an absolute DEM corresponding to the absolute elevation information under the radar image coordinate system is shown in FIG. 8, then geocoding is carried out on the absolute elevation information to obtain geocoded absolute elevation information, the geocoded absolute elevation information is elevation information under a geodetic coordinate system, and the absolute DEM corresponding to the geocoded absolute elevation information is shown in FIG. 9; in addition, first elevation information of the target area can be obtained by executing the SRTM task, a first DEM corresponding to the first elevation information is shown in fig. 10, a left numerical value in fig. 8-10 represents the number of pixels in the y direction, a lower numerical value represents the number of pixels in the x direction, a right numerical value represents the elevation, and a unit is m; it can be seen that fig. 8 and 9 are both finer than the texture of fig. 10, that is, compared with the first DEM corresponding to the SRTM task, the resolution of the absolute DEM before and after geocoding is higher, that is, the absolute elevation information before and after geocoding better conforms to the actual elevation information of the target area, the average value of the error between the absolute elevation information after geocoding and the actual elevation information is 1.6586m, the root mean square error value is 5.06m, and is lower than the elevation error (16m) corresponding to the SRTM task, and the acquisition time of the first elevation information corresponding to the SRTM task is too early and has poor timeliness.
It should be noted that steps S401 to S406 may be implemented by a processor.
EXAMPLE III
Based on the same technical concept as the foregoing embodiments, a third embodiment of the present invention provides an apparatus 1 for acquiring radar elevation information, as shown in fig. 11, where the apparatus 1 includes: a first information acquisition unit 11, a second information acquisition unit 12, and an information processing unit 13; wherein
A first information obtaining unit 11, configured to obtain interference phase information of a target area according to an interference radar image of the target area;
the second information acquisition unit 12 is configured to acquire initial elevation information of a target area by using a radar stereo measurement technology;
the information processing unit 13 is configured to perform land leveling processing on the interference phase information according to the initial elevation information to obtain differential phase information; and sequentially performing phase unwrapping and elevation inversion on the differential phase information, and combining the initial elevation information to obtain absolute elevation information.
Optionally, the second information obtaining unit 12 is specifically configured to obtain a stereopair corresponding to the target area by using a radar stereopsis technique; obtaining three-dimensional coordinates of image points with the same name in the stereoscopic image pair according to the stereoscopic image pair and the image construction model corresponding to the target area; and carrying out coordinate conversion on the three-dimensional coordinates of the same image point to obtain initial elevation information.
Optionally, the second information obtaining unit 12 is specifically configured to convert the three-dimensional coordinates of the image points of the same name by using a geocoding method to obtain converted three-dimensional coordinates of the image points of the same name, where the converted three-dimensional coordinates are coordinates in a geodetic coordinate system; and obtaining initial elevation information according to the Z-axis coordinate value of the converted three-dimensional coordinate.
Optionally, the second information obtaining unit 12 is specifically configured to establish a constellation model by using a range-doppler equation; determining two-dimensional coordinates of image points with the same name in the stereo image pair according to the imaging geometric relation corresponding to the radar stereo measurement technology; and obtaining a three-dimensional coordinate corresponding to the image point with the same name according to the conformation model and the two-dimensional coordinate of the image point with the same name.
Optionally, the second information obtaining unit 12 is specifically configured to obtain image gray scale information of a stereo pair, and perform window search on the stereo pair based on the image gray scale information to obtain a disparity of image points with the same name; and obtaining the three-dimensional coordinates corresponding to the image points with the same name according to the conformation model, the two-dimensional coordinates of the image points with the same name and the parallax of the image points with the same name.
Optionally, the second information obtaining unit 12 is specifically configured to perform abscissa subtraction and ordinate subtraction on the two-dimensional coordinates of the image points with the same name, respectively, to obtain the parallax of the image points with the same name; and obtaining the three-dimensional coordinates corresponding to the image points with the same name according to the conformation model, the two-dimensional coordinates of the image points with the same name and the parallax of the image points with the same name.
Optionally, the information processing unit 13 is specifically configured to obtain initial phase information according to the initial elevation information and an imaging geometric relationship of the interferometric synthetic aperture radar; and carrying out land removing processing on the interference phase information by using the initial phase information to obtain differential phase information.
Optionally, the information processing unit 13 is specifically configured to perform phase unwrapping on the differential phase information to obtain unwrapped differential phase information; performing elevation inversion on the unwrapped differential phase information to obtain differential elevation information; and obtaining absolute elevation information according to the initial elevation information and the differential elevation information.
In practical applications, the first information acquiring Unit 11, the second information acquiring Unit 12, and the information Processing Unit 13 may be implemented by a processor 14 located on the radar elevation information acquiring apparatus 1, specifically, implemented by a CPU (Central Processing Unit), an MPU (micro processor Unit), a DSP (Digital Signal Processing) or a Field Programmable Gate Array (FPGA), and the like.
An embodiment of the present invention further provides an apparatus 1 for acquiring radar elevation information, as shown in fig. 12, where the apparatus 1 includes: a processor 14, a memory 15, and a communication bus 110, wherein the memory 15 is in communication with the processor 14 via the communication bus 110, and the memory 15 stores one or more programs executable by the processor 14, and when the one or more programs are executed, the processor 14 performs the method for acquiring radar elevation information according to the first embodiment.
Embodiments of the present invention provide a computer-readable storage medium storing one or more programs, which are executable by one or more processors 14 and when the programs are executed by the processors, implement the method for acquiring radar elevation information according to the first and second embodiments.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention.
Claims (11)
1. A method for acquiring radar elevation information, the method comprising:
acquiring interference phase information of a target area according to an interference radar image of the target area;
acquiring initial elevation information of the target area by utilizing a radar stereo measurement technology; the initial elevation information is a Z-axis coordinate value of a same-name image point in the stereo image pair corresponding to the target area in a geodetic coordinate system;
according to the initial elevation information, land leveling processing is carried out on the interference phase information to obtain differential phase information;
and sequentially performing phase unwrapping and elevation inversion on the differential phase information, and combining the initial elevation information to obtain absolute elevation information.
2. The method of claim 1, wherein the obtaining initial elevation information for the target area using radar stereo measurement comprises:
acquiring a stereopair corresponding to the target area by utilizing the radar stereopair technology;
obtaining three-dimensional coordinates of image points with the same name in the stereoscopic image pair according to the stereoscopic image pair and the conformation model corresponding to the target area;
and performing coordinate conversion on the three-dimensional coordinates of the image points with the same name to obtain the initial elevation information.
3. The method according to claim 2, wherein the coordinate transforming the three-dimensional coordinates of the homonymous image points to obtain the initial elevation information comprises:
converting the three-dimensional coordinates of the image points with the same name by adopting a geocoding method to obtain converted three-dimensional coordinates of the image points with the same name, wherein the converted three-dimensional coordinates are coordinates in a geodetic coordinate system;
and obtaining the initial elevation information according to the Z-axis coordinate value of the converted three-dimensional coordinate.
4. The method of claim 2, wherein obtaining three-dimensional coordinates of image points of the same name in the stereo pair according to the corresponding conformation models of the stereo pair and the target area comprises:
establishing the conformation model by using a distance-Doppler equation;
determining two-dimensional coordinates of image points with the same name in the stereo image pair according to the imaging geometric relation corresponding to the radar stereo measurement technology;
and obtaining a three-dimensional coordinate corresponding to the image point with the same name according to the conformation model and the two-dimensional coordinate of the image point with the same name.
5. The method according to claim 4, wherein obtaining three-dimensional coordinates corresponding to the image points of the same name according to the two-dimensional coordinates of the conformation model and the image points of the same name comprises:
acquiring image gray information of the stereopair, and carrying out window search on the stereopair based on the image gray information to obtain the parallax of the homonymous image point;
and obtaining a three-dimensional coordinate corresponding to the image point with the same name according to the conformation model, the two-dimensional coordinate of the image point with the same name and the parallax of the image point with the same name.
6. The method according to claim 4, wherein obtaining three-dimensional coordinates corresponding to the image points of the same name according to the two-dimensional coordinates of the conformation model and the image points of the same name comprises:
respectively carrying out horizontal coordinate subtraction and vertical coordinate subtraction on the two-dimensional coordinates of the homonymous image points to obtain the parallaxes of the homonymous image points;
and obtaining a three-dimensional coordinate corresponding to the image point with the same name according to the conformation model, the two-dimensional coordinate of the image point with the same name and the parallax of the image point with the same name.
7. The method of claim 1, wherein the land removing the interferometric phase information from the initial elevation information to obtain differential phase information comprises:
obtaining initial phase information according to the initial elevation information and the imaging geometric relation of the interferometric synthetic aperture radar;
and carrying out land removing processing on the interference phase information by using the initial phase information to obtain differential phase information.
8. The method of claim 1, wherein the sequentially performing phase unwrapping and elevation inversion on the differential phase information and combining the initial elevation information to obtain absolute elevation information comprises:
performing phase unwrapping on the differential phase information to obtain unwrapped differential phase information;
performing elevation inversion on the unwrapped differential phase information to obtain differential elevation information;
and obtaining absolute elevation information according to the initial elevation information and the differential elevation information.
9. An apparatus for acquiring radar elevation information, the apparatus comprising: a first information acquisition unit, a second information acquisition unit and an information processing unit; wherein
The first information acquisition unit is used for acquiring interference phase information of a target area according to an interference radar image of the target area;
the second information acquisition unit is used for acquiring initial elevation information of the target area by utilizing a radar stereo measurement technology; the initial elevation information is a Z-axis coordinate value of a same-name image point in the stereo image pair corresponding to the target area in a geodetic coordinate system;
the information processing unit is used for carrying out land leveling processing on the interference phase information according to the initial elevation information to obtain differential phase information; and sequentially performing phase unwrapping and elevation inversion on the differential phase information, and combining the initial elevation information to obtain absolute elevation information.
10. An apparatus for acquiring radar elevation information, the apparatus comprising: a processor, a memory and a communication bus, the memory in communication with the processor through the communication bus, the memory storing one or more programs executable by the processor, the one or more programs, when executed, causing the processor to perform the method of any of claims 1-8.
11. A computer-readable storage medium, having one or more programs stored thereon, the one or more programs being executable by one or more processors to perform the method of any of claims 1-8.
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