CN110109104B - Array SAR (synthetic aperture radar) equidistant slice imaging geometric distortion correction method - Google Patents
Array SAR (synthetic aperture radar) equidistant slice imaging geometric distortion correction method Download PDFInfo
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Abstract
The invention discloses an array SAR equidistant slice imaging geometric distortion correction method, which is based on an array SAR downward-looking or side-looking imaging geometric model and an equidistant slice three-dimensional imaging principle, and comprises the steps of firstly calculating the slant range from an antenna of an array SAR imaging system to each unit of an equidistant slice, then estimating the offset of each unit of the equidistant slice according to the slant range, and finally carrying out interpolation resampling and image unit offset on the offset, thereby realizing the imaging geometric distortion correction processing of the array SAR equidistant slice. The method has the characteristics of no need of prior information of a DEM (digital elevation model) of an observation scene, quick geometric correction processing and the like, is simple to realize, high in efficiency, high in precision and good in applicability, does not need prior information of the DEM and the like of the known observation three-dimensional observation scene, can effectively solve the problem of geometric distortion correction of equidistant slice imaging of the array SAR, and can be suitable for geometric distortion correction of equidistant slice three-dimensional imaging of the array SAR under the condition of sparse array.
Description
Technical Field
The invention belongs to the technical field of radar, and particularly relates to the technical field of Synthetic Aperture Radar (SAR) imaging.
Background
Synthetic Aperture Radar (SAR) has become an important means for earth observation at present as a remote sensing imaging technology with all-time, all-weather and rich information content, and is increasingly widely applied in the fields of national economy and military such as terrain image generation, target detection and reconnaissance, target accurate striking, national soil resource exploration, natural disaster monitoring and the like, and the documents are named as 'Liu nationality, Ding Xiao Li, Chen Yong Qi, and the like', a new technology of synthetic aperture radar interference [ J ] earth science development in a very potential space-earth observation, 2000,15(6): 734-. SAR image geometric correction is the basis for widespread application of SAR images. Array SAR (laser) is a new SAR three-dimensional imaging technique that has been of great interest in recent years. In essence, the array SAR utilizes a synthetic aperture technique to achieve a resolution along a track direction (i.e., an azimuth direction), utilizes a beam forming technique to achieve a resolution of a sliced track, and utilizes a pulse compression technique to obtain an elevation resolution, thereby obtaining three-dimensional information of a scattering point of an observation target. For details, see the document "Sun Long, Jiangkai, Shijin. array three-dimensional SAR system technology research [ J ]. Radar science and technology, 2016,14(3): 279-285". Compared with a conventional SAR two-dimensional imaging system, the array SAR three-dimensional imaging system can work in a plurality of imaging modes, such as side-looking, strabismus, downward-looking, forward-looking and the like, breaks through the limitation and the deficiency of the conventional SAR imaging mode (the conventional SAR can only work in the side-looking imaging mode generally), and refers to the literature of Peng-Ming, Wang-Yan, Tan Wei, and the like. Therefore, the array SAR has great research value and application prospect in the fields of national defense, military and resource management, such as all-weather and all-day three-dimensional terrain surveying and mapping, target positioning and identification, information acquisition and the like.
At present, most of array SAR three-dimensional imaging processing algorithms adopt an equidistant slicing processing idea. For example, in order to improve the processing efficiency of array SAR three-dimensional imaging, the array SAR rapid three-dimensional imaging is realized by adopting the distance direction-along course-tangential course dimension division, the specific algorithms comprise a three-dimensional distance-Doppler (RD) algorithm, a three-dimensional variable scale (CS) algorithm and the like, and the algorithm can be essentially equivalent to a three-dimensional imaging processing process of distance compression imaging and equidistant plane imaging (along course-tangential course plane), and is detailed in the document "Ztonghao. For another example, for sparse three-dimensional imaging processing of an array SAR, such as a spectral estimation imaging algorithm or a compressive sensing imaging algorithm, in order to facilitate sparse imaging model construction and reduce sparse reconstruction computation, it is generally required to divide array SAR three-dimensional echo data into a plurality of equidistant slices, and then perform individual imaging processing on each piece of equidistant slice data, which is described in the document "wecisn. However, for the array SAR equidistant slice three-dimensional imaging, all equidistant targets in a three-dimensional observation scene are projected onto a certain equidistant slice in a three-dimensional imaging space, so that the three-dimensional imaging result and the real three-dimensional observation scene usually have severe geometric distortion. In order to more accurately reflect the target distribution of the three-dimensional observation scene, the geometric distortion correction needs to be carried out on the three-dimensional imaging result of the equidistant slice of the array SAR.
To date, for geometric distortion correction of a conventional SAR two-dimensional image, a related scholarly has proposed various geometric correction algorithms, which mainly implement geometric correction by means of external DEM data, trajectory data, calibration point positions, and the like. For example, in the DEM analog image correction method, an SAR orbit data and an observed terrain digital elevation model are generally used to generate an analog SAR image, and a coordinate difference value of a same-name point between the analog image and a real image is automatically obtained by an image matching method, so as to realize geometric correction of the SAR image, which is described in the document entitled "a quasi-automatic method for geometric correction based on image simulation [ J ] the remote sensing academic report 2003,7(2):106 + 111". For example, a distance-doppler model correction method is used for realizing geometric correction of the SAR image by establishing a distance-doppler equation under an SAR motion model and estimating position offset of a calibration point by using the distance-doppler model, which is detailed in a literature of < J > Radar report of spaceborne SAR geometry based on a continuous motion model, 2013,2(1):54-59 >. And as for a statistical model geometric correction method, aiming at adverse factors such as incapability of accurately obtaining a DEM corresponding to the SAR image, a correction scheme decision model is established by utilizing prior conditions to realize geometric correction of the SAR image from the principle of generating geometric distortion and the essence of a correction process. However, conventional SAR two-dimensional imaging geometric distortion correction usually requires observation of a terrain DEM, prior information, or a calibration point position, and the like as a premise, and when these preconditions are not satisfied, it is difficult to realize SAR image geometric correction. In addition, compared with the traditional SAR two-dimensional imaging, the array SAR three-dimensional imaging system has obvious differences in the aspects of imaging mode, image dimension, geometric distortion characteristics and the like, and the traditional SAR two-dimensional imaging geometric distortion correction method is used for geometric distortion correction of the array SAR three-dimensional imaging and is difficult to obtain a satisfactory geometric correction effect.
In order to overcome the defect of the existing SAR geometric correction method in array SAR equidistant slice three-dimensional imaging, a new geometric correction method suitable for the array SAR is provided by combining the geometric distortion characteristic of the array SAR equidistant slice three-dimensional imaging, and the geometric distortion correction processing of the array SAR three-dimensional image is realized.
Disclosure of Invention
The invention provides an array SAR (synthetic aperture radar) equidistant slice imaging geometric distortion correction method, which is based on an array SAR downward-looking or side-looking imaging geometric model and an equidistant slice three-dimensional imaging principle, and comprises the steps of firstly calculating the slant range from an antenna of an array SAR imaging system to each unit of an equidistant slice, then estimating the offset of each unit of the equidistant slice according to the slant range, and finally carrying out interpolation resampling on the offset and image unit offset, thereby realizing the imaging geometric distortion correction processing of the array SAR equidistant slice. The method has the characteristics of no need of observing scene DEM prior information, quick geometric correction processing and the like, and can be suitable for correcting the geometric distortion of the three-dimensional imaging of the array SAR equidistant slice under the condition of sparse array.
For the convenience of describing the present invention, the following terms are first defined:
The array synthetic aperture radar imaging is a synthetic aperture radar technology which fixes a linear array antenna on a load motion platform and is vertical to the motion direction of the platform, combines the motion of the motion platform to synthesize a two-dimensional plane array to realize array plane two-dimensional imaging, and then utilizes the radar beam direction echo delay to realize distance one-dimensional imaging, thereby realizing the three-dimensional imaging of an observation target, and the technology is shown in documents of' Liuzhang, Wang Jing, Nidoku, and the like.
Definition 2, standard SINC interpolation resampling method
The standard SINC interpolation resampling method is a classic interpolation resampling method for performing interpolation resampling on data to be processed in a SINC function interpolation mode, and is detailed in a literature that 'several interpolation algorithms in a Yuweidong, Wushumei, distance-Doppler method are compared to [ J ]. Electron and informatics, 2001,23(3): 308-312'.
Definitions 3, Standard image Unit position offset method
The standard image cell position shift method refers to a method for shifting cells in an image according to a certain shift amount, and is described in documents "liu kui fang, wang fortune qiong, cinnarizine.
The invention provides a geometric distortion correction method for array SAR (synthetic aperture radar) equidistant slice imaging, which comprises the following steps of: step 1, initializing array SAR imaging system parameters required by geometric distortion correction:
initializing array SAR imaging system parameters required for geometric distortion correction, comprising: an observation space of the array SAR is a ground three-dimensional coordinate system and is marked as X-Y-Z, wherein X represents a horizontal plane horizontal axis, Y represents a horizontal plane longitudinal axis, and Z represents a horizontal vertical axis; the array SAR imaging system performs uniform linear motion along the parallel direction of the Y axis; reference position of array SAR imaging system antenna, noted as PTAnd P isT＝(xT,yT,zT) Wherein x isTIs expressed as the reference position of the antenna on the X axis, yTIs expressed as the reference position of the antenna in the Y-axis, zTRecording as the reference position of the antenna on the Z axis; recording the radar incident angle of the array SAR imaging system as theta; according to the array SAR imaging system and the observation scheme, the position parameters of the initialized array SAR imaging system required by the invention are known;
step 2, initializing image parameters of the array SAR equidistant slice three-dimensional imaging:
initializing image parameters of array SAR equidistant slice three-dimensional imaging, comprising the following steps: the equidistant slice three-dimensional imaging space of the array SAR is a horizontal plane transverse axis, a horizontal plane longitudinal axis and an arrayA three-dimensional space formed by the SAR distance directions is recorded as X-Y-R, wherein the horizontal plane horizontal axis and the vertical axis of the imaging space are the same as the horizontal plane horizontal axis and the vertical axis of the observation space in the step 1, and R represents the distance direction of the imaging space; three-dimensional images corresponding to array SAR equidistant slice three-dimensional imaging are marked as I0(i, j, k); wherein i, j, k are natural numbers respectively, and i is 1,2, …, NX，j＝1,2,…,NY，k＝1,2,…,NRI is marked as a three-dimensional image I0(I, j, k) in the ith cell of horizontal axis X, j is marked as three-dimensional image I0(I, j, k) in the jth cell of the horizontal vertical axis Y, k being denoted as the three-dimensional image I0(i, j, k) the k-th cell in the distance direction R, NX、NYAnd NRRespectively marked as three-dimensional images I0(I, j, k) total number of cells in horizontal axis, horizontal vertical axis and distance direction, three-dimensional image I0The dimension of (i, j, k) is NX×NY×NR(ii) a Three-dimensional image I0(I, j, k) the two-dimensional image corresponding to the k-th distance direction is marked as Ik(i,j)，k＝1,2,…,NRIn which IkThe dimension of (i, j) being NX×NY，Ik(I, j) is also referred to as I0(ii) the kth equidistant slice of (i, j, k); three-dimensional image I0(i, j, k) the distances between adjacent units in the horizontal plane horizontal axis, horizontal plane vertical axis and distance direction are respectively marked as dx, dy and dr; the kth equidistant slice Ik(i, j) the position of the unit corresponding to the ith horizontal axis and the jth vertical axis is denoted as Qk(i,j)，i＝1,2,…,NX，j＝1,2,…,NY，k＝1,2,…,NR(ii) a The kth equidistant slice Ik(i, j) center of reference position, denoted as Ok，k＝1,2,…,NR(ii) a According to the processing scheme of the array SAR equidistant slice three-dimensional imaging, all image parameters required for initializing the array SAR equidistant slice three-dimensional imaging are known;
step 3, calculating the slant distance from the array SAR antenna to the image unit:
by the formula Rk(i,j)＝||PT-Qk(i,j)||2And calculating to obtain the k-th equidistant slice I from the array SAR antennakSkewing of all cells in (i, j)Distance, denoted as Rk(i,j)，i＝1,2,…,NX，j＝1,2,…,NY，k＝1,2,…,NRWherein P isTReference position, Q, of the array SAR imaging system antenna obtained for the initialization of step 1k(I, j) is the k equidistant slice I obtained by initializing in step 2k(i, j) the ith horizontal axis and the jth vertical axis in the lighting unit correspond to the positions of the units, | · | ceiling2An L2 norm operator notation representing a vector; by the formula R0(k)＝||Ok-PT||2Calculating to obtain the k-th equidistant slice I from the array SAR antennak(i, j) reference slope distance, denoted as R0(k)，k＝1,2,…,NRIn which O iskInitializing the k equidistant slice I obtained in step 2k(i, j) a reference location center;
and 4, calculating the relative position offset of all units of the equidistant slice:
using formula Dk(i,j)＝[Rk(i,j)-R0(k)]D, calculating to obtain the kth equidistant slice IkThe relative position offset of all the cells in (i, j) is denoted as Dk(i,j)，i＝1,2,…,NX，j＝1,2,…,NY，k＝1,2,…,NRWherein dr is the three-dimensional image I obtained by initialization in the step 20(i, j, k) adjacent cell pitch in the direction of distance, Rk(I, j) is the k-th equidistant slice I from the array SAR antenna obtained in the step 3kSlope of all cells in (i, j), R0(k) Slicing the array SAR antenna obtained in the step 3 to the kth equidistant slice Ik(ii) a reference slope distance of (i, j);
using the standard image cell position shift method, for IkAll cells in (i, j) are offset by an amount Dk(i, j) performing position offset to obtain the kth equidistant slice after the position offset, and recording the k equidistant slice as
i＝1,2,…,NX，j＝1,2,…,NY，k＝1,2,…,NRIn which Ik(I, j) is the three-dimensional image I initialized in the step 20The kth equidistance slice in (i, j, k), Dk(I, j) is the k equidistant slice I obtained in step 4k(i, j) the relative positional offsets of all the cells in (i, j);
step 6, slicing at equal intervals to synthesize a three-dimensional image:
using a formula
Calculating to obtain an array SAR three-dimensional image, and marking as IS(i,j,k)，i＝1,2,…,NX，j＝1,2,…,NY，k＝1,2,…,NRWherein
For the 1 st equidistant slice after the position offset obtained in step 5,
for the 2 nd equidistant slice after the position offset obtained in step 5,
for the Nth position after the position deviation obtained in the step 5RSlicing at equal intervals;
and 7, carrying out interpolation resampling on the three-dimensional image:
three-dimensional image I by adopting standard SINC function interpolation resampling methodS(I, j, k) performing interpolation resampling to obtain an array SAR three-dimensional image marked as I 'after interpolation resampling'S(i,j,l)，i＝1,2,…,NX，j＝1,2,…,NY，l＝1,2,…,NZIn which N isZRecording the three-dimensional image I 'after interpolation resampling'S(I, j, l) the total number of cells on the horizontal plane vertical axis Z, l being a natural number, l being represented by a three-dimensional video I'S(I, j, l) the first unit in the horizontal plane vertical axis Z, IS(i, j, k) is the array SAR three-dimensional image obtained in the step 6;
and 8, performing horizontal and vertical axis correction on the three-dimensional image:
subjecting the product obtained in step 7 toVitamin I's'SMultiplying the position value of (I, j, l) on the horizontal vertical axis Z by 1/(1+ cos (theta)), obtaining the array SAR three-dimensional image after horizontal and vertical axis correction, and recording the three-dimensional image as IF(i,j,l)，i＝1,2,…,NX，j＝1,2,…,NY，l＝1,2,…,NZWherein θ is the radar incidence angle of the array SAR imaging system initialized in the step 1, and cos (·) is a cosine function symbol; i isFAnd (i, j, l) is the final image after the array SAR equidistant slice three-dimensional imaging geometric correction.
The invention has the innovation point that the geometric relation between an array SAR system and an equidistant slice three-dimensional imaging image is utilized, and the method for correcting the geometric distortion of the equidistant slice imaging of the array SAR is provided.
The method has the advantages of simple realization, high efficiency, high precision and good applicability, does not need prior information such as DEM (digital elevation model) of the known observation three-dimensional observation scene, and can effectively solve the problem of geometric distortion correction of the equidistant slice imaging of the array SAR.
Drawings
FIG. 1 is a schematic block diagram of a process flow of a method provided by the present invention;
FIG. 2 is a table of simulation parameters for an array SAR system according to an embodiment of the present invention;
Detailed Description
The invention mainly adopts a simulation experiment method for verification, and all steps and conclusions are verified to be correct on MATLABR2016 b. The specific implementation steps are as follows:
initializing array SAR imaging system parameters required for geometric distortion correction, comprising: an observation space of the array SAR is a ground three-dimensional coordinate system and is marked as X-Y-Z, wherein X represents a horizontal plane horizontal axis, Y represents a horizontal plane longitudinal axis, and Z represents a horizontal vertical axis; the array SAR imaging system performs uniform linear motion along the parallel direction of the Y axis; array SAR imaging system skyReference position of the line, denoted PT＝[3000,0,3000]m, wherein the antenna is at a reference position X of the X-axisT3000m, reference position Y of the antenna on the Y axisT0m, reference position Z of the antenna on the Z-axisT3000 m; the radar incidence angle theta of the array SAR imaging system is 45 degrees;
step 2, initializing image parameters of the array SAR equidistant slice three-dimensional imaging:
initializing image parameters of array SAR equidistant slice three-dimensional imaging, comprising the following steps: the equidistant slice three-dimensional imaging space of the array SAR is a three-dimensional space formed by a horizontal plane transverse axis, a horizontal plane longitudinal axis and an array SAR distance direction, and is marked as X-Y-R, wherein the horizontal plane transverse axis and the horizontal plane longitudinal axis of the imaging space are the same as the horizontal plane transverse axis and the horizontal plane longitudinal axis of the observation space in the step 1, and R represents the distance direction of the imaging space; three-dimensional images corresponding to array SAR equidistant slice three-dimensional imaging are marked as I0(i, j, k); where I, j, and k are natural numbers, and I1, 2, …,100, j 1,2, …,100, k 1,2, …,512, I is a three-dimensional image I0(I, j, k) in the ith cell of horizontal axis X, j is marked as three-dimensional image I0(I, j, k) in the jth cell of the horizontal vertical axis Y, k being denoted as the three-dimensional image I0(I, j, k) in the kth cell in the distance direction R, three-dimensional image I0(i, j, k) the total number of cells in the horizontal axis, the horizontal vertical axis and the distance direction is NX＝100、NY100 and NR512, three-dimensional image I0The dimension of (i, j, k) is 100 × 100 × 512; three-dimensional image I0(I, j, k) the two-dimensional image corresponding to the k-th distance direction is marked as Ik(I, j), k ═ 1,2, …,512, where IkDimension of (I, j) 100X 100, Ik(I, j) is also referred to as I0(ii) the kth equidistant slice of (i, j, k); three-dimensional image I0(i, j, k) adjacent cell pitches in horizontal plane horizontal axis, horizontal plane vertical axis and distance direction are dx ═ 5m, dy ═ 5m and dr ═ 1m, respectively; the kth equidistant slice Ik(i, j) the ith horizontal axis and the jth vertical axis correspond to the position Q of the cellk(i,j)＝[(i-50)dx,(j-50)dy,(k-256)dr]m, i ═ 1,2, …,100, j ═ 1,2, …,100, k ═ 1,2, …, 512; the kth equidistant slice Ik(i, j) reference position center Ok＝[0,0,(k-256)dr]m，k＝1,2,…,512；
Step 3, calculating the slant distance from the array SAR antenna to the image unit:
by the formula Rk(i,j)＝||PT-Qk(i,j)||2And calculating to obtain the k-th equidistant slice I from the array SAR antennakThe slope of all the cells in (i, j) is denoted as Rk(i, j), i ═ 1,2, …,100, j ═ 1,2, …,100, k ═ 1,2, …,512, where P isTObtaining the reference position P of the array SAR imaging system antenna for the initialization of the step 1T＝[3000,0,3000]m，Qk(I, j) is the k equidistant slice I obtained by initializing in step 2k(i, j) the ith horizontal axis and the jth vertical axis correspond to the position Q of the cellk(i,j)＝[(i-50)dx,(j-50)dy,(k-256)dr]m，||·||2An L2 norm operator notation representing a vector; by the formula R0(k)＝||Ok-PT||2Calculating to obtain the k-th equidistant slice I from the array SAR antennak(i, j) reference slope distance, denoted as R0(k) K is 1,2, …,512, wherein OkInitializing the k equidistant slice I obtained in step 2k(i, j) reference position center Ok＝[0,0,(k-256)dr]m；
And 4, calculating the relative position offset of all units of the equidistant slice:
using formula Dk(i,j)＝[Rk(i,j)-R0(k)]D, calculating to obtain the kth equidistant slice IkThe relative position offset of all the cells in (i, j) is denoted as Dk(I, j), I is 1,2, …,100, j is 1,2, …,100, k is 1,2, …,512, where dr is the three-dimensional image I initialized in step 20(i, j, k) adjacent cell pitch in the direction of distance, Rk(I, j) is the k-th equidistant slice I from the array SAR antenna obtained in the step 3kSlope of all cells in (i, j), R0(k) Slicing the array SAR antenna obtained in the step 3 to the kth equidistant slice Ik(ii) a reference slope distance of (i, j);
using standard picture elementsPosition shift method, pair IkAll cells in (i, j) are offset by an amount Dk(i, j) performing position offset to obtain the kth equidistant slice after the position offset, and recording the k equidistant slice as
I-1, 2, …,100, j-1, 2, …,100, k-1, 2, …,512, wherein Ik(I, j) is the three-dimensional image I initialized in the step 20The kth equidistance slice in (i, j, k), Dk(I, j) is the k equidistant slice I obtained in step 4k(i, j) the relative positional offsets of all the cells in (i, j);
step 6, slicing at equal intervals to synthesize a three-dimensional image:
using a formula
Calculating to obtain an array SAR three-dimensional image, and marking as IS(i, j, k), i ═ 1,2, …,100, j ═ 1,2, …,100, k ═ 1,2, …,512, where
For the 1 st equidistant slice after the position offset obtained in step 5,
for the 2 nd equidistant slice after the position offset obtained in step 5,
for the Nth position after the position deviation obtained in the step 5RSlicing at equal intervals;
and 7, carrying out interpolation resampling on the three-dimensional image:
three-dimensional image I by adopting standard SINC function interpolation resampling methodS(I, j, k) performing interpolation resampling to obtain an array SAR three-dimensional image marked as I 'after interpolation resampling'S(I, j, l), I ═ 1,2, …,100, j ═ 1,2, …,100, l ═ 1,2, …,1024, where the resampled three-dimensional image I 'is interpolated'S(i, j, l) total number of cells N in horizontal plane vertical axis ZZ1024, l isThe natural number l is a three-dimensional video I'S(I, j, l) the first unit in the horizontal plane vertical axis Z, IS(i, j, k) is the array SAR three-dimensional image obtained in the step 6;
and 8, performing horizontal and vertical axis correction on the three-dimensional image:
obtaining the three-dimensional image I 'obtained in the step 7'SMultiplying the position value of (I, j, l) on the horizontal vertical axis Z by 1/(1+ cos (theta)), obtaining the array SAR three-dimensional image after horizontal and vertical axis correction, and recording the three-dimensional image as IF(i, j, l), i is 1,2, …,100, j is 1,2, …,100, l is 1,2, …,1024, where θ is the radar incident angle θ of the array SAR imaging system initialized in step 1 is 45 °, and cos (·) is the sign of the cosine function; i isFAnd (i, j, l) is the final image after the array SAR equidistant slice three-dimensional imaging geometric correction.
Claims (1)
1. A geometric distortion correction method for array SAR equidistant slice imaging is characterized by comprising the following steps:
step 1, initializing array SAR imaging system parameters required by geometric distortion correction:
initializing array SAR imaging system parameters required for geometric distortion correction, comprising: an observation space of the array SAR is a ground three-dimensional coordinate system and is marked as X-Y-Z, wherein X represents a horizontal plane horizontal axis, Y represents a horizontal plane longitudinal axis, and Z represents a horizontal vertical axis; the array SAR imaging system performs uniform linear motion along the parallel direction of the Y axis; reference position of array SAR imaging system antenna, noted as PTAnd P isT＝(xT,yT,zT) Wherein x isTIs expressed as the reference position of the antenna on the X axis, yTIs expressed as the reference position of the antenna in the Y-axis, zTRecording as the reference position of the antenna on the Z axis; recording the radar incident angle of the array SAR imaging system as theta; according to the array SAR imaging system and the observation scheme, the position parameters of the initialized array SAR imaging system are known;
step 2, initializing image parameters of the array SAR equidistant slice three-dimensional imaging:
initializing image parameters of array SAR equidistant slice three-dimensional imaging, comprising the following steps: equidistance of array SARThe slice three-dimensional imaging space is a three-dimensional space formed by a horizontal plane transverse axis, a horizontal plane longitudinal axis and an array SAR distance direction and is marked as X-Y-R, wherein the horizontal plane transverse axis and the horizontal plane longitudinal axis of the imaging space are the same as the horizontal plane transverse axis and the horizontal plane longitudinal axis of the observation space in the step 1, and R represents the distance direction of the imaging space; three-dimensional images corresponding to array SAR equidistant slice three-dimensional imaging are marked as I0(i, j, k); wherein i, j, k are natural numbers respectively, and i is 1,2, …, NX，j＝1,2,…,NY，k＝1,2,…,NRI is marked as a three-dimensional image I0(I, j, k) in the ith cell of horizontal axis X, j is marked as three-dimensional image I0(I, j, k) in the jth cell of the horizontal vertical axis Y, k being denoted as the three-dimensional image I0(i, j, k) the k-th cell in the distance direction R, NX、NYAnd NRRespectively marked as three-dimensional images I0(I, j, k) total number of cells in horizontal axis, horizontal vertical axis and distance direction, three-dimensional image I0The dimension of (i, j, k) is NX×NY×NR(ii) a Three-dimensional image I0(I, j, k) the two-dimensional image corresponding to the k-th distance direction is marked as Ik(i,j)，k＝1,2,…,NRIn which IkThe dimension of (i, j) being NX×NY，Ik(I, j) is also referred to as I0(ii) the kth equidistant slice of (i, j, k); three-dimensional image I0(i, j, k) the distances between adjacent units in the horizontal plane horizontal axis, horizontal plane vertical axis and distance direction are respectively marked as dx, dy and dr; the kth equidistant slice Ik(i, j) the position of the unit corresponding to the ith horizontal axis and the jth vertical axis is denoted as Qk(i,j)，i＝1,2,…,NX，j＝1,2,…,NY，k＝1,2,…,NR(ii) a The kth equidistant slice Ik(i, j) center of reference position, denoted as Ok，k＝1,2,…,NR(ii) a According to the processing scheme of the array SAR equidistant slice three-dimensional imaging, all image parameters for initializing the array SAR equidistant slice three-dimensional imaging are known;
step 3, calculating the slant distance from the array SAR antenna to the image unit:
by the formula Rk(i,j)＝||PT-Qk(i,j)||2And calculating to obtain the equal distance from the array SAR antenna to the kthSection IkThe slope of all the cells in (i, j) is denoted as Rk(i,j)，i＝1,2,…,NX，j＝1,2,…,NY，k＝1,2,…,NRWherein P isTReference position, Q, of the array SAR imaging system antenna obtained for the initialization of step 1k(I, j) is the k equidistant slice I obtained by initializing in step 2k(i, j) the ith horizontal axis and the jth vertical axis in the lighting unit correspond to the positions of the units, | · | ceiling2An L2 norm operator notation representing a vector; by the formula R0(k)＝||Ok-PT||2Calculating to obtain the k-th equidistant slice I from the array SAR antennak(i, j) reference slope distance, denoted as R0(k)，k＝1,2,…,NRIn which O iskInitializing the k equidistant slice I obtained in step 2k(i, j) a reference location center;
and 4, calculating the relative position offset of all units of the equidistant slice:
using formula Dk(i,j)＝[Rk(i,j)-R0(k)]D, calculating to obtain the kth equidistant slice IkThe relative position offset of all the cells in (i, j) is denoted as Dk(i,j)，i＝1,2,…,NX，j＝1,2,…,NY，k＝1,2,…,NRWherein dr is the three-dimensional image I obtained by initialization in the step 20(i, j, k) adjacent cell pitch in the direction of distance, Rk(I, j) is the k-th equidistant slice I from the array SAR antenna obtained in the step 3kSlope of all cells in (i, j), R0(k) Slicing the array SAR antenna obtained in the step 3 to the kth equidistant slice Ik(ii) a reference slope distance of (i, j);
step 5, carrying out position offset on the equal distance slicing units point by point:
using the standard image cell position shift method, for IkAll cells in (i, j) are offset by an amount Dk(i, j) performing position offset to obtain the kth equidistant slice after the position offset, and recording the k equidistant slice as
i＝1,2,…,NX，j＝1,2,…,NY，k＝1,2,…,NRIn which Ik(I, j) is the three-dimensional image I initialized in the step 20The kth equidistance slice in (i, j, k), Dk(I, j) is the k equidistant slice I obtained in step 4k(i, j) the relative positional offsets of all the cells in (i, j);
step 6, slicing at equal intervals to synthesize a three-dimensional image:
using a formula
Calculating to obtain an array SAR three-dimensional image, and marking as IS(i,j,k)，i＝1,2,…,NX，j＝1,2,…,NY，k＝1,2,…,NRWherein
For the 1 st equidistant slice after the position offset obtained in step 5,
for the 2 nd equidistant slice after the position offset obtained in step 5,
for the Nth position after the position deviation obtained in the step 5RSlicing at equal intervals;
and 7, carrying out interpolation resampling on the three-dimensional image:
three-dimensional image I by adopting standard SINC function interpolation resampling methodS(I, j, k) performing interpolation resampling to obtain an array SAR three-dimensional image marked as I 'after interpolation resampling'S(i,j,l)，i＝1,2,…,NX，j＝1,2,…,NY，l＝1,2,…,NZIn which N isZRecording the three-dimensional image I 'after interpolation resampling'S(I, j, l) the total number of cells on the horizontal plane vertical axis Z, l being a natural number, l being represented by a three-dimensional video I'S(I, j, l) the first unit in the horizontal plane vertical axis Z, IS(i, j, k) is the array SAR three-dimensional image obtained in the step 6;
and 8, performing horizontal and vertical axis correction on the three-dimensional image:
obtaining the three-dimensional image I 'obtained in the step 7'SMultiplying the position value of (I, j, l) on the horizontal vertical axis Z by 1/(1+ cos (theta)), obtaining the array SAR three-dimensional image after horizontal and vertical axis correction, and recording the three-dimensional image as IF(i,j,l)，i＝1,2,…,NX，j＝1,2,…,NY，l＝1,2,…,NZWherein θ is the radar incidence angle of the array SAR imaging system initialized in the step 1, and cos (·) is a cosine function symbol; i isFAnd (i, j, l) is the final image after the array SAR equidistant slice three-dimensional imaging geometric correction.
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