CN115100243A - Ground moving target detection and tracking method based on sequential SAR image - Google Patents
Ground moving target detection and tracking method based on sequential SAR image Download PDFInfo
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Abstract
The invention discloses a ground moving target detection and tracking method based on sequential SAR images, which provides a high-performance processing algorithm for a ground detection mode of an airborne radar, an unmanned aerial vehicle imaging radar and a geographic mapping radar, and can effectively improve the detection and positioning performance of a moving target with unknown information; the method provides a new ground moving target tracking technology, so that the ground sensing and detecting capabilities of an airborne radar, an unmanned aerial vehicle imaging radar and a geographic mapping radar are greatly improved; the method provides a high-precision ground unknown information moving target tracking and positioning processing method for an airborne radar, an unmanned aerial vehicle imaging radar and a geographic mapping radar, breaks through the key technology of accurate tracking of an unknown moving target, and provides technical support for accurate positioning and tracking of a moving target in a dynamic environment; besides the airborne radar, the method also provides a SAR-GMTI processing solution for the detection and tracking of moving targets of other fields such as the satellite-borne radar.
Description
Technical Field
The invention relates to an airborne radar ground sensing technology, in particular to a ground moving target detection and tracking method based on sequential SAR images.
Background
The multi-channel Synthetic Aperture Radar (SAR) has the capability of realizing two-dimensional high-resolution imaging under all-weather conditions, and in the fields of military application, traffic monitoring and the like, the multi-channel SAR has the capability of detecting a Ground Moving Target, namely Ground Moving Target Indication (GMTI), besides acquiring a high-resolution SAR image, and a plurality of national scientific research institutions have developed research and tests on SAR-GMTI technology. The multi-channel SAR-GMTI system can effectively utilize information among channels, effectively suppress clutter and retain moving target information, and meanwhile provides more degrees of freedom for speed measurement and positioning of moving targets.
Currently, commonly used multi-channel SAR-GMTI techniques mainly include a Phase-centered Antenna (DPCA) technique, an Along-Track interference (ATI) technique, and a Space Time Adaptive Processing (STAP) technique. However, the processing technology based on the SAR-GMTI can only obtain a detection result of a moving target once, namely only one trace point is obtained, and the moving target cannot be tracked, unless a beam-bunching working mode is adopted along with the movement of the platform.
The prior art closest to the patent is published in a video SAR moving target imaging algorithm in a remote sensing and remote measuring journal, and provides a method for imaging a video SAR moving target based on a polar coordinate algorithm, which can realize imaging and detection of a ground moving target in a bunching mode. However, the prior art is only used in the beamforming SAR mode, the application scenario is usually small, and the moving target detection and tracking cannot be performed on a large-area ground scenario or an interested area.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a ground moving target detection and tracking method based on sequential SAR images, which is applied to a strip imaging mode, completes the detection, positioning and track association of a ground moving target aiming at a large scene and realizes the tracking of an unknown moving target.
The technical scheme is as follows: the invention relates to a ground moving target detection and tracking method based on sequential SAR images, which comprises the following steps:
(1) design a multi-channel joint adaptive clutter suppressor w opt ＝μR -1 a(v r ) Performing clutter suppression on data of 1 to n channels, wherein R (i, j) ═ E { Z (i, j) Z H (i, j) } is a multi-channel joint data covariance matrix,
a multi-channel joint data vector composed of data at (i, j) coordinate positions of 1-n channels;
(2) designing a two-dimensional constant false alarm detector, detecting a moving target according to a result after clutter suppression, and judging that the target is detected at the (i, j) coordinate position in the image when the amplitude S (i, j) of each detection unit simultaneously meets the following five conditions:
S(i,j)≥K 1 S cv (i,j)
S(i,j)≥K 2 S cv (i,j-1)
S(i,j)≥K 2 S cv (i,j+1)
S(i,j)≥K 2 S cv (i-1,j)
S(i,j)≥K 2 S cv (i+1,j)
wherein S is cv (i, j) is the two-dimensional clutter background level, K 1 、K 2 Is a constant coefficient;
(3) motion parameter estimation, including radial velocity, is performed on the detected moving objects one by one
Velocity in azimuth direction
And azimuth position
Wherein Δ φ, λ, v a 、d、R 0 、
Respectively obtaining interference phase, wavelength, platform flight speed, channel spacing, slope distance and frequency modulation rate estimated values;
(4) SAR imaging is carried out on the data of the channel 1 to obtain a sequential image 1, and a moving target point trace is superposed on the image;
(5) re-selecting echo data of 1-n channels according to a certain time delay interval, repeating the steps (1) to (4) to obtain M sequential SAR images of the target point track of the superimposed motion;
(6) locking and registering the sequential SAR images of the M overlapped motion target point tracks by using a designed sequential SAR image tracking and locking technology shown in figure 2;
(7) and according to the flow designed by the attached figure 3, performing point/track association processing on the motion target point track in the M sequential SAR images after locking and registration to obtain the motion target track.
A computer storage medium having stored thereon a computer program which, when executed by a processor, implements a sequential SAR image-based ground moving object detection and tracking method as described above.
A computer device comprises a storage, a processor and a computer program stored on the storage and capable of running on the processor, wherein the processor executes the computer program to realize the ground moving target detection and tracking method based on the sequential SAR images.
Has the advantages that: compared with the prior art, the invention has the following advantages:
1. the invention provides a high-performance processing algorithm for the ground detection mode of the airborne radar, the unmanned aerial vehicle imaging radar and the geographic mapping radar, and can effectively improve the detection, positioning and tracking performance of the moving target with unknown information;
2. the invention provides a novel ground moving target tracking technology, which greatly improves the ground sensing and detecting capabilities of an airborne radar, an unmanned aerial vehicle imaging radar and a geographic mapping radar;
3. the invention provides a processing method for tracking and positioning a moving target of high-precision ground unknown information for an airborne radar, an unmanned aerial vehicle imaging radar and a geographical mapping radar, breaks through the key technology of accurately tracking the unknown moving target, and provides technical support for accurately positioning and tracking the moving target in a dynamic environment;
4. besides the airborne radar, the invention also provides a SAR-GMTI processing solution for the detection and tracking of moving targets in other fields such as the satellite-borne radar.
Drawings
FIG. 1 is a schematic diagram of a three-channel SAR-GMTI;
FIG. 2 is a flow chart of steps of a sequential SAR image tracking locking technique;
FIG. 3 is a flowchart illustrating steps of a sequential SAR image-based moving target detection and tracking method;
FIG. 4 is a sequential SAR image and a moving target detection result;
fig. 5 shows the result of reconstructing the moving object trajectory.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
A ground moving target detection and tracking method based on sequential SAR images comprises the following steps:
(1) signal modeling
FIG. 1 is a geometric diagram of a ground moving object and an airborne platform. Wherein v is a The speed of the carrier, t is the slow time of the azimuth, P is the ground moving target and the coordinate is (x) 0 ,y 0 ,0)，v r 、v y And v x Respectively radial velocity, range velocity and azimuth velocity of the target, a, B, C being the phase centers of the three channels.
Taking a three-channel ATI method as an example, the interference processing is performed to obtain the interference phase delta phi of the moving target through the cancellation images of AB and BC, and the radial speed of the moving target can be obtained through the interference phase as follows:
the azimuth offset is thus obtained as:
because the azimuth velocity of the moving target can cause defocusing of the moving target, the azimuth velocity can be solved by estimating the Doppler frequency modulation of the moving target, and if the frequency modulation slope is estimated, the azimuth velocity is obtained
The relation between the azimuth speed and the frequency modulation slope of the moving target is as follows:
the moving target azimuth velocity estimation can be obtained:
the radial velocity and the azimuth velocity of the ground moving target are accurately estimated, so that the motion velocity vector of the target can be obtained as follows:
wherein
And
the estimated radial velocity and the estimated azimuth velocity are respectively, and theta is an included angle between a velocity vector and the radial velocity.
(2) Sequential SAR image moving target detection and tracking
When the system is in a strip working mode, after SAR imaging is carried out on the moment of irradiating the moving target, only one-time trace point information of the moving target can be obtained, the track of the moving target cannot be obtained, and the track information of the moving target is more important for target track prediction and target intention judgment.
Further analysis shows that if the azimuth aperture width of the transmitting antenna is D, the equivalent 3dB azimuth beam width is theta 3dB When SAR-GMTI processing is performed, in order to reduce the influence of distance walking due to the motion of a moving object, an imaging method with a short synthetic aperture time, such as demamp, is usually selected, and if the number of accumulated points corresponding to the synthetic aperture time satisfying the resolution required for SAR-GMTI is Num single And when two adjacent images are imaged, no data overlap exists, the number of sequential SAR images that can be obtained within the whole beam irradiation range is:
wherein Num is the total number of pulses in the irradiation range of the azimuth beam, Ls is the synthetic aperture length corresponding to the irradiation range of the whole azimuth beam, and R 0 PRF is the repetition frequency, distance of action.
And (2) carrying out moving target detection and positioning treatment introduced in the step (1) on the sequential multi-channel SAR obtained according to the time sequence, so as to obtain the moving target point trace information in each sequential SAR image.
(3) Sequential SAR image tracking locking technology
FIG. 2 is a flow chart of a sequential SAR image tracking lock-in technique process, which is based on an R-D model. The R-D model consists of three equations in total:
a distance equation, a doppler shift equation, and an earth data model. h is a point P on the ground to
The normal distance of the oblate ellipsoid is indicated. The solution of the distance equation and the Doppler shift equation must be established by taking the ellipsoid as the referenceAbove the coordinate frame of (a). The point coordinates thus determined
Also in this coordinate frame.
The processing flow of the sequential SAR image tracking locking technology shown in the attached figure 2 comprises two steps:
1) taking the first image as a reference, taking the center of the platform as an origin, obtaining the longitude and latitude of a reference point in the SAR image according to parameters such as the longitude and latitude, the acting distance, the Doppler, the track angle and the like of the radar platform, and selecting a road where a concerned moving target is located as a reference point for registration in GMTI application;
2) and then finding a corresponding point in the sequential SAR image according to the latitude and longitude of the reference point of the first image, and intercepting a part corresponding to the scene of the first image by taking the point as the center of the sequential image.
Wherein the in-process registration comprises a transformation of a plurality of coordinate systems: image plane coordinate system → flight coordinate system rotation, flight coordinate system → northeast sky coordinate system, northeast sky coordinate system → geocentric space rectangular coordinate system, geocentric space rectangular coordinate system → space geodetic coordinate system. For the multi-channel SAR-GMTI system in the strip mode, large angle rotation does not exist between the obtained sequential SAR images, and the coordinate transformation can be relatively simplified.
(4) Correlation processing technology for moving target point track and flight track
1) Trace-point preprocessing
There is a strong correlation between the observed data of the true target echo in the sequential images and a false alarm is not. Therefore, the real target and the false alarm can be discriminated by using the characteristic, the point trace signal meeting a certain judgment condition can be used as the real target by using the space geometric characteristic of the trace data of the real target point, the correlation between the amplitude and the phase, the distance of the target, the consistency of Doppler information and the like as the judgment condition, and the information is extracted for further processing.
2) Point track and flight track joint correlation processing
The joint correlation processing of the point track and the flight track is to perform optimal correlation processing on the established flight track and the newly found point track, so that the phenomenon of flight track splitting caused by missing correlation and the phenomenon of flight track error fusion caused by error correlation are avoided as much as possible.
Fig. 3 shows a complete processing flow of the moving target detection and tracking technology based on the sequential SAR image.
(5) Test verification
And (4) carrying out test verification by using the measured data of the four channels SAR-GMTI of a certain airborne radar. The speed of the carrier is 120 m/s. The range of action is 60 km. 3 cooperative targets are arranged on a road vertical to the course of the carrier in the scene, the road runs at a certain distance and the same radial speed in the same direction, and the radial speed is 3 m/s. The SAR imaging azimuth resolution ratio is analyzed by 3m, the calculation is carried out according to the method in section 3, 14 sequential SAR images can be obtained by the cooperative target in the beam irradiation time, the attached figure 4 shows that 4 sequential SAR images are respectively provided with the serial numbers of 1, 4, 7 and 10, 3 moving targets are detected and positioned by adopting the multi-channel SAR-GMTI technology introduced in sections 1-2 after each imaging, the moving targets are respectively represented by squares, circles and triangles, and the parameter estimation results of the moving targets are shown in Table 1. The method comprises the steps of taking road intersection points in sequential images with the sequence number of 4 as reference points (shown by cross-shaped star points in the figure), tracking and locking all sequential SAR images by adopting the method, respectively tracking the positions of the reference points in the sequential images (also shown by the cross-shaped star points), intercepting scenes in the same area of the sequential image sequence after tracking and locking, and intercepting the scenes with the size of 550 x 400 in the experiment. Due to the difference of the imaging time of the sequential images, the position of the moving target is changed on the road, and after the moving targets detected by all the sequential images are processed by 3.2 sections, clear tracks can be obtained, as shown in figure 5, tracks of 3 moving targets, namely a square, a round and a triangle, are formed. The above results verify the effectiveness of the method.
Claims (3)
1. A ground moving target detection and tracking method based on sequential SAR images is characterized by comprising the following steps:
(1) design a multi-channel joint self-adaptive clutter suppressor w opt ＝μR -1 a(v r ) Performing clutter suppression on data of 1 to n channels, wherein R (i, j) ═ E { Z (i, j) Z H (i, j) } is a multi-channel joint data covariance matrix,
a multi-channel joint data vector composed of data at (i, j) coordinate positions of 1 to n channels;
(2) designing a two-dimensional constant false alarm detector, detecting a moving target according to a result after clutter suppression, and judging that the target is detected at the (i, j) coordinate position in the image when the amplitude S (i, j) of each detection unit simultaneously meets the following five conditions:
S(i,j)≥K 1 S cv (i,j)
S(i,j)≥K 2 S cv (i,j-1)
S(i,j)≥K 2 S cv (i,j+1)
S(i,j)≥K 2 S cv (i-1,j)
S(i,j)≥K 2 S cv (i+1,j)
wherein S is cv (i, j) is the two-dimensional clutter background level, K 1 、K 2 Is a constant coefficient;
(3) motion parameter estimation, including radial velocity, is performed on the detected moving objects one by one
Velocity in azimuth direction
And azimuth position
Wherein Δ φ, λ, v a 、d、R 0 、
Respectively estimating interference phase, wavelength, platform flight speed, channel spacing, skew distance and frequency modulation rateA value;
(4) SAR imaging is carried out on the data of the channel 1 to obtain a sequential image 1, and a moving target point trace is superposed on the image;
(5) re-selecting echo data of 1-n channels according to a certain time delay interval, repeating the steps (1) to (4) to obtain M sequential SAR images of the target point track of the superimposed motion;
(6) locking and registering the sequential SAR images of the M overlapped motion target points by using a designed sequential SAR image tracking and locking technology;
(7) and performing point/track association processing on the motion target point track in the M sequential SAR images after locking and registering to obtain the motion target track.
2. A computer storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements a sequential SAR image-based ground moving object detection and tracking method according to claim 1.
3. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor when executing the computer program implements a sequential SAR image based ground moving object detection and tracking method as claimed in claim 1.
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| CN117237199A (en) * | 2023-11-15 | 2023-12-15 | 中国科学院长春光学精密机械与物理研究所 | Method for generating simulation GMTI radar image based on unmanned aerial vehicle aerial photography |
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| CN117237199A (en) * | 2023-11-15 | 2023-12-15 | 中国科学院长春光学精密机械与物理研究所 | Method for generating simulation GMTI radar image based on unmanned aerial vehicle aerial photography |
| CN117237199B (en) * | 2023-11-15 | 2024-01-26 | 中国科学院长春光学精密机械与物理研究所 | Method for generating simulation GMTI radar image based on unmanned aerial vehicle aerial photography |
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