Wide-angle staring synthetic aperture radar ground moving target indication (WasSAR-GMTI) has garnered attention due to its capability to monitor a stationary area over an extended period and ability of tracking moving targets. Recently, the research on moving target trajectory reconstruction has also raised interest. However, the low positioning accuracy and impractical assumption of traditional method which makes it can hardly practical application. We propose a novel precise trajectory reconstruction of moving target in this paper. First, we segment the echo into subapertures, after clutter rejection and radial velocity estimation, quasi-maximum likelihood (QML) is applied to estimate polynomial phase signal (PPS) parameters of phase history. And then, Levenberg-Marquardt (LM) algorithm is applied to decouple the motion parameters. Based on the motion parameters, the coarse trajectory can be reconstructed. After that, the envelope history of moving target is extracted. Modeling the motion trajectory of the moving target in segments and estimate the trajectory of each segment using the corrected envelope history and coarse trajectory. Finally, after processing all segments, the precise trajectory of moving target is obtained. The effectiveness and practicability of the proposed algorithm were demonstrated by the processing results of experimental WasSAR data.

Wide-angle staring synthetic aperture radar ground moving target indication (WasSAR-GMTI) has been widely recognized for its long-term observation capabilities of fixed areas and its achievement in moving target tracking. Recently, the research on moving target trajectory reconstruction has also raised interest. However, the neglect of height-dimensional information makes it difficult to apply in the scene with terrain undulation. In this paper, a three-dimensions (3-D) trajectory reconstruction method with L-antenna which combines interferometry SAR (InSAR) and GMTI technique is proposed. Meanwhile, it’s the first time that L-antenna is applied in 3-D geo-location of moving target. Firstly, the echo is segmented into several sub-apertures and the lever arm compensation and back projection (BP) imaging are required to register the multi-channel images. Secondly, the along-track multi-channel is processed which contains clutter rejection and radial velocity estimation. Thirdly, the cross-track interferometric phase extraction is proposed and 3-D geo-location of moving target is estimated. Apart from extracting height-dimensional information from interferometric phase directly, a method based on digital elevation model (DEM) is also proposed. And the comparison of the two methods is given in this paper. The processing results of real data have confirmed the efficacy and practicality of the proposed algorithm.

As a new observation mode, wide-angle staring synthetic aperture radar ground moving target indication (WasSAR-GMTI), which can observe the fixed area for a long time and achieve moving target tracking, has attracted a lot of interest. However, with increasingly complex flight trajectories and application scenarios, the performance of traditional method tends to degrade. In this article, a novel approach based on post-Doppler space-time adaptive processing (PD-STAP) and imaging method is proposed. First, selecting and extending training data from repeat-pass data can obtain accuracy estimated clutter covariance matrix (CCM). Moreover, the relationship between extended quantity of training data and clutter suppression performance is further analyzed in this article, and then, the joint-pixel PD-STAP (JP PD-STAP), which utilizing auxiliary units under test cell along range direction, is performed to overcome the effect of residual range curvature after keystone transform (KT). Finally, after clutter suppression, the parameters and imaging method based on WasSAR system are proposed. The multidimensional parameter is simplified as 1-D line search problem, which has high efficiency. Considering the curvilinear trajectory, the back-projection (BP) is adopted to process. Inserting parameters into BP can be seen as coarse motion compensation (MOCO), and the further spectrum compression (SC) method and phase gradient autofocus (PGA) is performed to obtain refocus and relocate imaging of moving target. The real-measured WasSAR data processing results demonstrated the effectiveness and practicability of the proposed algorithm.

A unique mode known as wide-angle staring synthetic aperture radar ground moving target indication (WasSAR-GMTI) allows for the dynamic surveillance of moving targets over a wide range of azimuth angles. Despite WasSAR-GMTI develops rapidly, the parameter estimation and trajectory reconstruction of moving target in a three-Dimensional (3-D) field have not been solved well in WasSAR. In order to address this problem, a framework based on 3-D velocities’ and 3-D positions’ estimation is proposed in this article. On account of the derived equivalence, it is possible to characterize moving targets in WasSAR-GMTI and achieve the decoupling of velocity and position. First, for the multidimensional velocities’ estimation, the joint interferometric phases of several subapertures are utilized. Then, to estimate the multidimensional positions, the signal of moving target in WasSAR is modeled as a polynomial-phase signal (PPS). We tackle the issue of 3-D positions’ estimation through the coefficients of PPS estimated by cubic phase function (CPF) method. Finally, 3-D trajectory reconstruction of moving target is accomplished by combining the results of multiaperture estimation. The proposed method extends the parameter estimation to the 3-D case, and the applications of WasSAR-GMTI are spread. Moreover, the parameter estimation of moving target is addressed independently, namely without auxiliary information of priori road detail. The estimation accuracy of the proposed method is evaluated by the simulated data, and the validity and feasibility of the proposed method are demonstrated through the results of real data.

The performance of multi-channel synthetic aperture radar (SAR)-based ground moving target indication (GMTI) is inevitably restricted by channel imperfections and imbalances, and channel calibration procedure is incorporated into the scheme accordingly. The adaptive two-dimensional calibration (A2DC) algorithm is sensitive to outliers and suffers from correction errors. To solve the problem, a modified A2DC (MA2DC) algorithm is proposed in this letter. By improving Doppler calibration model, the proposed MA2DC is more robust than the A2DC algorithm. It can effectively suppress clutter while maintaining detailed features of moving targets, after which the detection capability of moving targets in SAR-GMTI is improved. Its performance is demonstrated by the Gotcha data, which is publicly released by Air Force Research Laboratory.

Multi-channel wide-angle staring synthetic aperture radar ground moving target indication (WasSAR-GMTI) has attracted a lot of interest for its ability of moving target detection and trajectory reconstruction. However, the parameter estimation of moving target is easily affected by clutter and noise which deteriorate the performance of the following geo-location. In this paper, a novel approach for trajectory reconstruction of moving target based on road line is proposed. Firstly, after performing multi-channel calibration, a novel Doppler centroid estimation and correction method is proposed. This method is not depended on attitude information of platform, nor does it require scene uniformity as a prior condition, which has high robustness in complex environment. And then, the weighted adaptive matched filtering (WAMF) and modified Gaussian mixture probability hypothesis density (GMPHD) is performed for velocity estimation and tracking. Last, the error items affecting geo-location accuracy were analyzed in detail. And a novel two-step geo-location method based on road line is proposed to correct geo-location error which can be applied in complex road network. The proposed method only needs one-dimensional parameter searching which has high efficiency. The real-measured WasSAR data processing results demonstrated the effectiveness and practicability of the proposed algorithm.

For synthetic aperture radar (SAR) images, there are many defocused moving targets with azimuthal deviation. Ground moving target indication (GMTI) is developing rapidly to detect moving target for traffic surveillance and military vehicle tracking. In this paper, multi-channel SAR-GMTI technology is studied and a moving target detection method based on clutter suppression interference (CSI) and relaxation-based cyclic (RELAX) is proposed to detect moving target efficiently and accurately, the time of which is only 0.22% of the time by global RELAX. Combined with multi-channel signals, CSI is performed to detect targets of interest. Then, RELAX is applied to further reduce false alarm and estimate radial velocity for geolocation. Experimental SAR data processing results show that the method is effective for moving target detection and parameter estimation.

Displaced phase center array (DPCA) and along-track interferometry (ATI) have been widely used for ground moving target indication (GMTI) in multi-channel circular synthetic aperture radar (CSAR) system. In ideal conditions, these methods can suppress background clutter effectively. However, the nonideal movement of platform may create a nonzero crab angle, which will induce a cross-track baseline offset and affect GMTI processing seriously. This letter analyzes the influence of crab angle on interferometric phase theoretically. Here, we propose a two-step phase calibration method to greatly improve the performance of CSAR-GMTI by eliminating the range-varying phase error. This method is independent of imaging and GMTI processing. Simulated and measured data results verify the correctness of the theoretical analysis and the validity of the proposed method.