Abstract: A method of predicting a target type in a set of target types from at least one image is provided. At least one image is obtained. A first and second set of confidence values and associated azimuth angles are determined for each target type in the set of target types from the at least one image. The first and second set of confidence values are fused for each of the azimuth angles to produce a fused curve for each target type in the set of target types. When multiple images are obtained, first and second set of possible detections are compiled corresponding to regions of interest in the multiple images. The possible detections are associated by regions of interest. The fused curves are produced for every region of interest. In the embodiments, the target type is predicted from the set of target types based on criteria concerning the fused curve.

Abstract: Signal processing methods useful in single-antenna multiple-pass interferometric synthetic aperture radars. The signal processing methods compute an initial elevation estimate from the phase difference between a pair of images (A0, A1) with a relatively small elevation angle difference (i.e., a short interferometric baseline) and uses it to initialize the elevation estimation process for pairs of images (A0, A2) with longer interferometric baselines. The method may be used to process images that are coherent, or not necessarily mutually coherent. The outputs of the methods comprise a terrain elevation map that mitigates for atmospheric error and a turbulence map.

Abstract: A family of multiple scale adaptive filters and filtering methods that automatically adapt their impulse response width to local data characteristics, optimizing the accuracy, yield, and/or detail of interferometric measurements. A prefilter with fixed impulse response width is applied to a complex interferogram. The phase of the prefiltered complex interferogram is unwrapped. Then, a weighted combination of the phase-unwrapped, fixed-filtered interferograms is computed using a data-dependent criterion function. The resulting weighting function at each resolution element is typically a nonlinear function of interferogram magnitude and coherence for each fixed filter output at that resolution element.

Abstract: A method of computing and correcting phase errors due to atmospheric turbulence in a dual-antenna multiple-pass synthetic array radar (SAR) interferometer system. The method improves topographic mapping accuracy at very long ranges. The method computes an atmospheric correction from the residual phase difference between a two-pass interferometer output (containing atmospheric phase errors) and a dual-antenna single-pass interferometer output (for which atmospheric phase errors cancel because the two channels are collected simultaneously). The residual phase measured in a single resolution element is then filtered by averaging over an area of many resolution elements, typically on the order of several thousand resolution elements. This exploits the long correlation distance of the atmospheric phase errors to reconstruct the dominant low-frequency part of the error spectrum. In addition, unwrapping the phase of the output of the complex Wiener filter produces an atmospheric turbulence measurement map.

Abstract: A method of providing accurate elevation data from three or more complex SAR images. A SAR vehicle is operated to produce a number of SAR images at different grazing angles. The present method provides precise elevation maps derived from the SAR images. In a multiple channel variant of the present invention, more than two antennas collect SAR data from various grazing angles, increasing sensitivity while resolving the ambiguity problem in a mathematically optimum manner. A multiple pass variant of the present invention collects data from more than two passes, and from various grazing angles (interferometric "baselines"). The multiple pass approach and associated processing preserves the high sensitivity of the long-baseline available from dual pass IFSAR while resolving the ambiguity problem in a mathematically optimum manner. Accuracy and ambiguity resolution are improved with each additional pass or channel. The method processes raw SAR data to produce a plurality of complex images therefrom.

Abstract: A method for automatically selecting subareas from reference image data such that registration accuracy is optimized between images. Optimal subarea selection reduces the on-line computation and reference data storage required for multi-subarea correlation or, alteratively, improves its effectiveness. Example results for a synthetic aperture radar (SAR) image are described. The results indicate that the automatic subarea selection method of the present invention reduces on-line computation by a factor of 2 to 3 (relative to random subarea selection) without degradation in accuracy. The present selection method minimizes the predicted total mean squared registration error (MSE). The total MSE is predicted in terms of the position and predicted measurement covariance (derived from local image statistics) of each candidate subarea. Combinatorial optimization procedures select a predetermined number of subareas to minimize total MSE.

Abstract: Apparatus including a multi-scale adaptive filter for smoothing interferometric SAR (IFSAR) data in areas of low signal-to-noise ratio (SNR) and/or coherence while preserving resolution in areas of high SNR/coherence. The multi-scale adaptive filter uses simple combinations of multiple linear filters applied to a complex interferogram. The multi-scale adaptive filter is computationally efficient and lends itself to parallel implementation. A pyramid architecture comprising a plurality of cascaded stages is employed which reduces the computational load and memory required for implementation of the processing algorithm. The multi-scale adaptive filter implements a processing algorithm that may be applied to standard IFSAR data. Its input is a complex interferogram (the conjugate product of two complex images) and its output is a filtered interferogram (A) which is passed to an information extraction processor, that extracts a terrain elevation map, for example.

Abstract: The present invention is an interferometric SAR system and processing method that combines multi-pass SAR interferometry with dual-antenna SAR interferometry to obtain elevation maps with accuracy unobtainable by either method alone. A single pass of the dual-antenna system provides coarse elevation maps. High accuracy maps are obtained through additional passes, with accuracy determined by the number of passes. The processing method combines the acquired data to provide a calibrated, high precision, low ambiguity elevation map, using approximate least-squares and maximum-likelihood processing methods. The present dual-antenna SAR interferometer collects two complex SAR images from slightly different elevation angles on a single pass using two antennas on the same platform. The present invention provides calibrated maps that have coarse precision but are nearly unambiguous because of the small interferometer baseline.

Abstract: A terrain height radar system and processing method comprising a high resolution synthetic aperture radar (SAR) mounted on an air vehicle and a SAR signal processor containing a signal processing algorithm or method for computing terrain height and radar backscatter power. The system contains motion sensing and navigation functions that also provide data to the signal processor to provide motion compensation. Signal processing algorithms in the method compensate for planar motion of the air vehicle for variations of terrain height in the field of view. The algorithms also compensate for nonplanar motion of the radar, and for scatterers in or very near to a reference plane in the field of view. The algorithms exploit defocusing due to displacement from the reference plane to estimate the terrain height above the reference plane. The algorithm is computationally efficient because the bulk of the radar signal processing is common to both the SAR function and the terrain height estimation function.