Classification of Targets in SAR Images Using ISAR Data

Feature-based classification of targets in SAR images by using ISAR measurements was studied, based on polarimetric SAR and ISAR data acquired with the MEMPHIS radar system of FGAN-FHR. The data contained one T-72 battle tank, one BMP combat vehicle, and several confusers. The resolution was 75 cm. Nine features were studied of which four were analyzed: area, coefficient of variation, weighted-rank fill ratio and VV/VH ratio. Of these features the only one that resulted in certain separability was the weighted-rank fill ratio. But to classify the targets using only one feature is not reliable, especially considering the resolution. Neighbor number and HH/HV ratio were successfully used to separate the targets from natural clutter false alarms. 1.0 INTRODUCTION Because of the growing use of unmanned aerial vehicles for reconnaissance, surveillance, and target acquisition applications, the interest in synthetic aperture radar (SAR) systems is increasing as well, mainly due to their all-weather capability. A study for the Dutch Ministry of Defense was initiated, in order to investigate the possible role for SAR imagery in ground surveillance applications. This study is performed within the framework of the NATO/SET-069 research group. With the participation in the SET-069 group, TNO gained access to high resolution SAR and ISAR data of several targets and scenes. These data are maintained by the SET-069 group in order to study automatic target recognition techniques making use of millimeter wave imagery. FGAN-FHR contributed to the data set with data from the MEMPHIS Ka-band radar system, [1]. In 2002 MEMPHIS was used in an airborne side-looking configuration to record SAR images of the Greding proofing ground in Germany. During these experiments various targets were lined up, among which, one T-72 and one BMP. Four images were recorded from four perpendicular flight directions. A subset of one can be seen in Fig. 2a. The SAR data are fully polarimetric; HH, HV, and VV polarization channels are available. The depression angle is 20°. In 2004 MEMPHIS was used for tower/turntable ISAR measurements, [2]. Measured were a BMP infantry fighting vehicle, a ZSU-23-4 self-propelled antiaircraft gun, and a T-72 main battle tank. The ISAR data are VV and VH polarized. The depression angle is 17°. Looking at the FGAN data, the idea came into being to set up a classifier to classify the T-72 and the BMP in the SAR data using their ISAR measurements as training data. Several techniques exist, such as feature based, [3]-[5], and template based, [6]-[7]. Due to the resolution of the SAR data (75 cm), a feature-based strategy was chosen. In this paper the FGAN SAR and ISAR data will be analyzed. Targets will be detected and the relevant target features will be extracted. Subsequently, the features will be compared to the features extracted from reconstructed ISAR images of the T-72 and the BMP, in order to pinpoint these vehicles in the SAR image. RTO-MP-SET-096 5 1 UNCLASSIFIED/UNLIMITED UNCLASSIFIED/UNLIMITED de Wit, J.J.M.; Dekker, R.J.; van den Broek, A.C. (2005) Classification of Targets in SAR Images Using ISAR Data. In MMW Advanced Target Recognition and Identification Experiment (pp. 5-1 – 5-8). Meeting Proceedings RTO-MP-SET-096, Paper 5. Neuilly-sur-Seine, France: RTO. Available from: http://www.rto.nato.int/abstracts.asp. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 01 MAY 2005 2. REPORT TYPE N/A 3. DATES COVERED 4. TITLE AND SUBTITLE Classification of Targets in SAR Images Using ISAR Data 5a. CONTRACT NUMBER