Principles of Modern Radar - Volume 2 1891121537

14.4 Synthetic Aperture Radar 639TABLE 14-2Publicly Released SAR Data SetsMSTAR Gotcha Lynx ADTS GTRIResolution 0.3 m × 0.3 m 1 ft. 1 ft × 1ftPolarization HH Full Unknown Full FullDepressionanglesAspectangles17 ◦ 8 angles 41–44 ◦ 22.5 ◦ and 40 ◦ 27.99 ◦ to31.93 ◦ in0.0138 ◦ steps360 ◦ 360 ◦ 360 ◦ 325–training angles,68 test anglesFrequency X-band, 9.6 GHz X-band Ku-band Ka-band,32.6-37 GHzTarget types Military (armored Civilian vehicles Military (armored Armor/militarypersonnel carriers, and calibration personnel carriers, vehiclesbattle tanks, targetstanks)vehicles), confusorsEnvironmenttypesNatural andman-made(cultural) clutter(∼30 km 2 )Parking lotRural, suburban, andurban, NM and FL(10 km 2 )Stockbridge, NY(rural) and Ayer,MA (Urban) instripmap mode0 ◦ to 360 ◦ in0.05 ◦ stepsX-band, 9.6 GHzMilitary(M2’s and T72)corner reflector effect, and edge currents [10]. Because SAR imagery of a complex objectis highly aspect dependent and affected by overlay at steep incidence angles [10], it isnecessary to acquire images at many aspect and depression angles (see Figure 14-1 for anexample of how target features change with depression angle) or to develop the requisitesimulation capabilities. It should also be mentioned that while image libraries exist formicrowave and millimeter-wave systems, libraries in ultra high frequencies (UHF) arelimited [11].14.4.2 Step 2: Select the Feature SetThe available features and their quality depend heavily upon the type of radar used toobserve the targets. SAR radars vary widely with application, encompassing such diverseforms as polarimetric SAR, bistatic polarimetric SAR, millimeter wave SAR, and ultrawidebandSAR.FIGURE 14-1BMP-2 vehicle attwo depressionangles:a) 15 degrees andb) 17 degrees.(Reproduced fromMSTAR dataset withpermission.)(a)(b)