Principles of Modern Radar - Volume 2 1891121537

260 CHAPTER 7 Stripmap SAR3 m SAR OpticalFIGURE 7-1 Two renderings of Albuquerque Airport with SAR on the left and an overheadoptical photograph on the right. (Images courtesy of Sandia National Laboratories.)hidden and buried objects. Finally, phase information in complex SAR imagery may beexploited to estimate terrain height or changes to the scene over time.A great variety of platform motion histories are capable of producing usable SARimagery. One specific case is known as stripmap SAR. In SAR vernacular, stripmap mayrefer to the data acquisition geometry, a corresponding image formation technique, orboth. The key characteristics of a stripmap collection are:• The platform moves in a straight line. (This is in contrast to the curved and circularpaths often employed by spotlight systems.)• Transmit and receive antennas are pointed to a fixed angle, frequently broadside, normalto the direction of flight.• Transmit and receive beam patterns are not steered in angle during data acquisition (asopposed to spotlight mode).Stripmap image formation techniques are designed to produce focused SAR imagesconsistent with these conditions.While the stripmap geometry may appear overly specific and constraining, there is arich history of collecting and processing SAR data in such a manner, particularly withinthe remote sensing community. The SAR image in Figure 7-1 is an excellent example of astripmap product with respect to both the collection geometry and image formation. Thefollowing features motivate the stripmap mode:• Stripmap yields the finest cross-range resolution possible without sparse or interruptedcoverage.