Principles of Modern Radar - Volume 2 1891121537

338 CHAPTER 8 Interferometric SAR and Coherent Exploitation(a)FIGURE 8-1 Example InSAR images. (a) Spaceborne image of Los Angeles basin fromSRTM data. Grayscale represents wrapped height. (Courtesy of NASA/JPL-Caltech.) (b) 3-Drendering of a high resolution airborne InSAR image of Karlsruhe Palace. (From Brenner andRoessing [1]. With permission.)generate DEMs. Both spaceborne and airborne InSAR systems are in common use, andInSAR elevation maps can be generated from either stripmap or spotlight SAR imagery.Figure 8-1 illustrates two examples of 3-D scene renderings generated from InSAR DEMs.Figure 8-1a is a visualization of the Los Angeles area generated from space shuttle data.The image is 41 km wide by 29 km tall (25 × 19 miles) and has a resolution of 30 m. Theflat Los Angeles basin is in the center and lower left of the image. The runways of LosAngeles International airport are visible, as is the Marina del Rey just to the north of theairport. The Santa Monica and Verdugo mountains run along the top of the image. ThePacific coastline is on the left. In this image, the grayscale is related to scatterer heightrather than reflectivity. 2 Figure 8-1b shows a 3-D rendering of an airborne InSAR DEMof the Karlsruhe Palace in Germany. The image covers about 10 km 2 at a resolution finerthan 0.1 m and is an excellent example of very fine-resolution urban InSAR [1].In this chapter we introduce the concepts, techniques, and applications of InSAR withan emphasis on DEM generation. After a brief introduction to DEMs, the fundamentalequations relating interferometric phase measurement variations to terrain elevation variationsare derived from simple geometric considerations. The major algorithmic stepsrequired to form an InSAR DEM are then discussed, and a number of existing air- andspace-based InSAR systems are described.In addition to DEM generation, the closely related coherent SAR exploitation techniquesof terrain motion mapping and change detection are briefly introduced in thischapter. They provide high-quality measurements of changes in, respectively, the terrainprofile over time or the reflectivity of the terrain. Another coherent exploitation technique,ATI, uses similar methods to detect terrain motion and moving targets in a scene. Thebasic concepts of ATI can be expanded to combine SAR imaging with space-time adaptiveprocessing (STAP) methods for interference suppression, an idea developed furtherin Chapters 10 and 11 of this book.(b)2 Although not available here, InSAR images typically rely on pseudo-color mappings to make the heightdetail more perceptible to the eye. Color versions of these and other selected images from this chapterare available online (http://www.scitechpub.com/pomr2).