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Synthetic Aperture Radar Polarimetry by Yunjin Kim, Jakob J. van Zyl

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CHAPTER 4

POLARIMETRIC SAR CALIBRATION

A polarimetric radar system measures the scattered power from the terrain being imaged. Before these measurements are useful for further quantitative analysis and comparison to models, the measured power values must be converted to normalized radar cross sections. Polarimetric radar measurements require additional corrections: Not only the amplitudes but the relative phases between channels must also be calibrated. In this chapter, we shall examine the steps required to calibrate polarimetric radar measurements in detail.

4.1 POLARIMETRIC RADAR SYSTEM MODEL

To better understand the corrections we need to apply to a radar image during the calibration process, let us first discuss the implementation of such a radar system in the context of potential error sources. Figure 4-1 shows the block diagram of a typical polarimetric radar system.

Figure 4-1 Calibration of polarimetric radar. A polarimetric radar is implemented by alternatively transmitting signals out of horizontally and vertically polarized antennas and receiving at both polarizations simultaneously. Two pulses are needed to measure all the elements in the scattering matrix

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In reality, the radar system is not perfect. For example, rather than transmitting the signals through an antenna with a single, pure polarization, there might be some leakage into the orthogonal polarization channel. ...

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