The Imaging Radar System

Abstract

Understanding remote sensing with imaging radar can be more difficult than with optical imaging because the technology itself is more complicated and the image data recorded is more varied. Since there are so many concepts and techniques to be assimilated, this chapter provides an overview of the topic as a framework for the later chapters. It also draws attention to the knowledge assumed on the part of the reader.

First, we should establish why we are interested in radar imaging as a remote sensing modality. A simple answer can be found by examining the wavelength of the radiation used compared with that of the visible and infrared radiation employed in optical remote sensing. Optical imaging technologies operate at wavelengths of the order of 1µ or so – that is a millionth of a metre. Radar imaging, on the other hand, is based on microwaves that have wavelengths of the order of 10cm – approximately 100,000 times as long. With such a disparity in wavelength one would expect that features on the earth’s surface would appear differently at microwave than they would optically. That is certainly the case. In many situations the data types are complementary in that what is difficult to discern one is sometimes more easily discriminated in the other. As a result combined optical and radar data sets feature in geographic information systems.