ABSTRACT
The nature and precision of the information that it is possible to extract from a remote sensing system depend both on the sensor that is used and on the platform that carries the sensor. For example, a thermal-infrared scanner that is flown on an aircraft at an altitude of 500 m may have an instantaneous field of view (IFOV), or footprint, of about 1m
or less. If a similar instrument is flown on a satellite at a height of 800 to 900 km, the IFOV is likely to be about 1 km
. This chapter is concerned with the general principles of the main sensors that are used in Earth remote sensing. In most cases, sensors similar to the ones described in this chapter are available for use in aircraft and on satellites, and no attempt will be made to draw fine distinctions between sensors developed for the two different types of platforms. Some of these instruments have been developed primarily for use on aircraft but are being used on satellites as well. Other sensors have been developed primarily for use on satellites although satellite-flown sensors are generally tested with flights on aircraft before being used on satellites. Satellite data products are popular because they are relatively cheap and because they often yield a new source of information that was not previously available. For mapping to high accuracy or for the study of rapidly changing phenomena over relatively small areas, data from sensors flown on aircraft may be much more useful than satellite data.
