6.2 Geometric Characteristics of Image Data

Remote sensing data are data digitized by a process of sampling and quantization of the electro-magnetic energy which is detected by a sensor. In this section, geometric characteristics of sampling are described, while radiometric characteristics by quantization are explained in 6.3.

IFOV (Instantaneous Field Of View) is defined as the angle which corresponds to the sampling unit as shown in Figure 6.2.1. Information within an IFOV is represented by a pixel in the image plane.

The maximum angle of view which a sensor can effectively detect the electro magnetic energy, is called the FOV (Field Of View). The width on the ground corresponding to the FOV is called the swath width.

The minimum detectable area, or distance on the ground is called the ground resolution. Sometimes the projected area on the ground corresponding to a pixel or IFOV is also called the ground resolution.

In remote sensing, the data from a multiple number of channels or bands which divide the electromagnetic radiation range from Ultra Violet to Radio Waves are called multi-channel data, multi-band data or multi- spectral data.

In general, multi-channel data are obtained by different detectors as shown in Figure 6.2.2. Because the detectors are located at slightly different positions, and the light path of different wavelengths is a little different from each other, the images of multi-channel data are not identical in geometric position. To correct such geometric errors between channels is called registration.

The term registration is also used for registration of multi-temporal (or multi-date) images.


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