*2.10.7. Classification of digital satellite data*

The basic characteristics of digital image acquired by remote sensing method are composed of pixels. According to [24], the intensity of each pixel corresponds to the mean radiance measured electrically over the ground area corresponding to each pixel. Each pixel has digital number (DN) corresponding to the average radiance measured in this pixel. This number from quantizing the original electrical signal from the sensor result into positive integer values using a process termed analogue-to-digital signal conversion [90]. The DNs comprising of a digital image are recorded over numerical ranges as 0–255, 0–511, or higher. These ranges correspond to the set of integers that were recorded using 8-, 9-, and 10-bit binary computer coding scales, respectively. In such numerical formats, the image can be analyzed with the aid of computer [91]. A digital image is a 2-dimension array of elements; the corresponding area on the earth's surface was stored in each element emitted from the energy. The spatial arrangement of the measurements defines the image or image space, depending on the sensor; data are recorded in n bands.
