Digital Image

A digital remotely sensed image is typically composed of picture elements (pixels) located at the intersection of each row i and column j in each K bands of imagery. Associated with each pixel is a number known as Digital Number (DN) or Brightness Value (BV), that depicts the average radiance of a relatively small area within a scene (Fig. 1). A smaller number indicates low average radiance from the area and the high number is an indicator of high radiant properties of the area.

The size of this area effects the reproduction of details within the scene. As pixel size is reduced more scene detail is presented in digital representation.

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Figure 1 : Structure of a Digital Image and Multispectral Image

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