For a signal power P compared by ratio to a reference power , the formal definition is . DeciBels often are used in radar, such as in measures of reflectivity , for which the dynamic range may span several factors of ten. The unit is named in honour of Alexander Graham Bell, inventor of the telephone. For image interpretation, use of the term is not recommended because it does not account for the effects of Earth curvature, and it does not conveniently include effects of local slope in the scene. It is more appropriate for engineering description of the vertical antenna pattern at the radar itself.
Detection removes phase information from the data file.
Reflectivity of a smooth surface and the penetration of microwaves into the material are determined by these two quantities. Numerical number, between zero and 255 for example, assigned to each spatial grid position in the file representing the brightness levels of an image . The digital numbers may be related to sigma nought of scene elements through the process of calibration . For enhanced backscatter , the dihedral must be open to the radar, and have the axis of intersection at right angles to the direction of illumination. A distribution may have extensive low level tails or sidelobes .