Abstract: SLAR Imagery is not just a Picture

Louis F. Dellwig

The aerial camera, sensing in the same part of the electromagnetic spectrum as the human eye, generates data in pictorial form which are easily translated into familiar objects by the interpreter. Unfortunately, interpreters make this same translation from pictorial form to familiar objects in other sensor displays, not realizing that in regions of the electromagnetic spectrum other than the visible, terrain-energy interaction results in a record of target characteristics which are not detectable by the human eye. Because of the similarity in overall appearance between a side-looking airborne radar display and an aerial photograph taken at low sun angle, geoscientists commonly tend to interpret SLAR images in terms of optical signatures, and thus fail to extract maximum d ta from imagery.

The radar return signal is basically a function of the complex dielectric constant and surface roughness of the target, the intensity of the return signal for any given system being controlled by the incidence angle. However, this signal can be effectively interpreted only in the light of knowledge of the imaging system's parameters. Variations in frequency, polarization, depression angle, resolution, look direction, and dynamic range all strongly influence the overall character of the return signal. With a full understanding of these characteristics of an imaging system, one can realize optimum revelation of data content.

APG Search and Discovery Article #90974©1975 AAPG Mid-Continent Section Meeting, Wichita, Kansas