Geophysical survey method comprising detecting infrared in two wavelength bands

Claim 1

A METHOD OF GEOPHYSICAL SURVEYING WHICH COMPRISES THE STEPS OF: FLYING AN AIRCRAFT AND RADIOMETRIC APPARATUS ASSOCIATED THEREWITH ALONG A PREDETERMINED TRAVERSE OVER A TERRAIN TO BE SURVEYED; PRODUCING FIRST AND SECOND PHOTO RECORDS REPRESENTATIVE OF INFRARED RADIATION IMAGES OF SAID TERRAIN, SAID FIRST AND SECOND RECORDS BEING RESPECTIVELY REPRESENTATIVE OF A SHORTER WAVELENGTH BAND WITHIN THE INFRARED REGION AND A LONGER WAVELENGTH BAND WITHIN SAID REGION; SUBSEQUENTLY INCREMENTALLY COMPARING THE DENSITIES OF CORRESPONDING PORTIONS OF SAID FIRST AND SECOND RECORDS TO PRODUCE AN INFORMATION SIGNAL INDICATIVE OF THE INTENSITY DIFFERENTIAL BETWEEN THE TERRAIN RADIANCES IN SAID LONGER AND SHORTER WAVELENGTH BANDS; AND CHARTING SAID INFORMATION SIGNAL ON A PHOTO-MAP OF SAID TERRAIN TO VISUALLY INDICATE THE DIFFERENTIAL INFRARED RADIANCE CHARACTERISTICS OF THE MATERIALS IN SPACED PORTIONS OF THE TERRAIN.