REMOTE SENSING GEOBOTANY AND AIRBORNE GAMMA-RAY DATA APPLIED TO GEOLOGICAL MAPPING WITHIN TERRA FIRME BRAZILIAN AMAZON FOREST: A COMPARATIVE STUDY IN THE GUAPORE VALLEY (MATO GROSSO STATE, BRAZIL)

摘要

This paper comprises a comparison between the vegetation response in ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) multispectral optical imagery and possibly equivalent bedrock/regolith/soil response in airborne gamma-ray spectrometry grids, employing a tropical rainforest area in the Brazilian Amazon as a control. The applied technique comprised band ratios using a fixed near infrared band (numerator) divided by individual visible and shortwave infrared bands (denominator). These band ratios were subsequently submitted to principal component analysis, and the high frequency information is smoothed by low pass filtering. The colour compositions selected for interpretation were sharpened by the first principal component of the original ASTER bands through an IHS transform in order to add albedo/texture information -lost through band rationing -back to the imagery. The products show a plausible coherence with airborne gamma-ray data and field observations, proving that the proposed processing strategy applied to low cost multispectral data can provide useful geologic information in inaccessible vegetated areas.