SOME OBSERVATIONS ON A COMPARATIVE AERIAL-PHOTOGRAPHY INTERPRETATION OF A LANDSLIPPED AREA

All aerial photography interpretation must be used with caution. When well done and supported by ground truth exercises they can be a valuable aid to site investigation, depending on the quality and scale of the aerial photographs and the skill and background of the interpreter. A rare situation has arisen where eight interpretations of a landslip complex in gently folded Tertiary marine sediments overlain by young colluvium and covered by dense equatorial rainforest were made by different professional interpreters. This is used as an opportunity to illustrate the potential difficulty in obtaining a reliable interpretation. Five of the interpretations were made without knowledge of a major new landslip which occurred in an area of existing landslips and three were made with knowledge of the new landslip, all using the same pre-major new landslip aerial photographs. Of the five made without knowledge of the new landslip, two did not identify existing landslips at the site and three partially identified landslips but each in a different configuration. With knowledge of the new landslip the interpreters identified old features in the aerial photographs similar to the features produced or exposed by the new landslip.