The Transport Research Laboratory (TRL) recently developed and tested a suitable procedure for speeding up earthwork protection routines, based on taking large-scale aerial photographs from a helicopter. Trials in several countries show that its results are compatible with those achieved by engineers on site, and also quicker and cheaper to obtain. Two 70mm colour photographs are taken for each site to provide sufficient detail; one is at an oblique angle to the ground, to locate problems, and the other is vertical, to obtain a wider view and make simple measurements. Each image records about 250m of road, and is linked to a global positioning system (GPS). An earthwork condition assessment is conducted, to identify signs of deterioration, consider their likely causes and consequences, and evaluate the critical characteristics of each earthwork. The assessment's results are input into a database, which is then used to produce the following types of information: (1) hazard maps, risk maps, and repair priorities; (2) earthwork inventories; and (3) detailed assessments of specific problems. This analysis procedure is illustrated with reference to a study of a section of the Kennon Highway in The Philippines, about 240km from Manila. Local engineers can easily learn to adopt this technique.
Abstract