Accurate height information from airborne laser-altimetry

High single point precision and high point density can be obtained by airborne laser-altimetry, using GPS positioning and INS attitude determination. In this paper the authors analyse the main error sources, including: (1) internal laser sensor errors, (2) GPS and INS errors, (3) atmospheric effects, (4) terrain roughness, reflectivity and slope, (5) presence, height and type of vegetation, and (6) integration and synchronization of laser, GPS and INS. Their analysis reveals that when laser-altimeters are well-calibrated accuracies at decimetre level can be achieved. However, the accuracy is very sensitive to terrain type, terrain coverage and used filters to remove from the DEM undesired objects such as buildings and trees. In particular pointing accuracy, which depends on the pointing jitter of the scanning mirror and INS attitude determination, is a main error source, especially over high relief terrain. Another major problem is the automatic removal of undesired objects, such as houses