Laser altimetry and its application in geographic scanning

Laser altimetry is a technique whereby reflections of a laser beam are used to measure the altitude of an aircraft above the ground based on a round trip delay measurement. With current improvements in short laser pulse generation and high resolution time and amplitude measurements, the same technique is now used to measure topographical features of the ground surface. In addition to surface elevations obtained from high resolution delay measurements, information on the nature of coverage of a target surface can be obtained from high resolution intensity measurements of the returned echo signal. In this technique, global positioning and navigation guidance are needed to provide reference on the position and pointing attitude of the measuring equipment. Both aspects of the altimeter system, namely, echo signal measurements and position referencing, determine the accuracy and resolution of the technique. This paper reviews the principles and basic aspects of a pulsed laser altimeter, and discusses the utilization of data provided by laser altimetry in geographic scanning for urban and environmental studies.