Application of Airborne Laser Scanner

This dissertation explores the use of an Airborne Laser Scanner (ALS) for various types of aircraft Terrain-Referenced Navigation (TRN) techniques. Using the methods explored, an ALS-based TERRain Aided Inertial Navigator (TERRAIN) was developed, flight tested, and shown capable of providing meter-level positioning accuracy in real-time. The ALS-based TRN techniques discussed are constrained to the information found in the terrain shape domain. The techniques used and position solution characteristics of ALS TRN can vary significantly from traditional radar altimeter-based TRN; these variations are primarily due to two differences in the information contained ALS TRN verses traditional radar altimeter-based TRN. The first difference being that traditional radar altimeter-based TRN sense the terrain contours traversed in the along-track direction, whereas ALS TRN measures in the along-track and in the cross-track direction. The second difference is that the ALS's narrow laser beamwidth (typically less than a milli-radian) has resolution sufficient to identify not only the ground, but objects on the ground such as buildings; whereas, a the radar altimeter's relatively large beamwidth (anywhere between 3 degrees to 90 degrees) primarily senses the terrain. These differences increase the spectral content of the ground measurement data in the ALS-based system thus permitting high-accuracy position estimates. The ALS TRN navigation techniques explored include a method which estimates the position based on the best match between ALS data and a high resolution/accuracy terrain database. Variations on this technique are discussed include a method to classify non-terrain and terrain features from the ALS data, allowing for the use of features with large gradients (sharp edges), such as buildings. Also explored is the certification path for a ALS-based landing system.