Terrain Reference Navigation using Airborne LAser SCAnner (ALASCA) … Preliminary Flight Test Results

Jacob Campbell, Maarten Uijt de Haag and Frank van Graas

Abstract:	Results compiled from flight tests of a proof-of-concept terrain reference navigation system using an Airborne LAser SCAnner (ALASCA) are presented in this paper. In the proposed Terrain Reference Navigation (TRN) system, the user position is estimated by matching ALASCA data with a known terrain databases. The ALASCA used in the flight tests provides high accuracy range measurements (sub-decimeter) at a very high data rate (>20 kHz) with a terrain measurement spatial density of < 5 m. Comparison of the airborne laser scanner measurements with a terrain database (with similar highresolution characteristics) results in a large number of independent measurements; these measurements can be used to estimate both position and attitude: results of the position (horizontal and vertical) estimation are described in this paper. The terrain navigation methods detailed in this paper include both exhaustive search methods for the minimum in the error space and gradient based search algorithms. The problem associated with the latter method is the possibility that the method “settles” on a local minimum in the error space rather than the global minimum if it is not properly designed. Characteristics of the error space shape are discussed. This discussion provides insight into the ability of optimized methods to find the minimum in the error space. The performance of the algorithms detailed in this paper are evaluated using data collected over Reno, Nevada with an Optech LiDAR system on NASA’s DC-8, and previously collected NOAA LiDAR data. Post-processed Kinematic GPS-based (KGPS) positions will be used for the aircraft truth reference. Results from exhaustive minimum error search solutions and gradient based minimum error search solutions are included.
Published in:	Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004) June 7 - 9, 2004 Dayton Marriott Hotel Dayton, OH
Pages:	671 - 678
Cite this article:	Campbell, Jacob, de Haag, Maarten Uijt, van Graas, Frank, "Terrain Reference Navigation using Airborne LAser SCAnner (ALASCA) … Preliminary Flight Test Results," Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004), Dayton, OH, June 2004, pp. 671-678.
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