High Accuracy GPS Carrier-Phase Positioning for ATLAS Airborne Mapping System

S. Mole, M. Westwood, J. Goddard, P. Kightley

Abstract:	An advanced airborne survey system, (ATLAS: Airborne Topographic Laser System), has been developed by QinetiQ for ground mapping, at altitudes above 500ft. The total system design accuracies were specified as 0.1m absolute position standard deviation and 0.075m relative position standard deviation for points on the ground. The ability of ATLAS to provide high accuracy and high density (~18 points/m2) surveying at altitudes above restricted flight levels provides users with greater operational flexibility and a significant performance increase over existing airborne survey systems. The airborne system comprises a geo-referencing unit, based on integrated GPS and inertial navigation technology, combined with a scanned time-of-flight Light Detection and Ranging (LIDAR) system. The georeferencing unit measures the position and attitude of the platform and the LIDAR generates angle and range data to the terrain being mapped. A bespoke recording system captures the data with a Universal Time Coordinated (UTC) synchronised time-stamp to enable post-processed reconstruction of a cloud of data points that will give a three-dimensional representation of the terrain, referenced in European Terrestrial Reference System 1989 (ETRS89) or International Terrestrial Reference System 1989 (ITRS89) coordinates. The ATLAS system uses civil dual-frequency twelvechannel GPS receivers with an aircraft-grade Inertial Navigation System (INS) and QinetiQ High Accuracy Kinematic Carrier-Phase positioning algorithms. This paper summarises the design, evaluation and performance of the GPS algorithms. The ATLAS system (geo-referencing + LIDAR) has been shown to operate inside its 0.1m standard deviation total absolute accuracy design specification and its 0.075m standard deviation relative design specification during flight trials on a Twin Squirrel helicopter. The geo-referencing sub-system has also been shown to operate inside its 0.02m standard deviation design accuracy.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	2649 - 2655
Cite this article:	Mole, S., Westwood, M., Goddard, J., Kightley, P., "High Accuracy GPS Carrier-Phase Positioning for ATLAS Airborne Mapping System," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 2649-2655.
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