Fusion of Reference-Aided GPS, Imagery, and Inertial Information for Airborne Geolocation

Alan G. Evans, Udayan V. Bhapkar, James P. Cunningham, Bruce R. Hermann, John Dugan, J. Zandy Williams, David C. Campion and Oscar L. Colombo

Abstract:	A remote sensor suite is described that utilizes kinematic and differential GPS, a digital camera, and a tactical- grade Inertial Navigation System (INS). The camera and INS are fixed to a scan platform housed in a turret. The turret is attached to the chin of a light, single-engine aircraft. Real-time differential GPS positioning along with the real-time INS observations provide a pointing vector to a specific location on the ground, allowing the camera to continuously stare at that location as the aircraft flies by. Post-mission integration of the camera position and attitude, along with image information, can provide the ground locations of any point in the image in World Geodetic System (WGS-84) coordinates. Accurate geolocation of ground targets was demonstrated using data collected during a test conducted near Duck, North Carolina in October and November 1999. GPS pseudorange and phase measurements, as well as data from an inertial measurement unit (IMU), were collected in real-time; however, processing was done after the test. Absolute positions from the aircraft were obtained from either short- or long-baseline kinematic reference-aided GPS. Short-baseline kinematic GPS provided aircraft positions with centimeter-level accuracy, while multiple- reference, long- baseline, kinematic GPS (greater than 1000 km) provided decimeter-level accuracy. The use of these positions permitted more accurate IMU/camera attitude estimation than that achievable using standard differential GPS techniques. In particular, sub-milliradian standard errors for camera pointing accuracy were demonstrated. Target geolocation was performed using a two-image triangulation method. Meter-level target positioning errors were obtained for a circular aircraft trajectory with an average range-to-target of 2500 m. These target coordinates were verified by fusion with registered imagery.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	1703 - 1712
Cite this article:	Evans, Alan G., Bhapkar, Udayan V., Cunningham, James P., Hermann, Bruce R., Dugan, John, Williams, J. Zandy, Campion, David C., Colombo, Oscar L., "Fusion of Reference-Aided GPS, Imagery, and Inertial Information for Airborne Geolocation," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 1703-1712.
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