Tactical Far Target Location Using Position And Azimuth From A P(Y) Code GPS Attitude Determination System

Charles J. Pruszynski, Karl W. Ulmer, Christopher W. Phelps and Michael P. St. Peter

Abstract:	The Long Range Advanced Scout Surveillance System (LRAS3) is a battlefield reconnaissance and surveillance sensor system developed for U.S. Army Project Manager Night Vision/Reconnaissance, Surveillance and Target Acquisition (PM NV/RSTA) by Raytheon Electronic Systems (RES). The LRAS3 sight integrates the Army's Second Generation HTI FLIR technology, a day TV camera, and an eyesafe laser rangefinder into a large, single aperture optical system to provide a high performance day/night target acquisition capability. The LRAS3 will be deployed on the High Mobility Multipurpose Wheeled Vehicle (HMMWV) in the current force and on the reconnaissance variant of the Interim Armored Vehicle (IAV) in the Interim Brigade Combat Team (BCT) for use by Army scouts to detect, identify and locate tactical threat targets at extended ranges. The LRAS3 includes a Far Target Location (FTL) capability that enables the scout to determine the geodetic location of any detected target with a very high degree of accuracy. Far Target Location requires three pieces of information; own location, target range and lastly, target bearing. The first two elements are easily provided by a GPS receiver and laser rangefinder. Predecessor systems have typically employed either a digital magnetic compass or an inertial sensor for the bearing determination task. The digital magnetic compass has been the long standing, low cost azimuth sensor solution, but it is handicapped by unpredictable behavior and marginal accuracy performance in vehicle installations. Inertial sensors can provide high accuracy and reliability, but at the penalty of higher cost, weight and power consumption. GPS Attitude Determination Systems provide the systems engineer with a new intermediate level of azimuth determination capability that can be employed in this and related direction-finding sensor applications. This new approach to the target location problem has been successfully developed, demonstrated and is now entering production in a military tactical application. In the LRAS3, the sight sensor position and target bearing are determined by a Rockwell Collins P(Y)-code GPS attitude determination system that is fully integrated into the sensor sight housing. Data from the two antenna, 0.5 meter baseline, GPS system is combined with data from a two-axis pitch-roll inclinometer to provide a complete 3- dimensional attitude solution for the sensor optical line of sight. This paper describes the configuration of the GPS Interferometer Subsystem (GPSIS) and its integration into the LRAS3 sight system housing. Various lessons learned during the integration of the system are described, including the use of a software-based compensation method to correct the carrier phase measurement distortions introduced by the physically constrained antenna and ground plane installation. Summary test results of the LRAS3 Far Target Location performance are presented.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	2937 - 2945
Cite this article:	Pruszynski, Charles J., Ulmer, Karl W., Phelps, Christopher W., St. Peter, Michael P., "Tactical Far Target Location Using Position And Azimuth From A P(Y) Code GPS Attitude Determination System," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 2937-2945.
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