Static Azimuth Determination Using a Single Handheld GPS Receiver

John Kelly, Erik Bogensberger and Eric Rammelsberg

Abstract:	A novel application of a developed GPS-based algorithm (time relative positioning) for military gun laying and pointing is presented for use in a static azimuth determination application. The method takes advantage of the lack of selective availability errors within the GPS system to make the time-relative algorithm found within the gun laying application usable for SPS short-baseline azimuth determination. A single GPS receiver is utilized in a "body-static" configuration emulating the use of a typical handheld magnetic compass. The user is permitted to perform an arm motion but is not allowed to traverse or otherwise move their "body" during the derivation of the azimuth. Time-relative GPS positioning is then performed over a very short ~1m baseline (the length of a typical user’s arm) to provide a body-static azimuth oriented in the direction of the user’s hand and referenced to true north. Several advantages of this method include the ability for GPS to additionally correct for magnetic declination errors when providing appropriate reference of the resolved azimuth to north or any user defined reference. The derivation of azimuth within the GPS receiver in electronic form additionally allows storage into memory (waypoint or distance use) or immediate transmission via tactical or other radio. A more operational benefit is that a single device (GPS receiver) may be utilized for both position and azimuth reference in contrast to today’s need to use first a compass and then a GPS receiver. The ability to derive GPS based usable azimuths eliminates the cost of including magnetic or other forms of externally derived azimuth circuitry. The detriment is obviously the need for acquisition of GPS signals in order to operate although this limitation is being countered by the significant commercial and military increase in GPS-based equipment utilization and resultant desire of need. This paper presents a detailed description of the problem under solution, the background of the time-relative methodology and its adaptation to the body-static azimuth application, and results from recent field testing indicating its utility for estimating true body-static azimuths of +/- 5 degrees of accuracy (~36 compass segments) at 95% probability levels. This level of accuracy exceeds current casual ground navigation desires for eight to sixteen compass rose partitions of resolution with minimal expense to the receiver's operation and is on par with the +/- 1 to 5 degrees of potential error existent in alternative methods. It is proposed that a form of this application may be of significant interest to commercial and military based GPS receiver manufacturers looking to support cost-effective means of static azimuth derivation.
Published in:	Proceedings of the 57th Annual Meeting of The Institute of Navigation (2001) June 11 - 13, 2001 Albuquerque, NM
Pages:	790 - 796
Cite this article:	Kelly, John, Bogensberger, Erik, Rammelsberg, Eric, "Static Azimuth Determination Using a Single Handheld GPS Receiver," Proceedings of the 57th Annual Meeting of The Institute of Navigation (2001), Albuquerque, NM, June 2001, pp. 790-796.
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