Effect of Ice Loading of a GPS Antenna

Kyle O'Keefe, Jim Stephen, and Gérard Lachapelle, Rodolfo, A. Gonzales

Abstract:	The theoretical attenuation and reflection properties of RF signals at GPS frequencies are first reviewed. The results of a series of tests conducted in May 1998 to determine the performance of Raytheon Systems’ WAAS antenna when covered with a layer of ice approximately 0.5 inch thick are then presented. This type of testing is necessary as many of these antennas will be located at remote, unmanned stations and will be required to operate effectively under cold weather conditions. The effect of ice loading is quantified by observing changes in (1) the signal-to-noise ratio (SNR), (2) the position errors and (3) the number of cycle slips observed. The 0.5 inch wet surface ice loading lead to a reduction in SNR of about 3 dB, a raw code horizontal differential position rms error increase of 1 m and a significant increase in the number of cycle slips observed. The 3 dB loss can be explained by the reflection of GPS signals at the air-ice interface in addition to attenuation of the signal transmitted through the ice. A simple model shows that most of this 3 dB loss is due to reflection. To verify this, further tests were conducted under colder temperatures in early January, 1999 using various ice thicknesses to analyse the effect of a dry ice surface.
Published in:	Proceedings of the 1999 National Technical Meeting of The Institute of Navigation January 25 - 27, 1999 Catamaran Resort Hotel San Diego, CA
Pages:	861 - 869
Cite this article:	O'Keefe, Kyle, Stephen, Jim, Lachapelle, Gérard, Rodolfo,, Gonzales, A., "Effect of Ice Loading of a GPS Antenna," Proceedings of the 1999 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1999, pp. 861-869.
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