GPS Signal Disturbances by Water in Various States

Cyrille Gernot

Abstract:	This paper describes an investigation of the tracking performance of GPS receivers under water in various states. In order to grasp the importance of the problem at hand, a study of the different properties of the water molecule and the influence of an electromagnetic wave on it is first proposed. From that, a model is developed to represent the theoretical attenuation and reflection properties of RF signals at GPS frequencies. Finally, several tests have been performed to confirm the theoretical model proposed. One of those tests investigates the affect of the polarization the water molecules on the transmission of GPS signals. In order to insure a perfect control over the path of the signal and generate the polarization, an RF GPS signal simulator, a directional antenna and a high voltage generator were used. The results are shown through the observations of signal-to-noise ratio (C/N0) and relative standard deviation on the pseudorange (RStd). A 4 cm layer of ice was also tested, resulting in a reduction of signal strength of about 2 dB and an increase in pseudorange standard deviation of approximately 17 cm. Similarly, snow was found to have an even smaller effect on the signal. A 14 cm layer of snow in the line of sight reduces the C/N0 by 2 dB and adds 8 cm on the RStd. On the other hand, 1 mm of water is enough to stop a GPS signal or at least reduce greatly its strength. Indeed, with this amount of liquid water, the C/N0 is lowered by about 9 dB and the tracking becomes hardly realizable. Finally, it was observed that polarizing the water using a very strong electric field, even if no gain has clearly been observed, the GPS receiver managed to track the signal during the whole length of the test.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	2187 - 2195
Cite this article:	Gernot, Cyrille, "GPS Signal Disturbances by Water in Various States," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 2187-2195.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In