Seasonal Effect of Tree Foliage on GPS Signal Availability and Accuracy for Vehicular Navigation

G. Lachapelle, J. Henriksen, and T. Melgara

Abstract:	The seasonal effect of deciduous tree foliage on GPS signal availability and accuracy for vehicular navigation is investigated. GPS signals in the upper UHF part of the spectrum are line-of-sight and suffer much attenuation under tree branches and their leaves. An important question is to whether significant variations will occur between seasons due to the presence or absence of deciduous foliage. Two types of performance variations are investigated, namely signal availability and accuracy. In the presence of leaves, signal availability is expected to decrease. Since multipath is expected to increase, accuracy is expected to decrease as well. In order to investigate this aspect and possible correlation with different receiver technologies, tests were conducted at normal cruising speeds along selected tree-lined streets of Calgary under both seasonal conditions with multi- channels wide and narrow correlator spacing C/A code receivers. The tests were conducted in DGPS mode to assess effectively repeatable positioning accuracy. Test results are presented and analysed. They reveal that the effect of foliage on signal availability is a function of the number of channels available and, to some a lesser extent, on receiver characteristics. Foliage is also found to have a significant effect on positioning accuracy. Narrow correlator spacing technology produces significantly better positioning accuracy under foliage conditions due to its better multipath rejection capability.
Published in:	Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994) September 20 - 23, 1994 Salt Palace Convention Center Salt Lake City, UT
Pages:	527 - 532
Cite this article:	Lachapelle, G., Henriksen, J., Melgara, T., "Seasonal Effect of Tree Foliage on GPS Signal Availability and Accuracy for Vehicular Navigation," Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994), Salt Lake City, UT, September 1994, pp. 527-532.
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