Forest canopy, terrain, and distance effects on global positioning system point accuracy

Abstract

Tests were conducted to determine lhe realizable accuracies of the Global Positioning System under eastern North American forest conditions. The effects of terrain, forest canopy, number of consecutive position fixes, and WOP on accuracy were evaluated. Position accuracies were determined for a total of 27 sites: three replicate sites selected for all combinations of three canopy (deciduous, conifer, open) and three terrain (ridge, slope, valley) types. Each site was visited over a span of nine months to collect position data, for ten replications per each of 27 sites to collect 60, 100, 200, 300, and 500 position fixes. The mean difirentially corrected positional accuracy for all sites was 4.35 metres, with 95 percent of the mean positions estimated within 10.2 metres of the true value. The least accurate differential position data were observed at conifer sites. Positional accuracy was higher for deciduous sites and highest at open sites. Mean positional accuracy increased from valley to ridge locations. Mean accuracy increased with increasing number of position fixes collected per point. When the number of position