Influence of the juxtaposition of trees on consumer-grade GPS position quality

Abstract

Static horizontal position accuracy of a consumer-grade GPS receiver was estimated in a young loblolly pine (Pinus taeda) plantation in Georgia (USA) to determine whether the arrangement of trees had any influence on position quality. No significant relationship was observed between static horizontal positional accuracy and environmental variables (air temperature, relative humidity, and atmospheric pressure) or the planned positional dilution of precision (PDOP) of the NAVSTAR satellite configuration. However, in a semi-spatial sense, we found moderate correlation between average positional error and a few forest structure measures. For example, we observed that as hardwood (deciduous species) basal area and hardwood tree count within 4 or 5 m of a test point increased, the average positional error tended to increase. No significant correlation was observed using forest structure values obtained within 3 m of each test point. However, some directional effects were observed with increases of pine tree count, pine basal area, and total live tree basal area within 4 or 5 m of each test point. And using rose diagrams (circular histograms), we observed that in some sense there was a negative attraction between the location of live trees and the position determined by the GPS receiver.