Impact of forest canopy on quality and accuracy of GPS measurements

Global Positioning System (GPS) technology has become an essential tool in the Earth observation field for georeferencing, classification and accuracy assessment activities. While it was developed to be employed primarily in the open, many users nowadays operate GPS receivers in less favourable conditions. We investigated the impact of varying types and degrees of forest cover overstorey on GPS data collection, accuracy and precision. While the occurrence of canopy overhead may degrade the positional precision by one order of magnitude, it is the presence of the foliage itself (leaf-on condition) that plays a major role in the signal reception and the positional accuracy. The relationship is inverse, with increasing relative canopy closure resulting in decreasing logging efficiency and accuracy. We also found that under larger forest canopy the Position Dilution of Precision (PDOP) values may improve signal reception without deteriorating accuracy. Moreover, the relationship between degree of canopy closu...