| This study assessed the accuracy of GPS data collected under variable northeastern forest canopy using the Leica SR530 GPS receiver. In detail, coordinate quality estimates, baseline length and collection time, canopy density, and leaf off and leaf on accuracies were assessed for both combined and code corrected solutions. GPS coordinate quality is usually defined in terms of precision because it is difficult to assess the accuracy of points not part of a network. Conditions under which the GPS receiver is used can significantly alter accuracy as the signals are blocked or reflected. Point locations used to compare with GPS acquired positions were established independently of GPS using conventional surveying techniques. The reference network was constructed in Heiberg Forest located in Central New York. The software coordinate quality estimates were an unreliable estimate of GPS accuracy under forest canopy. Code corrected positions provided higher average accuracies for all aspects studied. Increasing the baseline length increased the average error approximately 4m for combined and 1m for code corrected positions. Increasing the collection time from 20 to 30 minutes had little effect on the average error. GPS accuracy had no direct correlation to canopy density, but the range in errors increased with increasing canopy density. Collection under leaf off and leaf on conditions generally did not affect GPS accuracy. The average horizontal accuracy ranged from 1.13 to 5.40 m and 0.95 to 2.22 m for combined and code corrected positions, respectively. |
