Seasonal Variation of GPS Accuracy and Precision in Forest Road Mapping

GPS receivers are frequently used for engineering activities in forests; however, a number of factors, including natural barriers (mountain and tree canopy) in the forested areas, affect their accuracy. The aim of this study was to evaluate the accuracy and precision of a consumer-grade GPS (Colorado 300) receiver in road mapping. For this purpose, a length of 12.2 km of main forest road was selected in the Hyrcanian forest, northern Iran, and a ground truth map was extracted from the National Cartographic Center maps. The forest road was mapped in four seasons for three days to evaluate the seasons’ effects on the location accuracy and five- and ten-meter buffers were used for the same purpose. The results of two-way ANOVA showed that there were significant differences in the precision and accuracy of the GPS receiver due to the season. The best and worst mean accuracy and precision were in spring (24.45 m and 24.97 m) and autumn (56.10 m and 53.65 m), respectively. The findings showed a positive effect of averaging (5-61% improvement in relation to season) on the position accuracy. Also, ANOVA did not show any significant differences between the overlay lengths due to season in both the five-and ten-meter buffers. It can be concluded that consumer-grade GPS receivers could meet forestry needs. The averaged accuracies in spring are acceptable for many forestry applications and satisfy the mapping requirements.