Accuracy assessment of perimeter and area calculations using consumer-grade global positioning system (GPS) units in southern forests

Abstract

Field foresters have long required a method of accurate measurement of perimeter and area during forest management activities. Perimeter and area assessments that can be derived from individual waypoints collected via global positioning system (GPS) units can be an expensive endeavor. A question of concern for practicing foresters is as the cost of GPS units increase does the accuracy of waypoints and any derived perimeter and area assessments also increase? This research evaluated whether the dynamic collection of waypoints using consumer grade GPS units ranging from $50 to $700 provide a sufficient level of accuracy for the calculation of perimeter and area under three types of canopy cover: a newly established 3-year-old pine plantation, a 13-year-old pine plantation nearing first thinning, and a 40-year-old mixed pine/hardwood stand. Perimeter and area accuracy was not related to cost indicating that inexpensive GPS units provide an accurate waypoint location when used to derive perimeter and area measurements. When compared to a professional survey of each cover type, the average perimeter root mean square error (RMSE) ranged from 18.72 ft (0.41% of total perimeter) in the 40-year-old mixed pine/hardwood stand to 108.50 ft (2.43% of total perimeter) in the 13-year-old pine plantation. The average area RMSE observed ranged from 0.07 acres (0.22% of total acreage) in the 3-year-old plantation to 1.32 acres (4.67% of total acreage) in the 13-year old pine plantation. For many forestry applications needing a perimeter and acreage assessment, these levels of accuracy should be more than sufficient. Copyright © 2013 by the Society of American Foresters.