LOCATING DELINEATED WETLAND BOUNDARIES IN COASTAL SOUTH-CAROLINA USING GLOBAL POSITIONING SYSTEMS

A six-channel Global Positioning System was used to locate eleven poin ts on wetland boundary lines. The latitude and longitude of these poin ts were compared to locations obtained by a second order ground survey . Operating criteria and tree foliage coverage varied over a 19-month period of data collection (February 1992 to October 1993). Canopy cove rage levels sampled within a hurricane impacted area, did not increase horizontal position error as much as percent of readings that had onl y 3 satellite (2D) coverage. If at least 60 readings were made at each point and more than 50% of the total readings had 4 satellite (3D) co verage, the average horizontal distance error was 3m. Beginning in Jun e 1993, with appropriate adjustments in data collection and data manip ulation, 5-m accuracy was obtained 95% of the time regardless of time of year, level of canopy coverage, or height of antenna. These accurac ies seem to be sufficient for boundary surveys of delineated wetlands for routine regulatory purposes. Criteria for data collection should b e specified so that the accuracy of the data can be evaluated.