Global Positioning Systems (GPS)
A Trimble Pro XR Global Positioning Systems (GPS) was used to mark the starting and ending points of the ground penetrating radar (GPR) lines. GPS helps to accurately lay out points and lines on an aerial photograph of Half Moon Lake. The Percent Dilution of Position (PDOP) was relatively low, because of the open research area. PDOP measures the geometrical strength of the GPS satellite configuration, in other words the amount of error in your position. PDOP’s less that 4 gives the best accuracy (under 1 meter) and anything over a PDOP of 8 provides poor accuracy. Our lowest PDOP was 2.1 at the starting point of Line 5. We downloaded the GPS data using Pathfinder Office 2.80 software. Raw GPS data, uncorrected appears jagged. Using ArcGIS 9.2 software, it is possible to correct skewed data in an editing session.