Topographic Mapping, LORAN-C, and GPS Accuracy for Aerial Telemetry Locations

Abstract

Although the accuracy of recording aerial locations by some methods has been evaluated for known ground points, none had been tested for unshown points, which is commonly the case for radiomarked animals. We compared the accuracy and precision of 6 methods for recording simulated-animal, transmitter locations after estimating their positions by aerial telemetry. We tested topographic mapping, uncorrected LOng-RAnge Navigation system, version C (LORAN-C), bias-adjusted LORAN-C, uncorrected Global Positioning System (UGPS), aircraft navigational, non-correctable GPS (NGPS), and differentially corrected GPS (DGPS) for single-pass, single-point, telemetry locations using the same pilot, observer, and aircraft. Location errors (LE) for all methods were distributed normally. We found differences in accuracy among methods and within recording systems. One method, LORAN-C (xLE = 385.5 m), differed from the other 5 methods, including bias-adjusted LORAN-C (xLE = 128.3 m). Among GPS methods, multiple-range comparisons separated NGPS (xLE = 122.1 m) from UGPS (xLE = 80.7 m) and DGPS (xLE = 73.1 m). Mapping (xLE = 77.0 m) was comparable to UGPS and DGPS. Comparison of habitat patch size with a 95% confidence area will determine each method's usefulness for habitat selection studies.