ASABE Technical Library - Abstract

Abstract. Hawaii‘s forested watersheds are exceptionally difficult terrain often only accessible by helicopter. Obtaining accurate GPS positions of events and features is a major problem in Aerial surveillance and mapping in these remote landscapes. Our study analyzed the performance of survey-grade (Trimble R10), mapping-grade (Trimble Geo 7 and Juno 5) and consumer-grade (ASUS Nexus 7, Motorola Droid Turbo, and Garmin Foretrex 401) GPS receivers, recording inside the fuselage of a Hughes 500D helicopter while conducting low-altitude surveillance flights in the mountainous terrain of the East Maui Watershed (Hawaii, US) searching for invasive plant species. The survey-grade GPS performed poorly with frequent interruptions of the carrier phase signal particularly in low-altitude flight lines where skyline visibility was reduced by steep topographical obstructions flying where hemispherical skyline was reduced by >50% in many areas. The Geo 7 mapping-grade receiver was capable of utilizing carrier- or code-phase GPS (49% and 42% of total, respectively), allowing for more consistent position acquisition. The horizontal RMSE calculated against the post-processed carrier phase data of the Geo 7 mapping-grade receiver, was 2.5m, 7.3 m, 8.6 m and 10.1 m, for the Juno 5, Foretrex 401, Nexus 7 and Droid Turbo, respectively, with 3D deviations averaging 2.2 times greater. In these aerial operations signal lock was compromised by obstructions due to the main rotor of the aircraft and the topography.