HIGH TIMES IN THE GREAT VALLEY: REMOTE SENSING BY UNOCCUPIED AERIAL VEHICLE (UAV)

Unoccupied Aerial Vehicles (UAVs) are promising new platforms for the procurement of low-altitude, high-resolution aerial photographs for use in geologic research. Only a few studies have used UAVs to study geology from the air, but recent improvements in digital image technology allow UAVs to collect inexpensive aerial images for use in the fields of geophysics, geomorphology, surface hydrology, environmental geology, and soil science. We conducted aerial surveys of three sites in Cumberland County, Pennsylvania using a four-megapixel digital camera mounted on radio-controlled model airplanes and a ground-tethered weather balloon. Vertical and oblique images were obtained at altitudes between 1.5 and 330 m above ground. The images were manipulated to produce photomosaics, orthorectified maps, and anaglyphs using commercially-available software including Adobe CS, AutoCAD, and Anaglyph Maker. Images were used to identify, highlight and quantify geologic and environmental features including streams of leachate discharging from a landfill, stream meander morphology, and large-scale fracture traces at a municipal well field.

The resolution of our aerial images was 3 cm or better, which is between two to twenty times greater than traditional aerial photographs. The UAVs were capable of targeting areas less than 0.1 km2, which would be impractical and dangerous using full-scale aircraft. UAV aerial images cost approximately 1000 times less than their full-scale counterparts. The main drawback to using model airplanes as a platform was their imprecise handling, especially in windy conditions. The weather balloon was sensitive to winds as low as 5 km/h, which made it vulnerable to tree limbs and resulted in a maximum safe altitude of 15 m. We conclude that UAVs are effective, versatile, safe and inexpensive platforms for low-altitude aerial imagery, and can serve as an invaluable tool for the contemporary geologist.