Abstract

Oak Ridge National Laboratory has developed an Ultrasonic Ranging and Data System (USRADS) and interfaced the system with a Geonics EM31 terrain conductivity meter. The system tracks the EM31 operator's position by measuring the traveltime of ultrasonic pulses from a transducer carried in a backpack, to microphones mounted on stationary receivers deployed in the survey area. A microprocessor-controlled radio transmitter, also carried in the backpack, transmits the terrain conductivity data to a mobile base station (van or truck), where the EM31's X-Y position, and the electromagnetic quadrature and in-phase readings are automatically recorded each second by a portable computer. USRADS can track the surveyor for distances of up to about 120 m from the base station with an accuracy of about 10 cm. USRADS potentially offers several advantages for surface geophysical surveys: (1) when elevations are not required, USRADS saves time and money because a measurement grid does not have to be surveyed before the geophysical work begins, (2) data are directly recorded by a portable computer and are available for analysis in the field, and (3) refining or expanding the coverage of an anomaly does not require additional surveying to add extra grid points. We discuss a field study where we surveyed roughly 8000 m 2 of Solid Waste Storage Area 4 (SWSA 4) on the Oak Ridge Reservation collecting over 2700 in-phase and quadrature measurements in 45 minutes. The high density of measurements provided sharp resolution of waste trench boundaries.

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