Argus Technologies has developed the EM3 to perform mobile, noninvasive underground surveys. Depending on the terrain, nearly 50 lane-miles can be surveyed per day. Argus’ EM3 technology is an adaptation of conventional hand-held electromagnetic (EM) instrumentation. Such instruments have been used successfully in near surface geophysics and soil studies for over 20 years. Argus Technologies advanced the base technology to include: 1) mobilizing or placing the instrument on wheels; 2) combining three receivers into one instrument for a nested view of subsurface conditions in successive depths; 3) speeding up data acquisition rates, 4) simultaneously tagging incoming data with real time kinematic (RTK) GPS X, Y, and Z coordinates with centimeter-level accuracy; and 5) developing proprietary data collection and processing software. The result is an instrument that records three to six volumes of soil, to a maximum depth of 10 meters (about 30 feet) and an effective depth of 6 meters (about 20 feet), as it is towed behind an ATV traveling at 5-10 miles per hour. Typically three to four readings are recorded per meter and proprietary software packages are used to process and display raw data, generate contour plots, produce 2-dimensional (2-D) profiles, and display 3-dimensional (3-D) visualizations of the data through inversion modeling.
The IDEA project is a specialized application tailored to non-invasive preliminary surveys for highway construction. The EM3 provides fundamental information regarding the consistency or variability of subsurface materials, the presence or absence of buried objects, and lateral trends in soils and rock. This information is important because unknown subsurface factors such as relict or current transportation infrastructure, underground storage tanks or utilities, and unpredicted changes in soils or geologic strata complicate excavation work and trigger highway construction delays. The final report is available from the National Technical Information Service (NTIS # PB2007-109638).