Loupe is a new, portable, time-domain electromagnetic system specifically designed for rapid reconnaissance and near-surface conductivity measurements. The receiver and transmitter are each carried by one person on a backpack. Loupe incorporates a 3component coil sensor with 100 kHz bandwidth, a fast-switching transmitter loop, a simple user-interface and the ability to navigate and recover position using RTK GPS. By virtue of intelligent signal processing, carried out in real-time and in post-acquisition processing, Loupe will operate effectively in the presence of interference from power transmission lines and other sources of noise that traditionally degrade the performance of EM systems in urban areas. A completely portable time-domain EM system of this nature is unique. This paper will discuss the design and features of Loupe and likely applications for it. Here, we present an example of data from a geotechnical investigation. By the time of the conference, we expect to be able to present results from other work done with Loupe in exploration and mine projects. This system, and its results, will be compared against other techniques to illustrate the increase in near-surface resolution and speed of broadband data collection.
SummaryGeophysical investigations were carried out across a sports field created in the sand dunes close to the coast in Perth, Western Australia. It is understood that the site was previously used as a dump for rubbish. Undulations have developed on the surface of the oval, which are believed to be due to differential compaction of the rubbish underneath a cover of sand.The purpose of the investigations was to determine the sites contamination, subsurface materials, stability and costs associated with rehabilitating the site to be used as playing fields. A series of geophysical surveys were carried out using frequency domain EM, radiometrics, GPR, magnetics and resistivity. The site was then used as a test area for a new profiling TEM system called "Loupe". The new results are compared against previous results and the superior resolution in depth and better positional accuracy discussed. This is work still in progress at the time of submission but the Loupe System is a new generation instrument incorporating RTK GPS, fast sampling, high bandwidth and easy portability. The ability to resolve conductivity in 3D in the near surface using a rapid acquisition system will change how many geotechnical surveys are conducted.
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