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Geophysics

tTEM is a ground-based transient electromagnetic data acquisition system capable of mapping the soil structures to earth depths in the range from 0 – 70 m. The system is quick to deploy and is easily managed by a field crew of two people. It consists of an ATV towing the transmitter and receiver coils. To make it robust on even harsh farm fields the coils are mounted on sledges with runners. Typical driving speeds are 3-5 m/s, providing a measurement for every 3-5 meters. Distances between mapping lines are 10 – 20 m resulting in a full 3D map of the subsurface. The system is applicable for the mapping of raw materials (identification of sand, gravel and limestone), pollution mapping (tracking the hydrogeological setting around landfills and detecting leachate), and vulnerability mapping (estimating clay thickness which acts as a protective cover for our groundwater reservoirs).

The tMag system is a towed array of vector magnetic gradiometers.  Designed for hydrogeological and archaeological  applications, the array consists of 8 fluxgate vector magnetic gradiometer instruments, comprising 48 total magnetic sensors.  This ultra-high-resolution instrument records data at 200 Hz, resulting in a sample from each sensor every 2.5 centimeters along-line, with a lateral sensor spacing of 60 cm.  This allows for the mapping of nearly 70 hectares per day at an effective line spacing of 60cm. The system is easily deployed by a two-person field crew and consists of an ATV which tows the array on a sledge. The system is designed to detect tile drains, but would also work for detecting archeological structures and items. The tile drains can be detected by tMag because of the way the tiles were burnt, producing a net magnetization. Tile drains are typically around 10-20 cm in diameter, setting high requirements to the lateral resolution of the measurements in order to be detected.

 

tTem instrument
tTem
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tMag in action