The instrument utilizes at least one electromagnetic signal transmitter and at least one electromagnetic signal receiver with the receiver detecting a receiver signal responsive to the transmitter signal and indicative of subterranean details adjacent to the instrument. The instrument is attachable to a tow vehicle for transport and includes a GPS antenna and tags data gathered by the instrument with GPS position information. The instrument is formed in modular sections which can be removably attached for collapsing into a smaller space and to allow for flexible configuration of the instrument in various different ways. A wheeled carriage is provided to carry the instrument over the ground. Antennas for the transmitter and receiver, as well as circuitry and cooling systems are all provided to supply the instrument with high resolution and a clear signal indicative of the position and characteristics of subterranean details of interest.