The GEM-3 can be handheld for the 40cm and 64cm diameter heads. The 96cm diameter head must be mounted on a cart. The GEM-3 collects data at a constant interval in time. For a simple survey, the GEM-3 is self-sufficient for dead reckoning navigation and can store about 50,000 data points before it requires downloading to a PC, using a Windows-based software called WinGEM.
In “remote mode,” the raw ASCII data are available to be exported through an RS-232 port. This feature enables integrating the GEM-3 with a PC that can accept GPS or other navigation aids for precision surveys. In the remote mode, the GEM-3 can run continuously by downloading the data directly into a PC.
Handheld Survey with Audio Output
The GEM-3 can be used in a way similar to “mag-and-flag” so that the operator can flag targets in realtime. This approach can be useful in rough and vegetated areas where a systematic, or “georeferenced,” survey is difficult. The GEM-3 sensing head is only 0.5-inch (1.3cm) thick and can be easily slipped under shrubs. An optional audio produces a sound that represents the sum of quadrature responses at all frequencies. The quadrature component is relatively immune to magnetic geology and to variations in the sensor height.
Handheld Survey with GPS Navigation
The handheld GEM-3 GPS mount consists of two custom-made fiberglass tubes equipped with nylon screws so that they can be inserted and tightened along the GEM-3 handle boom. Two photos below show how the mount is assembled onto the GEM-3. An optional handle bar is provided to help carry the sensor. Customers may specify any extra features.
A handheld GEM-3 with a GPS antenna mount
GEM-3 Survey on a Cart
The GEM-3 Carts are built for large sensing heads, the 96-cm diameter head and possibly for an array of the GEM-3. The cart contains no metal parts and is built only with synthetic materials – fiberglass, nylon, and PVC. In fact, the cart is built in modules so that any other sensor platforms may be mounted between the two detachable wheel assemblies. The wheels are 50-cm in diameter with a foam-filled tire along with custom-built fiberglass axles. The cart includes a GPS antenna mount.
Upon order, customers may specify any extra features and functions. Contact Geophex for details.
Pushcart for a 96-cm diameter GEM-3 sensor head with a GPS antenna
Underwater GEM-3 Survey
With proper modifications for mounting and waterproofing, the GEM-3 also can be used for underwater surveys as shown below.
GEM-3 Data Examples
Since its debut in 1997, the GEM-3 has performed numerous governmental and commercial surveys. The table below lists only some of such surveys.
Partial list of GEM-3 surveys:
Jefferson Proving Ground III (1996), VI (1998), and V (2000), Indiana;
Fort McKinley, Alabama;
Aberdeen Proving Ground, Maryland;
Fort A. P. Hill, Virginia;
Fort Carson, Colorado;
Eglin Air Force Base, Florida;
Fort Ord, California;
Kahoolawe Island, Hawaii;
Brandenburg County, Germany.