Handheld 40-cm head
How to Survey with a GEM-3
Simple Handheld Survey
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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.
Handheld 40-cm head |
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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. See the GEM-3 data example in magnetic geology. |
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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.
GEM-3 Survey on a Cart
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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 dia sensor head with a GPS antenna |
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Underwater GEM-3 Survey
With proper modifications for mounting and waterproofing, the GEM-3 also can be used for underwater surveys as shown below.
Since its debut in 1997, the GEM-3 has performed numerous governmental and commercial surveys. Listed below is a partial list of such surveys. For data examples, go to GEM-3 Data Examples
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.
