I can't speak for my Australian colleagues, but I have successfully used the AlphaLab Earth Magnetometer

http://www.trifield.com/edcm.htm

The black box is now reduced to the size of a box of matches and the complete outfit costs some $US700.

This particular instrument does not interface with a computer to allow automatic transfer of readings. But it is ideal for walking along traverses to spot sudden changes in signal that can be more closely examined later.

Just to recapitulate (because, as others have pointed out, there has been some confusion in the posts) metal detectors work at shallow depth (say up to 30 cm) to locate ferrous and non-ferrous metals. Don't hire one - my local Aldi supermarket is now selling them for equivalent of $US45 - I kid you not.

Magnetometers work at depth and detect changes in the strength of the magnetic field. They locate ditches, footings of buildings, and localised spots of magnetic intensity such as kilns.

Richard Wright

>
>Subject: Re: Question RE metal detectors
>   From: George Myers <[log in to unmask]>
>   Date: Tue, 07 Jun 2005 14:01:15 -0400
>     To: [log in to unmask]
>
>Ten or so years ago I had the privilege of using a cesium proton
>magnetometer on a historic site in Saratoga Springs, NY. The EPA
>required an archaeology survey of the Superfund Priority Site, a
>former "city gas" production facility across from "Red Spring #1" on
>Excelsior Ave. on and under an active Niagara-Mohawk work/office yard.
>The company I worked for was sub-contracted be another company looking
>at contamination of the Groton, CT Navy sub properties, currently in
>the news to be "closed". A large water control feature ran under the
>"gas light" production facility emptying storm water into the nearby
>lake. The idea, despite the large current natural gas line under the
>facility, was to try to document the extent of the remains there
>without disturbing the active facility.
>
>The cesium proton magnetometer had a harness which held a small flip
>top computer running MS software, a car "starter switch" to take the
>readings (came also with software to sort out the up one line down
>another sequencing, could also be used in "timer" mode taking readings
>as one walked across various landscapes) and was the size of a small
>beverage can on the end of a short light aluminum rod, very efficient.
>Just before I was exposed to this (103 one summer day) it, I saw what
>I think may have been the same equipment being used by Australian
>archaeologists in Southeast Asia tracking down the origin of the
>"celadon" ceramic story, partly deduced from underwater archeology
>research. It sound whole acres I think of kilns buried beneath about 2
>meters I think of alluvium, which they found with the magnetometer, as
>firing earths creates magnetic anomalies. We used it to find the
>former "gasholder" base (it's twin still stood and eventually was
>placed on the US "National Register of Historic Places") and the
>various maps and photos were "ground truthed" from the survey, and
>shown to be still extant, in ruins, one brick "ring" the concrete
>block office building was cracking over (nearby fault line also,
>divides the Taconic from the Adirondack regions) as the site settled.
>It has almost all the stages of gas/electric production on site, too.
>
>However, I can't recall who made it. It came in a white "photon
>torpedo" looking case (aka "Star Trek") via parcel post, and was
>repaired once while we used it quite quickly. Any Aussie's know the
>thing's name?
>
>George Myers, Jr.
>Many shovel tests later...