Positioning methods used in treasure hunting

[99thpercentile]

I am curious what methods of positioning most people use in treasure hunting. I am a geophysicist who spends a lot of time looking for unexploded ordnance (UXO) where we want positional accuracy on the order of centimeters. I also study levees for potential failure zones and look for drug tunnels where we usually are happy with sub-meter accuracy. When I am planning a field job, I would first set up a site visit where we would go see the site to find all of the man made features, the boundaries of the site and anything else of interest and then GPS the coordinate of each to sub-meter accuracy. Then we would get all of the utility maps of the site, USGS topographic maps, geologic maps and any aerial imagery that is available. All of this information would be put into an ESRI ArcGIS database. From this information we would plan our field survey based on the type of target, depth of target and the physical properties of the soil at the site.

Here are the positioning systems that I use in the field:

To find a site:
Garmin Etrex series

For sub-meter accuracy:
Trimble Ag132 GPS ($5K) with OmniStar VBS subscription ($800/yr)
Trimble DSM-232 GPS ($5K) with OmniStar VBS subscription ($800/yr)

For better than 30 cm accuracy:
Trimble DSM-232 GPS ($5K) with OmniStar XP ($1500/yr) or HP ($2500/yr) subscription

For sub-centimeter accuracy:
Trimble 5700 RTK surveying system ($45K)
Trimble S RTS surveying system ($42K)
Leica 1500 RTS sruveying system ($42K)

 

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[Stroover]

I'm just an amateur, but I have an E-trek Legend (Garmin) which I use in conjunction with "easy gps" and "Google Earth" as well as "MapSource". It's relatively easy to link my gps to EasyGPS and Google Earth in order to give me a broad, as well as accurate picture of what I'm dealing with. As for pin-point accuracy like you deal with, that's just way outta my price range. A Detector Pro Diver is about as accurate as I can get.