Over the Hol weekend I was talking through the night with a friend and the conversation drifted onto the strange lumps in his field. Inspired by watching Time Team, (or the excellent single malt) we reconned that we could 'easily' knock up something to do some geo-phys and map what's under the ground. His field is HUGE, but I can borrow RF equipment from work and we can tow it on a trailer behind his Land Rover, all good so far. I can easily knock up a little circuit to take the reading from the RF receiver and store it into FLASH until we download it into a laptop (rather than tow my laptop !). All good so far, BUT here's the problem, GPS only gives a resolution of 10m and we are probably looking to go better, say about 0.25m.
I am looking for any suggestions to map the location of the readings. I don't think 'dead reconning' is going to be any good as the Land Rover bounces over the field (it's pretty rough). If it was inside I would probably measure the position using ultrasonics, but there would have to be an ultrasonic PA stack to broadcast across the field, and think of the dogs in the village ! I don't want to broadcast RF as it's a pain getting it legal (other than the stuff we need to fire into the ground). Our fav idea (so far) is to put poles on 3 corners of the field flashing IR LEDs, then measuring the angles to them on the trailer, doing a bit of trig and working out the position.
We are looking for any easier ways of doing this. any suggestions greatly appreciated