Overview

Build a buggy which has software controllable drives. Put a GPS receiver on it. Feed the receiver to a RPi. Get the RPi to command the buggy to move in some kind of systematic way. The buggy is not going to end up exactly where we want but I don't think this matters. Once we're at something like the correct place, stop. Get the metal detector to move in some kind of pattern to survey the surrounding area. Feed the results into the RPi. Build up a picture of the results using a graphical representation.

Buggy

GPS Receiver

Metal Detector

Detector indexer

RPi