There are many applications for GPR but the one I have been focussing on the most has been landmine and UXO detection. GPR is a popular sensor for this but by no means the only one. From big complex neutron sources to small thermal cameras and magnetometers a wide variety of sensors have been developed to detect landmines.
While we were focussing on GPR I wanted to explore what other sensors we could mount or fly alongside the GPR and that could provide a complimentary picture. This then crystallised into a summer project for Skycap intern Alex Davey. After some in-depth research into the spectrum of relevant sensors the decision was made to experiment with an active EMI sensor (i.e., metal detector).
To be honest I was rather sceptic that something useful could be done with a drone based metal detector given the proximity needed to the ground and the potential for two way interference. However, the initial numbers did not rule it out and extensive handheld testing with military grade detectors on real mines showed the idea may have some legs after all. If not for minimum metal AP mines, at least for the bigger stuff (please also note the caveats from post one).
We settled on some standard detection electronics & coil which Alex the customised and integrated with a fairly standard quadcopter testbed. The end result can be seen in the following video:
My own conclusion is that, while it seems silly initially, the core concept has been proven feasible, if definitely non trivial. That is still of course a long way away from being something that can be operationalised (if that makes sense at all), many challenges remain. In any case given the time and budget constraints it has definitely exceeded my expectations.
As a first next step I would like to switch to a larger coil and look into the terrain following aspect. As well as explore the passive EMI sensors, though they have their own bug bears.