10-15 years ago I worked on a prototype mine sweeping vehicle that had an array of coils that could detect a single firing pin backed up by a neutron backscatter array that could detect nitrogenous material. It created a waterfall plot display and had a paint jet array that would mark everything that it passed over. Parking lot tests showed that it could pick up a paper clip or any amount explosive. Sadly during a fly off against our competitors a Colonel who didn’t want us to win the contract blew it up with 60lbs of HE under the axle. It was enough to send the vehicle 45 feet as it tumbled through the air.