I have been to several LE courses on IED searching and detection. One technique the instructors used was this. Every time we left the classroom on break or lunch they would lock up the classroom. When we came back you had to tell what had been moved or added or taken away, they had several simulated devices they would place around the room, also outside in a field situation around cars sidewalks,etc.

Another technique is to establish what a normal situation looks like by taking a picture!! if it is blown up 8x11 the detail is very good and you can spot something that has been moved or added. I don't know how this would work in a large patrol area, but buildings,room,etc. work well. It was amazing how fast you will learn. Works best if several pictures are taken over time periods.

If this helps there are some other things you can do. Let me know.