The system, which presents both the pilot and the ground units with an identical colour map of the target area as well as GPS co-ordinates, works in real-time and has a range of about 50 km

I was curious: I wanted to colour in all those parts of the European map that had until then been grey.

To create a heat map, simply take any model of the system and shade or colour different areas of the model to indicate the ease or complexity of working on different each area.