Is this a bombing range or firing range area?

[Adriano Baumgartner]

Good night Gentlemen,

Could you enlinght me about this particular picture recently sold at Ebay, showing a low level Do 17 flying over this misterious things on the ground.

Is that:
a) Some kind of bombing range (for target practice)? If so, the crew seems very very low
b) Some kind of air to ground firing range (for gunners to practice air firing or air to ground firing)?

I had never seen such things depicted.

Many thanks for any input

Adriano B.