From the same institution which brought us the sublime book by Daniele Ganser, Secret Warfare : Operation Gladio and NATO's Stay-Behind Armies, a fascinating article by retired Irish Army colonel, Desmond Travers:
It was an open secret among analysts during the Cold War that the two major powers used satellite and high altitude surveys to assess each others aims, intentions and resources. Indeed it was US satellite surveillance which first noted the disparities between the USSR's claimed crop yields and the reality, as Khrushchev once bitterly observed to his US adversary!
Colonel Travers carefully compares the Soviet maps with those of the Ordnance Survey, noting how the Soviets included some objects that the OS did not, but neglected others. They seem to have been oddly attracted to water-mills! More chillingly, it looks like they may have been categorising Irish roads based on how militarily viable they were, for logistical support.
I encourage you to read this article, and gain another viewpoint on our rolling terrain. Imagine plotting tank-routes and support artillery...