[ops33]

I remember several years ago having some time to kill and found myself in the public library looking at a book of photos of the English countryside taken from 1000'. The detail that came out of those photos was remarkable; old roads, villages, walls, buildings, etc.

[WoofDog123]

possibly one of the two books titled 'prehistoric britain from the air.' the best on is B&W and has amazing examples of crop-marks, soil marks, etc.

the other is color and mainly deals with visible monuments.

[TXnMA]

Yep, I also recall some low altitude photos of the English countryside. The best ones were taken with a low, grazing sun angle (near sunrise or sunset -- or in mid-winter with no snow on the ground). The shadowing revealed lots of stuff...

Modern "Overhead imagery" is usually at mid-day, and you have to rely on color and albedo differences to reveal old sites.