Computational periscopy or witchdraft?
Retrieving an image from a "shadow". This is at least intriguing; possibly even fantastic.
Software has been developed to analyze the color of, and intensity of light reflected off of fairly non-reflective surfaces to create an image of "what you don't see" in a photograph.
I'm not sure of any surveying applications for this process...but give it some time.
Hey, I locate monuments and set monuments that are behind trees and stuff all the time, lol.
This is how the NDVI sensors work for agriculture monitoring and plant health images - even from satellite imagery. The Normalized Difference of Vegetation Index uses the infrared and near infrared light reflections in photographs to depict how well an area of vegetation is thriving.
Here's one from an ortho of a 2.5 acre lot in rural suburbia
These images and the concepts behind the original post could be used to indicate where a road may have been at one time, given that the plant health over top of the subsurface may not be as reflective as the surrounding right of way for one. The images may also lead the surveyor to a low area that's not obvious on the ground in a large tract. Modern technology can be used in a number of ways if you know how to utilize it for an intended purpose.