Some years ago ,General Railway Signal (now part of Alstom) peddled a service in which they would run a hy-rail truck down the track with google like cameras mounted on it.

Except that there was two such cameras mounted side by side about 7-8 feet apart, for a stereo view. These digital cameras were very high resolution for the time. Some time before the run, they would set GPS based surveyor's beacons along the r.o.w. to give very precise location data for each frame as the hy-railer moved along.

The idea was to then record the track and every feature on it. The recording was then presented on a PC display. With the stereo data available, any object in view could then be precisely located by putting the cursor on it. Would have been great for pre-construction asbuilt surveys.

The transit agency I was assigned to at the time didn't go for it. I have no idea if any agency or railroad did buy it. but it would have been a tremendous resource if they had. It could even be used for training simulators to help qualify engineers on specific lines.

No Doubt however, they would keep it to themselves - as they are not in the entertainment business. -- too bad!