My youngest step daughter who has a masters in Civil Engineering has gone back to work part time. She works at a small startup firm that reduces data taken by a low flying helicopter over railroad right of way. The 'Copter slowly flies at about 150 feet above the ground. The data is from GPS, photos, LIDAR and probably a couple other sensors.
I was amazed at the data reduction she does. She has two 21 inch LCD panels in front of her. Some kind of CAD software. It is something to see the different layers she makes up from the data. Railhead height, roadbed, structures, control boxes, under passes, over passes, culverts, power lines, probably stray sticks, you name it. I think she is doing some data reduction for BNSF and CSX.
Here is a link a railroad that has done this.
http://www.njtransit.com/nn_press_release.jsp?PRESS_RELEASE_ID=625
I was not aware anything like this was going on but you can see the reasons in the article.
rikc9
The LIDAR technology was developed by NASA. I've seen it used by the folks at Mt St Helens & other places. The result will be a very accurate map.
BTW I don't mean to scare you, but have you looked at Google Earth & earth imaging programs? I'm amazed by the clarity of the pictures. It's fun to trace the local ROW. Guess if you want to hide something, It had better be under some big trees!
FEMA has been using Lidar for the past 4 or 5 years to develop new floodplain maps. Their plan is to re-map almost the entire United States. It's a great new technology that has many, many benefits not only for railroads, but insurance and flood mitigation too.