dave2 wrote:IIRC it shines a beam of light out and measure the rebound to check for overhanging structures sand can be used to create a 3D shape pf each track and the distance of trackside structures such as bridges, power lines, signaling posts, platforms etc.
This allows a computer generated 'simulatoir'; to be created so you can tell if different classes of trains can go down a track without resorting to trial and error.
Cheers Dave, would never have imagined thats what it was for, thanks