So far the best free lidar data I've found comes from the US government agency NOAA. They have a web site at http://www.coast.noaa.gov/dataviewer/# where you can select an area and download the data. The best part about their site is you can choose the units & format for your area of interest. I've also found choosing only the "ground" points to be best for trackmaking. When you get the data into BTB, then you only have to classify the points between ground and road. Buildings & structures show up in the "ground" data as holes in the point cloud, so it's fairly easy to place structures accurately. Still, if something you need isn't in the "ground" data, like a building that you don't know the height of, then get all the points in a second download and delete the points you don't need. Poking around historic tracks ("ghost" tracks), often a property owner has purposely broken the pavement so hooligans don't go racing without permission. The majority of the surface might be in good shape except for rips down the middle or across the track every so often. Once you get a BTB track mesh lined up & track height calculated, then you can carefully navigate the track in 3D and delete the points that are obviously too high or too low. Recalculate the track height and presto, a restored racing surface! Other times, the earth has been moved to the extent that the point cloud is useless for the track surface (example: Bridgehampton Raceway turned into a golf course). So far I lay a narrow point-to-point track calculated to the point cloud as a guide, then loft another track into place using the narrow track and start laying down terrain. Test before considering this a final version.