TransDEM Forum

I'm experiencing problems where there is no elevation change is appearing in some areas. For example there is areas where the road is a lot lower than the rails but there is no change. Is there something i have to do to see this, any help would be appreciated

Where is your route project located and what kind of DEM data source are you using?

The route is located in western New York and I'm using 1/3 arc IMG DEMs from the USGS national map viewer.

I am not quite sure what the USGS policy is about man-made structures and their representation in NED DEMs. Mostly you'll find cuttings, high fills, ramps and abutments in 1/9 arc sec and often in 1/3 arc DEMs as well. Dams and causeways may even be found in 1 arc sec resolution. On the other hand, I have also seen 1/9 arc sec DEMs without apparent signs of transportation infrastructure.

Do the 1/3 arc sec DEMs of your project show cuttings, ramps etc at other places? If yes, could the missing features be the result of outdated data? A new highway, a new rail alignment?

The DEM is from 1998 but pretty much every thing has been there. There little to no elevation difference between rail, road and other infrastructure where there should be and I tried the 1 arc sec but its the same too. However the rail elevation seems to be accurate so maybe I just need to manually do the roads and other infrastructure.