How accurate?

[psferg]

Being new to TransDEM, I am curious as to how accurate I should expect the terrain to be. I have successfully imported a couple of maps into Trainz, and have started to play around with it in Trainz. Areas that appear to be more flat (looking at the topographic maps) are on slopes, and areas that have changes in elevation appear flat. Did I do something wrong? I am just wondering how accurate it is reasonable to expect. Also, is it typical that the trackage follows the terrain, as opposed to a graded roadbed, making it necessary to adjust the height of the track?

[geophil]

It depends on the DEM data source. The standard 3 arc sec SRTM data has a raster of approximately 60 x 90 m for temperate latitudes. USGS 1/9 arc sec NED DEMs have a raster of 2 x 3 m. The former will not resolve cuttings and embankments, the latter will. SRTM 3 arc secs will also have a limited steepness of mountain slopes.

See here for a comparison of US DEMs: http://forum.transdem.de/viewtopic.php?f=2&t=24