Here's some details in more detail.
1) It's payware - about $30 give or take.
2) The program does more than just replace the topology, which it does very nicely.
With TransDEM you can:
- Import DEM data of a specific area from nearly anywhere in the world. For people living in the US, we have a National Geologic Survey data server which supplies images and DEM data for the continental US, Alaska, and Hawaii.
- The program allow exact positioning of tile images or images directly on the surface of the topology. This includes historic topographic maps for the US.
- You can trace rail lines and have the program automatically lay the track in place. It has it's advantages and disadvantages.
- Trim down the baseboards to just include the route plus or minus boards on either side. This has it's advantages but also disadvantages as it's sometime easier to trim manually depending upon the terrain.
- By Using UTM coordinates, map data can be added to and a route expanded because sections add up.
- Creation of 3D tiles.
- Quite accurate too. I have seen height data within the tolerance of the baseboard grid in some places.
There is a bit of a learning curve, but the tutorials are well done and easy to follow.
So with the capabilities and accuracy of the program, it's worth getting for $30 or so.
The alternative older HOG with Microdem import of TIGER information is not accurate, though it's free and a lot more work to create the end results you want. With the older method, the routes, rivers, roads, and other necessary details can be off as much as 5 to 10 meters horizontally, which puts riverbanks on mountainsides and tracks in rivers.
Hope this helps.