TransDEM Forum

I have created a large DEM to cover the area of the Sierra Railroad in Northern California. The line runs from West to East but heads in a Northerly direction. I would like to crop part of the current DEM so that when I move it into the Trainz conversion I won't have some many "tiles" to delete before I begin "laying" track and assets. Or do I have to create smaller DEMs along the route and merge them together?

There are three options here.

• You can crop the DEM. That's particularly useful if the DEM covers a much larger area than traversed my your railway route. With the cursor set to the default pointer, drag a rectangular mask with your route on the inside. Select the scissors tool and click outside the rectangular mask to crop.
  
• You can (and should) limit the export area for your Trainz route. Again, this is done with a rectangular mask, crtead and positioned before you open the export dialog.

These first two options will always produce a rectangular area.

• You can (and should) also limit the creation of Trainz baseboards to the immediate vicinity of your route. This is a accomplished with the baseboard filter, activated in the Trainz export dialog. It needs basic vector data, the course of your route, to work.

The most efficient way is to combine all three options. First, crop the DEM if it's too big, but leave enough "breathing space". Then load your vector data (or draw new polylines and save them) to mark the course of your route. Finally, drag an export mask before opening the export dialog.

Thanks for the rapid response. I shall try all of your recommendations.