malikrthr wrote:
... I downloaded parts of NJ, NYC, upstate NY, Long Island, and Connecticut. ... I had 97GB. Today, I have 78GB of free space. ...
With TransDEM you are always running the risk of a project too big. Simply because much is automated and you just watch things happening.
But it's relatively simple math. The higher the resolution of the DEM and the bigger the DEM (talking about the cartographic data source here), the higher its storage needs, unfortunately resolution increasing it quadratically. It you have little disk space, stick to 1 arc sec DEMs. Do with 1:24k topo maps, refrain from aerial imagery wherever possible.
In TransDEM, make small modules, merge in Surveyor. Select DEMs to acquire in small modules, too, limit yourself to the data in the immediate vicinity of your route. You can't pack half of New England into one Trainz route anyway.
Instead of having to deal with 20GB of geo data you might be able to bring it down to less than 10% of it, by downloading only what you really, really need.
Taking a manual or less automated approach instead, like MicroDEM/HOG and/or Basemaps, you will less likely face memory or disk space issues for a very simple reason: It is much more cumbersome to produce usable data even for a small area. It's not the different "technology", TransDEM is not that fundamentally different from MicroDEM/HOG and Basemaps, it's automation that produces the huge output you may not be able to cope with.