Getting Topo Maps, Compliments of the US Government

So we're planning a backpacking trip to Glacier NP for this September. This just so happens to be the first major backpacking trip outside of California since a finally started using Topo! software a couple years ago. The great thing about Topo! is that you can trace your intended route and it gives you really spiffy elevation profiles (including distance of course) so you can get a sense of what the trip will be like.

This is *especially* useful for cross country trips when you try to put one together.

Great. So what's the problem? Well, as far as I can tell you can't just purchase additional state data disks for Topo! - you have to buy the whole thing over again but for a different state. That means I gotta shell out $79+shipping (eBay price) for a new copy of the software for use in Montana. Not cool.

There are a few other options:

1. Use Google's topo maps (click on the Topo layer inside regular Google maps). This is good, but doesn't get me the elevation profiles that I really care about.
2. Use one of the other online Topo services that want you to use them for large format printing. Ok, but still not giving me everything I need.

Still unsatisfied, I started thinking - "You know these guys must all be getting the same data (Topo! included), and that data is coming from the government, and the government usually gives stuff away for free. I wonder where I can get it!?!"

Turns out you can download al the GBs of map data you want, all compliments of the USGS and NASA:

ftp://e0srp01u.ecs.nasa.gov/srtm/

Yes, it is incredibly difficult to find what you're looking for amongst the volumes of cryptically named data, but you can also browse this data (but not really manipulate it) at:

http://seamless.usgs.gov/index.php

Then, there are some free viewers you can import the data into:

Tatuk GIS Viewer: http://www.tatukgis.com/Home/home.aspx
dlgv32 Viewer: http://mcmcweb.er.usgs.gov/drc/dlgv32pro/

This is all pretty hacky compared to a nice commercial software application like Topo, but if you've got the time to waste, you may want to take a look.