There isn't really any existing open source program for offline mapping, something that works even when you don't have a network. So long ago, I wrote Pytopo, a little program that can take map tiles from a Windows program called Topo! (or tiles you generate yourself somehow) and let you navigate around in that map.
But in the last few years, a wonderful new source of map tiles has become available: OpenStreetMap. On my last desert trip, I whipped up some code to show OSM tiles, but a lot of the code was hacky and empirical because I couldn't find any documentation for details like the tile naming scheme.
Well, that's changed. Upon returning to civilization I discovered there's now a wonderful page explaining the Slippy map tilenames very clearly, with sample code and everything. And that was the missing piece -- from there, all the things I'd been missing in pytopo came together, and now it's a useful self-contained mapping script that can download its own tiles, and cache them so that when you lose net access, your maps don't disappear along with everything else.
Pytopo can show GPS track logs and waypoints, so you can see where you went as well as where you might want to go, and whether that road off to the right actually would have connected with where you thought you were heading.
It's all updated in svn and on the
Most of the pytopo work came after returning from the desert, when I was able to google and find that OSM tile naming page. But while still out there and with no access to the web, I wanted to review the track logs from some of our hikes and see how much climbing we'd done. I have a simple package for plotting elevation from track logs, called Ellie. But when I ran it, I discovered that I'd never gotten around to installing the pylab Python plotting package (say that three times fast!) on this laptop.
No hope of installing the package without a net ... so instead, I
tweaked Ellie so that so that without pylab you can still print out
statistics like total climb. While I was at it I added total distance,
time spent moving and time spent stopped. Not a big deal, but it gave
me the numbers I wanted. It's available as ellie 0.3.
[ 19:24 Oct 30, 2010 More mapping | permalink to this entry | comments ]