How-To: Pocket-Sized Maps for the iPod
This is the result of an experiment to put a topo map of Mt. Cameroon on my iPod nano. I’m hardwired with a fascination for maps of all kinds (my post Crowdsource Mapping Cameroon is but one example) so you might say this was inevitable. The 4GB video nano replaced my trusty 60GB iPod which died high up on Mt. Cameroon over a year ago, so it seemed a fitting tribute.
The video nano stores thumbnails in a 5 x n grid, with each photo sized at 220 x 176 pixels. So, ideally, a map should be scaled to 1100 pixels horizontally by a vertical dimension divisible by 176. I just so happened to have a scan of a Mt. Cameroon topo map cropped to 1100 x 880 pixels, which factors just right for the nano. Here it is (click for the full version):
I could’ve chopped it up in Photoshop, sure—but who has the time? One of Larry Wall’s three virtues of a programmer is laziness, after all, and who am I to defy the master? Python seemed like the best tool to slice and dice the map with but I was missing PIL, the Python Image Library. A roundabout Google search landed me at this guy’s page where, lo and behold, he’d done a neat job of coding just what I had in mind. Done and done!
His script supports iPod video, photo and nano thumbnail formats, so I was set (albeit a tad disappointed at not hacking it myself). It generates tiles like so:
…which when stitched together produce a nice map on the iPod nano like this (click for a bigger view):
You can, of course, select any tile with the thumbwheel and get the full-sized map segment. As a 1:500,000 scale topo map with 500 ft. contour intervals, it’s more of a novelty than a practical tool for someone navigating the mountain. But I still think it’s pretty cool. Good maps of Cameroon (and Africa, generally) are difficult to find. If I can get ahold of a more detailed topo of Mt. Cam, I’ll superimpose the popular hiking routes, huts, landmarks and so on.
Here’s a nano-ready zip of Mt. Cameroon to download.
Thanks to jbuhler’s Maps for iPod, the right way.
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