A Grand Experiment

I love my Garmin, but the  map it came with was horrible, so I replaced it with one from OpenStreetMap. (This is not news; I got the map years ago.) The process is tedious but pretty simple: there are sites you go to, and you pick what parts of the world you want a map of, then they do some data processing and email you to let you know when you can download your map file. The files are huge, like 3-4 GB for the one I got for North America, and they take a while to process and even longer to download. But once you have the file, you just put it on a micro-SD card, stick it in your GPS, and voilà — a much better map!

Maybe it was the choice of map file I made back then, or maybe OpenStreetMap back then was less complete, but my map didn’t have many offroad trails. I didn’t feel the lack too sorely, since on most of my offroad rides I already know where I am, but after the last big ride — when I had become a bit lost — I looked at our path on the latest OpenStreetMap cycling map, and I saw all the trails through the strip mines — singletrack, jeep road and all. Boy, wouldn’t that have been nice to have on the ride! I also noticed that all the trails on Broad Mountain are now on the map, including the “secret singletrack.” I’ve done a couple of (road) rides recently, where I mapped out a course online and then downloaded it to the Garmin and used its routing features, “turn left onto Main Street in 100 yards” etc, to follow my course, and I thought that it would be a great thing to try routing with an offroad ride. The only thing I’d need would be routable trail maps…

My understanding of the Garmin 810 is that multiple maps can be installed and enabled, and I’d been reading up on how to make the Garmin maps. (For years I thought it would be a cool project to make small custom maps of local trail systems, either standalone or as add-ons to a base map, but other than some re-purposing of GPX tracks I never really pursued it.) I didn’t feel like going through the process of downloading another huge (updated) map of North America from that map service again, but generating much smaller add-on maps myself, using OpenStreetMap data and the same software the original map service used, seemed to be fairly straightforward, and I could make a smaller updated file to add to my base map.

So that’s exactly what I did: I downloaded the data for a region around Jim Thorpe and saved it on my machine, then ran a Java program called “mkgmap” to create the map file. Installed it on my Garmin, and voilà — the trails were there! I then created a course online, following some Broad Mountain trails I know well, and arranged to go riding with Rich B.

Results were mixed. Our ride was great, but the downloaded route beeped an error message while loading and would not do any routing, though it would show the route on the map, and would indicate if we went off course. I got home and found that I’d compiled the map without routing capabilities, so I recompiled and reloaded my new map; it still awaits testing since I don’t get up to Jim Thorpe in a very regular basis.

Meantime, I thought I’d make a similar map for the trails at Lake Nockamixon, since I did have immediate plans to ride there. I drew up a course to follow (which worked fine), and compiled a map of the Nockamixon area, but this new map would not display on, or even be recognized by, my GPS. I tried making a few other maps, but the only one that ever worked was the original Jim Thorpe one, and I have no idea why. I eventually got so frustrated that I went out and bought a new micro-SD card, and re-downloaded the map of North America, a process that took about six hours (though I wasn’t actually present for most of it).

My next offroad ride will include a test of the trail routing capability of my new map. It better work.

(Just as an aside: my resting heart rate this morning was 49 BPM.)

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