Dissolution

Beautiful weather so far this week, but I haven’t been able to get out quite yet. I did get to do some trail work at Sals on Sunday, while Anne did some hiking with Deb, so there’s that. Tomorrow is my volunteer day at the Canal Museum, and I’ll be riding over.

QGIS vs GRASS vs SAGA: I’ve been trying to work with some more geoprocessing tools, specifically Dissolve (where several regions that touch or overlap are combined into a single shape — their borders are “dissolved,” hence the name). I set up some small test shapes and tried dissolving them. It worked perfectly well with GRASS, but with QGIS the two shapes did not actually become one. I tried using SAGA, and got the same failure — WTF? I thought at first that both programs were broken, but then found out that the two shapes weren’t actually adjacent, there was an infinitesimal sliver of empty space between them; technically, they didn’t actually have a common boundary for these two programs to dissolve, while GRASS apparently has a built-in tolerance to handle slivers like this and just ran with it. The more you know…

More Maps: Check out Walking Purchase Park on the MTB Project. There were a few trails already done, but I added a bunch more, and it should now hopefully be a useful guide to the trail system there.