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How does Potlatch determine intersections? I went through their repo on GitHub, but I don't understand ActionScript. I searched the directory for the keyword "intersection," but there were only two results and they didn't seem too promising. From what I've been reading, nodes that are present in more than one way are considered intersections, I wanted to see this for myself and to my surprise, there were tons of extraneous points (thousands even in a small city). I thought about considering only the ways that had the "highway" tag on them, but I'm not sure if this is an exhaustive search of all the intersections considered by OSM - can someone please help?
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question asked: 09 Jun '15, 16:48
question was seen: 2,805 times
last updated: 10 Jun '15, 09:36
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From reading this question, it seems that you have some problem that you're trying to solve that may not be directly related to Potlatch2. Is that true, and if so, what is it?
Potlatch 2 can detect intersections, I wondering if anyone knows how they go about doing this and labeling them as intersections since nodes in OSM are not tagged with an intersections tag. I understand that a node that is in 2 or more ways could be considered an intersection, but I am only looking for the intersection of streets - simply doing this search gives us a lot of extraneous information such as the buildings that have borders that intersect, etc.
There is no other indicator except for the highway tag. Your approach seems sensible.
keep in mind that roads in OSM are split into several lines. For example, a road has to be split in two segments if you want to tag a change in max speed. This is also picked up as a possible intersection in Potlach. Depending on your needs, you might consider only including those nodes that belong to three or more ways tagged as highway=*. Keep in mind that "highway" is also used for footpaths etc, which you might want to exclude too.
Thanks scai. There are a lot of things going on with the Potlatch database that are very interesting to me - I know the code is open source, but are the databases used by the program open to the public as well?
good call joost, I'll keep that in mind
Does anyone know whether or not Potlatch is detecting these intersections, or are users marking them manually? I've seen a couple posts about how to merge ways and mark an intersection - does this mean that users have to mark them in order for Potlatch to display it?
What "Potlatch database"? Potlatch just uses the regular OSM database which you are free to set up on your own.
I'd like to see all of the nodes that Potlatch has tagged as "Intersections." I've already downloaded OSM data, but this tag on nodes does not exist.
There is no "intersection" tag. Potlatch just uses a heuristic for highlighting intersections. This is done by iD, JOSM and most other editors, too. It helps the user editing the map, that's all.
Where could I find this heuristic? I think it could potentially be pretty useful for what I'm trying to do. Thanks a bunch scai!
I'm not familiar with Potlatch2's code but this seems to be the relevant code line: https://github.com/openstreetmap/potlatch2/blob/9cab0567af82bf9e377bc42bfab96cdd9f95c68d/net/systemeD/halcyon/WayUI.as#L359
Thanks so much scai!