I use Strava Metroview and they create their edges (ways) based on the OSM ways available for that location. As I understand it, ways are created through a collection of nodes. What I don’t understand is what determines where ways end. A new way will start where the previous way ends, but why do they end where they do? Ways seem to be of varying size and I am trying to determine if there is a reasoning behind this or if it is just how they are created
Very often this is determined by changes in the characteristic of the objects in the real world. I suppose you are talking mainly about roads/streets/paths? Each section of way may be tagged with multiple characteristics, and wherever any single characteristic changes, a new way is needed in the OSM data.
That’s fairly obvious if a primary feature changes, e.g. a residential street becomes a track and then a path. It’s also not surprising where the name changes. It also applies to less obvious tags, e.g. surface, sidewalks. Or it may be driven by routes that include a way, e.g. if a bus route or waymarked cycling or hiking route includes a road up to a certain point but not beyond it, there will be a split at that point.
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Everything Alan said, as well as this: I know that when I edit OSM, if there is a way that has some feature or attribute about it that is in the middle somewhere, I am perfectly free to split the way at that node if I need to. Any OSM editor is, really (if it is necessary to improve the map). Split, join, extend…
For example, if I am “making” a bicycle route (which means including a collection of ways in a bicycle route relation as way elements), but I need to split a way so that the CORRECT collection of segments (ways) that make up all of the elements are properly in the relations, that’s OK. Right up until that point in time, the ways were simply “drawn in” by people who either initially created them, and/or modified them. Then, perhaps I came along and “modified” them again, because a particular set of segments needed to be pieced together in a certain method and order to make that bicycle route. Ways in OSM get modified like this all the time: sometimes split, sometimes their nodes moved a bit to be in a more exact alignment with the real world, sometimes extended, because, say, a road was extended “further.” All of this makes for a sometimes-interesting collection of ways, to say the least, so “good question!”
Part of the answer to your question is that “ways first start out as they are created…” and part of the answer is “and then ways are modified to accommodate what that mapping author needs to edit into the map to capture what s/he knows to be true as they map it.”
I hope that helps!