A segment includes an out--and back, how close to the turnaround?

Edit:  I created a segment on a ride I do with some regularity that includes an out-and-back in the middle of it.  I waited a while and when I checked, it had populated with many (all?) of my previous rides so they qualified.  IDK if there were a few that didn’t.  Next time I do that segment I’ll try cutting the out-and-back short by ~100 yards and see if it still qualifies. 

There is a margin of error Strava allows for GPS drift and other inaccuracies around segments. If it’s within ~10m or so it will be counted. If your out and back bit is rather long and you skip it, the containing segment will probably not get counted. 

Yep.  Garmin Edge units used to have trouble with out and backs since the outbound and return track points are very close and can even overly each other.  It would sometimes think I was on the way back when still out outbound. On a segment with an out and back, I could turn around prematurely and never be more than 10m from a track point. Let’s see if Strava “keeps track” and sees that i skipped some.  I expect it will, but proof is in the pudding. 

Welp.  Finally got around to doing that segment with the out-and-back.  I turned around 85 yards short of the turnaround. Strava still counted the segment as complete.  That means I got away with riding 170 fewer yards.  Next time, I’ll cut it even shorter and see what happens.  STRAVA should probably fix this. 

My understanding is that Strava focuses mostly on the start and end points of a segment and the a percentage of the points within the segment that are within a tolerance (not quite sure what that would be).  Depending on the length of the segment, turning around early would still satisfy the need for most of the points to be within tolerance and only a couple closer to the turnaround would show as outside and likely not trip the filters.  The longer the segment, the more you could “cut the corner” so to speak.  

This particular out-and-back is part of two segments.  A longer one that is 1.57 miles and another that is just the out-and-back itself and is only 0.48 miles.  STRAVA said both were completed.  The 0.48 mile segment is 845 yards total.  I cut that short by 170 yards, or 20%.  

OK.  I did this out-and-back segment again and turned around 266 yards short of the end for a total distance530 yards short.  This time, STRAVA did not count the segment complete.  That’s good, but accepting cutting it short by 170 yards isn’t.  IDK what the algorithm or threshold is, but it should be improved. 

The Strava algorithms have weak GPS receptions in mind, therefore you can’t really improve them to better match your turnaround use case without negative consequences for other people. But your experiments were worth it, now we know that these shape of segments are not really suited for comparisons between athletes, except it can be made sure that everybody turns at the same place (like in competitions).

I totally understand, but 85 yards is way too big of a tolerance.  I only tried that, which it accepted, and turning around 530 yard short, which I didn’t, and don’t know where between those two the transition is.  It doesn’t bother me as I’m not generally comparing myself to others on the segments, but I believe it’s something to be aware of and certainly possible for STRAVA to improve upon.