Match New Segments Not Working

BunBun! said:

but it doesn't always work.

It does not work when the route of the respective activity does not match perfectly all key points of the sector. It can happen not only due to a slightly different route taken, but also due to the limits of the accuracy of the GPS technology, Otherwise it seems to work fine

No, that's not it. I had activity with some segments but not all, so I used Match New Segments, after scan all segments disappeared and next scans didn't add them.

Before that update there was no problem, all segments were shown, so that's not GPS accuracy, some differences are ok.

Problem with segments usually happens with longer activities.

BunBun! said:

I had activity with some segments but not all, so I used Match New Segments, after scan all segments disappeared and next scans didn't add them.

Ah, OK, I did not see (yet) such behaviour. Did you try recreating all the sectors for that activity, and scanning for new ones again?

Well, that would be bad to delete segments and recreate them, all statistics would be lost and old activities would lost those segments too, and it would take a lot of time to recreate them. So, no, I didn't touch those segments.

Better not to have segments only in some longer activities, but keep them in shorter.

And I don't think recreating would fix this.

I checked again, and my 57 KM activity still has 0 segments.

This looks like there is a limit after it breaks (long activity with a lot of segments).

I'm having this issue as well. I created some segments a few days ago and tried to "match new segments" with my old activities. It is very sporadic which activities matched new segments and which did not. From the looks of it is not GPS accuracy, it is all just completely random which ones worked and which ones did not. Sadly more than half of my activities would not add new segments.

whittgu3 said:

From the looks of it is not GPS accuracy, it is all just completely random which ones worked and which ones did not.

It almost certainly is the GPS accuracy. A few weeks ago Garmin probably decreased the tolerance, hence the sensitivity is now even smaller than it used to be. The tolerace seems to be somewhere between 20-30m, and you won't see the deviations unless you really zoom to max and compare the tracks very closely.

The most critical is the starting point, and the biggest problem is hard to spot especially if the starting point is on a straight path. If you use the "Smart recording", new GPS keypoints are only logged when you change the direction, speed, elevation, or your HR changes, so it can easily happen that on a straigh line the keypoints are distanced many tens of meters. So if you are not lucky, one keypoint can be more than the 20-30m before the starting point of the Segment, while the next one is more than 20-30m after the starting point. 

So although the track may visually overlap perfectly, the Activity won't match the Segment, because the keypioints do not match the starting point. You will not see it immediately on the map, unless you zoom on the timeline and step through the keypoints one by one. You can improve the matching by switchning from the Smart Recording to Every Second Recording, in the GPS System Settings on the watch.

On the other hand, Garmin recently changed also the tolerance at the end point, that is for some incohemprensible reasons much more relaxed than it used to be. On segments I use, I see more and more matched Activities who only pass through the starting point of the Segment, follow it for little bit over the ½ of the way, and then turn to a completely different direction (or even in the reverse sense), and are still counted, while the moment they leave the segment is taken as the total time, making them so mostly the leaders of Segment. Recently I see such cases on practically every Segment I use, rendering the Leaderbord completely useless.

The issue I have with believing it is GPS accuracy is that I created segments from rides, and I have only done that particular ride once. However, the new segment is not showing up on the ride. How could this be possible if GPS accuracy was the issue? All the points should be identical. 

whittgu3 said:

All the points should be identical. 

From what I observed, it is rarely the case. For some reason, when a Segment is created from an Activity, the number of points is reduced, in the resulting Segment, and some keypoints may get interpolated, or moved. Try opening both the Activity and the Segment, zoom to max, and compare them point by point (especialy the starting point).

Makes sense. It seems that the solution is Garmin Needs to make the starting point less precise.