E53 

I have a Strava segment which is driving me nuts. A couple of years ago I did my pb at 1 minute and 41 seconds. I ride with a Garmin 1000, and with Garmin Connect turned on. Today I rode that segment at one minute forty seconds according to my Garmin, however, when the ride got downloaded to Strava at the end of my ride, it read one minute and 43 seconds. Frustrating! Garmin is probably not to blame because I seem to remember Strava doing the same thing when I didn't have the Garmin and I just used Strava on my phone. There is probably no solution to this problem, and forget about Strava support; it doesn't exist!

DrIsotope

Oh, it's definitely Strava. They "reinterpret" your GPS data during upload. Every segment has a defined GPS coordinate for it's start and finish. Unfortunately for us, the precision of consumer GPS units is about 10 meters, and can be worse at speed. So in one second, moving at say 20mph, your GPS inaccuracy could be 60+ feet. Strava will generally move you back to whatever the last GPS point was before you entered the segment, and do the same for the end-- pick the closest coordinate after the end. So you can cover an additional 60+ feet and get no credit.

Sometimes it falls in your favor, mostly it doesn't. Strava adds time to my segments and rides pretty much daily. I've KOM'd a segment by two seconds (via Garmin) and after upload got a tie for first. I recently lost a KOM where I in the compare efforts graphic, I was ahead by 5+ seconds with a few hundred yards to go, then the new 1st place just shot forward like he could ignore physics-- speed didn't change, he just covered the distance instantly. GPS errored in his favor that day.

sdmc530

I had this same thing happen two weeks ago. There is a shorter segment near my house and the KOM was 51 seconds. Its a bike path right next to a road. The road was closed one morning for road work and I was riding early. I rode on the street for the 1/4 segment and did it in 49 seconds according to my Garmin but Strava said it was 52 seconds....I was kind of mad that I didn't get the KOM. Strava is just its own worst enemy sometimes.

canklecat

Try different apps. Often I find logging to Wahoo Fitness or Cyclemeter, then uploading to Strava, works out better than recording directly to Strava. Fewer glitches too. I rarely rely on Strava to record rides after losing too many rides. Typically if Wahoo Fitness, Cyclemeter and my bike computer say I averaged 16 mph over a 30 mile route, Strava will show it as 14.7 mph. If Strava wants to seduce more middle aged paying subscribers they'd better cater harder to our delicate egos.

And GPS is only approximate so short segments aren't worth worrying about. I've hidden most vanity segments on Strava, those things someone created only 0.1 or 0.2 milettes in shortness and should have set to private. It just clutters up Strava.

The only segments I pay much attention to are around 5-10 miles long, or climbing segments of half a mile to a couple of miles long. There might still be a timing discrepancy of a second or two but it doesn't matter much over the course of a segment that takes 10 minutes to half an hour to finish.

If you want accurate measurements for short segments you could use a speedometer and fumble with the stopwatch feature while sprinting. Or get friends to time starts and stops, then trade off while each takes a crack at the same short sprint zone.

I think I have one "KOM" on a mile long loop, but it's flat so not really a KOM. I quit riding that loop after a fastest time of 20.something mph on a posted 20 mph speed limit residential zone.

Any KOM I can snag isn't worth the effort. I know a dozen guys my age and a few women who could beat my best time pretty much any day. I'm lucky to be solidly middle of the pack on any real climbing segment where a KOM means anything. I'm in the top ten on a couple of climbs but that's mostly due to the relative absence of Strava logs from young pro and amateur riders. The top ten are all either fairly strong but middle aged or older dudes, or two or three women pros. Seems like the young guys on the local pro team don't post on Strava, or don't post publicly so their records aren't displacing us MAMILs. I know they ride these routes because I see them on early morning training rides. But they don't show up on Strava. I reckon they're taking pity on the rest of us.

E53 

Okay, I guess I shouldn’t take the whole segment thing too seriously then. 😊

CliffordK

Actually, the issue is GARMIN.

Here is a segment with the opposite issue.
https://www.strava.com/segments/12973075
https://www.strava.com/activities/258703543#16784982100
KOM: 34.2 MPH, 47s.
Max speed on segment: 34.0 MPH
And on the analysis page: Average: 32.6 MPH.

So, according to Strava, the average for the KOM is faster than the Max speed. The result is that it makes it real tough to catch the KOM.

In this case, the cyclist is using a Garmin Edge 200 that takes a reading about every 5 seconds.

Strava seems to choose the start/stop point to the nearest 5 seconds (no idea why it isn't divisible by 5).

So, if you're lucky, Strava knocks off about 2 seconds on each end, and one's time ends up about 4 seconds low.

If you're unlucky, Strava adds about 2 seconds on each end, and one ends up about 4 seconds high.

Ideally, Strava would interpolate speed/movement. Although that wouldn't be ideal as speed may not be constant. Standing starts?

TO FIX
Some GARMIN devices apparently let you set the number of readings down to 1/second, or perhaps allows you to turn on or off "battery savings mode".

burnthesheep

I've won out and lost out due to this. And a few ties due to the same.

Isotope's explanation is correct. Also, this can be why your altitude on some really curvy routes (like a greenway or gravel trail) might be low. It doesn't detect a change in altitude since you didn't cross over part of the "mesh" of the altitude coords around you. So no credit there either.

I find routes running or biking with longer straight runs to be more accurate than ones with lots of little turns. Particularly turns and jukes that are really small.

Metrics for a cyclocross course are a joke with gps. Best you can do is just know your start/end point and manually utilize your lap function on a GPS. Just choose the start/end point at a far end of the course you don't get close to during the lap.

E53 

There's been some great responses to this post so far, and I'm glad I posted it. It all makes sense, and I'm going to try fumbling around with my Garmin to see if a change of settings will produce more consistent results.
For the record though; I CRUSHED, CRUSHED ,CRUSHED my segment today!!!! Although the Garmin read 1 minute 35.85 seconds, I got credited for 1 minute 39 seconds which took an entire two seconds off my previous time of 1 minute, 41 seconds which I've been trying to beat for three years!! Not only that...I am now in the top ten (10th) for my age group for that segment!!! My ego is through the roof right now, and I probably need bigger shirts and hats as a result.