Minimum Segment length ?

[Ian]

I noticed that someone recently asked that the minimum length of mountain bike Segments be decreased and the post was quickly archived by an admin on the basis that reverting Strava changes could not be discussed.

I have some sympathy for the poster - I was also somewhat frustrated by the recent increase in minimum length of bike Segments from 300m to 500m.  In my area there has been some good competition over Segments about 400 to 450m in length but such Segments can no longer be created or edited (the change happened as I was working on a new Segment of about 450m - it now finishes closer to a T junction than I would like but editing is no longer possible).

I don't remember seeing any requests from Strava users for such a change in the previous Strava Support forums so I wonder if someone at Strava could give some background to their reasons for making the change and their methodologies for determining minimum Segment lengths for each Activity type ?  Clearly measurement accuracy is a factor on shorter Segments, but even on a 300m bike Segment the accuracy should be within a couple of % which seems OK.

[dogofob]

This new minimum length has nothing to do with "accuracy of timing" but it certainly does degrade riders' safety when they can't shorten an unsafe segment that ends right at an intersection.  Fwiw - modern GPS units can track speed over 100, 200 and certainly 300m very well.  No, the change likely has to do with the execs wanting to save money on infrastructure overhead required to track a lot of short segments.  I wish they'd just say so if that's the case instead of lying to their customers.  I came upon this post after trying to create a safer version of a favorite hill whose segment ends right at a busy intersection.  Often I sit two meters from the end of it waiting on the light and cars in front of me.  I tried to shorten it by ten meters and found out I can't make anything close to this segment anymore thanks to their unilateral change.  With recent price hikes and other unsavory corporate behavior recently, I'll certainly be on the lookout for Strava's competition.

[dswest]

i'm not certain that your premise is correct. On Garmin, yesterday, I created an uphill sprint segment that I calculated to be 482m long. Today, someone clocked that segment at 48.5mph. This is clearly a recording error. Two other people broke 40mph. If you look at those people's rides, most did not even break 30mph even going downhill. So, perhaps there is some merit to timing accuracy claim...i'm going to have to do some research.

[anchskier]

@dswest - Are you sure it was a recording error and not just a case of someone not turning off their GPS after getting in the car and driving the segment?  Usually, when I see speeds in the 40-45mph range, it is simply because they had forgotten to turn off the GPS when they finished their ride and drove home.

[dswest]

Yes, there is no road adjacent--it's a bike path cutting through the desert. I held the KOM until recently...i logged me at 50, I was only doing 27.8 (from a standing start) which is not bad for an old guy on a pretty good grade. I covered the distance in 21.4 seconds according to my Garmin which measured .30 miles...i think the length is the problem--I think it's more in the neighborhood of 250m. The new KOM is 21.3 seconds. It's frustrating but there is clearly some measurement variation that is causing problems...Strava may have cause to set min. length given the vast array of GPS devices reporting location. I'm not happy about it, but I'm a data scientist by trade and the data tells me something is off.

[MakeStravaGreat]

Length isnt the problem. its ppl using cheaper watches with poor GPS settings. If you dont have the option of multi GPS then it sometimes posts incorrect data. It happens on longer segments too. I just flag it when i see it. my mates watch does it sometimes. 

[StuartB]

Is there not a method by which GPS accuracy can be detected and then the information used to disqualify segment times for that ride?

[MakeStravaGreat]

Make it only quality devices are allowed to be added to leaderboards? ive noticed that devices without the satellite option 'All + Multiband' offer average results at best. 

[dswest]

Presumably one could compare accuracy of place--does the GPS vary from the path within some tolerance, but it's very difficult to tell how accurate a particular GPS is without some kind of calibration. I suppose that if I had the time, and the data set, I could create a model that could detect with reasonable certainty if something was accurate (I'm a data scientist by trade) but, unfortunately, I have neither. What I do have is my own N of 1 data set which tells me mine is sometimes quite good and other times horrible (e.g. last week while riding the velodrome in LA when it put me in the LA river for a few laps...it also recorded my speed for my flying 200m at ~half of what it actually was!--there are official timings so the speed is known.

[MakeStravaGreat]

I own a Garmin Epix 2. It has the option of "All+Multiband". This option is extremely accurate. even when riding in places in the middle of nowhere and heaps of tree coverage. 
Mayb each activity should show the type of GPS setting too? 

[dswest]

I've come to the forum specifically to request shorter segments. I was just trying to create a 300m uphill sprint segment. I'm a sprinter and even super short 50m segments are important to track for me--as they are to most sprinters wanting to keep track of starts. Some of our races are only 200m long. We should be able to create short private segments, though public is also probably a desirable thing. As a short distance track sprinter, the 300 to 500 change might be a subscription deal breaker for me--500 is the longest sprint distance I train for...the shortening happened during a time when I was off the bike by Drs orders and I've just discovered the change as some segments I that were there in the past are missing--probably from the "cleanup". I'm very disappointed with Strava on discovering this change.