Strava accuracy and hill categories

tiglon84

I started cycling a month ago, and have been using Strava as an app on my phone for most of that time.

When I look at the stats after a ride, sometimes they just don't seem right. A few days ago I got home and Strava told me I'd been up an 18.5% climb at an average of 13.5mph. Even though it was only a third of a mile, I don't quite believe I could have ridden it at that speed, and I don't remember going up anything that felt that steep. The hill I've climbed which felt toughest is (according to Strava) just 15%, and I average about 8mph up there!

On a regular route, there are two sections which feel like hills to me. One is very noticably more difficult for me, but is not categorised as a hill at all, whereas the other (easier) one is cat 4.

Is it best to take Strava stats/measurements as a rough estimate?

Also it often tells me my average speed on a ride was 15mph, when quite clearly I've been racing around at 30mph like a pro

djm501

It's often cobblers. Here in Cardiff there is a cat 4 climb along the Cardiff Bay Barrage. That's like calling Brighton Pier a climb! The elevation estimates are certainly not right - you can ask it to correct elevation on the PC once you've uploaded. Barometric GPS devices give much better elevation and instant gradient readout but even they are not entirely accurate or reliable.

Grill

My favorite Cardiff cat 4 climb is North Road to the Gabalfa roundabout... It's flat FFS...

wongataa

The Strava terrain data isn't all that accurate. I've spotted a cat4 climb where in reality the road is pretty flat.

slowbike

djm501 wrote:

Barometric GPS devices give much better elevation and instant gradient readout but even they are not entirely accurate or reliable.

Strava quite often detects a Cat4 climb from Garmin 800 data from just outside the estate that I work in to the main road to the turnoff ...
There is a short gradient to the turn off, but it's a descent from the estate to the main road ... overall there is no climb involved ...

djm501

Grill wrote:

My favorite Cardiff cat 4 climb is North Road to the Gabalfa roundabout... It's flat FFS...

Another goodun http://www.strava.com/segments/4684601 flat as a pancake but Strava thinks it starts subterranean stylee

[hint to Strava - routes that follow a river bank rarely have a strong gradient]

Guanajuato

Its because Strava uses satellite data with a fairly large grid. So it misses a lot of little ups & downs. And if the grid happens to coincide with a building or dense tree cover, it won't be using the road height as the height.
The Tour of Britain finish for stage 2 this year is a great example - a short sharp climb on a steep hillside surrounded by buildigns & trees. Strava reckons it never gets above about 8%. But the road is steep enough to have a handrail. Steep enough that busses and lorries struggle when its wet. There's one section where the road climbs about a foot in the width of a doorway. That's a tad more than 8%.
According to Strava, the road through Ings near Windermere is steeper. But its actually flat. :-/

richard_farrant

This is my favourite, almost completely flat yet 27.5% gradient..

http://app.strava.com/segments/2831091

BrandonA

If a segment has an incorrect elevation profile all you need to do is raise a support case with Strava and they will resolve it. I've done this on numerous occasions and without fail the issue has been resolved in a timely manner. It really is that simple :roll:

cesco

Max speed is also a funny thing on Strava.

roger_merriman

with bike GPS devices due to the nature of them be they phone/Garmin/whatever and indeed strava and other mapping software.

you'll get silly high peak gradients and speeds, but thats expecting a level of accuracy that the system (GPS) was never designed for.

markhewitt1978

roger merriman wrote:

with bike GPS devices due to the nature of them be they phone/Garmin/whatever and indeed strava and other mapping software.

you'll get silly high peak gradients and speeds, but thats expecting a level of accuracy that the system (GPS) was never designed for.

That's 1970's tech for you

term1te

This is one of my favourites a 9.9km HC climb with one section at nearly 1200% http://app.strava.com/segments/2477756 Respect to everyone who has climbed that one!

If the first person to upload a section has altitude readings, does that get used, even if it is wrong? Or does Strava always calculate elevation from the map? In the linked segment, most of it is 300m below sea level. I've never been there, but suspect this isn't the case.

bartimaeus

It's down to rubbish GPS plots... GPS elevation data is often very poor, so you often see tracks starting at e.g. -50m and then correcting to e.g. +50m generating a sudden 100m elevation gain. Where Strava gets it wrong is that it automatically creates a segment when it detects what it sees as a Cat4 or bigger climb in this dodgy data... so you then have to ask them to remove the segment.