Accuracy of max hill gradients using route mapping software?

[fossyant]

Take it with a pinch of salt, but when zoomed in, and the hill looks like / it's very steep. Ignored that twice, one was a walk it was that steep - did wonder why it got to the top of the hill so quickly, and the other wasn't welcome after a long ride.

 

[ColinJ]

I find it very disconcerting that if you plot a long route, a stated 10% max gradient could in reality be a 20% max gradient.

The reason for @GuyBoden starting this thread and posting that comment is that I had warned him of 15-20% ramps on the route we would be taking on my Scammonden ride. We did it yesterday. I am sure that he would be happy to confirm that RideWithGPS had got it wrong and that I had got it right...

 

[Ming the Merciless]

It tends to be closer on normal rides perhaps the garmin can't record fast enough a some speeds

😂🤣 I’m sure it can cope with someone on a bike. It will record once a second regardless. Unless you’re approaching the speed of light on your TT I don’t think it’d struggle.

 

[a.twiddler]

(A creaking of knees, the rustle of a paper map). Put not all thy faith in electronickery, nor all thine eggs in one basket, young traveller. Have thee a back up map. (Dozes off again).

 

[GuyBoden]

The reason for @GuyBoden starting this thread and posting that comment is that I had warned him of 15-20% ramps on the route we would be taking on my Scammonden ride. We did it yesterday. I am sure that he would be happy to confirm that RideWithGPS had got it wrong and that I had got it right...

Yes, @ColinJ was correct the gradients on yesterday's Scammonden ride were much steeper than RideWithGPS predicted.

RideWithGPS predicted that Sowerby Croft Lane was a max 10.1%, when it was a lot more than that. My front wheel was lifting off the road.

I've been riding up my local Frodsham Hill via Bellemonte Road for the last month, which is stated as being 13%, in comparison, the Scammonden steep climbs were a lot steeper than that climb.

 

[presta]

How else are you going to measure it?

Put a clinometer on the bike:

Depends how granular you want to get with your gradients

I've just checked Plotaroute, and it quantises at horizontal increments of 90m.

I haven't done this segment since I got my Garmin.

View attachment 700109
I wonder what it will register during the near 800 feet vertical pitch?

That reminds me of the day when I walked from Oxfordshire to South America and back again.

 

[figbat]

I have a group social ride coming up later this week - the organiser sent out a GPX file that I imported into Wahoo for use on my GPS unit on the day. It might be a bit beyond me though...

 

[Dogtrousers]

I have a group social ride coming up later this week - the organiser sent out a GPX file that I imported into Wahoo for use on my GPS unit on the day. It might be a bit beyond me though...
View attachment 700138

Those descents/free falls look a bit scary.

 

[ianrauk]

I had exactly the same thing at the weekend. I was going up a typical Kent hill which is in a deep chalk cutting. I must have lost signal for a short while. I glanced down at my GPS and it was saying 26%. I thought "it's steep, but it's not that steep". No, the max gradient was not 38.4%

View attachment 700117
If I look at the same stretch going downhill (where I didn't lose signal) it's actually about 500m long (so I lost 200m when I had no signal) and has a max grade of 21%. It's definitely steep. But not vertical.

What hill is that?

 

[Dogtrousers]

What hill is that?

Sundridge hill, runs parallel to Hogtrough and Brasted but a bit to the east.

 

[Alex321]

I have a group social ride coming up later this week - the organiser sent out a GPX file that I imported into Wahoo for use on my GPS unit on the day. It might be a bit beyond me though...
View attachment 700138

I've done a little more elevation than that









so far this year

 

[HLaB]

😂🤣 I’m sure it can cope with someone on a bike. It will record once a second regardless. Unless you’re approaching the speed of light on your TT I don’t think it’d struggle.

Not quite super sonic, the bit it seems to c0cked up the reading on is a short sharp dip where I hit 41mph before the short sharp climb where I was able to carry the momentum. When I'm grovelling up hills at 4-7mph it seems to cope with that better. Garmin's dont seem to process well very short descents, Ive seen on some of those stupid segments (usually called 'speed trap') values of the likes of 433mph

 

[ColinJ]

Put a clinometer on the bike:
View attachment 700126

"Accurately measures the steepest of hills"... but it only works to about 20%!

 

[Alex321]

"Accurately measures the steepest of hills"... but it only works to about 20%!

Indeed. The steepest hill I ride maxes out at about 33% - fairly short, but still a real brute.

 

[Dogtrousers]

Indeed. The steepest hill I ride maxes out at about 33% - fairly short, but still a real brute.

Where's that? (And how did you measure it? )