Author Topic: DIY Mandatory Climbing Values  (Read 766 times)

Bianchi Boy

  • Cycling is my doctor
  • Is it possible for a ride to be too long?
    • Reading Cycling Club
DIY Mandatory Climbing Values
« on: July 08, 2018, 10:20:57 am »
Hi,

I have just submitted some mandatory route DIY events and have been surprised by the climbing figures. They are higher than expected. On Strava it shows as 2,612m and on the DIY page 3,785. On the Garmin (eTrex 30) it showed about 3,000 for the day. I know this has been a subject of great controversy over along time. Which do you consider the values closer to reality?

I have been using Strava to judge climbing recently and have found it to be quite consistent. This was a hard day and felt more like the DIY value.

BB

Set a fire for a man and he will be warm for a day, set a man on fire and he is warm for the rest of his life.

Re: DIY Mandatory Climbing Values
« Reply #1 on: July 08, 2018, 01:00:56 pm »
Strava is consistent, but it always under estimates.

LittleWheelsandBig

  • Whimsy Rider
Re: DIY Mandatory Climbing Values
« Reply #2 on: July 08, 2018, 01:08:48 pm »
HK's Wahoo seems to collect considerably more climbing than my Etrex 30x during the same ride. Which is more correct? I think estimates differ between web pages in a similar manner. Does it matter, provided you use a consistent method and know what the numbers 'feel like'?
Wheel meet again, don't know where, don't know when...

Kim

  • 2nd in the world
Re: DIY Mandatory Climbing Values
« Reply #3 on: July 08, 2018, 02:23:42 pm »
This is a sampling problem, so there's never going to be a 'correct' answer.  Consistency is all you can ever hope for.

If you're used to Strava's figures, then they're going to be the most meaningful to you.
To ride the Windcheetah, first, you must embrace the cantilever...

alfapete

  • Oh dear
Re: DIY Mandatory Climbing Values
« Reply #4 on: July 08, 2018, 02:37:07 pm »
Doesn't it depend on the 'units' of climbing used?

If you record every single metre of climbing you'll get a different figure from if you record every 10 metres - compare a gently undulating flattish section of 30km which might go up and down +/-1 metre repeatedly and will show, say 50m of climbing over its length. The same ride recording only 10m climbs or dips may show 0m of climb at the end. I guess contour counting on maps of different scales is another manifestation of this.

I've often cogitated on this, never vocalised it - other opinions may vary.

And this leads to this:
... there's never going to be a 'correct' answer.  Consistency is all you can ever hope for.
alfapete - that's the Pete that drives the Alfa

Kim

  • 2nd in the world
Re: DIY Mandatory Climbing Values
« Reply #5 on: July 08, 2018, 02:54:00 pm »
If you record every single metre of climbing you'll get a different figure from if you record every 10 metres - compare a gently undulating flattish section of 30km which might go up and down +/-1 metre repeatedly and will show, say 50m of climbing over its length. The same ride recording only 10m climbs or dips may show 0m of climb at the end. I guess contour counting on maps of different scales is another manifestation of this.

I've often cogitated on this, never vocalised it - other opinions may vary.

Both the precision with which you measure height, and the interval with which you sample it are important.  You can count every contour on a map, but that contour map itself is derived from someone going out[1] and measuring the height at intervals and joining the dots.  If a height measurement is taken every 10 metres, the map won't show a 3-metre-diameter hole, unless the sample happens to occur inside it.  (And then it doesn't show as a hole on the map, just the contour line being somewhere else.)

It's a well-established mathematical principle, and applies whenever you're converting some continuously variable property into a series of numeric values by sampling it at intervals.  Just as applicable to height measurements along a road, voltage measurements of an audio signal, or colour measurements on a grid of sensor elements in a camera.

https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem

You have to draw a line somewhere and decide that finer detail is irrelevant.  There's little point in mapping a road at the millimetre scale, lest the roughness of the chipseal massively inflate your cumulative climbing figure, just as there's little point in a CD player reproducing sounds above the threshold of human hearing.


[1] Or staying in an getting an orbiting radar to do the dirty work, whatever.
To ride the Windcheetah, first, you must embrace the cantilever...

frankly frankie

  • I kid you not
    • Virtual Alps
Re: DIY Mandatory Climbing Values
« Reply #6 on: July 08, 2018, 04:45:01 pm »
Though a road covered in rough chipping will make your ride quite a lot harder.  Often as much as 2 gears IME.

The other thing with mapped contors is that they rarely take into account the road engineering.  You could ride over a viaduct and record no elevation difference, but the map-derived figures will include the deep valley you cross.
"This is a complex subject, with a need for more than one highlighter pen."

Re: DIY Mandatory Climbing Values
« Reply #7 on: July 08, 2018, 05:12:37 pm »
In terms of AAA points, I don't think either the Strava or the AUK Route Validator figures count; the AAA man has his own program that does it.
The earth is vast and beautiful and contains many miraculous places. (Chekhov)

CrazyEnglishTriathlete

  • Miles eaten don't satisfy hunger
  • 3x Brimstone ancien 3x Pendle/Tan Hill DNF
    • CET Ride Reports and Blogs
Re: DIY Mandatory Climbing Values
« Reply #8 on: July 08, 2018, 05:59:22 pm »
I'm not sure how much this helps, but I get quite a lot of data from the Cambrian Series permanents, where the original climbing figures were done by contour counts (by Peter Coulson yonks ago when GPS probably stood for General Protection System).

Helen Kerrane's figures for the Cambrian 6C, which has a contour count of 11000m and an AAA man figure of 11700m had a Strava figure of 11836m and a Garmin figure of 11995m, so on quite an extended and very hilly scale Strava and Garmin were quite consistent with the AAA man.

In Cambrian (Wales) territory the contour counts are usually about 10 - 15% less than whatever GPS or Strava figure I get provided with.  Although there is a degree of sampling - contour counts are done on 10m intervals and so do miss some small ups and downs (common on the valley roads), I'm not convinced that the all of that difference is contributed by sampling.  On a 200km event with 3000m of ascent 10% is 300m, or 60 5m ups and downs in that 200km - which is a lot, given that valley roads (where you are mostly likely to get the missing 5m) are perhaps 50km of the total distance .  When I do contour counts I try to take into account cuttings and bridges.

I do occasionally get figures outside this range and occasionally a request to alter the climbing figure (thankfully I can rely on the AAA's man calculator to be an impartial judge).   Given the above I have always assumed that this has involved operator or technical error.

However, I lost confidence in Strava figures after seeing Zigzag's routes on Strava when we rode together in the Alps.   Having ridden the roads they were either up or down, there were no minor undulations in valleys.  So you couldn't In my logbook I calculated the climbing from the spot heights at the valley bottom and the col top, which the French maps reliably provided.  The Strava figures were typically 20% higher than calculations directly from the spot heights, so can only assume that the algorithm Strava used was designed to flatter a rider's performance in the Alps.
Eddington Numbers 120 (imperial), 165 (metric) 510 (furlongs)

Re: DIY Mandatory Climbing Values
« Reply #9 on: July 08, 2018, 06:56:51 pm »
This is a sampling problem, so there's never going to be a 'correct' answer.  Consistency is all you can ever hope for.

This ^^^^

I refer AUK members to the article in Arrivée last year.
As Cudzo says, the AAA man is using a program that is unique to AUK.   For UK rides it uses Ordnance Survey data and gives not just number of metres of ascent, but also the number of AAA points.  Its sampling has been 'tuned' to give the greatest possible degree of agreement with previous AAAssessment by longer-winded means. 

The key thing is that it is internally consistent (at least for UK - for other parts it has to rely on SRTM data) - and whether it gives greater or fewer numbers of metres than any other tool out there is largely irrelevant.

Kim

  • 2nd in the world
Re: DIY Mandatory Climbing Values
« Reply #10 on: July 08, 2018, 08:13:39 pm »
The other thing with mapped contors is that they rarely take into account the road engineering.  You could ride over a viaduct and record no elevation difference, but the map-derived figures will include the deep valley you cross.

Yes, hence barometric altimeters on GPS receivers - if you're on the side of a steep slope, a GPS-calibrated barometer is more likely to give you an accurate elevation reading than looking up a lat/long on a contour map.  (GPS alone has poor elevation accuracy, and can be unreliable in that sort of terrain.)
To ride the Windcheetah, first, you must embrace the cantilever...

Re: DIY Mandatory Climbing Values
« Reply #11 on: July 08, 2018, 08:22:05 pm »
Though barometric altimeters must be vulnerable to sudden weather changes, such as a thunderstorm. Or to people cheating by connecting them to vacuum cleaners!  ;D
The earth is vast and beautiful and contains many miraculous places. (Chekhov)

Re: DIY Mandatory Climbing Values
« Reply #12 on: July 08, 2018, 10:04:07 pm »
The other thing with mapped contors is that they rarely take into account the road engineering.  You could ride over a viaduct and record no elevation difference, but the map-derived figures will include the deep valley you cross.

Yes, hence barometric altimeters on GPS receivers - if you're on the side of a steep slope, a GPS-calibrated barometer is more likely to give you an accurate elevation reading than looking up a lat/long on a contour map.  (GPS alone has poor elevation accuracy, and can be unreliable in that sort of terrain.)

If you only have GPS altitude without a barometer a tiny bit of GPS drift can cause a massive amount of climb when you stand at the bottom of a steep cliff (the Citadel de Namur in the example on the screenshot):



A control in the café at the bottom near the bridge resulted in this drift, the route was directly along the river and then crossing the river via the Jambes bridge.

Datameister

  • EU Cake Mountain
Re: DIY Mandatory Climbing Values
« Reply #13 on: July 09, 2018, 01:38:31 pm »
then crossing the river via the Jambes bridge.

Did you have to walk across?   ;D

gets coat

Re: DIY Mandatory Climbing Values
« Reply #14 on: July 09, 2018, 05:03:53 pm »
I was testing out the OS data and digital contour counting with Steve Snook (previous AAA man) the back end of 2014.  It was really good at concurring with manual contour counting.  We got some outputs where the automatic calc and Steve's manual figures concurred exactly and Steve never revealed his figures before I ran some GPX through it. Another benefit compared with calculating or using heights of track point data was that it was fairly immune to the number of track points when it came to the climbing figures generated.  You had to put some pretty sparse, or ridiculously populated GPX through it to shift the climbing figures significantly.  Consistency and control is key for the AAA and climbing figures.  With third party sites you are dependant  on what they decide to do with their black box climbing figures which may well change over time.

grahamparks

  • London N19
    • My Instagram
Re: DIY Mandatory Climbing Values
« Reply #15 on: July 09, 2018, 09:22:48 pm »
However, I lost confidence in Strava figures after seeing Zigzag's routes on Strava when we rode together in the Alps.   Having ridden the roads they were either up or down, there were no minor undulations in valleys.  So you couldn't In my logbook I calculated the climbing from the spot heights at the valley bottom and the col top, which the French maps reliably provided.  The Strava figures were typically 20% higher than calculations directly from the spot heights, so can only assume that the algorithm Strava used was designed to flatter a rider's performance in the Alps.

Zig zagging alpine roads are about a worst case scenario for a geodata-based climbing algorithm because even a tiny horizontal error is going to make a huge difference in vertical values. Add in the relatively low resolution of most geodata and it’s a miracle the numbers are even close to correct. Imagine how much climbing you’d do to ride the exact same shaped path even 10m in any direction horizontally from where the road is.

When I wrote a cliimbing algorithm for my app I made it coalesce fuzzy elevation profiles into continuous climbs exactly as you have by only caring about the heights at the top and bottom. But if the vertical data is too messy or the top and bottom values are off then you still end up with the wrong answer.

(It’s far more likely that Strava’s engineers either optimised their algorithm for different things or, at worst, did a bad job than deliberately made it produce inflated numbers)

CrazyEnglishTriathlete

  • Miles eaten don't satisfy hunger
  • 3x Brimstone ancien 3x Pendle/Tan Hill DNF
    • CET Ride Reports and Blogs
Re: DIY Mandatory Climbing Values
« Reply #16 on: July 10, 2018, 11:16:27 am »
However, I lost confidence in Strava figures after seeing Zigzag's routes on Strava when we rode together in the Alps.   Having ridden the roads they were either up or down, there were no minor undulations in valleys.  So you couldn't In my logbook I calculated the climbing from the spot heights at the valley bottom and the col top, which the French maps reliably provided.  The Strava figures were typically 20% higher than calculations directly from the spot heights, so can only assume that the algorithm Strava used was designed to flatter a rider's performance in the Alps.

Zig zagging alpine roads are about a worst case scenario for a geodata-based climbing algorithm because even a tiny horizontal error is going to make a huge difference in vertical values. Add in the relatively low resolution of most geodata and it’s a miracle the numbers are even close to correct. Imagine how much climbing you’d do to ride the exact same shaped path even 10m in any direction horizontally from where the road is.

When I wrote a cliimbing algorithm for my app I made it coalesce fuzzy elevation profiles into continuous climbs exactly as you have by only caring about the heights at the top and bottom. But if the vertical data is too messy or the top and bottom values are off then you still end up with the wrong answer.

(It’s far more likely that Strava’s engineers either optimised their algorithm for different things or, at worst, did a bad job than deliberately made it produce inflated numbers)

Thanks for the correction.  It's probably my auditor's frustration at inflated numbers getting the better of me - a little bit like the amalgamation of a hill's maximum gradient with it's total length - "it's two miles at 20%" - that I used to hear applied to various hills around the UK, which, if taken literally would require a climb from sea level to 640m (2100 feet) in those two miles, which is a strip of tarmac I've yet to find, despite a penchant for finding stupidly steep hills to try to ride up  :facepalm:
Eddington Numbers 120 (imperial), 165 (metric) 510 (furlongs)

Manotea

  • Just 1 sob, Vassily
Re: DIY Mandatory Climbing Values
« Reply #17 on: July 10, 2018, 11:29:10 am »
As a point of information, AAA points are available for advisory and mandatory DIY routes; the requirement is for validation by gpx.

Re: DIY Mandatory Climbing Values
« Reply #18 on: July 12, 2018, 01:58:18 pm »
Though barometric altimeters must be vulnerable to sudden weather changes, such as a thunderstorm. Or to people cheating by connecting them to vacuum cleaners!  ;D

I've had some "interesting" elevation changes from Barometric measurements.

Every 24hrs MTB "race" I've done has a very clear drift in elevations which due to the lapped nature is quite obvious; I guess this is also obvious on long Time Trials too.

The other I've had is as you say when the weather changes suddenly, I once got caught out in a period of heavy rain on the flat bit of Fife, the elevation change was quite pronounced.

This has also reminded me of 3d world modelling from the NASA DEM data, 90m resolution which had some interesting effects, particularly when generating the Firths of Forth and Tay.

One of the easiest measure of seeing how good the source height data is when using maps is to run a line from one end of the Tay Road bridge to the other; it's a gentle slope running from 10m above Sea Level at the Dundee end, to 38m at the Fife end;
Ridewith GPS gives next to no ramp when using Google mapping on screen, and with OSM on screen gives a long ramp at 0.2% before a sudden spike a the fife landfall.
This is an issue for me as I tend to switch between the different map options when planning a route, so it's not unknown for me to have a sudden change in elevation profile on my planned routes as i've switched map to check where the next click should go. (You can also see this when doing routing as the different map options will result in a different routing algorithm being used)

Meanwhile both my Wahoo and Lezyne records from yesterday show a slope roughly as expected with the odd blip though over the whole ride they disagree by 320m of climb and 2km distance!

The Strava planner appears to use the same heightmap for all maps behind the scenes, but I find their interface rubbish for route planning compared to RWGPS.

Edit:
Missed 2 things
Previously the Tay Bridge data used to show a flat line to the 25ish M mark on some systems and then the land based rise; technically the RWGPS+OSM data is correct as it's showing land form, not route form (see also Taking the Lift to the bridge deck)

Also IIRC Strava use the data from the rides uploaded, so the elevation profile shown is probably taken from however many thousand Barometric data recordings have taken place over the bridge, which is likely why their values are very close to the data released by the Bridge board (it's very nearly spot on)

grahamparks

  • London N19
    • My Instagram
Re: DIY Mandatory Climbing Values
« Reply #19 on: July 12, 2018, 02:04:06 pm »
Barometric elevation drift on lapped rides was quite apparent on TG's rides. Apparently doing laps of the Leighton Buzzard bypass puts you closer to god:
https://www.strava.com/activities/1215439317


frankly frankie

  • I kid you not
    • Virtual Alps
Re: DIY Mandatory Climbing Values
« Reply #20 on: July 12, 2018, 02:23:04 pm »
There are two settings that really help with this stuff:
1. In the GPS - auto-calibrate = 'on'.
2. In your brain - OCD = 'off'.
"This is a complex subject, with a need for more than one highlighter pen."

CrazyEnglishTriathlete

  • Miles eaten don't satisfy hunger
  • 3x Brimstone ancien 3x Pendle/Tan Hill DNF
    • CET Ride Reports and Blogs
Re: DIY Mandatory Climbing Values
« Reply #21 on: July 13, 2018, 11:55:57 am »
I thought the whole problem with OCD was that the "off" switch didn't work  8)
Eddington Numbers 120 (imperial), 165 (metric) 510 (furlongs)