Here’s a thing:

Studying the figures for the HT550:
Even the slower riders are still showing an average moving speed of over 7mph… so if they stopped less…
(Alan (not one of the slower riders, at 7.7 mph, Trep at 7.1)

But the HT550 is shown as 550 miles and 16000 metres, which is 52480 feet.
However all the finished riders have an elevation gain of 36247 feet, quite a bit out from 52480, in fact 16233 feet difference.

So which is the correct figure ?

If it’s 36247 then that works out at 66 feet/mile.
Is feet per mile quite a strong indicator of the difficulty of a ride ? (Without getting bogged down in the other factors such as dry or wet, amount of mud, rocky or rubble-y, surface: short grass/long grass, number of gates…)

The amount of tarmac (that’s road) will make a massive difference of course.

I would have thought the slower riders would deteriorate more quickly as each day/mile passed, but it doesn’t seem to be the case…

Any thoughts ?

Most of my rides round here are above 110 feet per mile (no road or very minimal)… and I’m doing well at moving average speed of 6 mph.

So I guess that brings in another factor: age
But let’s forget that one.

Many moons ago when I did my SMBLA instructor training, 10kph was considered a reasonable figure for an all day off-road ride. I've found that it works pretty well especially in mixed ability / fitness groups and tends to pretty accurate over multiple days ... remember that's average speed though and not moving average.

No idea how much climbing there is in the HT. Always found most gps to be less than accurate, so never really think about it

As regards the Ascent figure, have a close look at the line drawn on the Trackleaders site. You'll see that it doesn't actually follow the track very closely. Every corner cut will likely add a chunk of ascent that doesn't exist.in real life. If that's the same as the gpx file that Alan issues then I'm not surprised it's some way out.

There have been enough finishers now that an average of their recorded figures will be pretty accurate.

Not sure about the course but would agree that GPS elevation data isn't very reliable ime.

I would have thought the slower riders would deteriorate more quickly as each day/mile passed, but it doesn’t seem to be the case…

Any thoughts ?

I don't think a rider's ability to maintain a pace is linked to fitness, more to experience or attitude. Conditioning rather than output fitness. As you get fitter you'll have a higher output for the same effort/stress level that's all. If you go above whatever your base endurance pace is (eg somewhere around mid Z2 into low Z3 with minimal time in Z4 or above) you'll tyre and deteriorate. The longest events might be a case of attrition for every rider in the end, or it may be there are riders who cope better if they find sleep easier to get when they have a chance. Certainly an interesting area of long distance racing.

Yes GPS data uses atmospheric pressure, which varies depending on weather, but overall does give an indication.

If I plot a route using Memory Map I think it does it using the contours.

I’ll try this sometime:
Note the ascent of a ride, or rides (as I do the same course/courses often), then import into Memory Map, then plot a route over that same line (so it’s using contours) and see what the results are

Interesting point(s) there James… (BTW how to copy someone else’s quotes - I’m on an iPad and it’s very fiddly to use copy and paste)

What’s Z2 etc ?
“
I don't think a rider's ability to maintain a pace is linked to fitness, more to experience or attitude. Conditioning rather than output fitness. As you get fitter you'll have a higher output for the same effort/stress level that's all. If you go above whatever your base endurance pace is (eg somewhere around mid Z2 into low Z3 with minimal time in Z4 or above) you'll tyre and deteriorate. The longest events might be a case of attrition for every rider in the end, or it may be there are riders who cope better if they find sleep easier to get when they have a chance. Certainly an interesting area of long distance racing.”

GPS elevation data isn't very reliable ime.

I once rode with three GPS devices and at the end of the righ there was no metric they agreed on not time, distance or elevation, IIRC distance [ 30 ish miles varied by nearly a mile , height by about 500ft I forget what time was

I don't think a rider's ability to maintain a pace is linked to fitness,

Whilst i get your point lets not pretend you can do a 200 mile ITT or the HT550 if you are not fit or that we dont get faster if we train.

GPS data uses atmospheric pressure

My GPS[ [phone for example] has no capability to do this and as it knows exactly where i am on the planet so why would it not just take that point as my height ?
I dont think they do that at all

ericrobo wrote: ↑Fri Jun 03, 2022 11:37 am Interesting point(s) there James… (BTW how to copy someone else’s quotes - I’m on an iPad and it’s very fiddly to use copy and paste)

What’s Z2 etc ?

I think you can just hit the " dark grey box icon to quote someone's post.

Z2 - traditional heart rate zones, or there's power zones for those who train on power levels. HR zone 2 is aerobic pace, as you go into Z3 you're starting to work anaerobically so there's some lactic acid fatigue that will build as the effort goes up from there. A trained rider can go into upper Z3 and Z4 (or above) more often without tiring as much the same rider w/o the training, but maintaining a pace (edit - a consistent pace) over a long distance is about staying in the right zone whatever level of fitness you have.
I've found it's quite easy to stay in Z2 by paying attention to your breathing, no HR monitor needed. If you need to breathe more than you would at about normal walking pace then your HR is going into your Z3 anaerobic level or above. It's hard to ride up any hill without going out of Z2 into Z3 though, so I don't think many riders stays in Z2 on an average ride.
All a bit geeky I know.. helped me understand training and pacing though. Mostly I only use it to stay familiar with my base / Z2 pace on road rides.

Lazarus wrote: ↑Fri Jun 03, 2022 12:00 pm

I don't think a rider's ability to maintain a pace is linked to fitness,

Whilst i get your point lets not pretend you can do a 200 mile ITT or the HT550 if you are not fit or that we dont get faster if we train.

Certainly we get faster if we train, our output at any level goes up and if you can pace that output you'll be faster over a long distance.
Yeah I'd agree you'd need basic fitness to get round the average race / ITT. By 'ability to maintain a pace' I mean a rider's knack of not getting carried away keeping up with others in the early stages then finding themselves popped halfway, how tortoises often beat hares in this sort of race. I suppose a trained / fit rider may be more likely to gain that experience, maybe those inclined to do the training work are more likely to be the 'off like a hare' competitive types.

ericrobo wrote: ↑Fri Jun 03, 2022 11:31 am Yes GPS data uses atmospheric pressure, which varies depending on weather, but overall does give an indication.

If you're looking at numbers from Strava Eric it will be a corrected figure using contours and info from previous GPS readings. It tends to be resonably accurate although will never be bang-on.

I suppose a trained / fit rider may be more likely to gain that experience*

I think the mental strength, once fit, is more important than the fit.
Ok time to go out and get some experience

Height data used by mapping systems like Strava is not very granular and often incorrect. That also affects the use of Lat/Lon to determine altitude.

Given stable weather conditions a GPS will tend to be more accurate than derivation from height data. However, we live in the UK where the conditions are less than ideal for this.

I don't think a rider's ability to maintain a pace is linked to fitness,

Just picking up on this ... I've often or at least sometimes thought that any rider with a degree of off-road experience and cycle fitness should be able to complete the BB200. To do so within the 36 hours requires an overall average speed of less than 6kmh or roughly 3.7mph which isn't much above the average walking pace.

OS software suggests 58,570ft or 17,852m
The middle loop, on my eTrex20 was 25,260ft or 7,700m in May
I'd agree that the Trackleaders data there is way off.

GPS elevation data is calculated by triangulation from the satellites the same as the position data is. Some GPS units preferentially use barometric altitude data if they also contain a barometric altimeter.

In 2018 I had 59,000 feet on my eTrex. On the tracklogs software the route is 'only' 536 miles, imagine my disappointment when I got to 536 miles and I wasn't back at the start

In Reverse wrote: ↑Fri Jun 03, 2022 12:19 pm

ericrobo wrote: ↑Fri Jun 03, 2022 11:31 am Yes GPS data uses atmospheric pressure, which varies depending on weather, but overall does give an indication.

If you're looking at numbers from Strava Eric it will be a corrected figure using contours and info from previous GPS readings. It tends to be resonably accurate although will never be bang-on.

After uploading the ride to strava (which it tends to take elevation data from the gos device, many of which are hsing barometric pressure as it used to be classed as more accueate than the contours from OS, but now things seem to be changing with the satellites etc), to swap from the imported ascent ypu can click the top right button and press 'adjust elevation'. It opens a button for 'use strava data'. I always do this and (I have no data to prove this but) feel its it's more accurate...

lune ranger wrote: ↑Fri Jun 03, 2022 12:52 pm GPS elevation data is calculated by triangulation from the satellites the same as the position data is. Some GPS units preferentially use barometric altitude data if they also contain a barometric altimeter.

Oh... Maybe my info might be out of date then. I read that (barometric) was used by Garmin 1000 and similar a few years ago now. Sattelites and battery conservation has obviously gotten bettee over them years..

https://support.strava.com/hc/en-us/art ... r-Activity

Link to how Strava adjust elevation and (think) their data is more accurate.

We’re both saying the same thing. If your GPS unit contains a barometric altimeter it tends to use that data - Edge 1000 does this.

Some of the discrepancy comes from sampling interval - how many data points your unit adds to the file.
The more data points added the more accurate the representation will be.
Other discrepancies come from atmospheric pressure variations over time - barometric altimeters need to be re-calibrated intermittently at know spot heights to keep data accurate.
There is also intentional and variable inaccuracies broadcast by the GPS, GLONASS, Galileo etc satellites themselves - this is all military tech originally. In the first Gulf War and at other times subsequently but much less dramatically the GPS signal was scrambled massively. Military units are capable of receiving the unadulterated signal but civvy ones aren’t.

Lazarus wrote: ↑Fri Jun 03, 2022 12:27 pm

I suppose a trained / fit rider may be more likely to gain that experience*

I think the mental strength, once fit, is more important than the fit.
Ok time to go out and get some experience

100%.

When I get home I'll check my figures.... the height gained per kilometre is pretty low for the ht when compared to the bb200 or yd300. I think there is only one 160k section that just reaches 4000m of climbing. But on this route height gain doesn't come close to gauging the hardness. It's all about the terrain on the two northern traverses and the great wilderness. In terms of maintaining a good pace technical riding ability plays a big part as you can make up a lot of time if you can bash through those bits quickly

Pedant alert

GPS does not do altitude using barometric altimeters. A GPS “unit “ may choose to do so but the system itself does not.

GPS is a time based system (a very very accurate one) so doesn’t use triangulation for location or altitude, the term used is “trilateration”

The Earth isn’t a sphere but an oblate spheroid which makes calculating altitude tricky. Most systems use a model called a geoid, which is accurate for a greater or lesser part of the globe, I forget the exact one used by the GPS but presumably on that is good for bombing the enemies of the USA. the OS use a different one which is more accurate for the UK. GPS altitude is the height above this geoid not sea level

Back on subject…

Altitude gain is only part of the difficulty of a route. Mostly it’s how you view the route mentally: be negative and 10m/km will feel hard; be positive and 30m/km won’t feel bad.

Fwiw the current Geoid model used for GPS is the snappily named GEOID18 afaik.

We covered GPS vs barometric elevation on Friday

Ta

Just on the way home from holiday and viewing on a phone so not read everything