GPS Need Not Apply.............Oh Alright

[hexhome]

Balloonists jerked my memory! To get accurate readings from a barometric altimeter, it has to be set to the current atmospheric pressure. Can you do this? In any case, pilots are taught that a barometric altimeter is for guidance! Accurate measurement of height (above ground) below 2500ft in instrument conditions should utilise a Radio Altimeter.

This might help progress our understanding of the only truly accurate way of measuring height above sea level http://www.altimetry.info/html/alti/welcome_en.html

[Ayesha]

Balloonists jerked my memory! To get accurate readings from a barometric altimeter, it has to be set to the current atmospheric pressure. Can you do this? In any case, pilots are taught that a barometric altimeter is for guidance! Accurate measurement of height (above ground) below 2500ft in instrument conditions should utilise a Radio Altimeter.

This might help progress our understanding of the only truly accurate way of measuring height above sea level http://www.altimetry.info/html/alti/welcome_en.html

Yes. The elevation of the runway needs to be dialed in before a sortie.

As far as I'm concerned ( tongue well in cheek ) a cyclist using an altimeter is tantamount to needing a crash hat on a golf course. The chances of it being of vital use is so remote, its beyond calculation.
There is not a hill ( mountains have snow caps on summer solstice ) in Great Britain that requires a cyclist or walker to need an oxygen cylinder.

We should have a poll, "What's the most important function on a bicycle GPS?" That should stir it up

[Brucey]

I think some may have missed CJ's point; if you want to know the total climbing in a day, and the GPS version of this measurement is inaccurate for some reason, then a BP altimeter readout offers a reasonably accurate method of totting up all the ups and downs in a day that doesn't need satellites or owt.

cheers

[RickH]

Absolute altitude isn't that important away from really big mountain climbs but the cumulative gains and losses are of interest, to me at least.

Since I've been logging it, day 2 of LEJOG out of Bodmin still stands as my most climbed in 1 day at 7631ft, despite forays in France & Spain in the Massif Central & The Pyrenees (the day going over the Port de Balles to Bagneres de Luchon comes second at 7465ft, albeit over a shorter distance).

Rick.

[Mick F]

............ day 2 of LEJOG out of Bodmin still stands as my most climbed in 1 day at 7631ft...........

7,631ft would equal 76miles ish?

Just done a 31mile ride today.
3,033ft

[RickH]

............ day 2 of LEJOG out of Bodmin still stands as my most climbed in 1 day at 7631ft...........

7,631ft would equal 76miles ish?

Just done a 31mile ride today.
3,033ft

We did 54 miles that day - the guy who organised the trip did seem to pick a hilly route, we went over both Bodmin Moor & Dartmoor. The standing joke became if we came to a junction and weren't sure of the route then the way that went up was usually the right way! I still enjoyed the trip though - but then I'm not exactly in Flatlandia, I average about 82ft per mile.

Rick

[Mick F]

Excellent!
Bodmin Moor and Dartmoor are a bit hilly to say the least.

One ride I like is up through Tavistock to Princetown, and then down through Yeleverton and home back through Tavistock.

28.5miles with 3,400ft of ascent.

[Ayesha]

Near where I live there's a hill ( Mucklows ) that has a traffic island at the bottom and a traffic Island at the top.
The traffic Islands are 1 mile apart and the one at the top is 300 ft higher than the one at the bottom.
If I ride 50 circuits I will have ridden 100 miles and accumulated 15,000 ft of climbing,

But I won't brag.

I only did four circuits and then went home.

[NATURAL ANKLING]

Hi,
You devils, you have qualified
http://www.ctcdevon.co.uk/devil99.htm
Only average 126 ft / mile You know you want to.

[swansonj]

What do we need to know the mileage for after all? I often get back from a tour with no clear idea of how far I've been - until one of the racing types that Kevin Mayne stuffed the CTC office with wants to know! I try to explain to these guys that touring is about the memories, the smiles and not the miles, but I don't think they really get it. So I cast my mind back to the numbers my GPS displayed towards the end of an average day and invent a plausible total. I can't imagine why any tourist would need to know the length of a day any better than to the nearest five miles/km and a fortnight's tour to the nearest hundred.

I take it you're not obsessed with your Eddington Number then, Chris!

[CJ]

As far as I'm concerned ( tongue well in cheek ) a cyclist using an altimeter is tantamount to needing a crash hat on a golf course.

Using and needing, your simile does not work. Nobody said a cyclist 'needed' an altimeter.

I am quite sure we do not need to know how much we've climbed any more - or any less - than we need to know how far we have ridden. I only brought altimeters into the conversation when people were anguishing over the fractions of a percentage point error in GPS measurements of the length of a ride.

I am happy to accept a 1% error in measuring total ride distance, but I object to a 50% error in total climb. Both are just for my own interest and enjoyment. I say "just", but isn't interest and enjoyment the main purpose of cycle-touring?

[meic]

Of all the different methods of measuring your altitude and the changes in it, I thought that the GPS with a barometric altimeter was the most accurate system that is commonly available.
I can not think of a better way to test it than sticking a device on something like the London Eye.
Is a definitive answer worked out by lasers from a few fixed points?


When it comes to using the figures for a "competitive" purpose, there starts to be rules to smooth things out.
Many in Audax think that undulations in the road surface should not count towards your altitude readings. Back in the contour counting days those undulations could be 20 metres deep.

I know a ride which measures 800m by contour counting, 1800m by GPS with barometer and 2,800 by Anquet mapping. I would like to know how somebody could decide what it actually is.
What is it that shows the GPS with barometer to be so inaccurate, when I do find it to be not too inconsistent?

I do think that the GPS with barometers were originally made with glider pilots and parachutists in mind rather than hikers.

Regardless of which way the barometric pressure swings my GPS always shows more descent than climbing on a circular route.

[Ayesha]

You should have got one in your Garmin box.

[meic]

Indication is all I am after, I am not attempting to land my glider in fog using the Vista.

Is there any better indication of the amount of climbing on my rides than said GPS?

If that is the case, what is the other source and why is it considered more reliable?

[Mick F]

Regardless of which way the barometric pressure swings my GPS always shows more descent than climbing on a circular route.

Always?

I've just looked at every single one of my rides of 2012, and I suggest I descended about 60% more occasions than ascended. Each one of my rides in 2012 was "circular".

This "error" can only be caused by my riding out at 9ish in the morning and getting home early afternoon. Air pressure tends to rise as the day warms up making it appear that I'd descended. I find that even indoors on the rollers, I'm descending more often than ascending ............ but it can be either.

Here's a couple of profiles of 20mile roller rides over four five mile bouts. Total times of each ride is about two or three hours.

These are with GPS turned off so absolute altitude is incorrect, but the relative ascent and descent is very evident.

The steps are caused by my stopping and starting the 705 between sessions.