General Discussion Triathlon Talk » inaccurate bike/run elevations as per Ironman? Rss Feed  
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2013-09-11 6:24 AM

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Subject: inaccurate bike/run elevations as per Ironman?
Recently raced Muskoka 70.3, second time doing it. Had a great time and must say they did an awesome job this year with the organizing. Almost twice as many peeps as last year. Very impressed. RD, Nick is amazing guy.

Anyway, on the website the bike elevation says total gain 2660. My garmin 910xt said 3900!
Same for the run, 300 ft as per website, 900 as per garmin!

Anyone else have these discrepancies?

Honestly, I don't really care. I enjoy the climbing and it makes for a challenging race. I just want appropriate compensation from Ironman Muskoka including:

1 free stinger gel
1 night free at Deerhurst
1 free qualify spot for 70.3 championships 2014

Is that too much to ask for?



2013-09-11 6:35 AM
in reply to: Jpro19

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Subject: RE: inaccurate bike/run elevations as per Ironman?
Every single Ironman branded race I have done, whether it be 70.3 or full iron, my Garmin have the elevation dramatically higher than what is on Ironman's website for the bike and run profile
2013-09-11 6:39 AM
in reply to: 0

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Subject: RE: inaccurate bike/run elevations as per Ironman?

i believe they have stated before that they know their estimates are off, way off in some cases.  it has to do with whatever method/source they are using to estimate.

of course underestimating elevation probably gets a few extra people to sign up that otherwise wouldn't have.  might not really be a mistake on their part.



Edited by Clempson 2013-09-11 6:40 AM
2013-09-11 6:40 AM
in reply to: Jpro19

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Subject: RE: inaccurate bike/run elevations as per Ironman?
There are different types of methods/technology to calculate elevation gains.  Which Garmin do you have? Some are more accurate than others.
2013-09-11 6:44 AM
in reply to: KathyG

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Subject: RE: inaccurate bike/run elevations as per Ironman?
The way I calculate elevation gain is usually by gut instinct and vision. I look at the hill, take an average estimate on the grade, measure the length of the hill by eye-balling it, and then do some calculations to get the elevation per each hill.

Just joking, being a smart .

I use the Garmin 910XT. I really like it. Helpful on the swim as well.
2013-09-11 7:13 AM
in reply to: Jpro19

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Subject: RE: inaccurate bike/run elevations as per Ironman?
Look at the IM Louisville bike course online. The gain is stated at 2,858ft. My garmin 910 (as well as every other source I have seen quoted) has the gain at over 6,000ft. I think most people entering that race are aware of what the real bike course is like but if you were going on the profile alone you would be in real trouble.


2013-09-11 7:33 AM
in reply to: clemson05

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Subject: RE: inaccurate bike/run elevations as per Ironman?
Originally posted by clemson05Look at the IM Louisville bike course online. The gain is stated at 2,858ft. My garmin 910 (as well as every other source I have seen quoted) has the gain at over 6,000ft. I think most people entering that race are aware of what the real bike course is like but if you were going on the profile alone you would be in real trouble.
I question.always the website as well as Garmin data. The truth is somewhere in between. IMLP has 4800 andmy Garmin was closer to 5500 to 6000 . Why I quoted this post was I was shocked to.see that you had imlou t a greater gain than imlp.......granted I have not done that iIM but I have been to the area and find it hard to believe the climbing is the same......not.saying 100% It's wrong but just doubtful
2013-09-11 7:39 AM
in reply to: FELTGood

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Subject: RE: inaccurate bike/run elevations as per Ironman?

Originally posted by FELTGood
Originally posted by clemson05Look at the IM Louisville bike course online. The gain is stated at 2,858ft. My garmin 910 (as well as every other source I have seen quoted) has the gain at over 6,000ft. I think most people entering that race are aware of what the real bike course is like but if you were going on the profile alone you would be in real trouble.
I question.always the website as well as Garmin data. The truth is somewhere in between. IMLP has 4800 andmy Garmin was closer to 5500 to 6000 . Why I quoted this post was I was shocked to.see that you had imlou t a greater gain than imlp.......granted I have not done that iIM but I have been to the area and find it hard to believe the climbing is the same......not.saying 100% It's wrong but just doubtful

I see IM Louisville coming in more often in the 4,000-5,000 ft range. The 910 seems to come in all over the place at times, more so than others.

2013-09-11 7:51 AM
in reply to: jillian_o

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Subject: RE: inaccurate bike/run elevations as per Ironman?
It's all strategic. WTC low balls the elevation to get more participants. More participants=$$$$
2013-09-11 8:21 AM
in reply to: Jpro19

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Subject: RE: inaccurate bike/run elevations as per Ironman?
GPS devices like garmin suck at elevations. The computations to triangulate on your position using satelite signals are quite precise in XY plane but less so in the Z. There are a number of extrapolatiions being made that introduce a bias toward increased vertical in both ascent and descent. The error is worse when you ride a course full of small, choppy hills, and its not as as bad if you ride a long, steady ascent and then descent.
Using a climber's barometric pressure based device will give better reading and actually surveying the land will give best.
2013-09-11 8:25 AM
in reply to: mgalanter

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Subject: RE: inaccurate bike/run elevations as per Ironman?
Originally posted by mgalanter

GPS devices like garmin suck at elevations. The computations to triangulate on your position using satelite signals are quite precise in XY plane but less so in the Z. There are a number of extrapolatiions being made that introduce a bias toward increased vertical in both ascent and descent. The error is worse when you ride a course full of small, choppy hills, and its not as as bad if you ride a long, steady ascent and then descent.
Using a climber's barometric pressure based device will give better reading and actually surveying the land will give best.


The 910xt uses a barometric altimeter to measure elevation.


2013-09-11 8:36 AM
in reply to: jlruhnke

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Subject: RE: inaccurate bike/run elevations as per Ironman?
Originally posted by jlruhnke
The 910xt uses a barometric altimeter to measure elevation.


I forgot about the 910x having that. In theory it should be more accurate that other Garmins. Though I imagine key to having it accurate is to calibrate the barometric altimiter at the start of the day.
Does it ask you for ambient air pressure (inches Hg or kPa) and/or current actual elevation ASL?

Back to the OP's point - I rode the IM70.3 Muskoka course this Sunday and it sure did _feel_ like a lot more climbing than 2,600ft.
2013-09-11 9:55 AM
in reply to: mgalanter

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Subject: RE: inaccurate bike/run elevations as per Ironman?
When you calibrate it, it asks for elevation at current location.
2013-09-11 2:48 PM
in reply to: jlruhnke

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Subject: RE: inaccurate bike/run elevations as per Ironman?
It will also self calibrate to rectify with the GPS elevation.
If you add a location (ex. transition zone) with a known elevation, it'll snap to that if you get close enough to that spot. I have a saved location at my house, and indeed, a message pops up (something along the lines of): elevation set. I do not know for sure whether it will reset elevation midrun if I pass in front of my house again. This is a big deal if the air pressure changes through out the day.

Here is an example of a 4-loop 50k run: http://connect.garmin.com/activity/252002366I did not have any saved locations. Over the 4hour:40minutes, the trough raised about 50ft and the peak a little more. Another consideration: without elevation correction, it reports total climb at 1550ft, but with it, 2200ft.
2013-09-11 7:15 PM
in reply to: mgalanter

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Subject: RE: inaccurate bike/run elevations as per Ironman?

Originally posted by mgalanter
Originally posted by jlruhnke The 910xt uses a barometric altimeter to measure elevation.
I forgot about the 910x having that. In theory it should be more accurate that other Garmins. Though I imagine key to having it accurate is to calibrate the barometric altimiter at the start of the day. Does it ask you for ambient air pressure (inches Hg or kPa) and/or current actual elevation ASL? Back to the OP's point - I rode the IM70.3 Muskoka course this Sunday and it sure did _feel_ like a lot more climbing than 2,600ft.

My Garmin 500 had IMC-Whistler's elevation at 6,400' which was on par with what everyone else reported.

My Garmin 910 had it at 10,000' which isn't remotely close.  It was a tough bike course but not that tough. Cool

2013-09-11 7:26 PM
in reply to: GMAN 19030

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Subject: RE: inaccurate bike/run elevations as per Ironman?
Elevation gain is a nearly random number as far as I can tell. Even using the same data, every program gets different results.

I took the same .tcx file from a recent hour ride. I then imported the ride into Strava, mapmyride, ridewithgps, Garmin connect, training peaks, and Golden Cheeta. I also wrote a quick program to take the 1 second elevation readings and add up the differences for what should be the "golden" number. I didn't use any elevation correction, so each piece of training software should be using the exact same data.

The "golden" numbers, which again was just a cumulative addition of the one second elevation readings from the file, totaled 3670 feet. The various programs ranged from 2420 feet to 4428 feet. And remember that this is all from the exact same file. If you use the elevation correction features of the various programs, the differences were about the same, though the numbers were quite different for some of them.

Anyway, that leads me to think it's best to ignore anyone's elevation claims and just ride. Mostly hard, sometimes easy. And yes, I have too much time on my hands.


2013-09-12 5:10 AM
in reply to: jlruhnke

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Subject: RE: inaccurate bike/run elevations as per Ironman?
Originally posted by jlruhnke

Originally posted by mgalanter

GPS devices like garmin suck at elevations. The computations to triangulate on your position using satelite signals are quite precise in XY plane but less so in the Z. There are a number of extrapolatiions being made that introduce a bias toward increased vertical in both ascent and descent. The error is worse when you ride a course full of small, choppy hills, and its not as as bad if you ride a long, steady ascent and then descent.
Using a climber's barometric pressure based device will give better reading and actually surveying the land will give best.


The 910xt uses a barometric altimeter to measure elevation.


The barometric altimeter makes it quite accurate, but you need to keep the firmware up to date. Older firm ware had some elevation issues, but those has been rectified.

The 310XT is horrible when it comes to elevation... GPS coordinates for elevation calculations will be quite off, especially over longer distances. The 910XT and the 810 works quite well and will be fairly accurate.
2013-09-12 5:56 AM
in reply to: audiojan

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Subject: RE: inaccurate bike/run elevations as per Ironman?
my 910 elevation is whacked. Firmware is up to date, yet my trainer ride today was done at 47000 ft.

Garmin says it may be broken, and I will likely need to send the watch back for a replacement.

MD
2013-09-23 6:49 PM
in reply to: audiojan

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Subject: RE: inaccurate bike/run elevations as per Ironman?
Originally posted by audiojan

Originally posted by jlruhnke

Originally posted by mgalanter

GPS devices like garmin suck at elevations. The computations to triangulate on your position using satelite signals are quite precise in XY plane but less so in the Z. There are a number of extrapolatiions being made that introduce a bias toward increased vertical in both ascent and descent. The error is worse when you ride a course full of small, choppy hills, and its not as as bad if you ride a long, steady ascent and then descent.
Using a climber's barometric pressure based device will give better reading and actually surveying the land will give best.


The 910xt uses a barometric altimeter to measure elevation.


The barometric altimeter makes it quite accurate, but you need to keep the firmware up to date. Older firm ware had some elevation issues, but those has been rectified.

The 310XT is horrible when it comes to elevation... GPS coordinates for elevation calculations will be quite off, especially over longer distances. The 910XT and the 810 works quite well and will be fairly accurate.


I agree that the actual elevation numbers recorded second by second in the device and the resultant files are accurate, the gain for the ride is widely variant depending on which software program you use to see the gain.
2013-09-24 1:06 PM
in reply to: Mike_D

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Subject: RE: inaccurate bike/run elevations as per Ironman?
Originally posted by Mike_D

my 910 elevation is whacked. Firmware is up to date, yet my trainer ride today was done at 47000 ft.

Garmin says it may be broken, and I will likely need to send the watch back for a replacement.

MD


Mine does the same thing...haven't called Garmin yet though. I just marvel at my total elevation gained at 137,000 feet when in reality it's probably 200. I'm such a stud. HA
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