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2009-03-25 12:22 AM

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Subject: climbing vs. elevation gain

I'm new to having hills to climb and was wondering what the difference is between garmin telling me that I climbed 1798 feet but my acent was 4670?  Motion Based has elevation gain at 5928.  Three numbers one ride i'm confused.  It was much easier in Florida, lots of zeros.

Thanks, Chris



2009-03-25 7:24 AM
in reply to: #2038419

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Subject: RE: climbing vs. elevation gain

I think that climbing is just the difference in elevation btwn the start and end of the ride.  Whereas accent(garmin) and elevation gain (MB) is the sum total of all the "ups" in the ride.

If this ride started and ended the ride at the same place climbing should be close to 0.   A possible reason for a high climb value in a loop ride would be if you started riding before the gps locked onto enough satellites for an accurate 3d reading.  It requires many more than just the 3-4 for good 2d data.  So even though the gps looks ready to go it'll still take more time for good data.

MB and Garmin and any other program that you upload the raw data to will give different values for accent.  It all depends on how it deals with the data.  The raw data will have some random spikes and such, good programs will smooth this out and not and it to the total accent.  Also each program aslo has to decide how much climbing you have to do before it gets added to the accent value.  In other words, if you ride a rolling road with 10 3 foot swales some programs will count that as 30 extra feet of accent otheres will dismiss it.

Then there's the argument that a gps without a built-in pressure altimeter never gives accurate altidude changes (the FR 305 does not have such).

2009-03-25 8:22 AM
in reply to: #2038419

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Subject: RE: climbing vs. elevation gain
papson14 - 2009-03-25 1:22 AM

I'm new to having hills to climb and was wondering what the difference is between garmin telling me that I climbed 1798 feet but my acent was 4670?  Motion Based has elevation gain at 5928.  Three numbers one ride i'm confused.  It was much easier in Florida, lots of zeros.

Thanks, Chris



I wouldn't believe the elevation number from your Garmin (assuming it's a 305). I have one and there's NO way it's accurate. On an out and back or a loop, the total ascent and total descent should be the same. Mine is never even close.


2009-03-25 8:44 AM
in reply to: #2038689

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Subject: RE: climbing vs. elevation gain
D.Z. - 2009-03-25 9:22 AM
papson14 - 2009-03-25 1:22 AM

I'm new to having hills to climb and was wondering what the difference is between garmin telling me that I climbed 1798 feet but my acent was 4670?  Motion Based has elevation gain at 5928.  Three numbers one ride i'm confused.  It was much easier in Florida, lots of zeros.

Thanks, Chris

I wouldn't believe the elevation number from your Garmin (assuming it's a 305). I have one and there's NO way it's accurate. On an out and back or a loop, the total ascent and total descent should be the same. Mine is never even close.

x2.  Data from my TRAINER ride last night:  elapsed time 1hour.  Total ascent 3874 feet.



Edited by Experior 2009-03-25 8:44 AM
2009-03-25 9:01 AM
in reply to: #2038569

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Subject: RE: climbing vs. elevation gain
StarGazer - 2009-03-25 6:24 AM

Then there's the argument that a gps without a built-in pressure altimeter never gives accurate altidude changes (the FR 305 does not have such).



That's not the real issue. Pressure based altimeters have the exact same problems as satelitte altimeters which is accumulated error.

Assume that you're riding a perfectly flat road. Every few seconds either type of altimeter will attempt to determine elevation and almost every time there will be some error. Because you're computing accumulated gain, errors in both directions add up to false climbing.

EG.
That perfectly flat road is at 500' elevation. You altimeter will come up with something like 510, 495, 505, 490, 500, 510, 490, 510, etc. Just that sequence results in 60 feet of false climbing and it could have only been one minute.

The way that software can correct the Garmin numbers is if it takes in the GPS coordinates of the ride and the creates it's own elevation numbers based on the same type of engine the BT route tracker has, which is a combination of USGS 40' contours and improved resolution between them from satelitte photos.

Bottom line, the Garmin climbing numbers are completely worthless.

Having said that, you can use any satelitte or pressure-based altimeter to get pretty close on a single long climb. If you assume, that the error at any given point is +-10 feet. Then if you take the elevation at the bottom of a climb and subtract it from the elevation at the top, you should get within 40 feet of the actual climb gain.
2009-03-25 9:05 AM
in reply to: #2038419

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Subject: RE: climbing vs. elevation gain
I'm not 100% sure the elevation shown on the 305 is accurate but when I look at the elevation chart it seems to be a pretty good reflection of the course I ran or biked. So that's nice to compare against my HR and/or cadence.


2009-03-25 9:54 AM
in reply to: #2038813

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Subject: RE: climbing vs. elevation gain

merlin2375 - 2009-03-25 10:05 AM I'm not 100% sure the elevation shown on the 305 is accurate but when I look at the elevation chart it seems to be a pretty good reflection of the course I ran or biked. So that's nice to compare against my HR and/or cadence.

Right.  That's correct -- and completely consistent with the post just above yours.

ETA:  But the error on the Garmin is, I think, somewhat worse than +-10 feet.  I just looked at the elevation data from my trainer ride last night, and while the average elevation is about right (around 280), there are plenty of spikes, some as low as 150 and some as high as 400.  As the other poster said, those add up.



Edited by Experior 2009-03-25 9:57 AM
2009-03-25 11:02 AM
in reply to: #2038981

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Subject: RE: climbing vs. elevation gain
Experior - 2009-03-25 8:54 AM
  • .. and while the average elevation is about right (around 280), there are plenty of spikes, some as low as 150 and some as high as 400.  As the other poster said, those add up.



  • Maybe the Garmin had more error because you were indoors? As I understand, the elevation accuracy is highly dependent on how many satellites are in play which can be blocked by all types of things like terrain, buildings, trees, etc. I live in a mountainous area where there are long climbs I've done for many years. On all the road bike routes, I can always estimate my elevation within 50' or so and compare it to my Garmin. I don't think I've ever seen a 150' error but every location is different.
    2009-03-25 11:40 AM
    in reply to: #2038981

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    Subject: RE: climbing vs. elevation gain
    Experior - 2009-03-25 10:54 AM

    merlin2375 - 2009-03-25 10:05 AM I'm not 100% sure the elevation shown on the 305 is accurate but when I look at the elevation chart it seems to be a pretty good reflection of the course I ran or biked. So that's nice to compare against my HR and/or cadence.

    Right.  That's correct -- and completely consistent with the post just above yours.

    ETA:  But the error on the Garmin is, I think, somewhat worse than +-10 feet.  I just looked at the elevation data from my trainer ride last night, and while the average elevation is about right (around 280), there are plenty of spikes, some as low as 150 and some as high as 400.  As the other poster said, those add up.

    You should turn off your GPS indoors.. your trainer info is completely irrelevant.  As for garmin accuracy on elevation, it is terrible. BT is way off.. the closest thing I have found to accurate is the elevation correction plug in for sportstracks. It uses something like 1 or 5 foot contours. This actually matches with mapmyride.com which is also pretty close.

    2009-03-25 11:42 AM
    in reply to: #2039151

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    Subject: RE: climbing vs. elevation gain
    breckview - 2009-03-25 12:02 PM
    Experior - 2009-03-25 8:54 AM ... and while the average elevation is about right (around 280), there are plenty of spikes, some as low as 150 and some as high as 400.  As the other poster said, those add up.

     

    Maybe the Garmin had more error because you were indoors? As I understand, the elevation accuracy is highly dependent on how many satellites are in play which can be blocked by all types of things like terrain, buildings, trees, etc. I live in a mountainous area where there are long climbs I've done for many years. On all the road bike routes, I can always estimate my elevation within 50' or so and compare it to my Garmin. I don't think I've ever seen a 150' error but every location is different.

    Yeah, I think you're right.  Error outdoors (according to my logs, comparing with elevations from mapmyride.com -- of course there's some error there too) appear to be anywhere from +-20 feet to +-75 feet, apparently depending on where I was riding.

     

    2009-03-25 11:47 AM
    in reply to: #2039250

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    Subject: RE: climbing vs. elevation gain
    slake707 - 2009-03-25 12:40 PM
    Experior - 2009-03-25 10:54 AM

    merlin2375 - 2009-03-25 10:05 AM I'm not 100% sure the elevation shown on the 305 is accurate but when I look at the elevation chart it seems to be a pretty good reflection of the course I ran or biked. So that's nice to compare against my HR and/or cadence.

    Right.  That's correct -- and completely consistent with the post just above yours.

    ETA:  But the error on the Garmin is, I think, somewhat worse than +-10 feet.  I just looked at the elevation data from my trainer ride last night, and while the average elevation is about right (around 280), there are plenty of spikes, some as low as 150 and some as high as 400.  As the other poster said, those add up.

    You should turn off your GPS indoors.. your trainer info is completely irrelevant.  As for garmin accuracy on elevation, it is terrible. BT is way off.. the closest thing I have found to accurate is the elevation correction plug in for sportstracks. It uses something like 1 or 5 foot contours. This actually matches with mapmyride.com which is also pretty close.

    I use the Garmin for cadence and 'speed' (magnet on the back wheel of course, not GPS) on the trainer. For some reason, when I turn the GPS off, the Garmin also refuses to use the magnet on the rear wheel to determine my 'speed' (although it will use the magnet on the crank to determine the cadence).

    I know that the 'speed' it reports is not accurate -- I use it within a workout to compare how I'm pushing at different points in the workout.  Example:  "last interval I was holding 24mph, so let's see if I can do that again". I know that the actual number has nothing to do with traveling 24mph, but it does allow me to compare my level of effort at different points in the ride.  (I have no power meter.Cry)  



    2009-03-25 12:15 PM
    in reply to: #2039266

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    Subject: RE: climbing vs. elevation gain

    I can't completely agree with everyone...

    I don't find the Garmin THAT bad.  Yes, there are errors, and yes, you have to take them for what they are worth, but many time my out and back routes have me ending withing 50-100 feet from start elevation to start.

    Plust I have back checked my Garmin with the BT elevations, or Mapmytri.com, and found they all agree within 10% or so...

    I think the garmin is good for ballpark.

    ALSO, the faster you go, the more acurate is seems to be.  So using it for running is FAR more worthless than bikind.  Using it on a motor cylce or car is even closer.

    2009-03-25 12:23 PM
    in reply to: #2039250

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    Subject: RE: climbing vs. elevation gain
    slake707 - 2009-03-25 10:40 AM
    BT is way off.. the closest thing I have found to accurate is the elevation correction plug in for sportstracks. It uses something like 1 or 5 foot contours. This actually matches with mapmyride.com which is also pretty close.


    I'll have to strongly disagree with "BT is way off", as I use it. I don't import Garmin data. I create routes by tracing them out in BT's Route Tracker and it's very accurate for my routes. I know because I've tested it against USGS benchmarks which are perfectly accurate and if needed, standard extrapolation/interpolation off 40' contours. It's easy because my climbs are long and sustained as opposed to rollers.

    Also, I didn't write the code but I have a feeling that the BT Route Tracker uses the same contour information that mapmyride.com uses. It's not like either one launched satellites and photographed the terrain in order to improve upon the USGS 40' contours. I don't know who actually did it. But whoever did either gives or sells this information to all the elevation mapping sites.
    2009-03-25 12:27 PM
    in reply to: #2039324

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    Subject: RE: climbing vs. elevation gain
    Aikidoman - 2009-03-25 11:15 AM

    I can't completely agree with everyone...

    I don't find the Garmin THAT bad.  Yes, there are errors, and yes, you have to take them for what they are worth, but many time my out and back routes have me ending withing 50-100 feet from start elevation to start.

    Plust I have back checked my Garmin with the BT elevations, or Mapmytri.com, and found they all agree within 10% or so...

    I think the garmin is good for ballpark.

    ALSO, the faster you go, the more acurate is seems to be.  So using it for running is FAR more worthless than bikind.  Using it on a motor cylce or car is even closer.



    You've missed the point. On your example "out and back..." those are two elevations readings. But when the Garmin computes total elevation gain, it must take those readings very often. Each time, the Garmin doesn't know if the gain from the last reading is real or error so it assume real. All that error adds up huge.
    2009-03-25 12:53 PM
    in reply to: #2039350

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    Sensei
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    Subject: RE: climbing vs. elevation gain
    breckview - 2009-03-25 10:27 AM
    Aikidoman - 2009-03-25 11:15 AM

    I can't completely agree with everyone...

    I don't find the Garmin THAT bad.  Yes, there are errors, and yes, you have to take them for what they are worth, but many time my out and back routes have me ending withing 50-100 feet from start elevation to start.

    Plust I have back checked my Garmin with the BT elevations, or Mapmytri.com, and found they all agree within 10% or so...

    I think the garmin is good for ballpark.

    ALSO, the faster you go, the more acurate is seems to be.  So using it for running is FAR more worthless than bikind.  Using it on a motor cylce or car is even closer.

    You've missed the point. On your example "out and back..." those are two elevations readings. But when the Garmin computes total elevation gain, it must take those readings very often. Each time, the Garmin doesn't know if the gain from the last reading is real or error so it assume real. All that error adds up huge.

    No I didn't.  I was responding to D.Z.'s post.  My ascent descent numbers are very close when I get back.  AND the ending, starting elevations.  They also are close to BT....

    This is only for Bike rides, though.  If I run, I'm way off.  Thats because the garmin takes a reading at every time interval (with some error) and then add/subtracts that from the previous point, whatever it is.  If you move only 30 feet, obviously you probably haven't move up or down that significantly, so the GPS error has more significance.  But if you have moved 100 yards on the bike, the reading probably caries more weight since you probably did move more vertically.

    Take that to the extreme and don't even move.  All teh garmin adds up is error, so it's 100% wrong.  OR, if you moved from base camp to the top of everest in 1 second, It could be very accurate within a couple feet - granted, if there is a lot of rolling hills in between, it won't catch them.

    Bottom line, my total ascent and desent have never been "way off".  Probably within 10% from each other.  Also probably within 10% of mapmytri, mapmyrun, BT, whatever.

    2009-03-25 4:03 PM
    in reply to: #2039343

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    Subject: RE: climbing vs. elevation gain

    breckview - 2009-03-25 1:23 PM
    slake707 - 2009-03-25 10:40 AM BT is way off.. the closest thing I have found to accurate is the elevation correction plug in for sportstracks. It uses something like 1 or 5 foot contours. This actually matches with mapmyride.com which is also pretty close.
    I'll have to strongly disagree with "BT is way off", as I use it. I don't import Garmin data. I create routes by tracing them out in BT's Route Tracker and it's very accurate for my routes. I know because I've tested it against USGS benchmarks which are perfectly accurate and if needed, standard extrapolation/interpolation off 40' contours. It's easy because my climbs are long and sustained as opposed to rollers. Also, I didn't write the code but I have a feeling that the BT Route Tracker uses the same contour information that mapmyride.com uses. It's not like either one launched satellites and photographed the terrain in order to improve upon the USGS 40' contours. I don't know who actually did it. But whoever did either gives or sells this information to all the elevation mapping sites.

    BT mapping by hand is not bad, but when you import from the garmin, which has a point every few seconds it gives completely wrong numbers.  An example
    http://www.beginnertriathlete.com/discussion/training/map.asp?routeid=34253

     BT lists as 2500 feet climbing, it is about 1000 ft or so. When I get home I can tell you what sports tracks uses for its contours.



    2009-03-25 4:53 PM
    in reply to: #2039151

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    Subject: RE: climbing vs. elevation gain
    breckview - 2009-03-25 10:02 AM
    Experior - 2009-03-25 8:54 AM ... and while the average elevation is about right (around 280), there are plenty of spikes, some as low as 150 and some as high as 400.  As the other poster said, those add up.

     

    Maybe the Garmin had more error because you were indoors? As I understand, the elevation accuracy is highly dependent on how many satellites are in play which can be blocked by all types of things like terrain, buildings, trees, etc. I live in a mountainous area where there are long climbs I've done for many years. On all the road bike routes, I can always estimate my elevation within 50' or so and compare it to my Garmin. I don't think I've ever seen a 150' error but every location is different.

    I read somewhere that the higher elevation and lack of deciduous trees in our area would mean more accurate readings.  I've checked my garmin against topo maps and it's usually pretty close.  That's one benefit to living where there's less O2.

    2009-03-25 5:00 PM
    in reply to: #2039993

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    Subject: RE: climbing vs. elevation gain
    slake707 - 2009-03-25 3:03 PM
    BT lists as 2500 feet climbing, it is about 1000 ft or so. When I get home I can tell you what sports tracks uses for its contours.

    I wonder if BT is using the imported climbing data computed by the Garmin instead of actually recomputing the climbing using its database and the imported GPS points.

    After I manually trace out my route, I click the "Reset Elevation Values" button so all the climbing is recomputed based on whatever database it uses. Sometimes before I do that step the climbing will be very obviously off, like 15,985' or even 65,889' or something. No idea why but obviously the programmer knows since he included the "Reset..." button.

    I wonder if you can do the same thing with imported Garmin data thereby forcing the BT Route Tracker to recompute all the climbing.
    2009-03-25 5:09 PM
    in reply to: #2040104

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    Subject: RE: climbing vs. elevation gain
    skarl - 2009-03-25 3:53 PM
    I read somewhere that the higher elevation and lack of deciduous trees in our area would mean more accurate readings.  I've checked my garmin against topo maps and it's usually pretty close.  That's one benefit to living where there's less O2.



    I bought my Garmin solely to track elevation. I usually ride down about 1000' from my house, to Frisco and then up about 1500' to Vail Pass. It's just two long hills with a couple small ones adding up to about 3000' over about 40 miles. My Garmin was all over the place but always way high. As I recall, it would range between like 4500' to 7000' depending on the day. I even sent it back and got a free new one, same thing. Now I only use it for mapping out trail runs which it does very well.
    2009-03-25 6:37 PM
    in reply to: #2040121

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    Subject: RE: climbing vs. elevation gain

    breckview - 2009-03-25 3:00 PM
    slake707 - 2009-03-25 3:03 PM BT lists as 2500 feet climbing, it is about 1000 ft or so. When I get home I can tell you what sports tracks uses for its contours.
    I wonder if BT is using the imported climbing data computed by the Garmin instead of actually recomputing the climbing using its database and the imported GPS points. After I manually trace out my route, I click the "Reset Elevation Values" button so all the climbing is recomputed based on whatever database it uses. Sometimes before I do that step the climbing will be very obviously off, like 15,985' or even 65,889' or something. No idea why but obviously the programmer knows since he included the "Reset..." button. I wonder if you can do the same thing with imported Garmin data thereby forcing the BT Route Tracker to recompute all the climbing.

    Marma explained it to me.  When you put the route in, it "reaches out" to google maps, I think and grabs the data for each point at a time.  For some reason, there is just a lot error that gets introduced when BT goes back and forth across the internet and google maps.  The more points and longer you take to put it in, the worse it gets.

    When you hit the reset elevations, all the points are in BT, so it does a faster or mass grab of vert info from google.  Somehow fixing it...

    To be fair, Marma gave me the layman's explination some time ago, and I'm paraphrasing it....  But yes, they know there is a problem with communicating with Google, so the added the reset feature.  I do that after loading every route, and it fixes it to be comparible to all the other mapping programs out there.

    2009-03-25 9:24 PM
    in reply to: #2040299

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    Subject: RE: climbing vs. elevation gain
    Aikidoman - 2009-03-25 7:37 PM

    breckview - 2009-03-25 3:00 PM
    slake707 - 2009-03-25 3:03 PM BT lists as 2500 feet climbing, it is about 1000 ft or so. When I get home I can tell you what sports tracks uses for its contours.
    I wonder if BT is using the imported climbing data computed by the Garmin instead of actually recomputing the climbing using its database and the imported GPS points. After I manually trace out my route, I click the "Reset Elevation Values" button so all the climbing is recomputed based on whatever database it uses. Sometimes before I do that step the climbing will be very obviously off, like 15,985' or even 65,889' or something. No idea why but obviously the programmer knows since he included the "Reset..." button. I wonder if you can do the same thing with imported Garmin data thereby forcing the BT Route Tracker to recompute all the climbing.

    Marma explained it to me.  When you put the route in, it "reaches out" to google maps, I think and grabs the data for each point at a time.  For some reason, there is just a lot error that gets introduced when BT goes back and forth across the internet and google maps.  The more points and longer you take to put it in, the worse it gets.

    When you hit the reset elevations, all the points are in BT, so it does a faster or mass grab of vert info from google.  Somehow fixing it...

    To be fair, Marma gave me the layman's explination some time ago, and I'm paraphrasing it....  But yes, they know there is a problem with communicating with Google, so the added the reset feature.  I do that after loading every route, and it fixes it to be comparible to all the other mapping programs out there.



    The 2500 feet is with reset elevation values.. google? you sure they are not using USGS data?

    My original elevation was worse (even higher) before the elevation correction ..  sportstracks (which I find to be the closest to what I view reality to be) elevation correction  uses srtm 1" viewfinder panoramas for US topo and srtm 3" viewfinder panoramas for the rest of the world

    http://en.wikipedia.org/wiki/Shuttle_Radar_Topography_Mission

    This is supposed to be the most accurate digital elevation model.

    Smoothing differences between online application also introduce or increase error in elevation

    Also my riding tends to be on rollers versus long steady climbs.. steady climbs are much easier to profile with elevation data.. even garmin got close when I climbed whiteface .. b ut my roller courses are way off

     



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