Motion Based Question

[Veronica]

How "off" is their altitude data? I know I've seen references to MB over reporting climb.

Looking at some of Jo's comparisons in her journal between her Ciclosport and her Garmin, it looks like Garmin can be off by as much as 45%. That's a huge difference!

Veronica

[maillotpois]

It's not really a Garmin issue, because the barometric adjusted Garmin data run through Garmin training center is pretty spot on - consistent with my old HAC4 data for the same rides and with other people's Polars, etc.

The problem is putting the data into MB without checking the new adjust feature in MB (I don't know what the new button is but there is now some option to allow MB to track more closely with the barometric data somehow. I don't use it so I don't know what it's called. We have a teammate who would always log our training rides and then broadcast his MB data and it would be at least 15% higher - really depended on the ride but it was always WAY higher. When he checked the adjust button on MB it went a lot closer to the GTC damat, but still maybe 5% high.)

[jobob]

I'm seeing that discrepancy between the elevation data from Garmin Edge 305 and my Ciclosport when I only run the Garmin data thru Training Center.

Through MotionBased, bah, forget about it! (unless you want to impress yourself with how much you really don't climb ) I didn't know there was a way to correct it though - I'll look for that adjust button.

The data on my Ciclosport tends to agree moderately well with Bikely mapping, and if anything might be a bit on the low side (maybe 10% lower than elevation gains from Polar). So as long as it still works, I'll take elevation gain off my Ciclosport.

[OakLeaf]

I just went looking for it again. Up at the top right of your Activity Dashboard there's an icon called "Activity Options." Click that. Then for a Garmin Edge with barometric altimeter, check "Auto-Correct GPS Signal Errors" and uncheck "Use MB Gravity Elevation Correction."

I can't attest to the accuracy of that vs. SportTracks correction vs. Training Center, though.

[jobob]

Cool, thanks, I'll give it a try.

[SadieKate]

Based on the statistical average of 1 ride (today's drop run in which I cleaned rock gardens I never had*):

SW/Ascent/Descent

SportTracks / 1,569 / 4,118 (using data smoothing)
GTC / 1,634 / 4,182
MB with both autocorrection and MB gravity / 2,029 / 4,614
MB with auto correction / 2,195 / 4,747
MB with all elevation corrections disabled / 2,263 / 4,815 (check mark cleared in auto correction and grayed out in MB gravity so that the page shows "corrections disabled)

I think I'll stick with GTC and SportTracks (for my Edge 305).

*just had to get that in there!

[Mr. Bloom]

I just went looking for it again. Up at the top right of your Activity Dashboard there's an icon called "Activity Options." Click that. Then for a Garmin Edge with barometric altimeter, check "Auto-Correct GPS Signal Errors" and uncheck "Use MB Gravity Elevation Correction."

I can't attest to the accuracy of that vs. SportTracks correction vs. Training Center, though.

I made the change too and this brought the climbing down to what I had last year on my Hilly Hundred route.

But, this is still 15% higher than the GeoBike Profile provided by the club.

HOWEVER, when I compare the MB elevation profile to the GeoBike Profile, the peaks and valleys track with precise accuracy.

So, this seems to indicate to me that the elevation profile is accurate, but the cumulative count is off in some way.

Does this make sense?

[OakLeaf]

How did the club obtain their data?

[Veronica]

Funny... I turned off my computer and walked away and was thinking about my post....

That link does only list 6 miles of climbing. But the profile says 3500 feet of climbing. So either that link does NOT list all the climbing or those 6 miles are WICKED steep.

Now think about this, if you hadn't factored in the 3,500 feet of climbing...

Six miles of climbing spread out in a in a 48 mile ride, with the longest climb being 1.3 miles, wouldn't you think the ride was kind of easy...

Maybe you would, maybe you wouldn't - all depends on who you are and where you're at. Bottom line - Ride Your Own Ride and have FUN!


Veronica

[SadieKate]

V, you know this: the roads as you travel farther east are built more and more vertically up the fall line and not the contour line as they do out here. Those river bluffs in the midwest are wicked steep and, as you know, it is hard to get into your climbing zone on "rollers" and those are long enough to actually force you into climbing mode as opposed to "momentum" mode.

This is what a friend has said about riding this stuff:
The "mere rollers" are constant, but after 100k of continuous, short 6-7% climb/descent cycles most people get a little rubbery in the leg.

Yeah, it is different than here in the wild, wild West.

Oakleaf, I don't live in Switzerland, but I've got a 23 mile climb nearly right from my door. The climb up Mt Diablo (on V's profile) rises the same elevation but in half the distance. I'd call both mountains. But I'm not arguing what is a hill or mountain, I'd just saying you can't "roll" over something the length of 3 and a half football fields in length. Your "mo" won't last that long. Though, wouldn't perpetual mo on a bike be wunnerful?

[maillotpois]

I'd agree on DMD Hamilton and diablo are the only mountains - but it that just a nomenclature issue? It is Mt. Hamilton and mt. Diablo after all, so maybe it's just what we're used to.

I love the rollers, even the long ones. And I love our sustained climbs. I'm not sure how well I'd do in the eastern part with the steeper shorter stuff. It would be hard to get in a rhythm with that.

And from what I've seen and ridden of the Alps/Pyrenees, they're more like our Sierra roads with reasonable to high gradients; however, they pitch you up between the switchback instead of in the switchback like we do here, so you can often get more climbing overall. It was weird to have the actual switchback be the flat part where you can recover because it's so often not the case here.

Back to the original issue - and I'm not sure if anyone noted this yet, but weather can affect the barometric corrections. I spent a morning climbing the geysers and I and the other 5 people with Garmins all showed we were steadily descending. It was VERY odd, but the weather was changing dramatically from rainy/cold to warm.

[jobob]

When I start & end my ride at the same place, usually the total ascent/descent values (and the start/finish altitude) agree within a few percent, but once in a while they're very different. I assume that's because of weather changes over the course of my ride.

[maillotpois]

When I start & end my ride at the same place, usually the total ascent/descent values (and the start/finish altitude) agree within a few percent, but once in a while they're very different. I assume that's because of weather changes over the course of my ride.

I get that a LOT if I start from home. I concluded that it's because it is hard to get a good satellite lock from my house in all the trees, and even though it "says" it has the satellites I think it really takes some time for them to lock on. (My car Garmin won't even try to figure out where we are til we've got all the way down to town.)

Your reason makes a lot of sense as well. I'm sure there are a lot of variables.

[SadieKate]

And from what I've seen and ridden of the Alps/Pyrenees, they're more like our Sierra roads with reasonable to high gradients; however, they pitch you up between the switchback instead of in the switchback like we do here, so you can often get more climbing overall. It was weird to have the actual switchback be the flat part where you can recover because it's so often not the case here.

Next time you're here and the trail is cleared, we'll ride the Flagline Tie singletrack. At the very end when your heart rate is highest the trail suddenly goes up the fall line and then the switchbacks and the trail between keep going up and up . . . and over roots and rocks. But then you get another 1000 ft above the South Fork drop. Yum.

Back to the original issue - and I'm not sure if anyone noted this yet, but weather can affect the barometric corrections. I spent a morning climbing the geysers and I and the other 5 people with Garmins all showed we were steadily descending. It was VERY odd, but the weather was changing dramatically from rainy/cold to warm.

Yup. But you've reported the weirdest case I've ever heard. Usually, it is just greater discrepancy between the climb/descent totals.

Just remember that weather patterns can cause some inconsistency, but generally not as much as GPS-only data.

[maillotpois]

Next time you're here and the trail is cleared, we'll ride the Flagline Tie singletrack. At the very end when your heart rate is highest the trail suddenly goes up the fall line and then the switchbacks and the trail between keep going up and up . . . and over roots and rocks. But then you get another 1000 ft above the South Fork drop. Yum.

Is it worse than Green Gulch? No thank you...