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Athens to Atlanta Roadskate (A2A Skate): Total Ascent, Elevation Gain; Barometric or GPS Data?

eebee's picture
Does anybody have the total ascent or elevation gain for the 87 mile Athens-to-Atlanta (A2A) course kicking around somewhere in their GPS or training files? I have googled all sorts of term combos, as well as searched this site. Blake's A2A mapmyride entry shows highest & lowest elevation but doesn't add it up for me :-). I'm feeling a bit fuzzy headed today so it's entirely possible I overlooked it, but please post that figure if you have it!

Location

United States
33° 59' 52.8972" N, 83° 44' 55.6044" W

Comments

roadskater's picture

Athens to Atlanta 87+ Mile Inline Skate Elevation Ascent Data

Hey...Nice topic, eebee. I looked for some stuff on motionbased because I was sure I had seen it. Here's a rough search that'll show several A2A trips. Looks like A2A may be 88 or 89 miles, ha!

 

Elevation varies wildly but take a look at each individual record and there's a lot of info there which is interesting and perhaps useful. For example, check out this one...

GPS Signal Quality is "Excellent" and the elevation settings use the MB Gravity Web Service. That means the signal was good enough to take the XY (lat lon) info and match it with professional survey data. This is used instead of the info in the user's GPS unit, since the Z (altitude) error is typically 1.5 times the XY (lat lon) error with GPS units anyway. Perhaps you can gather some sense from this info as to whose data might be most accurate.

For what it's worth, one wonderful thing about my old Polar 720i (or whatever it was/is) was the data uploads (as is the case with the Garmin Forerunner 305). I have barometric altimeter readings for five A2As (2 unofficial ones in 2005). According to those readings, total ascent was as follows:

 

Year Ascent
 2004
 4439
 2005 Outlaw
 4921
 2005 Sidekick
 4619
 2006
 5341
 2007  5059
 Average  4876

 

I hope this gives some help and that you'll share what you find elsewhere. I bet Uwe has some figures on this, and probably David K, and perhaps the a2a.net website (I know they used TopoUSA to create an elevation profile long ago.

Thanks for the question!

eebee's picture

Varies Wildly!

I assume your polar 720i readings are in meters. Those are comparable to the elevation records in feet on the Motionbased.com entries. I can't imagine over the whole 87 miles it's only 4,500 odd feet elevation. That's about what we covered at the Tour de Guilford (...or did we...?).

Thanks for all the info.  Uwe's elevation profile & details on the A2A website was the first place I looked.  I am astounded at the variation of elevation readings posted on those motionbased.com entries. I find it hard to believe that after all these millennia, humans don't choose good old physics and Earth-bound-triangulated elevations for inhabited areas of the planet for more accuracy over variable barometric pressure readings or satellite signals. I imagine even a shaky, hand-held gadget plus eye-balling would be a more reliable way to find altitude. I wonder how Mr. Mitchell did it. I'm sure I could research this :-)

I love the idea of the MB Gravity service. However, if the one Motionbased.com entry you mentioned is closer to correct, it's about half the elevation of the majority of the other entries. Then there's the suggestion that perhaps if you skate slower, there is more room for elevation-reading error. Hmm. So the spanky skaters got to Atlanta quicker and ended up with less climbing - or rather maybe it just felt like it to them. To the rest of us it felt like we climbed 16,000 feet that day.

I mean, I don't have to know what the real, honest and true elevation is, but pick a number and go up or down from there and be consistent. Maybe blasting a mountain with ultrasound, MRI or doppler radar would give a more effective reading :-).

Ok so the official answer is: You'll climb eleven thousand feet over the 87 miles of A2A, on the other hand it could be sixteen thousand feet over 88 miles! Uh...well it's just really hilly so start skating in May and hope you picked a sufficiently hilly terrain to train on :-). Come to think of it, a number of Floridians and Bart from the Netherlands beat me last year on A2A. BUT STILL! I'd like to find a consistent method for logging elevation.

roadskater's picture

Barometric May Beat GPS for Estimating Elevation Variance

This is not scientific measurement, just a "thought-experiment," but depending on the consistency of the weather, barometric may be way better than GPS for measuring total ascent. If you don't care about the accuracy of the elevation but more the variance throughout several hours starting from a ballpark figure, barometric can be very accurate. If a weather front comes through, all bets are off, though. I have a record of one 11-hour period wherein I measured heart rate, including during sleep overnight, to find my resting or sleeping pulse. The total ascent for that sleeping and sitting around was only 79 feet. This must have been during a relatively constant weather period regarding barometric pressure, but still, that's not a bad error level it seems to me. As we've noted before with caloric measurements on the Garmin Forerunner 305 versus the Polar HRMs we have used, I will consider the the GPS-only elevation in the 305 as suspect until otherwise I learn better. My elevation measurements should be in feet on the Polar 720i, and those figures are closer to the MotionBased Gravity estimate than are most of the Forerunner estimates I saw online. I find the Forerunner 305 to be excellent at measuring XY (lat lon) and route distances (laps are amazingly consistent even with some tree cover in Greensboro Country Park). Speed measurements also seem great and the unit tracks well and has WAAS corrections. But I'm guessing the altitude measurements of the Forerunner 305 are not as good as the Garmin eTrex Vista I would think (at least in open skyview), since it uses barometric AND GPS data to adjust for weather drift to keep the figures a bit closer to honest. I wonder if anyone with an eTrex Vista (other than me!) has done the whole route and posted it on motionbased.com. I wonder if I still have the data from one or more A2A excursions or the time to dig it out? I wonder if DavidK is listening in? If I find time I'll try to look at altitude data from multiple workouts at GCP to see if those figures are consistent. What really matters to me is to be able to compare routes and workouts with some confidence that relative to each other, at least, the readings are consistent. As for better ways of measuring, of course there is the survey method with the tripod and post and all that, but it would take a long time to skate or walk the route and take measurements along the way. I'd say rest stops would be closed before getting to the first one! As it is, I may start wearing the Polar on the other wrist or hanging off a pack or bottle to get that data too! I hope not.
roadskater's picture

Uwe Does What I Think I Might Do Someday

He's the data man. Those USGS topos often show elevations (usually) of intersections and I thought how easy to get the elevation of every turn. This was years ago I thought it and I got as far as getting almost all the topos in digital form and arranging them and all that, but it bogged down for me when some data was not available free, or I couldn't find it. But Uwe had already done lots of this it turns out...at least for a previous course of the A2A Roadskate...link from David K on InlineNC yahoogroups.com list... http://www.a2a.net/athelev2.html

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