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Old 05-16-14, 05:25 PM
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Walter S
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Location: Atlanta, GA. USA
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Originally Posted by Andy_K
Interesting. I gave that a try with my commute home. MapMyRide says it looks like this:



Google Earth says it looks like this:



Obviously Google Earth shows a bit more detail, but the thing that strikes me is that MMR claims the total elevation gain is 296 feet, while Google Earth puts it at 534 feet. Either way, it's mostly flat except for the kick at the end. The thing is I have found that my bike computer's altimeter does typically record nearly twice the elevation gain that Google Earth claims.

The other point of curiosity here is that MMR claims that the highlighted area at the end (the area selected by MMR as a "climb") has an average grade of 2.7% over 1.2 miles. While approximately true, this is also entirely irrelevant. Google Earth says that grade for the last quarter mile doesn't drop below 7% and gets as steep as 16.6%. That's the kind of thing I want to know when I'm choosing a route.



Keep in mind that gps-based altimeters do a very poor job of measuring the Z axis. Your position comes from basic triangulation. Since all the satellites are in the sky, they all have a much better idea of the X/Y than the Z.
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