Forums >Technical Support>Elevation inconsistencies on multiple requests for the same route
Get Lost :)
Hey, I tried to search for this but didn't find anything. When you are creating a map with the elevation feature on, it updates the elevation pointwise and comes up with the standard rise and fall numbers. I did this for a recent run, and it reported about 650 ft of vertical ascent. However, when I removed the elevation graph and then rerequested it, the new elevation came back 1009 ft. Doing this again on different days, for the same course map, resulted in another number - 996.3 ft. I'm not as worried about the difference between the last two figures, but the difference between the initial calculation and the new calculation is huge. Which one is correct?
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As a test (bored at work), I duplicated a route that I currently have saved as a course. I get pretty much the same elevation - like, within a few feet difference. Maybe there are regional or terrain specific issues going on? I dunno. Weird though.
Now, I do often see a significant discrepancy between the course map elevation and Garmin elevation.
San Francisco - 7/29/12
Warrior Dash Ohio II - 8/26/12
Chicago - 10/7/12
Good Bad & The Monkey
I'm running somewhere tomorrow. It's going to be beautiful. I can't wait.
Poor baby
Garmin elevation is useless.
Any idea what it's measuring? Could it be there's simply an error in the formula?
I once did a project for work where we had to use GPS coordinates to determine where bus patrons were getting on and off busses. We could then auto calculate their bus fare.
In our first software version, we had a slight error in the formula and in some situations, the bus stop that we zero'd in on was off by one or two on the same route. I'm sure glad we found that before the system went live.
Garmin does a reasonable job determining latitude and longitude through triangulation of the satellites it sees in the sky. It does a pretty mediocre job determining elevation using this method. The problem is not in any formula the Garmin uses, but rather in its inability to create and record the raw data on which the formulae apply. The formulae themselves are really just adding up the vectors generated through the Pythagorean theorem; they are pretty basic.
The reason that RA and other such websites have better elevation data is because they wipe out the Garmin elevation data and replace it with reference elevation data for the recorded coordinates.
wanderlost,
I don't see why there would be a discrepancy in the readings since your maps are created recently. I upgraded the elevation lookup earlier this year that increased elevation sampling rate which would explain the discrepancies in older maps.
I tried it on several of my long routes and the values are identical. Could you provide me with a map that's exhibiting the problem so I can investigate it?
eric :-)