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Help!: Elevation and descent

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    • CommentAuthorFree Memberpeteoc
    • CommentTimeMar 4th 2008
     
    peteoc

    Hi,

    I know the elevation and descent are not 100% correct, however on a route I travel 66.6 miles........upon returning to my house it has risen 30ft. Surly this should not happen?

     

    http://www.mapmyride.com/ride/united-kingdom/urmston/225509924

    • CommentAuthorFree Membertfarris
    • CommentTimeMar 6th 2008
     
    tfarris

    I had the same issue on mapping out a 200k brevet in KY this past weekend. Total ascent only came out to 1330 feet over 65 miles(total is an out and back route) but several guys w/ Garmins came up with approx. 4300 feet over 65 miles !! I think the problem is answered in the FAQ, where climbs less than 60 meters is not measured.  That makes sense on this route since 90 % of our climbing were constant rollers. The FAQ said the raw data is provided so I pulled the excel file from the map and computed my own accumulated ascents and it still came out to 1330 feet as well.

    Lesson learned: These maps are right on directionally, etc.  but don't trust the elevations !

    • CommentAuthorFree Membergmaclin
    • CommentTimeMar 23rd 2008
     
    gmaclin

    tfarris - Out of curiosity, after you downloaded the excel data, how did you determine the accumulated ascents?  The data in the files I've looked at from marathon routes (probably shorter than most of your bike routes) has elevation data roughly every 0.05 miles.  If you accumulate the data every 0.05 miles vs. every 0.1 or .2 miles (etc.) you get MUCH different results on your accumulated altitude gain. The bigger the distance you use to accumulate the ascent values, the smaller your total altitude gain will be when you are done.

     Greg

    • CommentAuthorFree Memberlcfree2
    • CommentTimeMar 24th 2008
     
    lcfree2

    I found an interesting "anomaly" regarding elevation.  I mapped out a 35 mile ride and it gave me 2000' of climbing.  When I did the ride, my altimeter came up to 3200' of climbing.  Rather a substantial difference that is only partially accounted for by the 60m rule.  What I found is that if I map each section of the ride separately, I get totally different numbers than if I map out the entire ride and the tolal of those numbers was much closer to what my altimeter gave me.    It seems that the longer the ride, the more inaccurate the elevation is.  (Once, when mapping out a long ride, I saw my total accumulated ascent actually decrease as I added a new point to the ride.)  So, henceforth, I will continue to map out my routes, but I will do a separate quick and dirty mapping of each ride section to determine elevation and include it in the notes.   How you break up the sections is obviously subjective, but I basically mapped out each significant ascent separately and then any segment that had a significant slow but steady climb.  If a section was flat or downhill, I didn't bother as I was more concerned with ascent than descent.  I've kept a record of these "sections" in my private maps so I can do an accurate calculation henceforth.  The area we ride has numerous ascents that can be mixed up numerous ways so this will serve us pretty well.  I will also continue to compare with my altimeter to check on accuracy.

     Linda

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