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Mapping Elevation

aya604aya604 Posts: 67
edited March 2008 in Tour & expedition
Hi

I have been using 2 brilliant sites to map routes :mapmyrun.com & bikely.com

Brilliant that is except they seem to give the wrong info for elevation.

Am I doing something wrong or is there another site which does this accurately. I am guessing hoping there is otherwise how is it done?

Cheers

aya

Posts

  • bahzobbahzob Posts: 2,195
    What do you mean wrong elevation? I use both. Find Bikely can be a pain for elevation so use mapmyride (usually with follow roads option). This gets the elevation profile pretty spot on but its total ascent numbers are low (because any climb less than 50m or so is ignored)
    Martin S. Newbury RC
  • aya604aya604 Posts: 67
    bahzob wrote:
    What do you mean wrong elevation? I use both. Find Bikely can be a pain for elevation so use mapmyride (usually with follow roads option). This gets the elevation profile pretty spot on but its total ascent numbers are low (because any climb less than 50m or so is ignored)

    OK i mean the wrong total ascent. I know its wrong cos if i map an audax or sportive it gives a different figure from the official one. The reason it seems is as you say it ignores climbs of less than 50 metres.

    So how do the audax or sportive organisers get their total ascent from? A mapping program like this or some other way.

    cheers
  • GeorgeShawGeorgeShaw Posts: 764
    Isn't it true that total ascent can be a bit of a problem for GPX data, especially on rolling roads. For example, if your consecutive data points are at altitude: 10, 15, 5, 10; have you really gone up and down 10 metres, or are these just measurement errors? You can put the same GPX data into different applications, and they will all give you different results for total ascent. Because they will all "smooth" the data, to take out measurement errors, in different ways.
  • bahzobbahzob Posts: 2,195
    Audax: The standard for Audax is to count contour lines.
    (see here for the details:http://www.aukweb.net/aaa/index.htm

    They also accept a GPS tracklog downloaded into Memory Map or similar.

    The Winter 2008 Audax Mag (no. 99) had a very good article by Steve Snook comparing these methods and bikely. It found that using a tracklog/memory map gave similar (but slightly higher) ascents than counting on an OS map and all these bore no relation to bikely which significantly underestimated the ascent. Similar will happen on mapmyride but they are clear about this (because any gain less than 50m or so is ignored. The difference can be lessened if the option to download into Excel is used and you do the calculation manually.

    Sportives: Use a different method than Audax. Slightly tongue in cheek I think its whatever gives the biggest number so as to make the ride look as tough as possible. Two ways this may happen are:
    - if the course is mapped on Memory Map but does not precisely follow the roads some contour lines can be double counted (imagine going round a hairpin, if you follow the road you will climb 5m or so, however if you cut the corner (not advised) you may go down 50m then "up" 55m)
    - if you ride with a computer that has an altimeter then you will get different numbers according to how frequently/sensitively is samples. I ride with a HAC4 that samples every 20 seconds and my total ascent is usually around 60-70% of someone who rides with an Edge that samples more frequently.
    Martin S. Newbury RC
  • aya604aya604 Posts: 67
    bahzob wrote:
    Audax: The standard for Audax is to count contour lines.
    (see here for the details:http://www.aukweb.net/aaa/index.htm

    They also accept a GPS tracklog downloaded into Memory Map or similar.

    The Winter 2008 Audax Mag (no. 99) had a very good article by Steve Snook comparing these methods and bikely. It found that using a tracklog/memory map gave similar (but slightly higher) ascents than counting on an OS map and all these bore no relation to bikely which significantly underestimated the ascent. Similar will happen on mapmyride but they are clear about this (because any gain less than 50m or so is ignored. The difference can be lessened if the option to download into Excel is used and you do the calculation manually.

    Sportives: Use a different method than Audax. Slightly tongue in cheek I think its whatever gives the biggest number so as to make the ride look as tough as possible. Two ways this may happen are:
    - if the course is mapped on Memory Map but does not precisely follow the roads some contour lines can be double counted (imagine going round a hairpin, if you follow the road you will climb 5m or so, however if you cut the corner (not advised) you may go down 50m then "up" 55m)
    - if you ride with a computer that has an altimeter then you will get different numbers according to how frequently/sensitively is samples. I ride with a HAC4 that samples every 20 seconds and my total ascent is usually around 60-70% of someone who rides with an Edge that samples more frequently.

    Thanks very much for such an informative reply. Is is possible to get access to that audax mag article. Is that mag for members? Ready to join anyhow after a great day at the Kingdom of Fife last Sunday - still recovering!!!!

    cheers
  • I use mapmyride and it's fine except when it comes to total ascent. What seems to work much better is the Anquet software which uses Ordinance Survey maps. Arm and a leg job so I can only afford my local area. Also not as easy to use as mapmyride with it's 'follow roads' facility.
  • bahzobbahzob Posts: 2,195
    aya604 wrote:
    bahzob wrote:
    Is is possible to get access to that audax mag article. Is that mag for members? Ready to join anyhow after a great day at the Kingdom of Fife last Sunday - still recovering!!!!

    cheers

    The Arrivee magazine comes as part of the Audax UK membership. There is mention in it that copies can be bought for £3 so you could contact them and ask if you can get a copy (its number 99).
    Martin S. Newbury RC
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