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Q for garmin users @ Sundrive Velodrome

  • 28-05-2013 5:24pm
    #1
    kumate_champ07
    Closed Accounts Posts: 7,150 ✭✭✭


    how do you find your GPS accuracy? mine drops a few times over a session, I sometimes lose 100meters.

    after checking a data file http://goldencheetah.org/ I can get more detailed info, I seem to lose cadence readings too so I adjusted the magnet today, maybe that will help.


    my speed increased by 1km/h as my cadence dropped from 120 to 117rpm yesterday, the speed reading seems to be accurate to +/-1km/h which isnt a big deal but its a little annoying.

    you can check what speed you should be at with a certain gear ratio and cadence here:

    http://software.bareknucklebrigade.com/rabbit.applet.html


    I would not trust the gps data for a flying 200m but its probably close enough for 1km tt.


Comments

  • #2
    TheBlaaMan
    Registered Users, Registered Users 2 Posts: 3,469 ✭✭✭TheBlaaMan


    kumate_champ07 wrote: »
    you can check what speed you should be at with a certain gear ratio and cadence here:

    http://software.bareknucklebrigade.com/rabbit.applet.html

    Sorry if this seems an obvious observation,......... 'gain' based on gear ratios and wheel circumferences etc are all very well, but speed also needs to take into account variables such as wind and frictional differences (=tyres) so +/- 1kmph seems pretty damn accurate to me?

    I imagine that you are allowing the GPS to 'settle' for 5-6 mins after it locates satellites in order for it to find really accurate elevation data? My Edge500 can be decidely iffy in this regards, so much so that I have set an 'elevation point' on my driveway where I park the bike for a few minutes before setting off on a spin.

    Again, apologies if all above seems obvious............I'm not trying to be 'smart'.


  • #3
    kumate_champ07
    Closed Accounts Posts: 7,150 ✭✭✭kumate_champ07


    well its 1 gear ratio for the whole session and no variables to equipment. I do wait a few mins for the signal each time I switch it on too.

    I had a 60km/h reading which should have been 56km/h a while ago, theres probably more errors from some of my sessions


  • #4
    Redmond101
    Registered Users, Registered Users 2 Posts: 178 ✭✭Redmond101


    I wouldn't trust the GPS data as a gramin is only accurate to within a few feet, based on the fact that its laps of an oval, the data can be inaccurate due circumfrance of the track. if not done already you could turn the gps off and rely on wheel cadence sensors. Perhaps use the two results for comparison


  • #5
    Beasty
    Administrators, Social & Fun Moderators, Sports Moderators Posts: 78,393 Admin ✭✭✭✭✭Beasty


    It's actually reasonably accurate at Sundrive. The track is 460m on the inside line an I normally record between 470m and 490m for the lap reflecting the fact I'm riding up the track. It can go a bit crazy on elevation though - I recorded 80m ascent in a 12 lap race last week.


  • #6
    sconhome
    Registered Users, Registered Users 2 Posts: 5,468 ✭✭✭sconhome


    Does the speed sensor not take precedence with Garmin? I know if you have a speed sensor fitted and are using a Polar unit the default is sensor first then GPS as mapping tool. A speed sensor set to the wheel circumference will alwasy be much more accurate than GPS for both speed and distance.


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  • #7
    Beasty
    Administrators, Social & Fun Moderators, Sports Moderators Posts: 78,393 Admin ✭✭✭✭✭Beasty


    amphkingwest wrote: »
    Does the speed sensor not take precedence with Garmin? I know if you have a speed sensor fitted and are using a Polar unit the default is sensor first then GPS as mapping tool. A speed sensor set to the wheel circumference will alwasy be much more accurate than GPS for both speed and distance.
    It does, but I don't have a speed sensor on my track bike so all my data is based on the GPS (and the speed/distance data on my Garmin is pretty consistent)


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