Garmin Edge - how accurate?

buspassman
buspassman Posts: 35
edited June 2008 in Workshop
Last week, on the three days I rode into work, my computer (Ciclosport 424) clocked 38.81, 38.83 and 38.82 miles. A pretty high accuracy rate by any standards. The altimeter function shows a similar level of accuracy. Does anyone have any experience with a Garmin Edge (or the new Nokia Tracker), and does it approach that kind of accuracy? I would expect not, but am prepared to be surprised.

Comments

  • Jamey
    Jamey Posts: 2,152
    In a word, no.

    The distance isn't too bad (though not as good as your computer) but the altitude is really only a rough guide.

    On my commute the distance reading can vary between 13.80 miles and 14.00 miles and anywhere in between. The altitude, well... It shows you the big hills and it's fine if you just want to see a rough profile of your route and see how the hills affected your speed/heart rate/etc but if you actually want to know the exact number of feet above sea level then you'll probably be disappointed.
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  • kettrinboy
    kettrinboy Posts: 613
    As far as distances are concerned the edge, well my edge at least is very consistent, on a 7.18 mile sprint which ive done over 25 times i use a roadsign as the finishing point and starting point and the edge says 7.18 every time, also on longer 25 mile routes ive followed exactly the same course several times and again it was within a few yards , tha altitude is usually within +/- 2or 3 metres but on odd days can be 10 to 15 metres out but thats just on mine dont know what other peoples are like
  • lesdon499
    lesdon499 Posts: 29
    I have to agree with the last chappie, had my 305 for 18 months and it is always bang on with distance. How do you guage height but it feels good to see how high you have climbed, or not :) Must be affected by barometric pressure or something like that! Think the calorie counter is bloody nuts though!
  • Cunobelin
    Cunobelin Posts: 11,792
    Most GPS will give an accuracy figure that is dependent upon the recieved signal. In most cases this will be within feet of the true measurement. However with this error you also need to ask how accurately you cycle.

    I looked at my 13 mile commute and roughly estimated the difference if I took all the inside and outside lines on corners and other "Shortcuts" I reckoned that I could change the distance by some 600 to 700 yards if I took it to extremes.

    The GPS is probably more accurate than my riding, so be aware of the other factors.
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  • Simon Notley
    Simon Notley Posts: 1,263
    To be pedantic, your computer is very precise... whether it's accurate is another matter. Your commute might be 39.7 miles and your computer is systematically underestimating as it relies on the accuracy of your wheel circumference. I have a Garmin and it certainly isn't that precise, but it does have the advantage of not requiring calibration. I would guess that the Garmin is typically within 1% of the true distance, but it depends a lot on the nature of the route and the quality of GPS reception. If you're calculating the distance after the ride it also depends on how many data points you recorded (the Garmin can be set to every second or 'smart' which is typically every 10 seconds).

    But to answer the question, no I don't think the Garmin can get close to 0.1% except on long, straight routes with good GPS.

    Simon

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