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Garmin 500 Elevation

AndyD2574AndyD2574 Posts: 1,034
edited February 2012 in Workshop
Just noticed on my Garmin that when I am in the house the elevation sits at -171 ft so my ride data is wrong as looks like I am under the sea!! How do I get teh elevation to correct itself as my house sits at 95ft above sea level.

Do I need to factory reset as never used to do this?
Specialized S Works Venge
Argon18 E114
Specialized Langster Single Speed
Scott Spark Expert 29'er
GT Avalanche
http://www.glasgowgreencycleclub.co.uk

Posts

  • bus_terbus_ter Posts: 337
    You can set an elevation reference point. I can't remember exactly how you do it (I got mine ages ago). But basically you manually set the elevation at your house, and when you turn it on it uses that to calibrate the altitude.

    I've found it's not very good at absolute values, but good at detecting changes. So it shows you the gradient you're riding up etc
  • mrdsgsmrdsgs Posts: 331
    try turning garmin off. go outside and then turn it on, once it has booted up, scroll to a page with elevation on and wait, you should see the elevation self correct a few feet at a time. Sorted in 30 seconds. This works on my 800. As soon as it settles and I press "start' and begin my ride, the display briefly says something like "location elevation has been calibrated".

    I think the problem is that that the barometric altimeter in the garmin is based on air pressure and temperature and therefore readings inside the house will be wrong (i am no scientist, this is educated guesswork!)
    Colnago Addict!
  • fish156fish156 Posts: 496
    Garmin Edge 500 manual page 46 - Setting Elevation Points

    I've got both home & work elevation set (as per the OS map), so altitude is correct when setting off on a ride.
  • meanredspidermeanredspider Posts: 12,550
    When you say you're IN the house, is tht what you really mean? There's no way the device can measure altitude with a really poor satellite lock. Altitude is the most difficult positioning by satellite. The Garmin compensates for this by using barometric pressure but that obviously changes over time. It needs to be calibrated on each ride - the device needs a fixed (known) altitude and then can be reasonably accurate after that - assuming no significant barometric changes due to the weather. As above, start the device with a good "view" of the sky and calibrate.
    ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH
  • rolf_frolf_f Posts: 16,015
    mrdsgs wrote:
    I think the problem is that that the barometric altimeter in the garmin is based on air pressure and temperature and therefore readings inside the house will be wrong (i am no scientist, this is educated guesswork!)

    Atmospheric pressure is no different inside a house than out. As MRS says, if you want absolute values to be correct then you need to re-calibrate. If you have a barometer in the house (not many do!) you can see how much atmospheric pressure changes over a few days via the scale.

    Relative values shouldn't matter so much - but I need to check my commuting history to determine the variance of the recorded altitude - I think there is a fair error though and I tend to think that the mapping websites might be a better way to assess the climb in a route. They may tend to under-report overall climb but the advantage is consistency.
    Faster than a tent.......
  • andyrrandyrr Posts: 1,534
    As a slight side-note, as I don't have a Garmin but have a GPS phone (NokiaX6) which I use with sports-tracker, after downloading an activity, when I view it on the website and then hover over the Ascent/Descent value it tells me "GPS altitude accuracy is lower than horizontal accuracy"
    Even on a relatively short ride/run on a circular route the ascent and descent values always differ by a small amount,
    Recent 32Km ride has 409M ascent and 449descent.
    Mapping may be the way to get the most accurate altitude recorded as opposed to GPS or barometric but from memory I think my Polar HR used to be fairly accurate for altitide, more so than the GPS my Nokia uses.
  • pdwpdw Posts: 315
    The barometric altimeter in the Garmin is very accurate once it's calibrated. I typically find that ascent and descent are within a few feet of each other even over long rides.

    To get it calibrated you either need to leave it with a good GPS signal for a good while before you start and it will slowly calibrate using the GPS signal, or you can program elevation points with a known altitude. If you press the start button within 30m of one of these points, it will immediately calibrate to the preset altitude. You can get the correct elevation for a known point using http://www.bikehike.co.uk - just plot a tiny course where you want to start and press "show elevation data".

    If you don't get it calibrated before you start, the elevation data will be skewed as it'll be calibrating itself throughout the first part of the ride.

    It's a shame that they didn't make it a bit smarter, and have it default to the last known altitude if it's initial GPS fix is in the same place as where you turned it off.
  • AndyD2574AndyD2574 Posts: 1,034
    Thanks for the responses all.

    Did what you said and turned it on, on teh bike outside and just left it..................slowly went from -271 ft to about +91 ft which according to an web site I found with elevation points on is pretty spot on.

    Will turn on and leave from now on before I set off so it fixes itself!

    Happy Days :D
    Specialized S Works Venge
    Argon18 E114
    Specialized Langster Single Speed
    Scott Spark Expert 29'er
    GT Avalanche
    http://www.glasgowgreencycleclub.co.uk
  • John.TJohn.T Posts: 3,698
    The Garmin 500 does not use GPS at all for elevation. If you have not set an elevation point for your ride start then it needs about 20 to 30 min to sort itself out before you start riding.
    A barometric altimeter is far more accurate than a GPS one. Elevation correction found on some sites is very good in some areas but poor in others depending on the mapping used by the site. I stopped using it in the UK.
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