Altitude meters.... do they work well ?

Discussion in 'Cycling Equipment' started by Aernout, Oct 28, 2003.

  1. Aernout

    Aernout New Member

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    Some computers can measure altitude and also keep track of the total altitude gain during the trip. I was wondering if these altitude meters are accurate enough to be useful.

    I'm curious about experiences that people have with these computers. For example: are there people who have made a trip with a known amount altitude gain and have they compared it with the result of the computer?

    Or two people who the same trip, both using an altitude meter. Do these computers show the same altitude gain at the end of the trip? Anybody tried this?

    I'm also curious what happens when you make a long trip in a completely flat area. Will the computer still show altitude gain caused by accumulated measurement errors or is the reading close to zero?

    Thanks!
    Aernout
     
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  2. armchair_spacem

    armchair_spacem New Member

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    I have a Polar S710 that samples and records altitude. I found it a nuisance b/c it needed recalibration fairly often (I live by the coast so a matter of walking to the beach and setting it at zero). It also sucjed up battery and memory, so I turned it off.

     
  3. alonblue

    alonblue New Member

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    I'm using the Polar S710 as well, but i do like the altitude feature. It is weather dependent, so the absolute altitudes of the places I ride in vary a lot, but the relative altitude is consistent enough, and this is what matters to me. In other words, I am not really thrilled by how high I am above sea level, but just want to know how much I climbed. Another great feature is that it shows the gradient (using the software after downloading the data).
    To get the real altitude of places, I take my GPS with me.

    The S710 has an ascent display, which accumulates all the positive differences of the altitude during the ride. It is ok on a climb, but on a flat it is affected by the falattest undulating road. You can do a flat ride and find out that you have climbed 500 meters. So I'm not using this function.
     
  4. Alexf

    Alexf New Member

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    All altitude meters work of barometric pressure (in exception of some GPS units) - as a result they have to be recalibrated when you reach known points - especially in a changing weather conditions - so unless you are hiking on well known trail and have a map with an accurate altitude marks that allow you to recalibrated once in a while - its more of a toy than anything else....
     
  5. J-V

    J-V New Member

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    None of the altimeters included with a cyclecomputer are going to be aviation-accurate, which is what you are talking about. I have two on my bike at the moment (Polar s720i and Ciclo 434m), and they always show some discrepancy, although typically it is minimal enough that it doesn't matter (75-200').

    As for people saying "mine always requires recalibration, so it's a pain"... well, welcome to the world of barometric altimetry. That's why pilots have to update their altimeters while flying, because pressure is typically changing, especially if you travel large distances (which we, as cyclists, tend not to do). The amount of pressure change during a typical ride isn't so significant (maybe changing the altitude by 100-200 feet); that's why often your altitude is different at the start/end of a ride. If you happen to ride during the time that a weather front is passing your location, it can be more extreme than this, but your ride wouldn't likely be much fun!

    If your instrument is in the house, then you take it out to ride, the temperature variation is going to throw it off a bit, even though most state they adjust for temperature fluctuations.

    Unless you want to know the best approximate of your current altitude while riding, it's completely unnecessary to 'calibrate' your altimeter in order to get accurate climb data. The ascent in feet is going to be the same whether it's calibrated or not.

    As far as showing an ascent during a flat ride, this could be due to both pressure and temperature fluctuations, as well as the simple accuracy of your instrument. There are few 'completely flat' courses out there; I sure wish I had one around me for flat time-trialing.

    I think that altimeters are very handy tools that represent the difficulty of a ride MUCH more accurately than just looking at mileage. I'm still constantly befuddled by how training programs and 'coaching tips' neglect actually quantifying climbs during riding, as it directly effects both your effort and your average speed.
     
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