computer distance error

Discussion in 'Mountain Bikes' started by [email protected]!, Jul 13, 2003.

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  1. Hi. Could someone please point me to resources about popular bike computers distance
    measurement error?

    TnX
     
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  2. Higb

    Higb Guest

    [email protected]! <[email protected]~qfish.com> wrote:
    > Hi. Could someone please point me to resources about popular bike computers distance
    > measurement error?

    That seems hard to generalize ... tire pressure, riding surface, riding style ... if you are
    measuring how fast the front tire is going around that will all affect the outcome.

    FWIW, I use a GPS now. That's going to average things out, and give me the speed between sattelite
    fixes, but that appeals to me. I can see my speed between map points (and elevations), and compare
    Monday's loop to Thursday's loop. (Downloading to the computer now and then.)

    I'm kind of shocked that Garmin sells a handlebar mount for the eTrex ... but other than the GPS
    turning itself off on minor fall-downs (not really crashes), it's held up pretty well. Knock wood.
     
  3. higb says:

    >I'm kind of shocked that Garmin sells a handlebar mount for the eTrex

    Shocked? Surprised (and pleased), maybe.. ;-)

    >... but other than the GPS turning itself off on minor fall-downs (not really crashes), it's held
    >up pretty well.

    Try not to fall down . My eTrex has put up with all kinds of cr*p, and still keeps going.

    Steve
     
  4. David Kunz

    David Kunz Guest

    Stephen Baker wrote:
    > higb says:
    >
    >
    >>I'm kind of shocked that Garmin sells a handlebar mount for the eTrex
    >
    >
    > Shocked? Surprised (and pleased), maybe.. ;-)
    >
    >
    >>... but other than the GPS turning itself off on minor fall-downs (not really crashes), it's held
    >>up pretty well.
    >
    >
    > Try not to fall down . My eTrex has put up with all kinds of cr*p, and still keeps going.
    >
    > Steve

    Had a 12-map for quite a while. Garmin's handlebar mount's not strong enough for a mountain bike
    though -- After the 4th time that it went flying, it finally split at the seams (I had already
    replace the lens with one that I carefully crafted out of lexan) -- still works, but I don't trust
    it's ruggedness or waterproofness any more :). Made my own mount and replaced it with a 76s (map,
    altimeter and compass) -- sweet
    :). Nice for mapping trails, not getting lost on new trails, long
    distance wandering on the roads in areas that I've never been, seeing where I've been and keeping a
    log of miles traveled. AND, it's accurate :).

    David
     
  5. David Kunz

    David Kunz Guest

    Stephen Baker wrote:
    > higb says:
    >
    >
    >>I'm kind of shocked that Garmin sells a handlebar mount for the eTrex
    >
    >
    > Shocked? Surprised (and pleased), maybe.. ;-)
    >
    >
    >>... but other than the GPS turning itself off on minor fall-downs (not really crashes), it's held
    >>up pretty well.
    >
    >
    > Try not to fall down . My eTrex has put up with all kinds of cr*p, and still keeps going.
    >
    > Steve

    Forgot...

    The battery turn-off on crashes (and any hard hits) are from the batteries momentarily losing
    contact. Try pulling the springs a little longer or carefully bending the contacts out a little. If
    you use rechargable batteries (like I do), make sure that the batteries terminals are clean. When a
    set starts doing that, I rub the ends on a piece of wood -- acts like a fine emory.

    David
     
  6. "[email protected]!" <[email protected]~Qfish.com> wrote in message news:[email protected]...
    > Hi. Could someone please point me to resources about popular bike computers distance
    > measurement error?
    >

    I imagine that a lot of 'error' if variation due to riding style, i.e. different riders will pick
    different lines. The same rider will probably pick different lines on different bikes. While I can
    imagine a group of roadies finishing a ride with identical distance measurements I wouldn't be
    surprised if MTBer's distances varied by a couple of 'points'.
     
  7. "higb" <[email protected]> wrote in message news:[email protected]...
    > [email protected]! <[email protected]~qfish.com> wrote:

    > I'm kind of shocked that Garmin sells a handlebar mount for the eTrex ... but other than the GPS
    > turning itself off on minor fall-downs (not really crashes), it's held up pretty well. Knock wood.

    I used the mount for a while (until I lost the little screw that holds the bracket to the back of
    the GPS). On really rough stuff I probably would trust a jersey pocket more. I once heard from a
    rider who used an external antenna mounted to his helmet.
     
  8. Super Slinky

    Super Slinky Guest

    [email protected]! said...

    > Hi. Could someone please point me to resources about popular bike computers distance
    > measurement error?
    >
    > TnX

    There is no error with my computer, because I program the tire roll-out.
     
  9. On Sun, 13 Jul 2003 14:24:08 GMT, higb <[email protected]> wrote:

    >I'm kind of shocked that Garmin sells a handlebar mount for the eTrex ... but other than the GPS
    >turning itself off on minor fall-downs (not really crashes), it's held up pretty well. Knock wood.

    Put a _thin_ slice of foam rubber inside the battery compartment, or wrap the batteries in tape, and
    your gps will not longer shut itself off.

    My foam is about 3/8" long by 1/4" wide by 1/16" thick. A strip of road bike handlebar cork of the
    same dimensions would also work well.

    Barry
     
  10. On 14 Jul 2003 01:35:47 GMT, [email protected] (Stephen Baker) wrote:

    >Dave Kunz says:
    >
    >>Garmin's handlebar mount's not strong enough for a mountain bike though
    >
    >Do tell? Mine has been on the bike for 2 years now, no breakage or battery turn-off. I admit i
    >don't mount the GPS on every ride (shuddup, Shaun....), but the mount survives - and this is with a
    >rigid fork, as I'm sure I've mentioned before. ;-)
    >
    >Steve

    Same here, and mine's sometimes even mounted to a road bike, the ultimate harsh ride.

    The Garmin mounts that I've seen break were tightened gorrilla tight on the bars. I've seen some so
    over tightened that they're cracked near the screw. The mount only needs to be tight enough for the
    GPS to not move under normal riding, but loose enough to move in a crash. For extra insurance, I
    wrap the hand lanyard around the bars and clip it to itself with a mini 'biner.

    My eTrex Vista has survived several mountain bike crashes, and a *wild* 35 mph road bike vs. sandy,
    wet railroad tracks melee.

    The road bike wreck destroyed a shifter lever, a helmet, a handlebar, a fork, a pair of shorts, and
    parts of me, but not the GPS.

    Barry
     
  11. On Mon, 14 Jul 2003 01:01:38 GMT, Super Slinky <[email protected]> wrote:

    >[email protected]! said...
    >
    >> Hi. Could someone please point me to resources about popular bike computers distance
    >> measurement error?
    >>
    >> TnX
    >
    >There is no error with my computer, because I program the tire roll-out.

    Bzzzt. Wrong! <G>

    All bike computers have some sort of error tolerance. For example, the published error for a Shimano
    Flight Deck is +/- 1% for speed, 30ppm for the clock, 50ppm for the stopwatch and ride time, and
    .05% for trip and overall distance. This info is located in the manual.

    Other units probably have similar tolerances, except they might not be published.

    Barry
     
  12. Shaun Rimmer

    Shaun Rimmer Guest

    Stephen Baker <[email protected]> wrote in message
    news:[email protected]...
    > Dave Kunz says:
    >
    > >Garmin's handlebar mount's not strong enough for a mountain bike though
    >
    > Do tell? Mine has been on the bike for 2 years now, no breakage or
    battery
    > turn-off. I admit i don't mount the GPS on every ride (shuddup,
    Shaun....),

    Uhhhmm, what? ',;~}~

    > but the mount survives - and this is with a rigid fork, as I'm sure I've mentioned before. ;-)

    I'm rigid again for my commutes (details soon) ',;~}~

    Shaun aRe
     
  13. Shaun Rimmer

    Shaun Rimmer Guest

    Stephen Baker <[email protected]> wrote in message
    news:[email protected]...
    > Shaun says:
    >
    > >I'm rigid again for my commutes (details soon) ',;~}~
    >
    > What, Kath got a job at Newtronics? ;-)

    Heheheheheh - I freaking wish! ',;~}~

    Shaun aRe
     
  14. David Kunz

    David Kunz Guest

    B a r r y B u r k e J r . wrote:
    > On 14 Jul 2003 01:35:47 GMT, [email protected] (Stephen Baker) wrote:
    >
    >
    >>Dave Kunz says:
    >>
    >>
    >>>Garmin's handlebar mount's not strong enough for a mountain bike though
    >>
    >>Do tell? Mine has been on the bike for 2 years now, no breakage or battery turn-off. I admit i
    >>don't mount the GPS on every ride (shuddup, Shaun....), but the mount survives - and this is with
    >>a rigid fork, as I'm sure I've mentioned before. ;-)
    >>
    >>Steve
    >
    >
    > Same here, and mine's sometimes even mounted to a road bike, the ultimate harsh ride.
    >
    > The Garmin mounts that I've seen break were tightened gorrilla tight on the bars. I've seen some
    > so over tightened that they're cracked near the screw. The mount only needs to be tight enough for
    > the GPS to not move under normal riding, but loose enough to move in a crash. For extra insurance,
    > I wrap the hand lanyard around the bars and clip it to itself with a mini 'biner.
    >
    > My eTrex Vista has survived several mountain bike crashes, and a *wild* 35 mph road bike vs.
    > sandy, wet railroad tracks melee.
    >
    > The road bike wreck destroyed a shifter lever, a helmet, a handlebar, a fork, a pair of shorts,
    > and parts of me, but not the GPS.
    >
    > Barry
    >

    The bracket didn't break -- it kept losing the GPS. The screw combined with the double-sided tape
    wouldn't hold a 4-battery unit. The screw ripped-out and I was afraid to put a bigger one in (I had
    no idea what electronics I might total if it's even a little too long).

    David
     
  15. On Mon, 14 Jul 2003 16:00:12 GMT, David Kunz <[email protected]> wrote:

    >The bracket didn't break -- it kept losing the GPS. The screw combined with the double-sided tape
    >wouldn't hold a 4-battery unit. The screw ripped-out and I was afraid to put a bigger one in (I had
    >no idea what electronics I might total if it's even a little too long).
    >
    >David

    Oh! You had a II or III series unit!

    I know what you mean about that mount. <G>

    Barry
     
  16. Super Slinky

    Super Slinky Guest

    Stephen Baker said...

    > [email protected] says:
    >
    > >and that would help because...?
    >
    > Because then the inherent inaccuracy of a piece of electronics wouldn't matter. You measure the
    > distance travelled on the map, having timed the ride, and there is your speed. Simple, efficient,
    > no batteries, etc.
    >
    > HTH! Steve

    I assume you are being sarcastic, but in case you aren't that would only work if you had a map for a
    particular trail and you completely trusted the distances given, which would be stupid. For $30 and
    a half hour of setup time you can get a damn nice computer which will give you accurate numbers. No
    need to be a retro-grouch for something so useful. If you time the ride you still need a watch, but
    if you have a computer, you can leave the watch at home and not get a tan line on your left wrist.
     
  17. Super Slinky

    Super Slinky Guest

    B a r r y B u r k e J r . <Keep it in the [email protected]> said...

    > Bzzzt. Wrong! <G>
    >
    > All bike computers have some sort of error tolerance. For example, the published error for a
    > Shimano Flight Deck is +/- 1% for speed, 30ppm for the clock, 50ppm for the stopwatch and ride
    > time, and .05% for trip and overall distance. This info is located in the manual.
    >
    > Other units probably have similar tolerances, except they might not be published.

    Well no shit. Damn near everything has 1% error. Those are some small numbers you posted. My point
    to the OP was that there might be a way to program his computer for better accuracy. If he is
    worried about 1% error, he should find something else to obsess about.
     
  18. On Wed, 16 Jul 2003 04:39:52 GMT, Super Slinky <[email protected]> wrote:
    >
    >Well no shit. Damn near everything has 1% error. Those are some small numbers you posted. My point
    >to the OP was that there might be a way to program his computer for better accuracy. If he is
    >worried about 1% error, he should find something else to obsess about.

    How do you know what he wants to do with it? For instance, a consumer GPS can often be considered
    extremely accurate for the outdoor enthusiast. For a surveyor, the same GPS might as well be
    miles off.

    You said, "No error", did you not? <G> The errors I posted are significant enough for Shimano to
    include them in the manual.

    Barry
     
  19. Jd

    Jd Guest

    Super Slinky <[email protected]> wrote in message
    news:<[email protected]>...
    > Stephen Baker said...
    >
    > > [email protected] says:
    > >
    > > >and that would help because...?
    > >
    > > Because then the inherent inaccuracy of a piece of electronics wouldn't matter. You measure the
    > > distance travelled on the map, having timed the ride, and there is your speed. Simple,
    > > efficient, no batteries, etc.
    > >
    > > HTH! Steve
    >
    > I assume you are being sarcastic, but in case you aren't that would only work if you had a map for
    > a particular trail and you completely trusted the distances given, which would be stupid.

    No, stupid is weighing down your bike with useless electronic crap.

    > For $30 and a half hour of setup time you can get a damn nice computer which will give you
    > accurate numbers.

    For $30, I can drive to the Monarch Crest and back. Riding one of the most epic rides in the country
    sure beats the hell out of a piece of useless crap on my handlebars. Numbers, yeah that's important.

    > No need to be a retro-grouch for something so useful.

    No need to listen to the hype and buy everything the media tells you that you need. Mindless drones
    are exactly what they need to keep the machine oiled.

    > If you time the ride you still need a watch, but if you have a computer, you can leave the watch
    > at home and not get a tan line on your left wrist.

    And that would give you higher style points with all of the other trendoids.

    JD
     
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