Re: Garmin Edge 305 Cyclometer

Discussion in 'Cycling Equipment' started by Eric, Jan 31, 2006.

  1. Eric

    Eric Guest

    Garmin seems to keep a premium price on thier products, but it is
    mostly deserved. I had a Magellan GPS years ago and they weren't even
    close to the equivalant Gamin unit. Since then I haven't considered
    anything else.
     
    Tags:


  2. the unit does not track speed and speed derivitives via satellite data
    but regular old ground data-is that correct?
     
  3. [email protected] wrote:
    > the unit does not track speed and speed derivitives via satellite data
    > but regular old ground data-is that correct?


    No, that's not completely correct. The Edge uses GPS for speed data
    where possible, but it will revert to the GSC-10 speed sensor when a
    satellite signal is not available (tunnels, heavy tree cover, etc.)
     
  4. Sandy

    Sandy Guest

    Dans le message de
    news:[email protected],
    Richard Bollar <[email protected]> a réfléchi, et puis a déclaré :
    > [email protected] wrote:
    >> the unit does not track speed and speed derivitives via satellite
    >> data but regular old ground data-is that correct?

    >
    > No, that's not completely correct. The Edge uses GPS for speed data
    > where possible, but it will revert to the GSC-10 speed sensor when a
    > satellite signal is not available (tunnels, heavy tree cover, etc.)


    This is a great subject about which I know nothing. It's nice to learn all
    this stuff.
    But, why would you want a GPS to measure ground covered by your wheels at
    the relaxed accuracies of a satellite, when you down-to-the-millimetric
    wheel kit will do better ? Or maybe there is an option to choose one or the
    other on this equipment ??

    --
    Sandy
    --
    Ce message, issu de l'agriculture biologique, a été rédigé avec des
    électrons recyclés. En conséquence, il est possible que des fautes
    d'orthographes s'y soient malencontreusement glissées.
     
  5. Neil Brooks

    Neil Brooks Guest

    "Sandy" <[email protected]> wrote:

    >Dans le message de
    >news:[email protected],
    >Richard Bollar <[email protected]> a réfléchi, et puis a déclaré :
    >> [email protected] wrote:
    >>> the unit does not track speed and speed derivitives via satellite
    >>> data but regular old ground data-is that correct?

    >>
    >> No, that's not completely correct. The Edge uses GPS for speed data
    >> where possible, but it will revert to the GSC-10 speed sensor when a
    >> satellite signal is not available (tunnels, heavy tree cover, etc.)

    >
    >This is a great subject about which I know nothing. It's nice to learn all
    >this stuff.
    >But, why would you want a GPS to measure ground covered by your wheels at
    >the relaxed accuracies of a satellite, when you down-to-the-millimetric
    >wheel kit will do better ? Or maybe there is an option to choose one or the
    >other on this equipment ??


    This is definitely but /one/ of the benefits of using a GPS for
    cycling.

    I enjoy using it to create an exact record of the route that I rode,
    then uploading the data to software like TopoZone [1] to create a 3-D
    version of the ride, allowing me to view grades climbed, calculate
    power output, and generally log interesting rides.

    Another fun advantage is the ability to 'get yourself hopelessly
    lost,' then--taking the GPS out of your backpack--find your way back
    with ease.

    [1] http://www.topozone.com/
    --
    Live simply so that others may simply live
     
  6. Sandy wrote:


    > This is a great subject about which I know nothing. It's nice to learn all
    > this stuff.
    > But, why would you want a GPS to measure ground covered by your wheels at
    > the relaxed accuracies of a satellite, when you down-to-the-millimetric
    > wheel kit will do better ? Or maybe there is an option to choose one or the
    > other on this equipment ??


    Well, first off, second-to-second GPS distance is very accurate as it's
    calculated from the GPS frequency doppler shift and isn't dependent on
    the accuracy of the position solution. The Edge then uses these
    calculations over roughly 2km to determine the circumference of the
    wheel. Unless you turn the GPS off, it will always use GPS signal
    first and speed sensor second.

    Now, why would one want to pay so much for a bike computer... I like
    being able to map out my rides, and I also like to be able to compete
    against myself. The Edge has a feature that allows you to show your
    progress against a prior workout in real time. A very cool feature.
     
  7. peter

    peter Guest

    Richard Bollar wrote:
    > Sandy wrote:
    > > But, why would you want a GPS to measure ground covered by your wheels at
    > > the relaxed accuracies of a satellite, when you down-to-the-millimetric
    > > wheel kit will do better ? Or maybe there is an option to choose one or the
    > > other on this equipment ??

    >
    > Well, first off, second-to-second GPS distance is very accurate as it's
    > calculated from the GPS frequency doppler shift and isn't dependent on
    > the accuracy of the position solution.


    The Doppler shift is the primary input in determining the current
    speed. But using only speed data and integrating over time to get
    distance traveled would result in significantly larger errors than
    considering the direct measurements of successive positions. In
    practice the Kalman filter computational techniques used in GPS
    receivers tend to incorporate all the available input data (current
    pseudo ranges and pseudo range-rates as well as recent history) to
    produce the best estimate of the outputs (current position, speed,
    heading, and distance moved)

    > The Edge then uses these
    > calculations over roughly 2km to determine the circumference of the
    > wheel. Unless you turn the GPS off, it will always use GPS signal
    > first and speed sensor second.


    Seems like a poor design decision. I've been using Garmin GPS
    receivers in lieu of a cyclometer for quite a few years now and find
    that the odometer functions are adequate for my purposes but are
    clearly inferior to a well-calibrated cyclometer that counts wheel
    revolutions to determine the distance. Responsiveness of the speed
    indication to changes is also limited compared to a regular cyclometer
    due to the once per second update rate of most consumer GPS units
    (incl. the 205/305 according to the specs I've seen).

    However, the magnet sensor that lets the unit determine speed &
    distance by wheel revolutions is an optional extra in some versions of
    this product so they may have wanted to keep the operation of them
    consistent by using GPS measurements as much as possible, even when
    less accurate.
     
  8. Lou Holtman

    Lou Holtman Guest

    "Richard Bollar" <[email protected]> wrote in message
    news:[email protected]
    >
    > Sandy wrote:
    >
    >
    > > This is a great subject about which I know nothing. It's nice to learn

    all
    > > this stuff.
    > > But, why would you want a GPS to measure ground covered by your wheels

    at
    > > the relaxed accuracies of a satellite, when you down-to-the-millimetric
    > > wheel kit will do better ? Or maybe there is an option to choose one or

    the
    > > other on this equipment ??

    >
    > Well, first off, second-to-second GPS distance is very accurate as it's
    > calculated from the GPS frequency doppler shift and isn't dependent on
    > the accuracy of the position solution. The Edge then uses these
    > calculations over roughly 2km to determine the circumference of the
    > wheel. Unless you turn the GPS off, it will always use GPS signal
    > first and speed sensor second.
    >
    > Now, why would one want to pay so much for a bike computer... I like
    > being able to map out my rides, and I also like to be able to compete
    > against myself. The Edge has a feature that allows you to show your
    > progress against a prior workout in real time. A very cool feature.
    >


    Can you use the Garmin Edge 305 without the speedsensor mounted?

    Lou
     
  9. michel

    michel Guest

    >
    > Can you use the Garmin Edge 305 without the speedsensor mounted?
    >


    I have the Edge 205, and it comes without a speed censor, and as far as
    I know the Edge 305 comes without one as well, here in the UK.

    As stated before: the speed the Edge gives, seems less stable than with
    a standard bike computer - possibly more so if going slow: e.g. when I
    was climbing the speed the Edge gave was continuously varying between
    13 and 16 km/h. I am quite sure with a normal bike computer I would see
    differences of about +/- 0.5 km/h.

    With the Edge 205 (without barometric altitude meter) the height
    fluctuates rapidly by something like +/- 10m. Consequently the grade it
    gives does not make much sense.

    At the moment I have to say I am a bit dissapointed with the Edge. The
    unit itself (hardware) seems okay (though I would have prefered
    replaceable batteries), but the whole unit seems to be set up more as
    an expensive trip-computer than a navigation tool. The Trainingscenter
    software works okay, but is extremely limited in functionality and only
    exports data in an uncommon .hst file (and all data in one file). The
    user manual is very very limited. That being said, I am still trying to
    get things to work the way I want, so maybe it will be okay after all.

    Anyone succeeded in uploading "Routes" from affordable software to the
    Edge? If I understand correctly the Garmin "Trip and Waypoint manager"
    is not compatible with the Edge. Although I am not willing to spend
    another £150 for the mapsource UK topo, would this give you this
    functionality? Is it at all possible? I managed to upload waypoints
    with 3rd party software, but these still need manual editing (on the
    Edge itself) to get them into routes, which will involve lots of
    button-pushing.

    Also: I thought this would be completely obvious, but where can you see
    the actual position where you are "at the moment"? Is it possible to
    set the datum such that the position it gives corresponds to the
    "Ordnance Survey" map coordinates?

    Finally: I believe the unit does not have WAAS, but have heared some
    conficting info - anyone know more about this?

    Cheers!
    Michel
     
  10. michel

    michel Guest

    Richard Bollar wrote:
    > [...] The Edge then uses these calculations over roughly 2km to determine the circumference of the wheel. [...]


    How do you know these things? I am quite sure it is not in the user
    manual?

    Are there any other sources of info, except the user manual?

    Cheers!
    Michel
     
  11. michel wrote:
    > Richard Bollar wrote:
    > > [...] The Edge then uses these calculations over roughly 2km to determine the circumference of the wheel. [...]

    >
    > How do you know these things? I am quite sure it is not in the user
    > manual?
    >
    > Are there any other sources of info, except the user manual?


    Well, I own an Edge 305, so that's how I know. When you ride, you get
    a message about 2km into the ride that says something like "wheel size
    calibrated." The size of the wheel does vary by a couple of mm on each
    ride. Seems like changes in air pressure or temperature would easily
    account for that variance.
     
  12. Lou Holtman wrote:
    >
    > Can you use the Garmin Edge 305 without the speedsensor mounted?
    >


    Definitely. In fact there's a version sold without the speed sensor.
     
  13. michel wrote:

    > Anyone succeeded in uploading "Routes" from affordable software to the
    > Edge? If I understand correctly the Garmin "Trip and Waypoint manager"
    > is not compatible with the Edge. Although I am not willing to spend
    > another £150 for the mapsource UK topo, would this give you this
    > functionality? Is it at all possible? I managed to upload waypoints
    > with 3rd party software, but these still need manual editing (on the
    > Edge itself) to get them into routes, which will involve lots of
    > button-pushing.


    I am told that if you have Training Center, that you can download
    MapSource directly from Garmin. Since I already own MapSource, I can't
    test. http://www.garmin.com/support/mappingsw.jsp

    > Also: I thought this would be completely obvious, but where can you see
    > the actual position where you are "at the moment"? Is it possible to
    > set the datum such that the position it gives corresponds to the
    > "Ordnance Survey" map coordinates?


    No on both counts. I assume you're locked into WGS84.

    > Finally: I believe the unit does not have WAAS, but have heared some
    > conficting info - anyone know more about this?


    I have seen no evidence that WAAS is supported on the Edge. None of
    the WAAS signals are shown on the satellite screen.

    You might also be interested in this page I created which shows some
    comparison data between the Edge and various other Garmin GPS
    receivers: http://www.bollar.org/edge305.htm
     
  14. On Wed, 01 Feb 2006 19:19:06 -0800, peter wrote:

    > The Doppler shift is the primary input in determining the current
    > speed. But using only speed data and integrating over time to get
    > distance traveled would result in significantly larger errors than
    > considering the direct measurements of successive positions.


    I don't see that at all. The path taken is not going to be a straight,
    level line between marked positions along the road. Hills will cause one
    sort of inaccuracy in using GPS data to determine distance, but the
    actual path taken will be a larger error. Now, it may be debatable which
    measurement you want, but certainly integrating speed over time gives a
    better measurement of distance actually traveled. Of course, a standard
    computer should find distance by simply counting wheel revolutions, which
    is more likely to be accurate than either, if it is set up properly.

    --

    David L. Johnson

    __o | The motor car reflects our standard of living and gauges the
    _`\(,_ | speed of our present life. It long ago ran down Simple Living,
    (_)/ (_) | and never halted to inquire about the prostrate figure which
    fell as its victim. -- Warren G. Harding
     
  15. peter

    peter Guest

    David L. Johnson wrote:
    > On Wed, 01 Feb 2006 19:19:06 -0800, peter wrote:
    >
    > > The Doppler shift is the primary input in determining the current
    > > speed. But using only speed data and integrating over time to get
    > > distance traveled would result in significantly larger errors than
    > > considering the direct measurements of successive positions.

    >
    > I don't see that at all. The path taken is not going to be a straight,
    > level line between marked positions along the road. Hills will cause one
    > sort of inaccuracy in using GPS data to determine distance, but the
    > actual path taken will be a larger error. Now, it may be debatable which
    > measurement you want, but certainly integrating speed over time gives a
    > better measurement of distance actually traveled.


    I think you missed the word "only" in my sentence above. The Kalman
    filter calculations of GPS units take into account both the velocity
    (Doppler) data and the position (range) data in trying to minimize the
    errors. Using *only* the Doppler data will result in larger errors.

    > Of course, a standard
    > computer should find distance by simply counting wheel revolutions, which
    > is more likely to be accurate than either, if it is set up properly.


    Agreed, and that was the main point of my post. If the unit has a
    wheel revolution counter then it seems silly not to use that data as
    the primary basis for both distance and speed measurements.
     
  16. peter wrote:

    > > Of course, a standard
    > > computer should find distance by simply counting wheel revolutions, which
    > > is more likely to be accurate than either, if it is set up properly.

    >
    > Agreed, and that was the main point of my post. If the unit has a
    > wheel revolution counter then it seems silly not to use that data as
    > the primary basis for both distance and speed measurements.


    What's the best way to do this? I've never been able to get better
    than 2-3% accuracy with my cycle computers. Then again, this was with
    various models of Polar HRMs which I have found to be really touchy.
     
  17. Lou Holtman

    Lou Holtman Guest

    Richard Bollar wrote:
    > peter wrote:
    >
    >
    >>> Of course, a standard
    >>>computer should find distance by simply counting wheel revolutions, which
    >>>is more likely to be accurate than either, if it is set up properly.

    >>
    >>Agreed, and that was the main point of my post. If the unit has a
    >>wheel revolution counter then it seems silly not to use that data as
    >>the primary basis for both distance and speed measurements.

    >
    >
    > What's the best way to do this? I've never been able to get better
    > than 2-3% accuracy with my cycle computers.


    A typical value of a wheelcircumference is 2100 mm. 2-3% of that is
    42-63 mm. That's a lot. You must be doing something wrong measuring the
    wheelcircumference.

    > Then again, this was with
    > various models of Polar HRMs which I have found to be really touchy.


    What do you mean by touchy?

    Lou

    --
    Posted by news://news.nb.nu
     
  18. peter

    peter Guest

    Richard Bollar wrote:
    > peter wrote:
    >
    > > > Of course, a standard
    > > > computer should find distance by simply counting wheel revolutions, which
    > > > is more likely to be accurate than either, if it is set up properly.

    > >
    > > Agreed, and that was the main point of my post. If the unit has a
    > > wheel revolution counter then it seems silly not to use that data as
    > > the primary basis for both distance and speed measurements.

    >
    > What's the best way to do this? I've never been able to get better
    > than 2-3% accuracy with my cycle computers.


    I put a dab of ink or paint on the tire of the wheel with the magnet,
    sit on the bike in a normal riding position and roll forward for a few
    tire revolutions. Then I use a tape measure to determine the distance
    of 3 or 4 circumferences and divide.
    Seems to be accurate to 0.5% or better based on comparisons with
    mileage markers on country roads. But I haven't used a regular
    cyclometer in quite a few years since the GPS measurements are close
    enough and I like to see where I am on the moving map.
     
  19. michel

    michel Guest

    Richard Bollar wrote:
    > I am told that if you have Training Center, that you can download
    > MapSource directly from Garmin. Since I already own MapSource, I can't
    > test. http://www.garmin.com/support/mappingsw.jsp
    >

    Thanks, will give it a try.

    > > Also: I thought this would be completely obvious, but where can you see
    > > the actual position where you are "at the moment"? Is it possible to
    > > set the datum such that the position it gives corresponds to the
    > > "Ordnance Survey" map coordinates?

    >
    > No on both counts. I assume you're locked into WGS84.


    So I bought a GPS that cannot tell me where I am?!?

    > You might also be interested in this page I created which shows some
    > comparison data between the Edge and various other Garmin GPS
    > receivers: http://www.bollar.org/edge305.htm


    Nice page!
     
  20. Lou Holtman wrote:
    > Richard Bollar wrote:


    > > What's the best way to do this? I've never been able to get better
    > > than 2-3% accuracy with my cycle computers.

    >
    > A typical value of a wheelcircumference is 2100 mm. 2-3% of that is
    > 42-63 mm. That's a lot. You must be doing something wrong measuring the
    > wheelcircumference.


    Possibly, but it's +/- 2-3 percent. I ride the same 26.1 mile loop day
    after day and the readings from the Polar are usually between 25.9 to
    26.7 with a fair number of readings outside that range. This is on two
    different bikes each of whcih I have calibrated separately. I am aware
    that I could be impacting the values by not making sure my tires are
    inflated consistently.

    Before the Edge, I didn't often take a GPS with me, so I only have 14
    samples, but the readings are all between 26.07 and 26.16

    >
    > > Then again, this was with
    > > various models of Polar HRMs which I have found to be really touchy.

    >
    > What do you mean by touchy?


    I find that it's difficult to get the sensor placement right so that
    the Polar will read the speed and cadence sensor at the same time.
    Also, since it's a wireless system, I always assumed that interference
    could be messing with the signal. I gave up trying to improve the
    value, as it was good enough for my purposes.
     
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