bike compass



P

Paul Nevai

Guest
Althoguh my Forerunner GPS has a built-in compass, it is
very small and shows N - NW, etc, only. I want a nice,
fancy, and accurate compass for my bike which is not fooled
by the magnetic field generated by my bike. Regular
[magnetic] compasses don't work. I tried about a dozen
different models.

The best would be a compass which can be permanently mounted
or one which has a bike mount accessory.

Any suggestions?

Thanks, Paul
 
P

Peter

Guest
Paul Nevai wrote:

> Althoguh my Forerunner GPS has a built-in compass, it is
> very small and shows N - NW, etc, only. I want a nice,
> fancy, and accurate compass for my bike which is not
> fooled by the magnetic field generated by my bike. Regular
> [magnetic] compasses don't work. I tried about a dozen
> different models.

If you don't want it to be based on the magnetic field, then
a GPS receiver is your most practical alternative. Most
units (Geko, eTrex, SporTrak, Meridian, etc.) have a display
that shows a large compass and they also can indicate your
current course direction numerically in degrees. [Your
Forerunner is an exception with a greatly simplified GPS
feature set.] But note that the GPS-based compass determines
the direction by seeing how your position changes. So if you
stop, the unit doesn't know the direction anymore.

> The best would be a compass which can be permanently
> mounted or one which has a bike mount accessory.
>

The Foretrex and Geko series are the most compact and they
have bicycle handlebar mounts available.
 
G

G Huang

Guest
Paul Nevai wrote:
> Althoguh my Forerunner GPS has a built-in compass, it is
> very small and shows N - NW, etc, only. I want a nice,
> fancy, and accurate compass for my bike which is not
> fooled by the magnetic field generated by my bike. Regular
> [magnetic] compasses don't work. I tried about a dozen
> different models.
>
> The best would be a compass which can be permanently
> mounted or one which has a bike mount accessory.
>
> Any suggestions?

The only compasses that are not fooled by your bike would be
good digital electronic compasses. I use one in my car. It
has a calibration algorithm that computes the correction
vectors while you drive around a circle a few times at a
constant speed. You can also specify the local magnetic
declination so that the displayed north is the true north.
It is, however, still a magnetic compass and still subject
to being "fooled" by the surrounding field distortions such
as nearby cars, steel structures, etc. GH
 
R

Ron Hardin

Guest
Aircraft compasses have a couple compensation magnets, and
you ``swing the compass'' by removing half the error by
diddling the magnets repeatedly as you point in known
directions. Then you draw up a table of corrections still
necessary (for X steer Y). So that's about the best you can
do with a magnetic compass. Magnetic courses don't work out
anyway owing to wind, so in the end it's just a way to start
and then it becomes a way to hold whatever heading works
after that.

The cheap Garmen eTrex GPS displays course to a degree, if
you're moving, based on position differences. I have two
and they generally agree to a degree, if you're in the open
and moving.
--
Ron Hardin [email protected]

On the internet, nobody knows you're a jerk.
 
P

Peter

Guest
Ron Hardin wrote:

> Aircraft compasses have a couple compensation magnets, and
> you ``swing the compass'' by removing half the error by
> diddling the magnets repeatedly as you point in known
> directions. Then you draw up a table of corrections still
> necessary (for X steer Y).

You don't need to go nearly so high-end for that feature.
Even the automotive compass I picked up at K-Mart for under
$10 has the adjustable orthogonally-placed compensating
magnets. It's not as easy to adjust as the electronic
versions but since the magnetic material in my car is fixed
in place it only had to be done once and it has remained
accurate for quite a few years. Residual errors are only a
few degrees which is not a significant concern for car
navigation.
 
M

Michael J . Kle

Guest
On 26 Jun 2004 22:19:37 GMT, [email protected] (Paul Nevai) wrote:

>Althoguh my Forerunner GPS has a built-in compass, it is
>very small and shows N - NW, etc, only. I want a nice,
>fancy, and accurate compass for my bike which is not fooled
>by the magnetic field generated by my bike. Regular
>[magnetic] compasses don't work. I tried about a dozen
>different models.
>
>The best would be a compass which can be permanently
>mounted or one which has a bike mount accessory.
>
>Any suggestions?
>
>Thanks, Paul

Paul, I believe that what you want is a flux-gate compass,
which is a lot less suspectible to extraneous fields.

Michael J. Klein [email protected] Dasi Jen, Taoyuan
Hsien, Taiwan, ROC Please replace mousepotato with
asiancastings
---------------------------------------------
 
Z

Zog The Undenia

Guest
Paul Nevai wrote:

> Althoguh my Forerunner GPS has a built-in compass, it is
> very small and shows N - NW, etc, only. I want a nice,
> fancy, and accurate compass for my bike which is not
> fooled by the magnetic field generated by my bike. Regular
> [magnetic] compasses don't work. I tried about a dozen
> different models.
>
> The best would be a compass which can be permanently
> mounted or one which has a bike mount accessory.

Get a carbon fibre frame? ;-)
 
R

Ron Hardin

Guest
Michael J. Klein wrote:
> Paul, I believe that what you want is a flux-gate compass,
> which is a lot less suspectible to extraneous fields.

Magnetic fields are magnetic fields. There's only one, and
you measure
it.

Flux gate is already electronic and so is used where
electronics has to read it, as well as where you want to put
the compass sensor away from field-adding metal and carry
the indication back to where the pilot can read it. You
could put the sensor in a plastic trailer I guess.
--
Ron Hardin [email protected]

On the internet, nobody knows you're a jerk.
 
J

Jee Doy

Guest
>Get a carbon fibre frame? ;-)

How about placing the sensor on top of the plastic
helmet? Unless you have a piece of metal imbedded in the
skull (A Beautiful Mind), you should be ok. That would be
a neat thing for the Cateye's and Timex of the world to
come up with.
 

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