On 1/4/2012 12:03 PM, Kevin Normoyle wrote:
> Iphone uses AKM AK8975 chip to sense the earth's magnetic field (four Hall
> effect sensors on a chip)
> so GPS isn't providing compass. I would think it's pretty accurate. Sure
> there's
> software and calibration, and the possibility for error, but I would imagine
> it's really good. I have a Garmin gps/compass that senses magnetic field for
> it's compass similarly.
If they have an app and GPS why on earth would they want to sense
magnetic North?
The nice thing about my GPS in the airplane is I don't have to convert
to get true North. With the magnetic compass you need to know the
magnetic variation or declination and add or subtract. IIRC When I fist
started flying it was + 5 degrees and now it's approaching - 7 in
Central Michigan. At one time it was zero. So for 50 years our runways
have all kept their same numbers. However they are fast approaching a
one digit change. This far North it can vary over 20 degrees in some
areas. In Northern Michigan it's even more than that, but due to the
iron deposits.
As for hams, it would seem to me that unless using a dish for EME or
very high gain array, "That looks about right" or "North is that way" is
close enough for tribanders and even pretty big monobanders. Those are
the only methods I've used for over 50 years on many antennas.
73
Roger (K8RI)
>
> -kevin
> ad6z
>
>
>
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