[time-nuts] OT - GPS and North

[J. Forster]

OK. Sme GPS receivers have magnetic sensors.  What do they do with/about
magnetic deviation.

-John

==============

> Tom Van Baak wrote:
>>> Does a stationary (not in motion) GPS receiver know where the North is?
>>
>> No, a stationary object is a point, not a line or a vector.
>> The notion of North (or any direction) has no meaning
>> to a point, by definition.
>
> You are mixing things a litte too much here. There is no direction
> within a 0-dimensional space, but a point as it is positioned in a
> 3-dimensional space has no problem to have an associated vector pointing
> either to a location or along some field such as the magnetic field.
>
> An electron is a point-charge, and reacts to a magnetic field or the
> electrostatic field.
>
> The antenna is certainly not a point, it is a sizeable object and it's
> phase centrum isn't a point either, it's just a handy approximation.
>
> It's just that normal GPS antennas and receivers isn't built for this
> purpose. A much smaller object than either the antenna or the receiver
> is the SO-8 packaged magnetic sensor you can buy cheaply and sense the
> magnetic field. A GPS receiver can be used to compensate for magnetic
> deviation if needed.
>
> Cheers,
> Magnus