[time-nuts] OT - GPS and North
Gary Chatters
gcarlistaa at garychatters.com
Sat Nov 21 23:09:30 UTC 2009
J. Forster wrote:
> OK. Sme GPS receivers have magnetic sensors. What do they do with/about
> magnetic deviation.
>
There is a field in one of the NMEA messages for magnetic deviation
which some GPS receivers fill in.
I do not know where they get the values. There is a mathematical model
available from an appropriate agency (I forget which one right now) that
can be used to compute magnetic deviation anywhere on earth. The model
is supposed to be good for about five years before the coefficients need
to be updated.
Gary
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