[email protected] wrote:
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
One model is called the World Magnetic Model
http://en.wikipedia.org/wiki/World_Magnetic_Model
That is the one I was thinking of. Follow the Wikipedia link to the
NGDC webpage: http://www.ngdc.noaa.gov/geomag/WMM/
New model due 15 December.
Gary
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