[time-nuts] OT - GPS and North

[Gary Chatters]

bg at lysator.liu.se 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