Hi Antonio:
----------------
That's an interesting question.
It turns out that one of the key military applications of GPS, in addition to
position and time, is to find North to high accuracy. This is needed to be
known to better that one grad (1/6400 of a circle). In that past it was done
using a theodolite integrated with a gyroscope (AG8 (Kern DKM1) North Finding
System). This system was heavy, cost the government about $250k and was very
easy to break.
http://www.prc68.com/I/Alidade.shtml#AG8
I think starting with the PLGR96 and now the DAGR there are two or more methods
of accurately finding North.
http://www.prc68.com/I/PLGR.shtml
http://www.prc68.com/I/DAGR.shtml#GLS
http://www.prc68.com/I/DAGR.shtml#AzD
In one method you place the receiver on stake #1, go to stake #2 (while not
obstructing the antenna to allow carrier phase tracking sats) then at stake #2
press enter and the GPS gives you the bearing and distance between the stakes.
In another method two GPS receivers are used. One at stake #1 and the other
first is synchronized to the one at stake #1 then moved to stake #2, press
enter, and go back to stake #1 and reconnect the two units. Again you get
bearing and distance between the stakes based on carrier phase processing
inside the GPS unit.
---------------------
Many GPS receivers have a built in World Magnetic Model. It's just a 12th
order polynomial fitted to the magnetic vector by Lon, Lat, Ele, date & time.
They're good for 5 years, see:
http://www.prc68.com/I/Sensors.shtml#EMF
For example the military DAGR has a built in magnetic compass that has the
deviation corrected based on the location and date so you can select either
true or magnetic bearings. Using the magnetic compass drains the battery so
there's an option to turn it off when not in use. There's no tilt correction
so the GPS receiver needs to be held level when using the mag compass.
Have Fun,
Brooke Clarke
http://www.prc68.com
iov...@inwind.it wrote:
> Does a stationary (not in motion) GPS receiver know where the North is?
>
> As far
> as I can understand, it doesn't, isn't it?
>
> Antonio I8IOV
>
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