In article ,
, Dave Doe says...

In article , lid, Bob
says...

Hi,

Thanks for replies and help.

What I was referring to are the new, modern, "glass" displays where most
everything shown is derived
from transducers located elsewhere.

e.g. when a display shows a Heading of, e.g., 075, it is of course
getting this info. from some kind of transducer, located elsewhere.

Is it derived directly from GPS ?
A Hall effect compass ?
or,... ?

Thanks again; interesting subject.

Well I'm not sure on that - perhaps others will reply. However,
cellphones usually use one or more magnetometers (hope I spelt that
right ). A GPS can't get a magnetic heading, only True.

I play with Arduino's a bit - and Googling 'arduino magentometer' gives
a few results, eg...
http://bildr.org/2011/01/hmc6352/
http://bildr.org/2012/02/hmc5883l_arduino/
http://eclecti.cc/hardware/hmc5843-m...ry-for-arduino

I *assume* that the compass in a glass display uses the same sort of
technology.

Apologies to the apostrophe police - that's terrible!

--
Duncan.