On Wed, 27 Oct 2004 18:41:29 GMT, "Gordon Wedman"
wrote:

In " The Radar Book - Effective Navigation and Collision Avoidance " by
Kevin Monahan, he points out that the compass bearing given by a GPS will be
unstable at low speeds. If you want your radar to show proper compass
bearings and work in the North-up/Course-up modes he says you must connect
to some type of fluxgate or gyro compass. So if you just connect your GPS
NMEA output to your radar it seems you may not get correct heading
information while creeping along at low speed, for example, in fog.

"Gary" wrote in message
m...
I saw a few people said something about needing a fluxgate compass. I also
have a Robertson AP3000X autopilot that is connected to a fluxgate
compass.
Am I going to need 3 cables now, or is the GPS most likely connected to
the
fluxgate compass already?


Monahan's book may predate the discontinuance of selective
availability. You have to be going very slowly indeed to make the GPS
track reading less stable than a mag compass nowadays.

It is easy enough to compare on your own boat.





Rodney Myrvaagnes NYC J36 Gjo/a

"Religious wisdom is to wisdom as military music is to music."