On 23 Feb 2007 08:13:31 -0800, "muelec" wrote:

I would like to control my Raymarine ST1000 Plus Autopilot, somehow
from a GPS without use of the internal compass. This would eliminate
the problems of the boat motions affecting the compass.
Is this possible?
Or can the boat motion / compass problem, in heavy sea, on a small
boat, be solved in an other way?
By wind vane control?

Thanks Urs

From my observations, an autopilot guided by GPS still uses its (or a)
compass as a heading reference.

When first engaging "steer by GPS", the autopilot will turn the boat
to the "bearing to waypoint" indicated by the GPS - and it can only do
that by comparing the compass heading to the GPS-provided bearing.
Once on-course, the autopilot turns its attention to the cross-track
error information provided by the GPS, and adjusts its "desired
heading" to minimize XTE - but it is still using its compass as a
heading reference.

You could add a SeaTalk compass to the system - the autopilot would
use that compass instead of its internal compass. I don't know if the
external compass would improve the pilot's performance to any
extent...


--
Peter Bennett, VE7CEI Vancouver BC, Canada
peterbb4 (at) interchange.ubc.ca
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