On 2008-04-30 10:30:07 -0400, Larry said:

Jere Lull wrote:
On 2008-04-27 20:46:09 -0400, Larry said:

The autopilot I used had no sensor for speed. Does any? It would seem
to me that there needs to be one because response to the wheel is
proportional to your speed underway.

Haven't been paying attention to this thread, but my tiller AP will
"read" some NMEA speed sentence and the swing can be adjusted.

Do you know if reading the NMEA sentences replaces the fluxgate compass
or is used for longer range navigation (plotting a course with
waypoints). Thanks

I think I should have said "phrase" instead of sentence.

I'm a little confused as the speed phrase I'm talking about from the
knotlog wouldn't be affected by the direction the boat was pointing.
The AP can adjust rudder sensitivity and calculate current set from
that speed phrase, as I recall.

The input from the fluxgate would have a different phrase (If our AP
can take an external one).

Our AP calculates a specific-width "lane" between two waypoints,
adjusting its heading (against internal or external fluxgate) vs GPS
heading depending partially with heading to the next mark, but it's
more concerned with getting back into the lane.

--
Jere Lull
Xan-à-Deux -- Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/