T&T: Most Popular Nav Software

[Peter Bennett]

Tuesday, September 25, 2007, 2:22:52 PM, Steve wrote:

SS> Yes, some thoughts.

SS> I have a Raymarine S3G corepack course computer, newest version (old
SS> Apelco had a bad fluxgate card). The computer ties into NMEA 1 "IN"
SS> directly on the course computer. I had similar problems, with the course
SS> XTE drifting off to about 60 yds before making a too noticeable 
SS> correction. I went into the options on the CE program, and in the 
SS> autopilot heading, there's a "sentences" setting. I unchecked all but
SS> about 4 of the NMEA sentences being sent to the AP, and decreased the
SS> refresh interval from 2 to 1 second. It helped. I've got much smoother
SS> course keeping now, and no more "NMEA port clogged" warnings. Evidently,
SS> the computer was sending more information to the AP than it needed and
SS> it couldn't sort out the data fast enough. I'm not an expert on this,
SS> but from what I gleaned from the CE help files, this is a variable thing
SS> that may require some trial & error to perfect. I'll play with it some
SS> more, then when I'm satisfied with the results, I'll print the sentences
SS> settings in the event I need to duplicate it.

I have a Raymarine S1 autopilot, and have experienced frequent 30
degree course shifts when the reported XTE reaches 0.02 miles.  I
reported this as a problem to Raymarine, and was told it was an
"improvement", but now realize that it is a problem for many users.
They are working on a fix for it.

The original firmware would do this abrupt course change if the XTE
exceeds 0.01 mile - but my Garmin GPS and nav programs only report XTE
to the nearest 0.01 mile, so the pilot doesn't really have much
opportunity to correct the XTE using gentle adjustments, before it
gets an 0.02 mi XTE, and says "oops - too far off", an lurches back
towards the desired track.

-- 
Peter Bennett, VE7CEI
Vancouver, B.C., Canada Ennos 31 "Honeycomb" GPS and NMEA info:
http://vancouver-webpages.com/peter Vancouver Power Squadron:
http://vancouver.powersquadron.ca