Gene Kearns wrote:
On Mon, 26 Dec 2005 12:33:13 -0500, Wayne.B
wrote:


On Mon, 26 Dec 2005 00:33:08 GMT, "Butch Davis"
wrote:


IMO, for the gps to compute a compass course to compensate for wind and
current it would have to have some means to acquire the inputs.

========================

Exactly right.


Anybody know of a GPS with this capability?


I'm not sure what you are trying to accomplish, but inputting wind speed
and current wouldn't help since both affect different boats in different
ways. A smaller, shorter boat, for example, is less affected by wind
than a taller, longer boat.

The purpose of a GPS is to do more than a compass. It will help you
correct for wind and current if you simply use it to get to your waypoint.

Dan

"Dan Krueger" wrote in message
ink.net...
Gene Kearns wrote:
On Mon, 26 Dec 2005 12:33:13 -0500, Wayne.B
wrote:


On Mon, 26 Dec 2005 00:33:08 GMT, "Butch Davis"
wrote:


IMO, for the gps to compute a compass course to compensate for wind and
current it would have to have some means to acquire the inputs.

========================

Exactly right.


Anybody know of a GPS with this capability?


I'm not sure what you are trying to accomplish, but inputting wind speed
and current wouldn't help since both affect different boats in different
ways. A smaller, shorter boat, for example, is less affected by wind than
a taller, longer boat.

The purpose of a GPS is to do more than a compass. It will help you
correct for wind and current if you simply use it to get to your waypoint.

Dan

I guess I am missing something here. Assuming the discussion is about a
decent chartplotter type GPS, why all the questions about wind and drift?
As I recall using the Raymarine system on my Navigator, I would transfer my
planned track or route from the paper charts to the chartplotter in the
morning before getting underway. The route would consist of several
waypoints, usually placed in the area of a navigation buoy on the paper
charts.

I'd then just follow the tracks from waypoint to waypoint, either by
manually steering the boat or by autopilot. If the boat marker started
drifting away from the track due to wind or current, I'd see it and correct
for it. The autopilot can be used in two modes. One simply steers to a
course heading with no correction for wind or drift. The "Navigate" mode
keeps the boat on the intended waypoint track, automatically correcting for
wind or drift and automatically steering the boat to a new course as
required by the waypoint settings.

Worked fine for 1500 miles to Florida. So what am I missing?

Eisboch

On Mon, 26 Dec 2005 19:55:05 -0500, "Eisboch" wrote:

Worked fine for 1500 miles to Florida. So what am I missing?

Nothing, that's the way most folks do it. The GPS displays COG
(Course Over Ground) which is the combined effect of Boat Speed
through the water, Heading, Current Speed and Current Direction, plus
any set due to a crosswind. It is impossible to separate the various
components without having a very sophisticated instrumentation system
such as the ones that many racing sailboats carry.

If you set both a "From" waypoint (sometimes done automatically), and
a "To" waypoint (destination), then the GPS can also calculate XTE
(CrossTrack Error). Most GPS units today can direct the autopilot to
minimize XTE and thus maintain a straight course regardless of current
or wind.

the original question was that if a computer (GPS) could work its magic
and do a no brains naviagtion by telling you where to steer to go from
point A to B WITH cross wind/current.

WITH NO MANUAL INPUT OR READING THIS PARAMETER OR THAT ERROR

Simply (and only) by giving you degree where you need to point your
bow.

Matt

wrote in message
oups.com...
the original question was that if a computer (GPS) could work its magic
and do a no brains naviagtion by telling you where to steer to go from
point A to B WITH cross wind/current.

WITH NO MANUAL INPUT OR READING THIS PARAMETER OR THAT ERROR

Simply (and only) by giving you degree where you need to point your
bow.

Matt


My answer: Yes, *BUT* it may take you a hell of a long time to get there.

Eisboch

On Mon, 26 Dec 2005 22:07:16 -0500, "Eisboch" wrote:

the original question was that if a computer (GPS) could work its magic
and do a no brains naviagtion by telling you where to steer to go from
point A to B WITH cross wind/current.

WITH NO MANUAL INPUT OR READING THIS PARAMETER OR THAT ERROR

Simply (and only) by giving you degree where you need to point your
bow.

===========================

That's not a GPS, it's called a navigation computer or calculator. It
will still require manual inputs, and they will be estimates at best.

The question as stated is of theoretical interest only since the
constraints imposed are quite artificial in the real world.

In the real world your GPS will in fact tell you where to point your
bow but it is a feedback mechanism, not a one shot calculation. Even
NASA makes mid course corrections based on observed vs calculated.