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Bill wrote:

> Can't speak for others, but I certainly pay attention
> when sailing, especially if steering by compass or a
> target object.  Even on the Great Lakes, where current
> is minimal, leeway on a fin (especially wing) keel can
> get up there in a hurry.  If the wind allows, I will steer
> 4-6d above the rhumb lime course going to weather depending
> on boat, wind, and waves.

Let me re-phrase the original question a little differently: On an
ocean passage (at least as I understand it...) you basically navigate
based on course and speed (i.e. DR positions) until you get a fix, at
which time you "refine" your DR to a known position (I'm also assuming
no electronic navigation aids here too).

So if you find that your fix is a fair ways off from your DR position,
do you alter your course (and maybe speed too) to compensate - or just
carry on as before and take the resulting error out each time you get a
good fix?

Not sure what the technique is on the ocean, for air navigation we're
always adjusting heading (and maybe speed if needed) based on
real-world conditions, but it's really a different problem because
there's usually a reference for the true course line (ground
contact/map reference for visual conditions, and electronic guidance
for instrument conditions).

> If I understand, DR is course and speed.  Once you factor in
> set, drift and leeway you are into the area of EP (estimated
> position).

I think you're right on that one, and I'll defer to your definitions
here.  :-)

--
GregR


> Gregg R wrote:
>
> > Along those lines, is it common in ocean navigation to try to
> estimate
> > set and drift (and I'd guess true wind and leeway, too) and factor
> that
> > into the DR position estimate?
> >
> > I know that in aviation navigation we have to calculate the heading
> for
> > a given leg based on wind correction angle, but I've never seen any
> > reference to a similar allowance being made for that by our
> ocean-going
> > counterparts.
>
> Can't speak for others, but I certainly pay attention when sailing,
> especially if steering by compass or a target object.  Even on the
> Great
> Lakes, where current is minimal, leeway on a fin (especially wing)
> keel can
> get up there in a hurry.  If the wind allows, I will steer 4-6d above
> the
> rhumb lime course going to weather depending on boat, wind, and
> waves.
>
> If I understand, DR is course and speed.  Once you factor in set,
> drift and
> leeway you are into the area of EP (estimated position).
>
> Bill


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