DR practice
 

"Wally" wrote in message ...
Joe wrote:
If you want to sail a course of 080, at a speed of 10 knots and you
sail thru a current having an estimated set of 140 and a drift of two
knots
What would be your course and speed made good?.

089,

exactly

11.14 knots.

..6 knots off, but close this aint horseshoes.


If you want to sail a course of 095 through a current having a set of
170 and a drift of 2.5 knots, using a speed of 12 knots
What would be your course and speed made good?.

106, 12.88 knots.

correct on the course. Still just a bit off on the speed.

What course should you have steered to get a cog of 095?


You want to sail a course of 265 and a speed of 15 knots through a
current having a set of 185 and a drift of 3 knots
What would be your course and speed made good?.

254,

Good, what course should you have steered to make a COG of 265?

15.8 knots.

One knot off.

Hell of alot better than Jax.

Joe

DR practice
 

JAXAshby wrote:
But to claim that there is "no qualitative difference between navigating" a
plane and boat just shows you have no practical experience doing either.


quite the contrary. it shows I have done both.

actually, in air nav you don't have to make as much allowance for winds, for
the speed of the an airplane is many times the speed of the winds, for the
aircraft flights under discussion here.


Oh? How much allowance do you give for currents on these airplanes?

otn

DR practice
 

ROFLMAO How do you come up with these responses?!!

otn

JAXAshby wrote:
over the knee, it sounds like you are starting to back peddle in anticipation
of **finally** understanding the concept of relative motion.


maybe, over the knee, you don't know what reference points are, or what
constitutes a reference point. jeffies, doesn't/didn't.

like Ragu, "It's in there".

jax, you really,really do need help with "reading comprehension".
You can't just take what someone writes and interpret it to suit your
needs or point of view ..... go back and read what he said, then before
you write something, take the time to think what it means.

otn

DR practice
 

ROFLMAO ....

JAXAshby wrote:
over the knee, it is physically impossible to know where you are without
outside references. if you doubt that, call any local college tomorrow
morning, ask for the physics dept and ask the first TA who answers the phone.
Don't be bothered that he or she is only maybe 19 years old. he or she knows
the answer even if you don't.


You are wrong when you say "DR" is never dead on (but that's beyond
your knowledge or experience).


absolutely not. it is physically impossible. period. (except by random
chance, but that defeats the definition).

ROFL. Jax, we all ready know you don't understand the terms used in
"DR", or how it can be applied/used, and the possible variations in
meaning that others may have for the term and it's use.
How then could we expect you to understand that "DR" can be "dead on" in
many cases, but your total lack of experience and low levels of
comprehension put this possibility way beyond your ability to understand?

otn

DR practice
 

"Capt. Mooron" wrote:


When confronted with common sense advise you simply retract your head like a
turtle and attempt to avoid the obvious.

A gross and cruel libel on turtles.

--
Flying Tadpole

-------------------------
Henpecked? Harrassed? Harangued? Join the chorus:
http://music.download.com/internetopera
http://www.internetopera.netfirms.com

DR practice
 

List Jackass and listen good. DR in flying is just compass and speed. In
marine navigation it is compass, speed, leeway, current and tide. By
allowing for these variables accuracy is much greater.


Cheers

JAXAshby wrote:

jeffies, you definitely said *you* know where *you* are because you have
reference points in DR. listen to me. you do NOT have reference points in DR.
you ONLY have where you started (and you don't even know where that is once
you have started), your speed through the medium and which direction mag North
is. That's it.


No jaxie, I didn't mention "known ladmarks" and I wasn't referring to
"pilotage." Its very simple: any DR plot begins with a known reference
point
called a "fix." If you knew anything about DR you would understand that. I
would guess that most pilots know what their starting point is - that's a
reference point.




"JAXAshby" wrote in message
...

jeffies is not smart (without asking his wife) to use the word "pilotage".

he

merely said something about known ladmarks. same same.


I didn't see anywhere, where Jeff introduced "pilotage" in a way to
change the definition.

DR practice
 

Yes that about sums your knowledge up.

Cheers

JAXAshby wrote:

yeah, all that physics science stuff.

DR practice
 

in the world of super computers, that used to be called "double-precision
[meaning calculated to 16 decimal places] guesswork".


precision math does not make guesses more accurate.

correction: that is an *estimated* 089, and an *estimated* 11.14
knots.

It's accurate with respect to the mathmatical principle being employed.


And even that *estimation* is off by whatever leeway you get from the
wind, whatever variation you get as to speed and direction, plus
whatever variation you get between the direction the boat points and
which way it heads under pefect conditions, plus whatever variation
you get in pointing and speed due to waves and wave direction and
speed and height.

I am perfectly aware that DR is not precise when applied in the field.
However, the principle has to be applied precisely when working out the
vectors - to do otherwise would be to introduce another layer of potential
error. The point is to produce the best estimate you can on the basis of the
available information. To take a bunch of estimates, and then screw up the
numbers would be stupid.


--
Wally
www.artbywally.com
www.wally.myby.co.uk

DR practice
 

jeffies, pahleeeeeeeeeeeeeeeeeeeeeze ask your wife to read every last thing you
write **before** you hit the post key. that way we won't see the trash you
wrote below.
PLEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEAAAAAAAAAAAAAAAAAA AAAASSSSSSSSSSSSSSSSSSSS
SSEEEEEEEEEEEEEEEEEEE. okay?

There are no aircraft flights under discussion here. However, if we're
talking
about planes where electronics might not be used, then the speed is probably
rather low, and the wind speed could easily be 20% of the plane speed.
Worse,
you could have a significant wind shift and have no idea it happened. In a
boat, the currents are usually under a knot, and rarely is the deviation from
the prediction more than knot. You seem to be basing your entire claim on
the
possibility of unexpected 10 knot current in totally random directions. This
show your complete lack of experience.

Further, your completely ignoring that fact that for piloting, a major part
of
navigation, there are many techniques that have no analogue in flying. But
you
wouldn't know anything about this, would you?




"JAXAshby" wrote in message
...
But to claim that there is "no qualitative difference between navigating"
a
plane and boat just shows you have no practical experience doing either.

quite the contrary. it shows I have done both.

actually, in air nav you don't have to make as much allowance for winds,
for
the speed of the an airplane is many times the speed of the winds, for the
aircraft flights under discussion here.

DR practice
 

jeffies, **if** you know where you are using known (sic) reference point, THEN
that is called pilotage, not deduced reckoning.

you have changed the definition of the term DR to that of pilotage. you can
change it to green Shinola if you wish but it still doesn't make it safe to
wonder around in a fog with rocks anywhere near by.

I never made any such claim. In fact, I was only asserting the simple fact
that
DR does involve known reference points.

I've never claimed the DR was "precise," I've only claimed that it is good
enough to be useful, and a necessary skill for any skipper that wishes to be
competent.

You're the one who claims that DR is so worthless that navigation without GPS
is
physically impossible. And since you've admitted to being lost with two
functioning GPS's onboard, its a good thing you don't actually go sailing at
all.



"JAXAshby" wrote in message
...
over the knee, jeffies brought it up as proof that DR was precise
navigating,
not me.

jeffies is not smart (without asking his wife) to use the word
"pilotage".
he
merely said something about known ladmarks. same same.


I didn't see anywhere, where Jeff introduced "pilotage" in a way to
change the definition.



..... and you, typically, took it out of context, and created a new
argument, which was unrelated to the discussion at hand, and tried to
pawn it off as "someone else said".
Lame attempt, try again.

otn