DR practice
 

no, joe, you are only guessing. as any pilot on the planet would tell you.

DR is speed vs time vs direction pointed, and your best guess as to where
that
puts you. that's it, nothing more.


Not that simple Jax. But let me try to help you to understand.

You go 5 knots " speed" "pointed" west thru a current that is going 5
knot to the north. You can do a DR plot that will tell you the
direction you actually went not the direction you were pointed. And it
will also take in account of current speed that may help or hinder
your speed. It's a real easy plot. Take out an old chart if you have
one and use the compass rose to help.... that's the way we teach the
kindergardners here.

Good Luck, and dont hurt yourself. Ask your mom for a crayon.

Joe

DR practice
 

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
 

JAXAshby wrote:
huh?

Well waddya know, an intelligent post. Navigation/navigating includes
the entire process of getting between point A and B. A big difference in
boats is that you can stop and check your work, whereas with a plane you
can't (well, you can circle for awhile, if you have the fuel). One
reason straight DR in zero visibility may be frowned on with planes.

otn

There is absolutely no qualitative difference between navigating an

airplane

and navigating a boat, except the airplane also has an instrument to tell

you

how far above the ground you are. none.


Don't know too many planes that can stop in midair and hover till they
figure things out....... (just for starters)

otn

DR practice
 

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, 11.14 knots.

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

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.

DR practice
 

JAXAshby wrote:

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
 

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
 

One
reason straight DR in zero visibility may be frowned on with planes.

no, the reason it is illegal is that you can not know where you are. period,
as in can not.

DR in a boat is okay when you are hundreds of miles from any rocks. It is not
okay when there is anything around to hit.

recreational boats regularly hit the rocks in fog upto recent history with the
advent of cheap Lorans and later GPS's and to a limited extent RDF (which had
much higher degrees of uncertainty).

DR practice
 

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

DR practice
 

"JAXAshby" wrote in message
...
jeffies, you definitely said *you* know where *you* are because you have
reference points in DR.

Show us where I said that. You're fantasizing an entire discussion, jaxie.
Time for those meds.

listen to me. you do NOT have reference points in DR.
you ONLY have where you started

That's one reference point ...

(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 another reference point.

That's it.

I think "2" is substantially difference than "0." You've just admitted that DR
has two reference points. Maybe you're catching on after all, jaxie.



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
 

Good Grief Jaxxies....... you are as idiotic as I originally assumed.

You have failed to locate the Gulf Stream..... you have failed to navigate
your way out of the idiotic stream of incredulous idiocy you've managed to
sail into inadvertently.

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

I can tell this while inebriated.... imagine how many of the sober are
holding you to ridicule!

CM

"JAXAshby" wrote in message
...
| One
| reason straight DR in zero visibility may be frowned on with planes.
|
| no, the reason it is illegal is that you can not know where you are.
period,
| as in can not.
|
| DR in a boat is okay when you are hundreds of miles from any rocks. It is
not
| okay when there is anything around to hit.
|
| recreational boats regularly hit the rocks in fog upto recent history with
the
| advent of cheap Lorans and later GPS's and to a limited extent RDF (which
had
| much higher degrees of uncertainty).