2 point question
 

I sent the folowing message more than 3 hours ago but it doesn't show
on Google News so I try once more. Sorry if it is a double.:

Should have been "unless you cross the equator exactly after the first
21 hours" instead of 7 - I thought you went North first. My teacher
apparently forgot to tell me to read the question thoroughly before
answering.

Maybe I should comment a bit further on the "geometrical component".
It could be defined as a trigonometrically function of your
start-latitude and your speed over the ground.
Hint: A "parallel", the circle that consists of al points at a given
latitude (for instance 56 degrees North), is larger (has a larger
circumference) than any parallel closer to the poles and smaller than
any parallel closer to equator, but they are all crossed by the same
number of longitudinal.

Peter S/Y Anicula

"Peter S/Y Anicula" skrev i en
meddelelse ...
"Thom Stewart" wrote:
......wouldld include leeway, tide, deviation and variation,
windage,
helmsmans error, etc.

That's pretty close, but you are missing one thing:
Unless you crossed the equator exactly after the first 7 hours which
is statistically very unlikely there vould also be a geometrical
component due to the fact that you are sailing on a globe
and not on a pancake.

Velocity over the ground (?) ("beholden fart" in my native
language)
in a unit of nautical miles
per 56 hours, would be the closest I can think of, but it doeen't
make
much sense.


Peter S/Y Anicula

2 point question
 

Donal--I'll give the points to you.

The point of this question was as follows.

If you travel a path where all other factors
are constant, and you do not return to your
starting point, something external force is
acting on your boat. That force is called
current, although it could be wind or
anything else--a barnacle on one side of
your bottom. Anything that you can't
explain is attributed to current.

I apologize if the question was too
vague.



Donal wrote

"Bart Senior" wrote

You sail directly East for 14 hours,
then South for 14 hours,
and then West for 14 hours,
and then North again for 14 hours.

Now if you draw a vector between your starting
position and your final position. What would you
call that vector?

A Tidal vector.

Donal

2 point question
 

Peter;

I have to give you the same advice I gave to the Jax. Re-read the
question. There aren't any distances given. The distance is a creation
of your own mind. Only time and directions were stated. The start and
the finish, in the problem, were different. The question, IN THE
PROBLEM. was what the line drawn (vector) between these two locations
(start & finish) was called. An Analytical Geometry Solution to a
navigational readings.

There are no distances asked for. There are no directions asked for.

The question; Name the line indicating the difference!!

Is that such a great PROBLEM? Can all the great minds, that have elected
to discuss this problem, admit they are looking for something other than
what was asked for! Don't be misled by Jax's ramblings ( He's caught in
the Gulf Stream again )

Ole Thom

2 point question
 

If you sail due east, north, west and south over the ground with the
same speed over the ground and there were no current, no leeway or
other "disturbing factors", you would still not end up at your
starting point (unless....). In fact on the northern hemisphere you
would end up in a position due west of your starting point.

(Assuming we are on the northern hemisphere): When you go back west on
a more northern latitude you will get further west than your starting
point, due to the fact that the meridians are closer together closer
to the pole. The north and south-going legs will even out each other,
but not so for the east and west going leg. If you don't believe me
try to plot it on your chart (and remember to use the right (but not
the same) latitude to measure the length of the nautical mile for your
east-going leg and for your west-going leg.

For this reason if would not give much meaning to call the difference
in start and end position current, set or a tidal vector.

Peter S/Y Anicula



"Bart Senior" skrev i en meddelelse
t...
Donal--I'll give the points to you.

The point of this question was as follows.

If you travel a path where all other factors
are constant, and you do not return to your
starting point, something external force is
acting on your boat. That force is called
current, although it could be wind or
anything else--a barnacle on one side of
your bottom. Anything that you can't
explain is attributed to current.

I apologize if the question was too
vague.



Donal wrote

"Bart Senior" wrote

You sail directly East for 14 hours,
then South for 14 hours,
and then West for 14 hours,
and then North again for 14 hours.

Now if you draw a vector between your starting
position and your final position. What would you
call that vector?

A Tidal vector.

Donal

2 point question
 

Yes Peter,

You're correct in what you've said but again you've deviated from the
origin problem. It doesn't matter THIS TIME!

Pete, this is and old trick question. used in teaching GREAT CIRCLE
NAVIGATION.
(Sorry Bart) Another explaination "Is a fat man wearing his belt under
his gut because the distance around his stomach is to large.

If the four legs were sailed in a vacuum, without tides and currents but
on a globe the start and finish would still be different. Since most DR
Navigation call the difference (Off Set) between start and finish Drift,
That was the term I used.
The etc was used to let Bart have his fun.

Horv, I know it doesn't make a difference in Units in this problem but
it did to Jax's conception.

Ole Thom

2 point question
 

Sorry Thom, but I still don't get it.

Lets say I wanted to visit my girlfriend, and she lives on an island
just west of my island. There is a lot of reefs in the area so to stay
clear I calculate a trip-plan that will bring me to her by sailing 14
hours east, 14 hours north, 14 hours west and 14 hours south. Since
there is no tide and no wind and the water is totally flat, I have to
use my twin engines (asymmetrical). Every thing goes as planed and
after 56 hours I arrive at my destination.

Would you still call the Vector from my start-point to my destination
for drift, current or any such thing?

Peter S/Y Anicula

P.S. Please, don't ask me how the reefs survive if there is no wind no
current and no waves.



"Thom Stewart" skrev i en meddelelse
...
Yes Peter,

You're correct in what you've said but again you've deviated from
the
origin problem. It doesn't matter THIS TIME!

Pete, this is and old trick question. used in teaching GREAT CIRCLE
NAVIGATION.
(Sorry Bart) Another explaination "Is a fat man wearing his belt
under
his gut because the distance around his stomach is to large.

If the four legs were sailed in a vacuum, without tides and currents
but
on a globe the start and finish would still be different. Since most
DR
Navigation call the difference (Off Set) between start and finish
Drift,
That was the term I used.
The etc was used to let Bart have his fun.

Horv, I know it doesn't make a difference in Units in this problem
but
it did to Jax's conception.

Ole Thom

2 point question
 

I forgot to mention, that the speed was absolutely constant during all
4 legs of the trip.

Peter S/Y Anicula


"Peter S/Y Anicula" skrev i en
meddelelse ...
Sorry Thom, but I still don't get it.

Lets say I wanted to visit my girlfriend, and she lives on an island
just west of my island. There is a lot of reefs in the area so to
stay
clear I calculate a trip-plan that will bring me to her by sailing
14
hours east, 14 hours north, 14 hours west and 14 hours south. Since
there is no tide and no wind and the water is totally flat, I have
to
use my twin engines (asymmetrical). Every thing goes as planed and
after 56 hours I arrive at my destination.

Would you still call the Vector from my start-point to my
destination
for drift, current or any such thing?

Peter S/Y Anicula

P.S. Please, don't ask me how the reefs survive if there is no wind
no
current and no waves.



"Thom Stewart" skrev i en meddelelse
...
Yes Peter,

You're correct in what you've said but again you've deviated from
the
origin problem. It doesn't matter THIS TIME!

Pete, this is and old trick question. used in teaching GREAT
CIRCLE
NAVIGATION.
(Sorry Bart) Another explaination "Is a fat man wearing his belt
under
his gut because the distance around his stomach is to large.

If the four legs were sailed in a vacuum, without tides and
currents
but
on a globe the start and finish would still be different. Since
most
DR
Navigation call the difference (Off Set) between start and finish
Drift,
That was the term I used.
The etc was used to let Bart have his fun.

Horv, I know it doesn't make a difference in Units in this problem
but
it did to Jax's conception.

Ole Thom

2 point question
 

Peter?

When was the last time you laid out a trip; point to point in Hours?
That is the hook!

A DR route point to point is laid out in Distance. (Miles not time) Each
leg to your Swertheart would be four legs, point to point in miles, with
calculated Drift/mile vectored in. Compass Dev & Var considered to set
up your course heading. When you had that all done, then and only then
would you estimate the lapsed time.
The old saying Pete, "Sailors schedule only departure times, after that
they only have control of direction."

Hope this clears up the problem.

Ole Thom

2 point question
 

Would you arrive at your destiantion if you left on a Friday?

Peter S/Y Anicula wrote

Lets say I wanted to visit my girlfriend, and she lives on an island
just west of my island. There is a lot of reefs in the area so to stay
clear I calculate a trip-plan that will bring me to her by sailing 14
hours east, 14 hours north, 14 hours west and 14 hours south. Since
there is no tide and no wind and the water is totally flat, I have to
use my twin engines (asymmetrical). Every thing goes as planed and
after 56 hours I arrive at my destination.

2 point question
 

"Peter S/Y Anicula" wrote in message
...

If you sail due east, north, west and south over the ground with the
same speed over the ground and there were no current, no leeway or
other "disturbing factors", you would still not end up at your
starting point (unless....). In fact on the northern hemisphere you
would end up in a position due west of your starting point.

Well!!! Excuuuse me!

Look, I don't often get points, so I feel that I must defend them.

In most places, the effect of tide would be much greater for a 14 hour
"square" than the curvature of the Earth.



Regards


Donal
--

2 point question
 

"JAXAshby" wrote in message
...
nav, are drinking in sympathy with moron?

consider that that seems likely.

consider also, nav, that moron is crashing towards serious medical
problems
because of his alcohol use.

I bet that you are not as healthy looking as you used to be?

Have you any recent photos?



Regards


Donal
--

2 point question
 

The effect of tide may be less than that of current...

Cheers

Donal wrote:

"Peter S/Y Anicula" wrote in message
...

If you sail due east, north, west and south over the ground with the
same speed over the ground and there were no current, no leeway or
other "disturbing factors", you would still not end up at your
starting point (unless....). In fact on the northern hemisphere you
would end up in a position due west of your starting point.


Well!!! Excuuuse me!

Look, I don't often get points, so I feel that I must defend them.

In most places, the effect of tide would be much greater for a 14 hour
"square" than the curvature of the Earth.



Regards


Donal
--

2 point question
 

"Nav" wrote in message
...
The effect of tide may be less than that of current...


Correct, but useless information for most seafarers.


Regards


Donal
--

2 point question
 

I did leave on a friday.

Peter S/Y Anicula


"Bart Senior" skrev i en meddelelse
t...
Would you arrive at your destiantion if you left on a Friday?

Peter S/Y Anicula wrote

Lets say I wanted to visit my girlfriend, and she lives on an
island
just west of my island. There is a lot of reefs in the area so to
stay
clear I calculate a trip-plan that will bring me to her by sailing
14
hours east, 14 hours north, 14 hours west and 14 hours south.
Since
there is no tide and no wind and the water is totally flat, I have
to
use my twin engines (asymmetrical). Every thing goes as planed
and
after 56 hours I arrive at my destination.

2 point question
 

Don--O

Might be greater but not as constant (G)

You're right Buddy, On my first reply I mentioned most of the thing that
would affect DRIFT but I threw in an Etc to not let the Cat out of the
bag.

Let's remember, Bart asked FOR THE NAME of the vector, not what caused
it.
Wally called it Leeway. Not wrong but incomplete. You called it Tidal
Drift (I think) Not wrong but again incomplete

Hey guys, the biggest Navi. Goof in history was made because of the
Global Curve. Chris Columbus thought he was in China because he had no
idea how much larger the Earth was at the equator. His distance for a
degree in nautical miles was half the distance in Europe than at the
middle.

He was just lucky as hell he found land by degrees where he did. He
thought that he had covered the unknown piece of the globe with his
"Chip Log" He assumed the World was round but the unknown was the rest
off the shape. That was still a question mark.

Ole Thom

2 point question
 

Don-o,

Bet he didn't get Laid when he got there. Friday is a bad luck departure
day an I'm
sure he was looking to get LUCKY (G)

OT

2 point question
 

"Well, if it wasen't for bad luck, I wouldn't have no luck at all."

Peter S/Y Anicula

"Thom Stewart" skrev i en meddelelse
...
Don-o,

Bet he didn't get Laid when he got there. Friday is a bad luck
departure
day an I'm
sure he was looking to get LUCKY (G)

OT

2 point question
 

You don't have currents? Here the currents typically run about 1 knot. I
think the gulf stream get up to about 4 knots.

Cheers

Donal wrote:
"Nav" wrote in message
...

The effect of tide may be less than that of current...



Correct, but useless information for most seafarers.


Regards


Donal
--

2 point question
 

Dave,

"Course made good" ? I was going to agree with you but as I started to
write this post, my mind changed.

Course made good is not the Vector. I guess Course Made Good would
apply. Don't know about the Speed part.

The time for the trip was 56 hrs and 56 hrs was sailed. No more no less.

The End of the trip, after 56 hrs wasn't at the starting position. Now,
was that the trips destination; To sail 4 legs of 14 hrs, 1 East, 1
south, 1 west, and 1 north. Was that the purpose of the Trip? I think
it was.

Now, the course made good created a position. From the question it seems
this was planned, which gave us a difference
(Which was planned for) This created the second point. The two points
were connect with a line, called a vector.

The name of this "Victor" is what was asked for in "the question"

Ole Thom

2 point question
 

"Nav" wrote in message
...
You don't have currents? Here the currents typically run about 1 knot. I
think the gulf stream get up to about 4 knots.



I'm not impressed. I deal with currents up to 10 kts.

http://www.mistweb.force9.co.uk/content/solent1.html

Regards


Donal
--

2 point question
 

"Dave" wrote:

I'd call it course and speed made good..

Dave , you definitely will get 2 Anicula-points for your answer. And I
am very happy to see that someone seem to agree with me on this.

I suggested "Velocity over the ground ..." which I think is the same,
(I assume that velocity has both a direction and a size). I am not
really that familiar with your language, but I think that "course and
speed made good" sounds simple and on the point.

The other answer that I liked was Scouts "a Resultant" which I also
think would be right, though not saying much.

If one sails a variety of courses that would put you in new position
(different from your start-position) if there were no leeway, current
etc., I think it is absolutely crazy to call it set, current or a
tidal vector or any such thing.
A good navigator might not always end up exactly where he planned, but
the art of navigation demands that you use a clear and precise set of
conceptions, and that you use them right.

This is the reason for my ardent spirit on this subject, though ardent
spirits also might have something to do with it.

Peter S/Y Anicula

P.S. Are you familiar with a boat called "Ardent Spirit" - I think it
was owned by someone called Besser. That boat used to make me drool.

2 point question
 

"Dave" wrote:
I'd call it course and speed made good..


Peter S/Y Anicula wrote:
Dave , you definitely will get 2 Anicula-points for your answer. And I
am very happy to see that someone seem to agree with me on this.

Oh yes, but I'm still a bit dazed by the question... it seems to me that
going around 4 sides of a large square is not really within the bounds
of VMG... usually 2 sides of a triangle are about the limit.

I was also suprised that nobody caught on to the diff in distance at
diff lattitudes... that was the first thing I thought of and was
surprised that it was not the point of the question.


I suggested "Velocity over the ground ..." which I think is the same,
(I assume that velocity has both a direction and a size). I am not
really that familiar with your language, but I think that "course and
speed made good" sounds simple and on the point.

Sure. Usually course made good and speed made good are two different &
seperate scalar entities. Velocity made good encompasses (pardon the
pun) both. VMG is usually thought of as the resultant speed toward an
upwind destination when tacking, or a downwind destination when reaching
back & forth; but it can just as easily apply any time you are not
heading directly toward your goal.

Fresh Breezes- Doug King

2 point question
 

You do know the difference between tide and current?

Cheers

Donal wrote:

"Nav" wrote in message
...

You don't have currents? Here the currents typically run about 1 knot. I
think the gulf stream get up to about 4 knots.




I'm not impressed. I deal with currents up to 10 kts.

http://www.mistweb.force9.co.uk/content/solent1.html

Regards


Donal
--

2 point question
 

Don-o,

We here in the Pac. NW deal with the same sort of Tidal Currents in the
Sound and Humbolt Current in the Ocean.

I know Mooron deals with the same thing in his area.

High Latitude sailors around the world all do

Ole Thom

2 point question
 

Thanks Peter,
that's only because I don't know much. Can't let that stop me from jumping
in the water.
Scout

"Peter S/Y Anicula" wrote
{snip}
The other answer that I liked was Scouts "a Resultant" which I also
think would be right, though not saying much.

2 point question
 

Thom,
the part I'm not getting is this: how do you know he's not back a the
starting point? I'm not saying you're wrong, just because I can't see the
logic in it, but I'd like to see the logic in it.
If we don't know how much distance he traveled on any leg, how come he can't
sneak up on the starting point again?
Scout

"Thom Stewart" wrote {snip}
The End of the trip, after 56 hrs wasn't at the starting position.

2 point question
 

Dave wrote:

Could you explain that? I would have thought that one NM is one NM
whether you're at the equator or the north pole.

Not if there's a longitude component - the length of a minute of longitude
decreases as one moves away from the equator.


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

2 point question
 

Mr. President?
Scout

"Dave" wrote
It depends on what the meaning of "is" is g.

2 point question
 

Scout,

He can't be at the starting point and be asking the name of the Vector
between the start and where he finished. Logical?

Also, even if there was no deviation due to Tidal drift, leeway etc,
just sail by "Timed Legs" on globe cannot make a square anywhere except
equal distance north & south of the equator or at the north or south
poles.

Scout, even if you sail a straight course you are sailing a curved line,
as far as elevation is concerned. This in itself will cause a course
change from East to South to be something different than a square corner
of a box.

Think of an ice cream cone, with the pointy end being north. Draw a
straight line from the lip of the cone to the tip (North) Now rotate the
cone 90 degrees and draw another line to the tip (North again) Now Scout
draw a line parallel to the lip of the cone, between those two lines. Is
it a square? Is it the same distance as the of the lip? It isn't is it?
Make it the same distance. Now, can you connect the ends with two
north---south lines to make a square?

I hope this help rather than confuse but I hope it helps explains the
problems of compass headings and expanding degree on a globe. It is a
concept worth getting a handle on.

Ole Thom

2 point question
 

Dave,

I too had trouble with the "Vector" but as the discussion has gone on,
vector just might be the right term

There has to be an angle back to the starting point as well as distance,
Both vector facters,

I'm not sure how you can say speed made good when we have no knowledge
of the distance or the speed of the trip. ( I believed he said constant
speed for the four legs)

What we have is Course heading and time of each of four legs.sailed on
an ocean. One question, a line(vector) drawn between the start and
completion without a name.

Ole Thom

2 point question
 

Dave wrote:
Could you explain that? I would have thought that one NM is one NM
whether you're at the equator or the north pole.

Yes it is, but a minute of longitude differs in length as you go north
and/or south.


Wally wrote:
Not if there's a longitude component - the length of a minute of longitude
decreases as one moves away from the equator.

Exactly. So it would be imminently possible for (as Peter said) to go,
say, 100NM east, then turn and go 100NM north, then 100NM west, and
finally 100NM south, and end up west of where you started (in the
northern hemisphere). If you stretch the distance out more, you end up
in a different hemisphere. This would work on land, too, so you can't
blame leeway or the tide.

Fresh Breezes- Doug King

2 point question
 

Dave,

A NM is 1/60 of a degree. A degree that is
360 divided into the length of the Equator. That is a NM anywhere. That
is a constant

A degree and a NM are equal at the Equator. A degree is only a constant
in measuring rotation with a circle being made up of 360 degrees. A
degree is not a linear measurement

OT

2 point question
 

yes it does Thom,
I get it - well done!
Scout

"Thom Stewart" wrote
{snip}
I hope this help rather than confuse but I hope it helps explains the
problems of compass headings and expanding degree on a globe. It is a
concept worth getting a handle on.

Ole Thom

2 point question
 

In most places where people are sailing, current would be
the greater effect.

Other factors, can all be lumped into something that for
lack of a better word is called current.

That is what I was taught.

DSK wrote

Yes it is, but a minute of longitude differs in length as you go north
and/or south.

2 point question
 

"DSK" wrote in message
. ..

I was also suprised that nobody caught on to the diff in distance at
diff lattitudes... that was the first thing I thought of and was
surprised that it was not the point of the question.

The original question mentioned a distance of 14 miles. What do yuu think
that the maximum offset could be?




Regards


Donal
--

2 point question
 

Last word ( Unless a special question for me.)
I was taught, any deviation for steered course was called "Drift" By
this discussion that may not be correct

Ole Thom

2 point question
 

Donal wrote:

The original question mentioned a distance of 14 miles.

It specified hours and, later, constant speed. Still, we can assume 1kt and
ask ourselves...


What do yuu think that the maximum offset could be?

28nm.


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

2 point question
 

Donal wrote:
The original question mentioned a distance of 14 miles.


I didn't see that. It looked to me like the speed & distance were
unspecified but assumed uniform on each leg.

Wally wrote:
It specified hours and, later, constant speed. Still, we can assume 1kt and
ask ourselves...



What do yuu think that the maximum offset could be?


28nm.

Is that with a really really bad compass ;)

From my limited knowledge of, and ability with, spherical trig, I get
an answer of somewhere around 0.8 meters starting at the equator... now
I have another question, would the offset be constant as you move
further north or south?

I also find it curious that "The Navigator(tm)" had nothing to say on
this point.

Fresh Breezes- Doug King

2 point question
 

I was taught that:

Speed is the forward motion through the water
Leeway is the sideways movement of the boat through the water
Current is the movement of the water over the ground
Steered course is the way you point
Sailed course is the direction that you move through the water
Course over the ground (is that called course made good ?) is the
direction you move over the ground
etc.

If one sails as you described in the question (on the northern
hemisphere), one sails toward a destination B that is west of the
starting-point A (if there were no current). The position after 56
hours is point C.
So, If your teacher taught you that when you sail from A toward B and
arrive at C then AC is the "current" then he must have been an
electrician and not a sailor. You could justify to call BC for
current, though the distance might be a result of more than just the
surface-waters movement over the ground.

Peter A/Y Anicula


"Bart Senior" skrev i en meddelelse
et...
In most places where people are sailing, current would be
the greater effect.

Other factors, can all be lumped into something that for
lack of a better word is called current.

That is what I was taught.

DSK wrote

Yes it is, but a minute of longitude differs in length as you go
north
and/or south.

2 point question
 

It's a trivial academic exercise.

Bwhahahhahahahaha

Cheers

DSK wrote:



Donal wrote:

The original question mentioned a distance of 14 miles.



I didn't see that. It looked to me like the speed & distance were
unspecified but assumed uniform on each leg.

Wally wrote:

It specified hours and, later, constant speed. Still, we can assume
1kt and
ask ourselves...



What do yuu think that the maximum offset could be?



28nm.


Is that with a really really bad compass ;)

From my limited knowledge of, and ability with, spherical trig, I get
an answer of somewhere around 0.8 meters starting at the equator... now
I have another question, would the offset be constant as you move
further north or south?

I also find it curious that "The Navigator(tm)" had nothing to say on
this point.

Fresh Breezes- Doug King