2 point question
 

DSK wrote:

Now that I have my referance library and a spreadsheet instead of a
pocket calculator and faulty memory, I'll try again. It's a more
interesting problem than I thought it'd be....

Yup, the south pole behaves differently - gonna to play with that later.


No, it increases. And the change isn't linear.

Yes, I realized this thinking about it on the drive home. So what is
it proportional to, the arcsine?

The function I used is: cos(lat) x 60

Since the cosine produces the same curve as a sine, but 90deg out of phase
[it starts high instead of low - cos(0)=1, sin(0)=0], for the first 0-90deg,
we're seeing the second half of the bendy top of the curve, followed by the
first half of the straightish negative-going part of the curve. The most
linear part starts at about 50-60 degrees and continues to the pole.


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

2 point question
 

Well thank you Bart for the points, that's all I wanted in the first
place.

Peter S/Y Anicula


"Bart Senior" skrev i en meddelelse
et...
Both Peter and Wally deserve 5 points for taking this
silly question so far.

Bart

2 point question
 

Wally wrote:

That doesn't quite sound right - if the leg along the outer circle,
plus the leg along the inner circle, add up to a total of 180 degrees
longitude, then the end point would be opposite the start point.

This is wrong - it should be the *difference* between E leg on outer circle
and W leg on inner circle that gives 180 degrees...

Start at 89d 42.447m S (roughly)...

The 14nm E leg traverses 45.7d longitude.

Go 14nm S to 89d 56.447m S...

The W leg covers 225.7d longitude.

Do 225.7 - 45.7 to get 180, and then go N 14nm to complete the course. You
are now on the original lat, but 180 degrees away from your start point. The
distance from the start is twice the minutes from the start latitude to the
pole...

90 - StartLat = 17.553 minutes from the pole

....which gives a distance of 35.11nm from the start to the finish.


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

2 point question
 

A few comments below:

Peter S/Y Anicula

"Wally" skrev i en meddelelse
...
Wally wrote:

That doesn't quite sound right - if the leg along the outer
circle, plus the leg along the inner circle, add up to a total of
180 degrees longitude, then the end point would be opposite the
start point.

This is wrong - it should be the *difference* between E leg on outer
circle and W leg on inner circle that gives 180 degrees...

Now you confuse me, isen't that what I said in the first place?


Start at 89d 42.447m S (roughly)...

The 14nm E leg traverses 45.7d longitude.

Go 14nm S to 89d 56.447m S...

The W leg covers 225.7d longitude.

Do 225.7 - 45.7 to get 180, and then go N 14nm to complete the
course. You are now on the original lat, but 180 degrees away from
your start point. The distance from the start is twice the minutes
from the start latitude to the pole...

90 - StartLat = 17.553 minutes from the pole

...which gives a distance of 35.11nm from the start to the finish.


So that would be around 210 nautical miles in my boat, assuming it
would keep a speed of 6 knot even with skies mounted under it - that
is well over 168 nm, and all that without any help from current.

Good work Wally! I will top Barts 5 points with a couple of
Anicula-points.




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

2 point question
 

Peter S/Y Anicula wrote:

Now you confuse me, isen't that what I said in the first place?

Yes. I had read yours as an addition (big arc = small arc + 180), but
somehow thought it was the wrong addition. I then realised that it was a
subtraction (big arc - small arc = 180), which it was what you had said, but
in a different way.


...which gives a distance of 35.11nm from the start to the finish.

So that would be around 210 nautical miles in my boat, assuming it
would keep a speed of 6 knot even with skies mounted under it - that
is well over 168 nm, and all that without any help from current.

If the legs were 14x6=84nm, there would be a factor involving the diameter
of the inner circle, which would increase to maintan the big-small=180
relationship between degrees covered on each arc. I think that means it
would be greater than 210.


Good work Wally! I will top Barts 5 points with a couple of
Anicula-points.

A good haul, considering I don't think I answered the original question...


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

2 point question
 

"Wally" wrote in message
...
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.

Do you mean 28 nautical miles???

Perhaps you meant 28 nautical metres!!!



Regards


Donal
--

2 point question
 

"Peter S/Y Anicula" wrote in message
...
You would start with the outer circle going east then go closer to the
pole moving south...
If the inner circle has an arc of 180 degrees plus the arc of the
outer circle, then the end-point should be opposite the start-point,
and the distance over the pole would be 2 x length of legs plus
diameter of inner circle: more than 28 nm in at 1 knot and
more than 168 nm at 6 knot.

Could you please repost that nonsense when I'm sober. Thanks.



Regards


Donal
--

2 point question
 

"Thom Stewart" wrote in message
...
Don-o,

Go back and read the question again. Miles are never mentioned. The legs
were direction (Compass) and time (14 hours) per leg

Well, OT, I take my hat off to you! I was wrong.

You seem to be the only one who is paying attention.



Regards


Donal
--

2 point question
 

Donal wrote:

What do yuu think that the maximum offset could be?
28nm.

Do you mean 28 nautical miles???

I actually meant 35.11 nautical miles. (Eventually...)


Perhaps you meant 28 nautical metres!!!

I don't think so...


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

2 point question
 

Donal wrote:

"Wally" wrote in message
...

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.


Do you mean 28 nautical miles???

Perhaps you meant 28 nautical metres!!!


What happened to yards and cables -don't tell the the EU has changed
that as well!

Cheers