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Board » General Discussion » Great circle versus loxodrome

Posted by
Nea


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2008-01-17 23:04:43
2009-01-18 15:52:02 - Great circle versus loxodrome
If the line from start to goal is the loxodrome, does sailonline calculate distances taking great circle into account.
Posted by
jakob


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2007-09-04 10:05:30
2009-01-21 14:30:27 - Re: Great circle versus loxodrome
I don´t really understand what you are asking for but the boats sail in loxodromes if constant cc is set. So does the course tool and "ruler".
...one of the guys behind the game...
Posted by
Velum SUI


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2007-11-07 09:37:58
2009-01-28 15:57:06 - Re: Great circle versus loxodrome
hmm, may I enhance the question?

I read in the manual:
"In Sailonline you can choose to navigate using great circles."

How?
I only know navigation using CC (loxodrome) and TWA, but not great circle navigation.

Can you explain?
Posted by
jakob


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2009-01-28 17:06:23 - Re: Great circle versus loxodrome
Well... in the old client you could chose. In the web-based client you cannot.. yet...
...one of the guys behind the game...
Posted by
captjack1942


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2008-01-18 03:24:03
2009-01-28 23:34:12 - Re: Great circle versus loxodrome
In the meantime there are a few web based calculators for great circle, I like this one (cause it is easy to enter lat/long in same format as sol chart): http://www.waypoint.org/gps1-calc.html
Posted by
Velum SUI


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2009-02-11 07:33:41 - Re: Great circle versus loxodrome
Last night I anchored at the coast,
because I had scheduled my tacks too early for the decreasing winds.

I am a newbie in this, I guess following idea was discussed already before, but I couldn't find anything on it, so:

A steering option like "steering towards a coordinate" could be useful for great circle navigation as well as to launch new commands by reaching a position (not by time). This would allow me to program a much more reasonable and reliable behaviour during my absences.

Sorry for this silly wish, but I am one of the old fashioned human beings that still require some hours sleep per day, have fixed working hours, but still enjoy this game very much.


--- Last Edited by Velum SUI at 2009-02-11 13:09:37 ---
Posted by
jakob


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2009-02-11 12:55:52 - Re: Great circle versus loxodrome
Hi! Your request is understandable, not new and logic. Different steering alternatives are discussed and on our list. Thanks for communicating :-)
...one of the guys behind the game...
Posted by
Zembu


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2008-12-15 20:58:27
2009-02-14 22:59:18 - Re: Great circle versus loxodrome
This is not a reply but a query related to this topic.
I think there is an error in the way the "ruler" works now. The map is Mercator Projection I believe, which is created by projecting the earth's surface onto a surrounding cylinder as if illuminated from within using a line light source from North to South poles. Thus the latitudes are horizontal, and towards the poles the area is stretched latitudinally. Using such a projection for Great Circle lines, a theoretical Great Circle line drawn on the earth's surface from Qingdao to Cape Horn and projected on your Mercator projected map would not go further south than necessary to round the horn. But your lines go far further south, and even traverse across Australia and other land. I think your algorithm for the Great Circle lines assumes some sort of projection as if from a point source at the centre of the earth instead of from a line source.
Posted by
Zembu


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2009-02-15 14:00:23 - Re: Great circle versus loxodrome
Further to my previous (2009-02-14 22:59:18) I see that I am wrong and you are right - as you knew all along I guess - you were just too nice to say so. Not having a globe of the world I experimented with a baseball, a flowerpot, a pencil and a pair of dividers, and I see that by my approximate method the line from Qingdao to Cape Horn could go as far as 70 degrees South. So your 75 degrees is I guess correct. Sorry for doubting you all! :-)

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