Facebook

Login

Support Sailonline

If you haven't already - join the SAILONLINE YACHT CLUB!

Please also consider making a donation - all amounts are greatly appreciated!

Board » General Discussion » Great circle versus loxodrome

Posted by
Nea


Users avatar

Posts
1
Registered at
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


Users avatar

Posts
364
Registered at
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


Users avatar

Posts
2
Registered at
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


Users avatar

Posts
364
Registered at
2007-09-04 10:05:30
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


Users avatar

Posts
239
Registered at
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


Users avatar

Posts
2
Registered at
2007-11-07 09:37:58
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


Users avatar

Posts
364
Registered at
2007-09-04 10:05:30
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


Users avatar

Posts
41
Registered at
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


Users avatar

Posts
41
Registered at
2008-12-15 20:58:27
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! :-)

Please login to post a reply.

Races

Next Race: 00d 00h 00m

Current Races:

Bluefin Tuna - Mexico Gulf to North Sea 2026

Join us and follow the Bluefin Tuna, as they migrate from their spawning grounds in the Gulf of Mexico to their feeding grounds in the North Sea off the coast of Norway. This 4300 nm race is part of our Ocean Championship and the final race of OCQ2 2026, and also the second leg of our Migration series. We will be sailing in our Gunboat 90. Race #2035
INFO by brainaid.de
Gunboat 90 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: OCQ2 - MIG - OCCH - SYC
Race starts: Jun 08th 11:00 Registration Open!
▶ Flash
GO TO RACE

Thessaloniki to Port Said 2026

Welcome back to the Eastern Mediterranean for the fifth race of our Magical Mediterranean Series. Only marginally less unlikely to be ever raced in real life during SOL’s lifetime than our previous race from Tobruk to Iskenderun, this 710nm race takes us from Greece’s ancient northern port of Thessaloniki through the Aegean island maze, south east into the Levantine Sea to a finish in modern Port Said, in splendid Swan 65s!
Race #1977
INFO by brainaid.de
Swan 65 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: MED - SYC
Race starts: Jun 06th 15:00 Registration Open!

▶ Flash
GO TO RACE

TuziTekwini TIMED Race 2026

Sailonline is delighted to have been invited again to partner with the King Shaka Yacht Club (KSYC) of South Africa to bring a virtual version of the Tuzi Tekwini Ocean Raceto our online community.
The Tuzi Tekwini Ocean Race is a near 90 nautical mile race down the east coast of South Africa from the port of Richards Bay to the port of Durban. Achievable in a single day and seen by some as an easy mile-builder, the course is more tactical than some think and should not be underestimated. This iconic race promises to be an unforgettable experience for yachting enthusiasts.
Our online version of the race will be a TIMEDrace so you may RE-REGISTER HEREto try again after finishing a run. You will have two weeks to test your skill and decision making after the race opens.
Race #2037
INFOby brainaid.de
Sailonline’s virtual yacht for all your runs will be our much-loved Farr 38 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ2 - TRCH - SUPBUD - SYC
RACE CLOSE: Saturday,
13 June at 23:00 UTC
Race starts: May 31st 12:00 Registration Open!
▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member WRmirekd
  2. Sailonline Yacht Club Member KaSToR
  3. Sailonline Yacht Club Member CriticalHippo
  4. Sailonline Yacht Club Member rafa
  5. Sailonline Yacht Club Member Panpyc
  6. Sailonline Yacht Club Member bonknhoot
  7. Sailonline Yacht Club Member HoratioPugwash
  8. Sailonline Yacht Club Member rumskib
  9. Sailonline Yacht Club Member CollegeFund
  10. Sailonline Yacht Club Member sassy63

View full list

Series

Mobile Client

SYC members have the benefit of access to our mobile/lightweight web client!

The mobile client