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 » RRS rules about mark roundings

Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2015-06-23 20:21:39 - RRS rules about mark roundings
28.2 A string representing a boat’s track from the time she begins to
approach the starting line from its pre-start side to start until she
finishes shall, when drawn taut,
(a) pass each mark on the required side and in the correct order,
(b) touch each rounding mark, and
(c) pass between the marks of a gate from the direction of the
previous mark.
She may correct any errors to comply with this rule, provided she has
not finished.

This was in response to a question that arose in the Practice Race at Kiele on 23 June 2014.
Do the SOL rules state it the same?

--- Last Edited by Rod at 2015-06-23 20:40:08 ---
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
kroppyer


Users avatar

Posts
347
Registered at
2010-02-05 15:25:55
2015-06-23 23:25:51 - Re: RRS rules about mark roundings
No.

One difference is that sol uses rhumb lines between marks. I'm sure that when drawing this imaginary string taut, it would follow a GC line, not a rhumb line. There might be more differences (I'm not sure because I find the RRS rule ambiguous).

In sol the course to be sailed in drawn on screen, order of roundings and direction of roundings is clear. While racing you can either round the next mark, or unround the previous, other marks are not in play.

Unrounding happens* when you cross the rounding line in the wrong direction and after crossing you've crossed the rounding line as many times in the correct direction as in the incorrect direction.

Rounding happens* when you cross the rounding line in the correct direction and before crossing you've crossed the rounding line as many times in the correct direction as in the incorrect direction.

Say we have marks A, B, C (in that order), then the rounding line of B is a line starting at B, moving away from A, B and C. Additionally, the rounding line lays on the bisector of angle ABC.

*) This is how I understand it should happen. I'm not entirely sure that this is the case when you sail multiple laps around the mark.

In any case, you should be able to round your next mark by sailing around it in the correct direction until it says "rounded", i.e. there's no "going in the wrong direction to unround". If you have trouble rounding the mark, it means you've already rounded in the wrong direction, all that's left is sailing around the mark in the correct direction.

----

Two more things:
- I don't like the RRS wording/theory.

- PRs are different.

--- Last Edited by kroppyer at 2015-06-23 23:34:20 ---
Posted by
Rod


Users avatar

Posts
392
Registered at
2010-06-24 22:30:48
2015-06-29 01:35:48 - Re: RRS rules about mark roundings
My interest stemmed from a consideration of the logic behind ANY mark rounding rule on the computer. If the SOL rule was to be applied to a spherical Earth, the projected 'rounding line' would circle the Earth and enter the mark from the rear, thus making the "miss, return and round correctly" of the RRS impossible. The field of action would have to be limited in total area to make it possible.
If the map used was to be a Mercator's projection, then no area limitation would be required.
In the case in point, if the turn mark had been just a small distance (3 pixels?) off shore, then the island could indeed have been rounded the "wrong" way,and all requirements for a successful rounding could have been met.
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
kroppyer


Users avatar

Posts
347
Registered at
2010-02-05 15:25:55
2015-06-29 13:00:55 - Re: RRS rules about mark roundings
Rounding lines in SOL are loxodromic (straight on Mercator projection). This has previously resulted in some weird DTF numbers. It is indeed very hard to define rounding a mark on a sphere. Gates almost always work, so I'd say that rounding a mark is similar to sailing through a gate with the mark to be rounded on one side, and some point on the course boundary on the other.

If there is a mark 3px offshore from an island, and only the rounding direction of the mark is specified (nothing about the island), you could indeed round the mark correctly, while 1) not rounding the island or 2) rounding is opposite to the mark. Sol doesn't work with islands that way. If we want to have a course round an island, we place the mark on the island, forcing your to round the entire island.

Please login to post a reply.

Races

Next Race: 00d 00h 00m

Current Races:

New Ice Age 2026 - Longyearbyen to Browerville


Although we have by no means exhausted the possibilities of ice boating on lakes at high latitudes or high altitudes, it was noticeable that as our 2025 Series progressed, there were calls from time to time for longer-distance challenges, and so in response to these calls we will pretend that global warming has reversed and as a result the coastal waters of Antarctica and Russia and Canada have fully (and smoothly!) frozen over offering us the possibility of a 4-race New Ice Age series in our trusted no-PL DN machines. Our first leg takes us 2600nm from Svalbard’s Longyearbyen east to North Alaska’s Browerville. You’ll be a few days on the ice, so dress warmly and take some provisions; go!
Race #1968
INFOby brainaid.de
DN PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: NIA - SYC
Race starts: Jan 22nd 07:00 Registration will open soon
▶ Flash
GO TO RACE

Cross the Convergence 2026 - Robinson Crusoe to Galapagos


Welcome to our first race of a new series of ocean voyages across the World’s convergence zones, this first race taking you north from south of the Tropic of Capricorn to the Equator-straddling Galapagos, home of magical iguanas and other exotic fauna (but no mythical kings, Dory) Departing from the island where in 1704 adventurer Alexander Selkirk inspired Daniel Defoe to write the best-seller "The Life and Adventures of Robinson Crusoe", by debarking off the unsound "HMS Cinque Ports", four months before she foundered off the coast of present-day Colombia, we will sail the 2200nm in our decidedly sounder and faster than the " Cinque Ports",
Ocean 50 !
Race #1983
INFOby brainaid.de
Ocean 50 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: CCZ - SYC
Race starts: Jan 16th 18:00 Registration Open!
▶ Flash
GO TO RACE

Bight of Bonny TIMED Race 2026

Welcome to the first TIMED race of 2026! Our race finds us in the Gulf of Guinea and the Bight of Bonny. Starting in Douala, Cameroon the 170 nm course takes us around the island of Bioko with its Caldera and tropical rainforests finishing in Calabar, Nigeria. The boat for this race is the sporty Farr 30. This is a TIMEDrace so you may RE-REGISTER HEREto try again after finishing a run. You will have 13 days and 11 hours to test your skill and decision making after the race opens.
Race #2004
INFOby brainaid.de
Farr 38 Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ1 - TRCH - SYC
RACE CLOSE: Saturday,
24 January at 23:00 UTC
Race starts: Jan 11th 12:00 Registration Open!
▶ Flash
GO TO RACE

Natuna Sea Race 2026


At 4.0N 108.2E lies the island of Natuna Besar, Great Natuna, surrounded by at least 154 islands, of which 127 uninhabited, Indonesia’s Natuna Regency, and all around this archipelago, the Natuna Sea, bordered by Borneo to the east, the Java Sea to the south, and the Malay peninsula to the west, and extending north to cross a disputed international border with China into the South China Sea. And it’s a border that matters, there’s gas here! But why worry, let’s race – 2050nm in our goo’ol’ Open 60s in between the production platforms, prowling destroyers and submarines.
Race #1997
INFOby brainaid.de
Open 60 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC
Race starts: Jan 06th 17:00 Registration Closed
▶ Flash
GO TO RACE

Cape Town to Rio 2026

Welcome to South Africa and RCYC's classic transatlantic Cape2Rio Race from Cape Town, South Africa, to Rio de Janeiro, Brazil. First run in 1971, this run is buddied with the IRL, Cape2Rio 2025 arranged by the Royal Cape Yacht Club with the cooperation of the
Iate Clube do Rio de Janeiro Despite this being announced the 2025 race (starting dec. 27) it is the 2026 SOL championship kickoff. This virtual version, will be raced once again in Mark Mills' 74ft speedster, the stunning C2R74.
Race #1996 INFO
by brainaid.de
C2R74 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
OCQ1 - OCCH - SUPBUD - SYC
Race starts: Dec 27th 12:00 Registration Closed

▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member KaSToR
  2. Sailonline Yacht Club Member WRmirekd
  3. Sailonline Yacht Club Member CriticalHippo
  4. Sailonline Yacht Club Member rafa
  5. Sailonline Yacht Club Member bonknhoot
  6. Sailonline Yacht Club Member Sax747
  7. Sailonline Yacht Club Member rumskib
  8. Sailonline Yacht Club Member vida
  9. Sailonline Yacht Club Member Panpyc
  10. Sailonline Yacht Club Member CollegeFund

View full list

Series

Mobile Client

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

The mobile client