Forum: The Racing Rules of Sailing

Virtual Mark rounding

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David Dalli
Nationality: Malta
I was recently  involved in a race in which keel boats were required to round a coordinate a number of times. Not an actual physical Mark. This has me wondering. Given the definition of room and the meaning of touch. Is rule 18 applicable or enforceable in any practical way?
Created: Today 15:29

Comments

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John D. Farris
Nationality: United States
Did the Sailing Instructions explicitly call the coordinate a “mark” or define a rounding area/radius?

How did they define “round” the coordinate (e.g., “pass within ___ meters,” “leave to port,” “cross a line,” etc.)?

Created: Today 15:42
Satish Kumar Kanwar
David,
This is an interesting question as there is no mark on the water. I would be keen to know how the scenario pans out in such a case wrt rule 18.
Created: Today 15:49
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Jim Capron
Nationality: United States
Did the NoR and/or the SIs invoke WS Appendix WP? That appendix and the use of waypoints as marks of the course have been around for at least three rulebooks.
Created: Today 15:59
Mark Townsend
Nationality: United States
Did you invoke World Sailing Development Rules & Appendices to the Racing Rules of Sailing Appendix WP - Rules for Waypoints in the NoR?

www.sailing.org/inside-world-sailing/rules-regulations/racingrules/

Created: Today 15:59
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Beau Vrolyk
Forum Moderator
I'd suggest a review of this document would be helpful.

https://www.sailing.org/tools/documents/OC13bRacingAroundWaypoints-%5B19446%5D.pdf
Created: Today 16:23
Eric Rimkus
Nationality: United States
As others have already commented there is a long standing WS appendix. 

It would be great if the OP could provide a copy of the regatta documents (NoR/SI) which could be quite helpful, or not. 
Created: Today 16:52
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Angelo Guarino
Forum Moderator
Nationality: United States
FWIW ... looking at Appx WP ..

WP1.2 Add new definition Waypoint:
Waypoint A geographic position on the surface of the water defined by WGS 84 latitude and longitude coordinates expressed in degrees decimal minutes (DDM).

WP1.3 The definition Zone is changed to:
Zone The area around a mark within a distance of three hull lengths of the boat nearer to it. The area of the zone at a mark that is a waypoint may be changed in the notice of race or sailing instructions. A boat is in the zone when any part of her hull is in
the zone.

The Appx does not define a min decimal-depth (sig-fig) for WGS84 location.  Therefore, the size of the location, depends upon the resolution.  
Created: Today 17:44
Mark Townsend
Nationality: United States
Just like using a regular mark! The clear ahead boat hails "no room" well before they reach the zone!
Created: Today 18:13
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Angelo Guarino
Forum Moderator
Nationality: United States
Created: Today 18:30
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Jim Capron
Nationality: United States
AG said: "Therefore, the size of the location, depends upon the resolution." I disagree. The waypoint 38 58N 76 28W is a dot on the surface of the water and is the same "size" as the waypoint 38 58.002N 76 28.005W. The zone is (likely) a 3 boat lengths circle around either of those dots.
Created: Today 18:55
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Angelo Guarino
Forum Moderator
Nationality: United States
Jim C ... look at the chart that I posted. A zero-decimal location has a resolution of >100km (can be located anywhere within a square-area with sides of that length).  Based on the chart I posted, for the purposes of being able to resolve entry into a 3 BL zone, a min on 5 decimal places should be described. 

Since we have a relative measure in the zone of 3 BL's, the zone's location needs to be specified to something substantially less than 1 BL for it to be usefully determined. 
Created: Today 19:02
Philip Hubbell
App WP does not answer the very good question.
Created: Today 18:46
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David Dalli
Nationality: Malta
The SI stated under Marks:
The Mark 3 will  be the coordinate....
APP WP was not invoked. I am happy that at least this sorts out the issue of wether it is possible to touch a coordinate. There is still the matter of given that  GPS location is accurate to between 2-8 m 95% of the time ( according to WS Judges Manual). How can one decide if room was given or when the zone was reached. 
Created: Today 19:06
Eric Rimkus
Nationality: United States
I think your event is fraught with issues if you are using waypoints and not involving Appendix WP. 
Created: Today 20:14
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Angelo Guarino
Forum Moderator
Nationality: United States
I know my point might sound like an old engineer/scientist geeking-out ... but it is basic to the sense of measurement and description. 

If I say something is 1 km away ... I'm describing something that has a less than 1/2km location resolution. 

Add a decimal .. 1.0km ... now it's a 0.05 location resolution.

If a location wants to be resolved for a 3 BL zone ... and 1 BL is 10-20m ... then the location should be located signicantly less than 10m.  1-2m should be fine ... so 5 decimal places.  
Created: Today 19:59
Eric Rimkus
Nationality: United States
The resolution is stated in the SI when the virtual mark is defined. If it uses WGS84 that usually is 3 decimal places, but if the mark is given with 2 or 1 decimal places that tells you the resolution applied. 
Created: Today 20:12
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Beau Vrolyk
Forum Moderator

Mr. Hubbll raises a good point.

In direct response to the original post by Mr. Dalli: Yes, I do believe Rule 18 can be applied successfully. Let's assume there is an overlap as the two boats enter the zone around a GPS waypoint. The inside boat, using their GPS, asks for Room. The outside boat shall then provide Room, and if she feels that the inside boat was not entitled to Room she will Protest. If there is a debate, it gets sorted out in a protest hearing.

However, during that hearing various key facts need to be discovered. An important one will be: there are two types of GPS available today. The relevant points are covered in the quote below from this source: https://rtkdata.com/blog/rtk-vs-gps-accuracy-2026/

"RTK vs GPS Key differences

  • Accuracy: RTK provides centimeter-level precision (1-2 cm), while standard GPS provides meter level-accuracy (3-10m)
  • Correction Method: RTK uses a base station to transmit real-time correction data to a rover, correcting for atmospheric and satellite errors instantaneously. Standard GPS relies on direct satellite signals without real-time corrections.
  • Application: RTK is ideal for high-precision tasks like drone surveying, autonomous vehicle guidance, and construction. Standard GPS is used for consumer navigation (smartphones, cars).
  • Cost & Complexity: RTK systems are more complex and expensive ($8,000–$80,000). Standard GPS is inexpensive and found in common devices."

At this time both "RTK GPS" and "standard GPS" are in use aboard various competing boats. As is stated above, the RTK GPS supports accuracy of 1-2 centimeters, while the standard GPS accuracy is 3-10 meters. During any hearing, it would be wise to discover exactly which sorts of GPS was being used and consider this when trying to determine the Room to which the inside boat was entitled.

At this time both GPS and RTK GPS are being used within the commercial starting systems of Vakaros and Velocitek respectively, to provide a more accurate method of determining OCS at the start of a race. That has brought up the obvious question, is the position accurate enough. Extensive testing over the last three years has shown that the 1-2 centimeter accuracy of RTK GPS is better than human visual line sighting, while the regular GPS is not.

As a result, Rule 18 will work just fine at the 1-2 centimeter accuracy of RTK GPS, at least as well as humans rounding a visible mark. It will be more difficult to resolve the 3-10 meter accuracy during a mark rounding for regular GPS. The most difficult situation will be if the two boats have different types of GPSs.
Created: Today 20:18
Philip Hubbell
I would rule, in a mark room situation, that the inside boat's GPS governs, regardless of its accuracy.
Created: Today 21:36
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