GPS detection of OCS?
Printed From: Yachts and Yachting Online
Category: General
Forum Name: Racing Rules
Forum Discription: Discuss the rules and your interpretations here
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=11247
Printed Date: 27 Jun 25 at 8:27am
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com
Topic: GPS detection of OCS?
Posted By: alstorer
Subject: GPS detection of OCS?
Date Posted: 07 Dec 13 at 8:27am
from the sailing watch thread
How do you propose squaring the definition of OCS (and finishing, as the same could give you finish times) with a wrist mounted unit? Or change it, so that OCS is the mast and require a mas mounted unit? Requiring a bow mounted unit would cause all sorts of definition and mounting problems with boat design, especially on anything with a bowsprit that launches through a snout ------------- -_ Al |
Replies:
Posted By: yellowwelly
Date Posted: 07 Dec 13 at 8:34am
| Is GPS accurate enough? |
Posted By: Brass
Date Posted: 07 Dec 13 at 9:16am
|
You may be aware ISAF Racing Rules Committee is running a Subcommittee investigating GPS/sensors for OCS. I understand that the positioning problem is addressed by measuring-in the sensor unit, then calculating an offset to the end of the bow, and possibly some sort of offset to allow for B-max. Problem with dinghies would be that that approach wouldn't cover hiking positions of crew, especially trapeze. Definition of start could be changed (by ISAF, not SI, cos SI cannot change Definitions), but you would need to be careful that you didn't come up with a definition that suited GPS/computers but did not suit mark one eyeball. |
Posted By: Rupert
Date Posted: 07 Dec 13 at 9:48am
|
I'm guessing that the Mk1 eyeball can, on most club startlines, tell to just a few inches whether a bow is over the line. I can't see GPS managing that at all.
------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: JimC
Date Posted: 07 Dec 13 at 9:58am
|
I was very much thinking on my feet... Agree about disqdvqntages of position etc, but I was mostly thinking about the communications aspect. Remember it doesn't have to be perfect, merely no worse than the current system. A mast base mounted transponder and offset probably works for one designs.
I imagine RRS changes would be needed, quite likely one that gave alternative definition of start for controlled races. |
Posted By: Lukepiewalker
Date Posted: 07 Dec 13 at 11:57am
|
It's a dream wishlist, we're not proposing anything...
------------- Ex-Finn GBR533 "Pie Hard" Ex-National 12 3253 "Seawitch" Ex-National 12 2961 "Curved Air" Ex-Mirror 59096 "Voodoo Chile" |
Posted By: alstorer
Date Posted: 08 Dec 13 at 10:07pm
I appreciate it was an off-the-cuff suggestion. But it's one that merits some investigation. Could have some sort of hybrid system combining transponders on the committee boat and pin-end mark with GPS ------------- -_ Al |
Posted By: craiggo
Date Posted: 08 Dec 13 at 10:13pm
|
Not sure if GPS is accurate to that level.
Could use a high speed camera and a Matlab script to check the image and determine who was over the line. |
Posted By: Rupert
Date Posted: 08 Dec 13 at 10:59pm
|
I prefer the idea of a high powered rifle set about 6" above the water. Any boats with holes in the bow were over. Any helms with extra holes in the bum were a long way over.
------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: JimC
Date Posted: 09 Dec 13 at 5:00am
|
Posted By: RS400atC
Date Posted: 11 Dec 13 at 11:06pm
No. |
Posted By: Mark Jardine
Date Posted: 12 Dec 13 at 9:59am
I got caught out that way in 1989 or 1990 in the Bosun nationals. Being a military regatta they were using a rifle and blanks for the starting gun and the plug went clean through my mainsail.  |
Posted By: ColPrice2002
Date Posted: 12 Dec 13 at 10:01am
|
"I got caught out that way in 1989 or 1990 in the Bosun nationals. Being a military regatta they were using a rifle and blanks for the starting gun and the plug went clean through my mainsail"
You're lucky it wasn't the old starting cannon! That had a much bigger wad (plus the gunpowder stains). Colin |
Posted By: Brass
Date Posted: 12 Dec 13 at 10:20am
Well over early and embarrassingly close to the committee boat were we?
|
Posted By: Mark Jardine
Date Posted: 12 Dec 13 at 10:23am
If anyone was going to get caught on that start line, it was me  |
Posted By: Presuming Ed
Date Posted: 12 Dec 13 at 11:04am
| Some might say that sailing in the Bosun nationals means you should get properly shot. But then sailing in the Bosun nationals is probably enough of a penance as it is. |
Posted By: Mark Jardine
Date Posted: 12 Dec 13 at 12:09pm
Back then there were a good number of them racing (49 in the 1990 nationals if I remember rightly) and it was the one event I beat a certain Steve Cockerill in! You do have a point though!  |
Posted By: yellowwelly
Date Posted: 12 Dec 13 at 2:24pm
| Brandon Lee was killed from a blank whilst filming The Crow... dangerous things them blanks. |
Posted By: alstorer
Date Posted: 12 Dec 13 at 2:48pm
|
Not sure if they still do it, but Thorpe Bay SC have been known to use a shotgun - blank rounds and aimed up and away from the line. Quite something to see someone stood atop the committee boat aiming a shotgun at the sky. ------------- -_ Al |
Posted By: Rupert
Date Posted: 12 Dec 13 at 3:05pm
|
Manor Park use a shot gun - quite a surprise on a small lake in the midlands!
------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: MerlinMags
Date Posted: 13 Dec 13 at 12:01pm
|
If you ever proved that GPS did have high enough accuracy, you'd need to make the units high-visibility and make sure they were mounted above decks.
Otherwise some rascal could shift their GPS unit sneakily to the transom, and poke their bow safely over the line. |
Posted By: Time Lord
Date Posted: 13 Dec 13 at 3:56pm
|
Much more likely that some geek would find a way to tweak their GPS unit so that it allowed them a boat length or two!! ------------- Merlin Rocket 3609 |
Posted By: alstorer
Date Posted: 13 Dec 13 at 7:45pm
Define "above decks". Rather less common these days to have a space frame arrangement, but with that, arguably "above deck" and "at the mas foot" are the same thing. However, I reckon some of the GPS problems the cherubs encountered at Queen Mary SC at the inlands might have been down to them tucking them under carbon foredecks. Radio signals don't pass very well through carbon. Carbon planes have to have glass fibre radomes, just like metal ones. ------------- -_ Al |
Posted By: alstorer
Date Posted: 15 Dec 13 at 9:19pm
|
Occurs to me:
If a system is made that is accurate and reliable enough, with Start and Finish definitions altered to suit, then accurately scoring pursuit races could be much easier! For the sake of argument, I'd use proximity to the next mark of the course. ------------- -_ Al |
Posted By: MerlinMags
Date Posted: 15 Dec 13 at 9:48pm
Visible to your competitors, so they know you're not cheating! |
Posted By: JimC
Date Posted: 16 Dec 13 at 1:42am
Indeed it would. It would solve the age old problem of working out what order the boats are in on the beats. Proximity to marks is far too crude though, think it has to be some some sort of vmg calc, otherwise you could have boats that are clearly ahead scored behind. I wonder if they considered using the tracks to aid scoring at Datchet. Trouble is you really do need DGPS,I've been tracking my canoe recently and the striking how much the boat moves around in all 3 dimensions when tied rigidly to the jetty between races! |