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Board » Technical Support » PROTEST VINEYARD RACE

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Posted by
NZL_PaulR


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2011-09-04 01:55:26 - PROTEST VINEYARD RACE
PROTEST First 4 boats look as though they have passed NORTH of The Cows. Yellow course line shows to pass The Cows to Starboard.

It may be the delay in updating tracks but is disconcerting at least!!

--- Last Edited by NZL_PaulR at 2011-09-04 01:57:20 ---
If it breaks, it's not strong enough!
Posted by
AGage


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2011-09-04 04:28:00 - Re: PROTEST VINEYARD RACE
Nothing wrong with their tracks... 1 & 4 even have a few pixels to spare at max zoom...
I help develop the client interface for the best online ocean racing sim there is... __/)/)_/)__
Posted by
ShamrockPirate


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2011-09-04 14:30:34 - Re: PROTEST VINEYARD RACE
Which brings up an interesting question.... Do buoy marks have the same characteristics as landmass? i.e. if you strike them, you go TWA=0? Or can they be "crossed over", like an SLI? I believe that if the servers sees the boat as rounded, it's all good, though it appears The Viking probably painted the Cows a different colour on the way by. ;>))

SP
Posted by
zero


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2011-09-04 16:05:11 - Re: PROTEST VINEYARD RACE
I really don't see how can you foul the computer. Computers are great but they are dumb; if they are programed to allow some "event" to happen if and only if "x" is greater than "1", no matter how much you plea, you will not get the "event" if your x is 0.9999999999999.

I don't think you can pass "over" the mark and still be counted as "rounded", that would mean "x"=1, the software is probably writen as "x">1 to be counted as rounded-the-mark.

No, a mark in the water is just a point defined by it's latitude and longitude, meaning you cannot "hit" and be stopped dead in the water at that point.

Disclamer: I am not a programer and have no idea how the Sailonline code looks like.

cheers,
Antonio
Posted by
AGage


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2011-09-05 07:52:05 - Re: PROTEST VINEYARD RACE
For x>1 you are correct zero, if you changed that to x>=1 then it is possible to have 0.999999999999999999999 return true for that (2nd) expression, due to the finite precision of machine computation...
HOWEVER - that is an extreme case.

I think it is technically possible to pass over a mark and have it count. Take an imaginary line that extends out from the mark - the direction parallel to that of a line which bisects the rhumblines to and from the mark... Now if you cross this line (which, while infinitely long, is bounded at one end by the mark) in the correct direction, a rounding is recorded. I do not know the exact code used, but in geometry on paper, if you hit the very end of a line (the mark in this case) it is considered that the lines intersect, ergo a fair rounding geometrically...

Consider though, that such small distances are really beyond the graphical fidelity of the client... At maximum zoom 1 pixel is still about 3 feet/1 metre - the scale indicator is 100 pixels long, and I have never seen it show less than 0.05 nm, which is almost exactly 1m per pixel.

Conclusion: Someone actually passing OVER a mark and having it recorded as rounded is an EXTREME EDGE-CASE, and would occur equally rarely (I doubt it has ever happened on SOL yet)... Ergo, it is not something the server should be programmed to deal with IMHO...

Also, as shown above, there is a 0.5m 'margin of error' in the pixels drawn in the client at maximum zoom, so from the client map it is impossible to tell if this actually occurred. Not to mention that the marks are drawn with 2px radius, so while only an infinitesimal point to the server, they appear as a buoy 4m in diameter on the map! (@max zoom)

Consider though, applying this to the finish line: if you hit the very very end of the line, should that count as a finish?
I think yes...
I help develop the client interface for the best online ocean racing sim there is... __/)/)_/)__
Posted by
zero


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2011-09-05 14:03:22 - Re: PROTEST VINEYARD RACE
Thanks Aaron,
This is all very interesting.
My limited knowledge of programing stops at MS-Basic.
Antonio
Posted by
NOR_Jawik


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2011-09-07 09:05:29 - Re: PROTEST VINEYARD RACE
@ Aaron

To put this on the knife edge (0.05nm <> 1 meter). What about the width of the boat when it rounds the mark. 125 cat has a width that would indicate that it is not sailing around the marker under these conditions. Most of the boats is wider than 0.05nm, as far as I know. In reality, we sail with knife edges and can give a damn about the width of the boat.
Posted by
AGage


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2011-09-08 12:27:24 - Re: PROTEST VINEYARD RACE
I think you have misunderstood.
At max Zoom, 100 pixels = 0.05nm (at least), so:
1 pixel is approx 1m at that scale (the scale indicator is 100px wide) - and different latitudes will have slightly different scales, so often 1 pixel will be > 1m

But again, to the server, your boat is just a point on the globe? It knows nothing of boat size.
So our boats are a moving point, rounding a point (mark).
I help develop the client interface for the best online ocean racing sim there is... __/)/)_/)__
Posted by
AGage


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2011-09-08 12:31:34 - Re: PROTEST VINEYARD RACE
NOR Jawik said @ 2011-09-07 09:05:29:
Most of the boats is wider than 0.05nm, as far as I know.
=====================
0.05nm is about 95m...
So they are much less wide than that

--- Last Edited by Aaron Gage at 2011-09-08 12:32:05 ---
I help develop the client interface for the best online ocean racing sim there is... __/)/)_/)__
Posted by
Spindrift


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2011-09-08 15:24:58 - Re: PROTEST VINEYARD RACE
"So our boats are a moving point, rounding a point (mark). "
taking the geometry example above and other mathematical axioms and postulates you could redefine the reference field so the mark point was moving around the boat point and the boat point was stationary. In which case a protest could not be upheld for hitting or passing over the mark, as it would have hit or passed under you.


--- Last Edited by Spindrift X5 at 2011-09-08 15:26:31 ---

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