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Board » General Discussion » Race ranking

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Posted by
Incognito


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2008-12-06 13:43:52
2009-05-22 07:20:35 - Race ranking
Hi SOLer's,

I think the topic has already been raised in the past. In leg 7, I notice that SOL's race ranking are looking strange

According to SOL, at 7:00 UCT, I was ranked 86th with more than 674 NM to go.

In brainaid's ranking however (http://sol.brainaid.de/pub/ranking-145.html), I was ranked 14th with 637 NM to go.

Quite a difference! And when I use the pliers or the pointer to calculate the DTG, I come to a figure similar to brainaid's.

Personnally, I remain convinced that SOL's ranking is not working properly. It would be nice to fix that.

Regards,

Francois
Posted by
jakob


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2007-09-04 10:05:30
2009-05-22 07:41:10 - Re: Race ranking
Different DTG-calculation routines apply with varying success in different situations. The SOL-scheme is designed to work fairly ok at all situations and requires little cpu. I do not know much about the Brainaid calcs. He has access to our code though so maybe he will help us with a new system ;-). Having said that, to be 6% off when there is over 600nm to go is maybe something we can live with. In the end the two systems converge, I promise.
...one of the guys behind the game...
Posted by
Incognito


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2009-05-22 08:19:44 - Re: Race ranking
Yes, Jakob, I know that both rankings will converge. :-)

Nevertheless, the differences are
very substantial in fact. More importantly, the SOL ranking presents a misleading picture of the race.

What I do not understand is that you were able to program broadly correct formulas for the pliers and for the mouse pointer, but not for the rankings.

Regards,

Francois
Posted by
skantorp


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2008-06-26 11:21:09
2009-05-22 08:46:39 - Re: Race ranking
seems to me that the sol ranking is based on a straight line to finish wheras brain is using the great circle to calculate distance and rank... might be wrong though...
Life is a holiday under the sun
Posted by
JuJu


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2008-12-24 09:50:12
2009-05-22 09:08:34 - Re: Race ranking
I'm guess that the pliers and mouse pointers are in the client (flash) code and the rankings are running on the database server where SQL doesn't make it easy/fast to do a great circle calculation (guess they don't have Oracle with the GEO option).
Posted by
jakob


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2009-05-22 10:16:26 - Re: Race ranking
I am starting to learn that Skan is seldom wrong :-) I will check. hold... Checked and Skan was right!! I used the rhumb-line. Now switched to great circle. BUT there will still be difficult occasions when there are intermediate waypoints... so the discussion will continue I bet. Thanks for caríng all!!
...one of the guys behind the game...
Posted by
Incognito


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2009-05-22 15:39:45 - Re: Race ranking
Thanks Jakob. When is it going to be implemented?
Posted by
jakob


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2009-05-22 18:15:19 - Re: Race ranking
It is implemented. :-)
...one of the guys behind the game...
Posted by
captjack1942


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2008-01-18 03:24:03
2009-05-22 23:46:05 - Re: Race ranking
How about some more head spinning observations?
@23:06 UTC for captjack1942:

SOL) #186 ; 481.6 mi to go.

Brain's ranking page) #109 ; 389.4 mi to go.

Ed Williams' great circle calculator (http://williams.best.vwh.net/gccalc.htm); 386.49 mi to go.


For the calcs: CJ1942 position @ 23:06 --- 54.52 N / 19.73 W.
Pin on Aran Is--- 53.15 N / 09.79 W.
Center of finish line off Galway --- 53.20 N / 09.12 W.
Earth model WGS84/NAD83/GRS80.

Also note that brain's position was updated @ 23:00. At 22.3 kts for 6 min =2.23 mi.

;-)
Posted by
Incognito


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2009-05-23 06:40:35 - Re: Race ranking
Jakob, I do not want to pest you, but there are still very large differences between DTG in ranking and as measured. For my boat right now: 267 NM vs 190 NM. That does not seem normal to me.

May I perhaps suggest that you check the coordinates of the waypoint used for the rankings? Or is it automatically linked to what is shown on the screen? For a sample of boats, I notice that the DTGs would be consistent with a waypoint slightly east of the Fastnet Rock.

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