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Board » General Discussion » Clarify marks

Posted by
Bingalup


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2011-11-21 13:37:12
2011-11-24 07:32:45 - Clarify marks
In the latest white Island race in the Boats tab there is a list of 5 marks which seem to be different to the "rounding" marks on the map.
What does DTG stand for and the number in the right and left columns

Do you have to pass on a particular side of these marks?
Posted by
Tempest


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2009-06-16 17:44:17
2011-11-24 17:20:42 - Re: Clarify marks
Mike , the marks in the boatlist are used for practice racing and do not refer to the marks in the real race. These boatlist marks disappear one hour before start
Posted by
NZL_PaulR


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2008-07-22 12:21:30
2011-11-25 06:45:55 - Re: Clarify marks
DTG = Distance To Go to the finish.

LHS: # = leaderboard position by the shortest DTG by great circle to finish, even though the boats may be many miles apart e.g. horizontally
If it breaks, it's not strong enough!
Posted by
AGage


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2008-12-27 10:31:57
2012-03-29 14:32:01 - Re: Clarify marks
DTG = Distance to Goal AFAIK...

Just a small point, and thinking it would be better as DTF ;-)
I help develop the client interface for the best online ocean racing sim there is... __/)/)_/)__
Posted by
NZL_PaulR


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2008-07-22 12:21:30
2012-03-29 22:49:58 - Re: Clarify marks
DTG = Distance to GO, pretty close to GOAL, but not always.
DTF = Distance to Finish.

Whilst they may seem to be the same, there could be a difference because of the shape of the earth. Similar to Great Circle vs Rhumb line.

Another time the FINISH may be the middle of the finish line, but if there is a bias / skewed finish, then distance to GO to the nearest "END" of the line may be shorter and equally can take longer than going to the furtherest "END" of the line.

In the same way, different GPS manufacturers (or software developers) can have slightly different meanings at different times.

E.g. when we do NOT have a destination waypoint active in our GPS, our VMG is Velocity Made Good into the WIND. If a destination waypoint (or Route) is active then our VMG value is really a VMC Velocity Made Good to the WAYPOINT / DESTINATION (if route is not active).

Whilst they can be similar at times they are NOT the same. Argueably the instruments should then show VMC (COURSE) or VMW (WAYPOINT), but they do not.

Similarily the Traverse Tables can give different distance results than simple Mercator chart plotting.

If it breaks, it's not strong enough!
Posted by
AGage


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2008-12-27 10:31:57
2012-03-30 04:17:59 - Re: Clarify marks
Well on SOL the value is computed to the closest point on the finish line (once on final leg) - but I'm not sure I see how the shape of the Earth can mean Goal and Go differ?

I just meant DTF seems to be a more widely used acronym than DTG...

The nautical software I use shows both VMG and VMC (when a waypoint is defined) - I would think instruments like onboard dont, just to keep the programming simpler - but yeah that could get confusing had you not read the manual fully!
I help develop the client interface for the best online ocean racing sim there is... __/)/)_/)__
Posted by
NZL_PaulR


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2008-07-22 12:21:30
2012-03-30 09:54:24 - Re: Clarify marks
and not all manuals are the same!!!
If it breaks, it's not strong enough!

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