RaceBox
English
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More simply put, if the start line is directly in front of you or behind you, then the start
line is the target. Otherwise, its whichever end of the line is closer to your bow.
5.2
How does the Race Box choose the path to the target?
The path to the target is simple. Its a straight line from your bow to the target. If the
centerline intersects the start line then the target is a straight path to the line, either in
front of you or directly behind you. Otherwise, the path is to whichever end of the line is
closer.
5.3
Distance and time to line calculations
Now that we know the target and the path to the target, its simple to calculate the
distance to the target. Remember, its the distance from your bow to the target,
regardless of your heading. Distance to the line can be presented in feet (FTL), meters
(MTL) or boat lengths (BL).
Time to the line (TTL) is calculated based upon the distance to the target point and your
current speed over ground. If your current course over ground will take you across the
starting line then the distance to line and time to line calculations will be fairly accurate.
If your target is one end of the line and you are not currently on a heading that takes
you directly to or away from the line, you must take into consideration several items.
First, when you turn to head toward the line, the target will change when your centerline
actually intercepts the line. Second, you should consider the time it will take to turn your
boat. Finally, consider that the speed of your boat will change after you turn it and come
up to speed on a new sailing angle (relative to the wind).
Time To Burn (TTB) calculations
Time To Burn tells the crew whether they will be early or late to the starting line, based
upon the time to the line
and
also based upon how much time is remaining before the
start. To calculate this data, the Race box takes your Time To Line (TTL) and subtracts
it from the time remaining until the gun.
If your TTL is 30 seconds and there are 40 seconds remaining before the gun, then
your TTB is +10; you need to “burn” off 10 seconds to avoid being late. Conversely, if
your TTL is 30 seconds and there are only 10 seconds to the gun, then your TTB is -20
and you're 20 seconds late. And of course if your TTL is 30 with 30 seconds left before
the gun, your TTB is 0.
Be careful with TTB. Always be mindful that pinging the line can only be so accurate,
and that the GPS receiver typically is off from 3 to 9 feet (1 to 3 meters). Wind
conditions can change quickly and there is always that other boat rudely stealing the
space you planned to put your boat into. Therefore, you will still want the crew making
their approach estimations on your final approach to the line.
