There are no specific regulations for timing a Head race (see Regulations). This is an unofficial code of practice drawn from other sports and from practical experience, together with a commentary.
The Start and Finish need to be clearly marked for the timers. A mark only on the far side from where the timers are placed is not sufficient, as it leaves material variation in where the timer considers a boat to have crossed the line.
It is not acceptable to mix times from different systems or timers and keep the same level of accuracy. For example, if a stopwatch is used, it is not acceptable to take most times from one watch, and take missing times from another. In this case, the times of one timer may legitimately be one tenth or more different from another. Instead an average of times must be calculated, and the average difference between timers applied to the missing time.
Likewise, if a hand-timing system is used, it is not acceptable to take a missing time from a video. In this case the video will not have the reaction time of the hand-timer. Instead: either an average of times must be calculated; or the video could be used to establish the gap between adjacent competitors and the gap applied to the hand times.
A regular stopwatch can be used for timing, although it should be certified by a calibration laboratory. Stopwatches are generally used to time quite short intervals and it should not be assumed they are accurate over longer periods.
If a stopwatch system is used, then as a guideline times should generally be given to the full second, and not tenths of a second.
Although a video camera can show time to the frame, it should also not be assumed that the time is accurate. To give accurate time a video camera needs to be locked to an external timing device, or time derived in a different way.
Timing devices will generally be synchronised before the start of the race. There are several different components of accuracy in synchronisation:
For example, two timing devices for Start and Finish will typically be synchronised before the start of the race. It makes no difference to the accuracy of results whether they are synchronised to GPS or a sun dial. The elapsed times of competitors will be the same.
If two timing devices are synchronised by hand by separate timers, and so have slightly different times, it will make a difference to the absolute elapsed time but not to the relative time between competitors, and so not to the placings.
If two timing devices are synchronised at different times, and even from different sources, then it will still not make a difference to placings, but the times should not be used for records since the absolute elapsed time will not be accurate.
Mostly the timing devices are synchronised at the same time so that times from different devices can be mixed, but this is not legitimate for hand timing because of the difference in accuracy of different timers.
If a timing device is synchronised to GPS, then if necessary it could be legitimate to re-synchronise it to GPS during the event, because all times will still be within the overall accuracy of the device. However if a device is synchonised to a wall clock, then it would not be legitimate to re-synchronise it during the event to a mobile phone, because the difference in time between the wall clock and the phone is not precisely known.
The ALGE-Timing device can be synchronised to GPS. Therefore it will be legitimate to re-synchronise a device during the event. For example, if two divisions are running in morning and afternoon, then it would be possible to re-synchronise the devices from two separate GPS units without returning to base.
The main difficulty in timing a Head race manually is to make sure that a time is assigned to the correct competitor. Obviously in a small event, or for a single competitor, or at the Start, this is easy. The difficulty arises when several competitors cross the finish line close together, and especially if they have lost their boat number.
The list of boats and the list of times are two independent data streams, and it is vital to synchronise them together. For example, if there are six times and six boats, then we can assume that each time is assigned to a boat in the order in which they finished. But if we have six times and seven boats, or seven boats and six times, then we cannot be sure of which time to assign to any of the boats. In the worst case the error could continue with each subsequent boat and time being out of sync.
The best way to deal with this is to match specific boats to times as often as possible. Then, if there is a mis-match, it can only lie between matched boats.