This proposal envisages a traffic light display, where green indicates "Clear" of the line, Amber "Near to the line" and red indicates "Over the line".
This paper describes a mechanism that would allow the relative positions of boats at the start of a race to be noted in a computer automatically, and would allow boats to be timed in as they passed a finish line.
With large fleets and keen competitors it has become very difficult to identify boats that are over the line at the start of a race.
It has also been impossible for the competitors to judge where they were in relation to the line because the line or transits became blanketed by other boats.
The use of Video equipment has proved to be a partial success, and has reduced the degree of unfairness, but at the cost of a considerable amount of Jury time, as well as the expense of camera equipment.
From the experience of a recent Cowes Week, where cameras were used it was possible to classify current errors as:
These errors were in addition to the general recalls occasioned by recognition of a large number of OCS boats.
General Recalls are themselves an unsatisfactory mechanism. As well as delaying the actual start, and the starts of subsequent classes they penalise the boats that do start correctly. After a number of general recalls the draconian black flag rule is often brought in to play. This may make life easier for the Race Committee, but at the expense of the competitors.
An electronic system is proposed that would have the following features
Because of the automatic features of the system the number of personnel required to run a regatta is reduced, although there should always be a mechanism for manual back up in case of catastrophic failure.
Almost all electronic mechanisms involve the use of a "transponder" on each boat. This is a specialised radio receiver/transmitter with two additional features. It has its own identity code built in to the receiver so that it only responds to signals addressed to that boat, and it has an indicator display to indicate the proximity of the line.
This proposal envisages a traffic light display, where green indicates "Clear" of the line, Amber "Near to the line" and red indicates "Over the line".
The base station can signal to the transponder what colour light to display, and when signalled the transponder can transmit a short code back to the base station.
This short code could be a set of position co-ordinates derived from an attached position receiver (GPS or Decca), or could be just a timing signal.
This proposal suggests that the transponder need not have any position receiver, or intelligence, but the position of the transponder may be obtained by fixed devices on committee boats or buoys, with all the intelligence concentrated at the committee boat. In other words the transmission itself is sufficient for the outside equipment to derive the position of the boat relative to the line.
A significant feature of this mechanism is that one or two transponders may be placed at each end of the line, one pair indicating the line itself, and the other pair the "Near the line" zone. The signals from these transponders act as reference signals and these references are used to counter any errors that occur, such as the line itself moving with waves and tide.
The outside equipment may derive the position of the transponder in a number of ways.
One of the simplest would be to use radio direction finding to derive the bearing of the transponder from antennae on the committee boat. This might be the simplest to implement but research is needed into the accuracy and discrimination that could be obtained.
The system proposed is a short radio hyperbolic mechanism The difference in time for the transponder signal to reach two fixed receivers is used to obtain a position line for each boat.
The fixed receivers are aligned on a base line at right angles to the starting line, and the position lines noted are a series of hyperbola that start off parallel with the starting line. The position lines are essentially parallel mid way between the receiving stations, and provides that the receiving antennae are mounted sufficiently far apart, and at right angles to the line good accuracy can be obtained, and indications of the "Clear" and "Near" zone may be obtained from a single pair of antennae.
The receiving antennae could be mounted on the committee boat, but the area of parallel position lines would be small and the accuracy would depend on the committee boat always being at right angles to the line. The antennae could be mounted on buoys or other boats close to the committee boat, linked with cable (weighted to be well below the surface). The laying of this cable in a seaway could well present difficulties, and "repeater units" may be needed. These repeater units would receive the signals from the transponder on one frequency and retransmit them on another. As small self contained units they could be mounted on buoys, placed ahead and behind the line.
The master station sends a poll identifying a specific boat. Only that boat will respond to the poll, and the receiving stations will only accept a response from that boat. Once the position of the boat is known the signal indicates which traffic light to light.
The transponder sends a signal identifying itself, along with a timing signal.
The receiving stations receive the timing signal and pass this to the master station. For distance reasons this may be through relay stations.
The master station receives the timing signals from the receiving stations and calculates the time difference between them. This time difference indicates the position line of the specific boat. The position line is passed to the computer.
The computer can then place the boat in the "Clear", "Near" or "OCS" categories, and passes this information back to the master station for the next poll to the boat.
The transponders have a fixed frequency receiver, an identity chip, a message decoder a fixed frequency transmitter, and three indicator lights.
When the receiver receives a coded signal that corresponds to its identity, it also receives a status signal which it uses to illuminate one of the lights. These would indicate
There are three base stations, the Master station and two Receiving stations.
The master station obtains a list of current transponder identities from the computer, as well as the status of each transponder.
It signals the transponders in turn with their status, and waits for signals from the receiving stations.
When it receives the signals from the receiving stations it notes the time difference between the signals, and compares this with the time difference noted from the reference transponder.
From the time difference the status of the transponder is noted, and passed back to the computer.
The receiving stations receive the signal from the master station and note the identity of the transponder being polled. They then wait for the transponder to respond, and when they receive the timing burst from the transponder signal this to the master station.
The base line needs to be relatively long, and ideally would be as long as the starting line. To enable the line to be this long there needs to be receiving relays mounted on other boats, or on buoys, that relay the signals from the transponders to the receiving stations. These relays need to be set up to introduce consistent signal delays.
If a transponder is out of range its signal cannot be received by the receiving stations. The master station allows a certain time for each transponder to reply, then issues the code for the next one in the list. The receiving stations only respond to the transponder that has been polled by the master station and discard all other signals.
The Computer is linked to the Master Station, and signals the identity of the transponder to be polled, and waits with a time out for a reply of the timing signal. It uses this reply to position the transponder into the appropriate category, (Red Yellow or Green) and passes this category to the master station on the next poll.
Each cycle of polls starts off with the reference transponder, although this can be disabled when it is seen that the reference transponder is no longer on the line.
The computer initiates polling from its entry list on the preparatory signal. During this time between the preparatory and starting signal the lists of boats in the three states is maintained on the screen. On the starting signal an instant list of the correct starters is obtained and the polling ceased for these boats.
When the polling stops the individual transponder lights remain as they were at the last poll. Thus for all the correct starters the lights will remain green or yellow.
The OCS boats will continue to be polled until they have been detected as being on the course side. Their lights will change to yellow as soon as they have crossed to the pre course side, and will then stay yellow, indicating that the boat has now started correctly.
After five minutes the polling for the OCS boats stops, to allow the polling for the next start.
The use of the system is possible for finishing, provided that the same base line can be used, or a new one established in time.
Polling is started for the class as the first finishers are seen to be approaching the line, and as each boat is finished its time is noted in the computer, and it's light turned red to confirm that the boat has crossed the line (or it extension).
The lights on the transponder provide feedback to the competitor during the start sequence, and he will know from the moment of the starting signal whether he was OCS and needs to return. He will see from the absence of lights if there is a malfunction.
When electronic starting is used there needs to be specific mention in the sailing instructions. For the definitions of starting and finishing the boat will need to be defined as the transponder. I.e. the boat is on the course side of the line if her transponder is, and similarly on the pre course side.
Sailing instructions will need to indicate the position of the transponder in the boat. such as "No further aft than the aft face of the mast".