Tournament Guidelines - Sure-Path GPS Boat Lane Tracking

Boat Lane Tracking
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Guidelines for Use of Sure-Path in Tournament
To minimise the risk of Sure-Path giving erroneous information in a tournament environment, the following procedures should be followed:

  1. Mapping the course: The procedure for mapping the course (slalom or jump) should be carried out as usual. In slalom, once buoys G1 to G4 (entrance and exit gates) have been mapped, Sure-Path will display the length of the virtual centre line from the entrance gates centre point to the exit gates centre point. This should be compared with the same as measured during homologation.

    1. If the course buoys are attached to individual fixed anchors, then mapping probably only needs to be done once, prior to the start of the tournament. But accuracy checks (see section 2) should still be done between rounds or series as deemed appropriate by the Chief Judge and Homologator.

    2. If the course is a floating course, there is of course the possibility of the course moving or distorting during the competition under the influence of wind and/or weeds. Since a GPS based system cannot compensate for such changes, it is the duty of the Chief Judge and the Homologator to ensure that the risk of the course not being in tolerance is minimised. If this cannot be achieved by suitable cross tethering, then a decision needs to be made as to whether it is appropriate to use Sure-Path at the event.

      The course mapping accuracy should be checked (as per section 2) and if necessary, redone in between rounds or series as deemed appropriate by the Chief Judge and Homologator.

      It is recommended that the mapping file be saved in a second file as a backup in the event of the loss of the main mapping file.

  2. Checking the mapping accuracy: Mistakes made in the mapping usually result in a marked error in deviation readings and are therefore very obvious the first time the boat goes through the course. To check for smaller errors or just plain bad practice when marking buoy positions, the following should be carried out prior to the event and prior to each series.With no skier behind the boat, do one pass of the course skimming the right hand guide buoys with the boat (ie deliberately driving to the right of centre) and note the overall offset. Repeat in the opposite direction and again note the overall offset. The offsets for each pass should be similar and to the right. If the two results differ by more than about 4cm, then it is likely that the mapped centre line is not the actual centre line. If so, remap the gates and repeat the test. If you are still getting strange results, check that the boat guide buoys are in line and are equal distances from the centre line (use the homologation survey and line of sight tests). Refer to Rule 25.08 b) sub sections 4 and 5.

    Note that if the course is remapped, the changes will not be reflected in the Boat Lane Tracking until it is re-selected to the Boat Lane using "Select Course...".

  3. Integration with Scoring Software: For R and L sanctioned tournaments, Sure-Path relies on a data link to the scoring software to obtain information about the boat, driver, skier, boat speed and rope length. For the data link to be in place, Scoring Mode must be set to "WaterskiConnect" and the Event Name set to the tournament sanction ID. This will be in the form YYNOCxxx where YY is the year, NOC is the country code and xxx is the numeric. If this is set correctly (and, importantly, is the same as the scoring software), Sure-Path will receive data for driver, skier, boat speed and rope length directly from the scoring software and can embed that data into the deviation file which can then be subsequently used for record verification if required. Note that if an event uses multiple lakes simultaneously, these can be segregated using the Event Sub ID field. Again Sure-path and the Scoring software must match for successful data transfer. This data link also means that all deviation data is stored on the server as it passes through and is available for post tournament verification of records etc.

    A confirmation that Sure-Path has connected and the Event Name is displayed bottom right of the main screen. Check that the Event Name is correct.

  4. During the Event: The driver and boat judge must be aware that the boat antenna must be in line with the centre of the boat, ie in line with the ski pylon (or at a known offset from centre and the appropriate setting made in the Rover Boat Lane Settings). Flying handles and/or people can knock the antenna mount out of position and therefore this should be checked on a regular basis and especially after a handle has been catapulted into the boat.

  5. Maximising reliability of the Sure-Path system: It is good practice to depower the whole system, including the base phone and base receiver at the beginning of each day. That said, some users have had their base setup running continuously since late 2019! If you know your base is reliable, then you don't always have to restart it.

    When re-powering, start with the base phone and base receiver and after starting the base phone app and connecting, ensure both progress bars on the phone app are animating as usual. Then re-power the rover phone and connect to the receiver as usual. Ensure that RTK Fix is achieved within a reasonable timescale.

    Note that the GPS satellites available in the sky vary from day to day and hour by hour. This means that the rover's ability to achieve RTK Fix is also a varying thing. If you find that the rover sometimes drops from Fix to Float, you can do the following to try and minimise the chances of this happening:

    1. Ensure the base antenna has as good a view of the sky as possible. The ideal is clear view of the sky down to 15 degrees above the horizon in ALL directions and we cannot stress enough the fact that the better the base antenna's position, the easier it is for the rover to cope with less than perfect GPS signals and achieve full RTK Fix. Achieving the ideal, usually involves elevating the base antenna to somewhere high where it is not overlooked by trees or buildings. In particular, avoid proximity to vertical surfaces such as walls of buildings that can give rise to reflected GPS signals which confuse the GPS receivers. If you move the base antenna, you will need to remap the course(s).
    2. Ensure the rover antenna is not mounted too low on the ski pylon and that no other equipment (such as a camera or other mount) is positioned above it. If site conditions (ie tall trees, buildings etc) are such that achieving RTK Fix is still unreliable, it is probably worth upgrading the rover antenna in the boat to a survey grade one as used for the base (ie the white dome shaped ones).

  6. Other reliability considerations:

    1. Powering the rover receiver: If the rover receiver is being powered from the boat's battery or a built in USB outlet, these can be unreliable when the engine is started or when the ignition is turned off. If the receiver is depowered (or even suffers a drop in volts), the rover phone can lose its bluetooth connection and may not re-establish it again cleanly (this is something of a feature with bluetooth "classic"). You can alleviate this by supplying boat power to the charging socket of a small USB power bank (4000mAH is sufficient)  and then powering the receiver from the power bank. Effectively, the USB power pack acts as a buffer between the boat's power and the GPS receiver. Another benefit to using a power bank is that any voltage spikes from the boat's power do not get through to the receiver. There have been a small number of cases where such spikes have fried the receiver and it is not a cheap replacement.
    2. Heat: Mobile device operating systems, Android included, will start to shut down apps if they think the device is overheating. In extreme cases, the device will be turned off. This is especially true for the rover phone since the screen is usually set to a high brightness and is sitting in a position in the boat that is usually exposed to direct sunlight. If the ambient temperatures at a tournament are 30°C or above, it is highly recommended that consideration be given to shielding the phone from direct sunlight and/or providing some sort of additional ventilation to the area. This could be provided by something like a USB powered fan mounted on the dash or windscreen and directed at the phone. It goes without saying that the base phone also should not be left in direct sunlight or in a particularly hot environment.
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