GPS and internet location and tracking have become common place and almost taken for granted. However, when GPS information such as histories, or internet tracking information is presented as evidence at a protest hearing, a deeper understanding is necessary to apply the appropriate weight.
Single GPS location history (Snail Trail)All boat navigation GPS systems offer the ability to save and download the performance for later review. Whether this single-source information can be useful at a hearing depends very much on the issues. Although accurate, a boat’s positions alone usually do not offer much useful information. It does not include information about other boats’ positions, where a mark was located, or the ends of a starting line. Information on boat speed may be helpful in determining wind speed.
If the protest is about rule
19.2(c) against a boat that sailed into an inside overlap between the protesting boat and a nondescriptive shore some kilometers away, the GPS trail may offer useful information on the water depth and the distance inshore where the depth might be unsafe for sailing.
Internet Tracking & Application Display InformationTo attract more visitors to event websites, commercial tracking systems are used to create publicity and promote the event. Small GPS position transmitters (trackers) are placed on boats or clipped to a crewmember as well as marks and starting lines. At local events, this information is transmitted to a shore base. In offshore races, the information is sent via satellite to the race headquarters. In both cases the raw data are entered into a display application and shown on the event's website. Races and individual teams can be followed over the internet from anywhere in the world.
The tracks shown in the graphical displays are not always based only on accurate position fixes. If position fixes from trackers are missing or if the software thinks they are out of position, the software might estimate the missing position fixes and eliminate fixes that look to be out of position. This can result in estimated tracks shown in the graphical display that may be different from the real track sailed.
When ashore, sailors and coaches will review the race using the tracking system. Boats may ask to present tracking information as evidence about an incident on the water in a protest hearing. Race officers will sometimes compare the tracking information with their finishing sheets to locate a missing boat or answer a scoring enquiry that may lead to a request for redress.
While the core technology in use by the different tracking service providers is basically the same, there are many different approaches in the final delivery of the tracking system product. Every tracking service provider uses GNSS receivers to capture the basic geolocation data at regular intervals. The minimum raw data captured by the tracker for each position fix includes latitude, longitude, timestamp and tracker ID. The geographic positions are updated repeatedly within the GNSS receiver up to 10 times per second, but the frequency of fixes available from (or published by) the tracking system may vary from one or two fixes per second to up to one per hour or (s)lower for oceanic races.
Frequently Asked QuestionsHow often is the boat’s position sampled? Answer: although the GPS can sample 10 times per second, the presentation is seldom that often. To save space in the memory chip, or to save money in the satellite data transfer, not all positions are transmitted or displayed. In a thirty-minute dinghy race, that might be only once per second. In a transoceanic race, that might be once every ten or thirty minutes.
How accurate are the positions? Answer: there are many different factors affecting the accuracy of the position such as cost of the GPS unit and atmospheric conditions. Typically, 95% of the time, the accuracy is 2 to 8 meters.
Are the marks of the course tracked? Answer: most of the time. Race committees will install trackers on the marks of the course, including both ends of the start and finish lines. This should be confirmed by the event’s tracking team. Race committees do not usually place trackers on permanent or government buoys.
Can the tracking system show overlaps and collisions? Answer: competitors will sometimes present tracking information in a hearing to show a collision or an overlap at the zone. In almost every case, the information from the tracking system will be inconclusive by itself. The graphical representation of the boat is almost never to scale. You can test this by comparing the length of the boat icon at various levels of zoom.
Other considerations in a hearingSince competitors are entitled to present evidence that they consider relevant, they may bring animated video clips of an incident they saw in the tracking system. The competitor will be basing the presentation on derived information, and it is important for the judges to know what it real and what is virtual.
Because the enhanced graphics can lead competitors and judges to the wrong conclusions, there are a few things the protest committee can do to manage the presentation of tracking data in a hearing.
Before the first race, the protest committee should discuss the tracking system being used. Review the instructions, verbal or written, that the sailors receive about the installation of the trackers on the boat. Know where the trackers are intended to be installed on the boats. Find out the sampling rate.
Review the tracker application. Zoom in and zoom out, observe the scaling, start and stop the race display, and know how to declutter the screen by removing boats and tags. Determine the accuracy of the tracking units and what averaging or smoothing is applied to the information.
Ask the provider to explain the depiction of the three-length zone.
Ask the race committee if trackers will be installed on marks and race committee boats and where they will be located.
It is the responsibility of the party to provide the equipment to display tracking data.
During a hearing, get the verbal evidence from the parties first, before the presentation of the tracking clips. Let the parties question each other’s verbal evidence. Make sure the protest committee understands the facts from the verbal evidence. Tracking data is always easier to assess when it is presented in support of the description of the incident by the parties.
Normally judges would not view tracking information before the hearing. If the tracking information is seen by a judge without the parties present, it must also be included either as evidence submitted by a party, or by the protest committee.