Gone are the days of manual key entry of sail numbers and timing equipment. Today, each competitor carries a Locosys GT31 GPS data logger unit. The introduction of GPS units has revolutionised the timing and accuracy of the event. So long as the unit is switched on, carried by the competitor and returned before the closing time at the end of the day, the competitor's positions and speed can be reliably determined.
Where a unit gains and maintains a high-quality signal lock, it accurately records the competitor's position every second of the day. The units are normally housed in waterproof bags and strapped to the competitor's arm. In order to aid results processing, each unit is individually identifiable and allocated to a single competitor by means of a configured username and the unit serial number.
Results Generation Process
Results are generated daily in "near-time" when all of the competitor's GT31 units have been collected after the day's competition. The data is downloaded from each competitor's unit directly from the SD Card that is inserted into a laptop and read. The day's GPS data files are copied to the laptop and validated via Weymouth Speed Week's Event Manager software; using the software to validate and copy the datas removes many potential errors caused by manual operation.
The initial set of data, comprising the GPS data files from all competitors, is processed firstly by Manfred Fuchs’ GPSResults software in order to define the course positions and course open/close times and to select all of the competitor's qualifying GPS runs. The software then calculates the speed, duration and direction of each valid 500m run recorded by each GT31 unit and outputs the raw results for further results processing. The GPSResults software is a professional version that includes event-specific customisation with course gate plotting and basic results generation features.
These “preliminary results” files for a specific day are then read by Tim Daish’s Excel macro, SSerpant, where some more clever calculations are performed to combine the results with the appropriate competitor information from the registration file. The resulting data is then sorted and output as the various results reports we require. Result processing can also look up the wind speed and direction as recorded during the time of the run and calculate the average values; results can include speed-to-wind speed ratios and course angle sailed relative to the wind.
The day's results and an overall leaderboard are then made available through publication on the website and announcements made via the WSW Facebook page. Results can also be printed and posted up in the marquee/room in time for a morning's briefing.
GT-31 GPS Signal and Data Quality
Results are processed based upon the contents of the GPS Data files recorded by each competitor's Locosys GT-31 Data Logger. The Organisers are not responsible for the quality of the data recorded by the GT-31 and any variances or exclusions caused by loss of satellite signal. We have begun to see a number of GT-31 specific issues that can affect the amount and quality of data recorded.
It is always in your best interests to ensure that your GT-31 is in good working order prior to sailing. This includes, but is not limited to the following:
- that the SD card is of a size recognised by the unit:
- DO NOT rely upon the internal memory of the data logger; the internal logging is a backup against card failure;
- that the SD Card is formatted and properly recognised by the unit;
- that the unit is fully operational, including the toggle button;
- that the battery maintains charge and starts the day with a sufficient level of charge to last throughout your sailing day;
- that the unit acquires multiple satellite locks and maintains a high-quality signal at all times;
- a minimum of 5 satellites is required (the more satelltes the unit can lock onto, the higher the signal quality)
- the maximum Horizontal Dilution of Precision (HDOP) is 5. (higher DOP values indicate a lower quality signal and less accurate positional data, see table below)
- that the unit is worn in a way during sailing that maintains a good and strong satellite signal;
- that the unit is always used within a good waterproof pouch whilst sailing.
|1||Ideal||This is the highest possible confidence level to be used for applications demanding the highest possible precision at all times.|
|1-2||Excellent||At this confidence level, positional measurements are considered accurate enough to meet all but the most sensitive applications.|
|2-5||Good||Represents a level that marks the minimum appropriate for making business decisions. Positional measurements could be used to make reliable in-route navigation suggestions to the user.|
|5-10||Moderate||Positional measurements could be used for calculations, but the fix quality could still be improved. A more open view of the sky is recommended.|
|10-20||Fair||Represents a low confidence level. Positional measurements should be discarded or used only to indicate a very rough estimate of the current location.|
|>20||Poor||At this level, measurements are inaccurate by as much as 300 meters with a 6 meter accurate device (50 DOP × 6 meters) and should be discarded.|
DOP table copied from wikipedia (http://en.wikipedia.org/wiki/Dilution_of_precision_(GPS))
Results Ratification and Publication
All results are subject to ratification. The results of each day of the event are validated by the organisational team in order to ensure their accuracy prior to publication.
At any point during Speed Week, any competitors found to have been incorrectly classed will be reclassified; results for all pevious days will be re-processed in accordance with the changed classifications and may therefore change previously published results. The Weymouth Speed Week organisers wish to ensure that all competitors competie equally and fairly against their peers in the prize catergories in which they are entitled.
Results are published on the web and in printed format for competitors at the morning brief. Results are published in good faith and are based upon the data recorded by the competitor's GT-31 units and read and processed by the organisers results processing software in combination with the published course gate data and the competitor classifications held. Competitors are requested to check that their entry information is correct or advise if their or other competitors information is incorrect.
Where run data is required to be excluded, new run data is required to be included or competitors have to be reclassified, then results will be reprocessed and republished.
Lodging an Appeal/Query and Subsequent Investigation
It is recognised that competitors may have access to software that enables them to review their own GPS run data and that there are circumstances in which a competitor may raise a query or lodge an appeal against the published results. In such a circumstance the following procedure applies...
It is in the interests of all parties to work together to resolve issues amicably. The WSW team want to identify and publish speed results based on accurate and reliable data recorded by the GT-31 units. If any competitor identifies an issue with the published results they must call by phone or talk in person to the organisers at the earliest opportunity and within 24hours of the publication of results.
- state your name
- identify your GT31 username and serial number
- provide the date and time(s) of competition to which the query relates
- describe the nature of the issue identified
- if you have data available from a backup unit, submit the data to the organisers
- your issue will be logged and investigated
The organisers will invesigate any identified issue to the best of their abiilities and will always attempt to recover data so that it can be included in the results:
- issues and discrepancies will be investigated as quickly as possible;
- data recorded upon the SD card will be scrutinised;
- backups from the GT-31's internal data logger will be used when the SD card has no data recorded;
- backups from a 2nd GT-31 will be reviewed and used if considered more suitable than the original GPS data file, where available;:
- runs generated from the recorded GPS data must meet the required level of quality and accuracy and meet signal quality threshold levels:
- GPS data will be used by default where the data records that a minimum of 5 satellites was used to determine position AND where the HDOP relating to the signal at that time was less than 5. In order to maintain accuracy through results processing, the signal quality threshold levels will only be lowered by exception.
NOTE: Following investigation of an advised issue using the official event results processing software and any republication of the results, the decision of the Weymouth Speed Week organisational team is final.