Portsmouth Yardstick 2019

ClassNational 2019 PNSuggested PNConfidence LimitUTLSC 2019 PNUTLSC 2018 PNIncrease
from 2018
Laser 4.7120711620.341192117022
Laser Pico 1/U/0**133013390133013300
Laser Radial114511040.631119110910
RS 200104610630.0410471051-4
RS Aero 51136001136
RS Aero 71065001065
RS Aero 91014001014
Streaker Wave**119012240119011900

* National PN not provided – RYA provided PN based on Trend data

** National PN not provided – UTLSC 2018 PN used


Portsmouth Yardstick

Some classes are faster than others. E.g. A Laser is faster than a Topper.
To enable boats from different classes to compete against each other in the same race classes are given a Portsmouth Yardstick Number (PN).
These PNs are used to calculate a corrected time from the elapsed time. The person with the lowest corrected time is the winner and so on.

Corrected Time = Elapsed Time * 1000/ PN for that class


How have UTLSC PNs been set in the past?

For several years the RYA has been providing National PNs for each class based on data from many sailing clubs.

UTLSC has been uploading results to the RYA since 2013. The RYA provides an analysis tool that gives a Suggested PN for each class based on UTLSC  data alone. At the same time the RYA recognises that if there is insufficient data provided the Suggested PN is not statistically sound, so they also provide a Confidence Limit for each class based on the volume and stability of the data.

From 2015, at the recommendation of the RYA, UTLSC decided to use the Suggested PNs and Confidence Limits to calculate the UTLSC PNs for the following year.  The UTLSC PN moves from last year’s UTLSC PN towards the Suggested PN according to the Confidence Limit.
However if the Confidence Limit is 0 the National PN is used.

UTLSC 2018 PN = UTLSC 2017 PN + ((Suggested PN – UTLSC 2017 PN) * Confidence Limit)

E.g. For the LASER

     UTLSC 2017 PN:           1077
     Suggested 2018 PN:     1069
    Confidence Limit 2018:  54%

    UTLSC 2018 PN:   1073 = 1077 + ((1069-1077)*54%)


How have UTLSC PNs been set for 2019?

There has been concern that we are not making best use of the data collected nationally. So, with approval from the RYA, the committee has decided to calculate the 2019 UTLSC PNs by moving from the National PNs towards the Suggested PN according to the Confidence Limit. The Suggested PNs and Confidence Limits will be based on 2013-2018 UTLSC race results.

UTLSC 2019 PN = National 2019 PN + ((Suggested PN – National 2019 PN) * Confidence Limit)

E.g. For the LASER

     National 2019 PN:         1099
     Suggested PN:               1070
    Confidence Limit 2018:   77%

    UTLSC 2019 PN:   1077 = 1099 + ((1070-1099)*77%)