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AA+ v1.50

May 2, 2012

Just to let everyone know that v1.50 of AA+ has been released. Updates for this version include:

  • To further improve the accuracy of the CAADynamicalTime::DeltaT method, the code now uses a lookup table between the dates of 1 February 1973 to 1 April 2012 (for observed values) and predicted values from April 2012 till April 2015. These values are as provided by IERS Rapid Service/Prediction Center at http://maia.usno.navy.mil/ser7/deltat.data and http://maia.usno.navy.mil/ser7/deltat.preds. This lookup table will of course need to be kept up to date as IERS update this information. As currently coded there is a single discontinuity of c. one second in early April 2015. At this point http://maia.usno.navy.mil/ser7/deltat.preds indicates an error value for DeltaT of about 0.9 seconds anyway.
  • A new CAADynamicalTime::CumulativeLeapSeconds has been provided. This method takes as input the Julian Day value and returns the cumulative total of Leap seconds which have been applied to this point. For more information about leap seconds please see http://en.wikipedia.org/wiki/Leap_second. Using this method you can now implement code which converts from Terrestial Time to Coordinated Universal time as follows:
    double TerrestialTime = some calculation using AA+ algorithms(JD);
    double DeltaT = CAADynamicalTime::DeltaT(JD);
    double UniversalTime1 = TerrestialTime – DeltaT/86400.0; //The time of the event using the UT1 time scale
    double TerrestialAtomicTime = TerrestialTime – (32.184/86400.0); //The time of the event using the TAI time scale
    double CumulativeLeapSeconds = CAADynamicalTime::CumulativeLeapSeconds(JD);
    double CoordinatedUniversalTime = (DeltaT – CumulativeLeapSeconds – 32.184)/86400.0 + UniversalTime1; //The time of the event using the UTC time scale
Categories: Web Site Updates
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