In message <[email protected]>, "Richard B. Langley" writes: >Quoting Poul-Henning Kamp <[email protected]>:
>> So which datum is used for the zero meridian, which defines the UT* family >> of timescales ? > >That would be the current ITRF as established by the IERS: ><http://www.iers.org/MainDisp.csl?pid=42-17> >It is a realization of the ITRS: ><http://www.iers.org/MainDisp.csl?pid=97-108> OK.... And since WGS84 is not rigidly linked to ITRS, doesn't that mean that in order to use DUT1 broadcasts to point a telescope (precisely[1]) you also need to the ITRS/WGS84 difference at your place ? Has anybody calculated what the worst case DUT1 difference is in the WGS84 datum ? Poul-Henning [1] Yes, I know telescopes do not use dead reckoning at this level of precision (yet ?) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [email protected] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ LEAPSECS mailing list [email protected] http://six.pairlist.net/mailman/listinfo/leapsecs
