Quoting Poul-Henning Kamp <p...@phk.freebsd.dk>: > In message <1230738511.495b944f91...@webmail.unb.ca>, "Richard B. Langley" > writes: > >Quoting Poul-Henning Kamp <p...@phk.freebsd.dk>: > > > >> 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 ? > > > >The current version of WGS84 differs from the current version of ITRF by > >only a few > >centimetres. WGS84 was purposely updated to agree as closely as possibly > >with ITRF. > > But it is not guaranteed to keep close, is it ?
Yes, it is. Geodetic reference frames are established these days by essentially adopting the coordinates of the reference stations (primarily GPS) and their velocities. The WGS84 reference sites are basically a subset of those used by IERS. =============================================================================== Richard B. Langley E-mail: l...@unb.ca Geodetic Research Laboratory Web: http://www.unb.ca/GGE/ Dept. of Geodesy and Geomatics Engineering Phone: +1 506 453-5142 University of New Brunswick Fax: +1 506 453-4943 Fredericton, N.B., Canada E3B 5A3 Fredericton? Where's that? See: http://www.city.fredericton.nb.ca/ =============================================================================== _______________________________________________ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
