[LEAPSECS] Schedule for success

[Richard B. Langley]

Quoting Poul-Henning Kamp <phk at phk.freebsd.dk>:


> In message <1230738511.495b944f91ce3 at webmail.unb.ca>, "Richard B. Langley" writes:

> >Quoting Poul-Henning Kamp <phk at 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: lang at 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/
===============================================================================