[evlatests] Large Bz error?

[Rich Moeser]

Vivek Dhawan wrote:
> Looking under the lamp post for the usual things:
>
> EOP looks correct - I compared the numbers in the
> WIDAR data header to the USNO file here:
>
> http://gemini.gsfc.nasa.gov/solve_save/usno_finals.erp
>
> I next tried to compare the XYZ antenna positions in the
> AIPS header (via SDM and CASA) to the VLA pad positions
> in the VLBA database which purport to be in ITRF:
>
> $SCHED/catalogs/locations.dat
>
> There is 20-30cm of difference in all Y & Z axes,
> between a pad's location in the WIDAR header and its
> location in the SCHED/USNO database. Its not just
> a longitude shift since Z is involved. The error is
> (to within ~1cm) independent of which pad I compare.
>
> It is also not clear whether including the continental
> drift term (12.73 years since the USNO solution epoch)
> is useful or not - X is better with the correction, but
> the discrepancy is about 30cm in at least 2 axes with
> or without the drift put in.
>
> Where do those WIDAR positions come from?
>
>   

The station positions in the SDM are derived using the geodetic location 
constants x=-1601185.4, y=-5041977.5, and z=3554875.9 and adding the 
station offsets x, y, and z from the parameters database.

--Rich