[daip] UVCON and UVPLT bugs (31DEC06)

[Michael Bietenholz]

-- both these based on 31dec06 aips; Timestamp 2006.12.15:05:12:04

1:  UVCON's calculation of when the source elevation for seems to be wrong
in the case of a VLBI array:

when I run UVCON with, e.g.,

infi 'AIPSTARS:VLBA_UVCON'
APARM 8.4095211 0 69.02, -6 6 3 19.6608 32
BPARM 0;

ie. supposedly having an elevation cutoff of 3degs, I get a file which
has data for SC (antenna 10) when the elevation at SC (according to
UVPLT, REFANT=10; BPARM 11 15 0) is below 0.

When I changed APARM(6) to 10 degrees, I lost some SC data from the
end of the simulated run, ie. where the elevation at SC was HIGH
rather than from the beginning, where it was low, as one might expect.

Could you confirm this bug for me?  I'm refereeing a paper which
might have problems because of it.

2: (more minor) when UVPLT is plotting the hour angle for a
visibility, it reasonably tries to plot the average HA for the two
antennas involved in a particular baseline.  It neglects the fact that
HA is an angle and HA=-12h is the same thing as HA=+12h.

This is probably unimportant for the VLA, where, where HA is the same
for all antennas, but can lead to very confusing results, because
UVPLT will average HA_1 = +11h and HA_2 =-11.02h to produce HA_avg =
-0.01h Averaging HA correctly would lead to a value of HA_avg =
11.99h.

   thanks,

          michael b