[daip] CLCAL: interpolation over blanked values

[Olaf Wucknitz]

Hello,

I am (not for the first time) having problems when interpolating or 
extrapolating calibration solutions from a calibrator to target sources.
Interpolation can of course only be done between good solutions. The 
problem occurs if there are blanked solutions at either end of the scan. 
In such a case CLCAL should neglect these values and instead interpolate 
between the next good values, but this is not the case.
This seems to be true for interpolation and extrapolation.

A typical example is the extrapolation from the last calibrator scan to a 
target scan starting directly after it. If the last values of the 
calibrator are blanked, no solutions are extrapolated.

Currently I am smoothing the solutions a bit (with DOBLANK=0), which 
unblanks most (but not all) of the bad values. 

My current workaround is to call SNSMO before CLCAL and do the wanted 
smoothing (DOBLANK=0) there. After that I call CLCAL with DOBLANK=1 and 
extended smoothing to unblank all values. This seems to work, but a better 
solution would be to fix CLCAL so that its interpolation interprets 
blanked solutions in the same way as non-existing entries.


I remember having related problems with blanked solutions in SNSMO in 
July 2003 when the phase wrap was handled incorrectly around 
blanked solutions. That was corrected by Eric (11363. July 30, 2003).


Cheers,
Olaf