[daip] UVCON / UVPLT issues

[Leonia Kogan]

Dear Ian,

Youl find the answer between the lines

Ian Heywood wrote:

> Dear Leonia, Eric,
> 
> I'm trying to redo some simulations using the new version of UVCON which 
> I've obtained by not only running the midnight job, but also by 
> reinstalling AIPS prior to this for good measure.
> 
> I'm still getting some peculiar behaviour. The attached file shows the 
> UVPLT output of elevation against time (BPARM 11 15) for all antennas, 
> for both the old buggy simulation and the new one.
> 
> Two things I don't understand are:
> 
> 1) Each antenna in the new simulation has apparently the same elevation 
> value. Since elevation when observing a source is dependent on the 
> latitude of the antenna, and the simulation is for a global array, 
> should they not be spread out over this plot as with the old simulation? 
> (A plot of these parameters for real VLBA data shows a spread similar to 
> the old UVCON plot.)
I guess you use UVPLT with both ant=0 and refant=0.
If you want to see the plot of elevetion you need specify REFANT = N
and you should get the plot of elevation for antenna N!
You need to change refant if you want to get the elevation plot for 
another antenna. You will see the relevant change at the header of the plot.

> 
> 2) According to the plot of the new UVCON data, visibilities are still 
> being recorded at negative elevations despite APARM(6) being set to zero.
> 
> Any light you can shed on these matters would be most appreciated.
> 
> All the best, and thanks in advance for your time.

UVCON still does not create visibilities if one of the baseline antennas
has elevations lower than aparm(6)
To check it use UVPRT to print out amplitude for the baseline with 
negative elevations for one of the antennas and you will see that the 
visibilities corresponded to the negative elevations for one of the 
baseline antennas are not there

Let me know the result please

Leonid

> 
> -Ian
> 
> ------------------------------------------------------------------------
>