[daip] UNCON and IMAGR

Eric Greisen egreisen at nrao.edu
Mon Jun 15 11:26:58 EDT 2009

Hans-Rainer Kloeckner wrote:
> Dear Eric,
> 	once agin I'm sorry for bothering you.
> We are trying to run a SKA simulation that will contain several  
> thousands  (~3000-5000) of antennas.
> Is there a limit in the numbers of antennas that can be processed in   
> imagr and uncon? If so, could you please point me to the relevant  
> sections in the source code that needs editing or is  there an easier  
> way to increase the number of antennas?

The worst problem is that the format limits the number of antennas to 
255  (BL = 256 * A1 + A2).  It is true that IMAGR will ignore the 
baseline so long as no calibration or flagging is done.  I am surprised 
that UVCON does not encounter this limit - that would be an error on its 

There is a clever trick from Miriad which aips does not implement that 
allows antenna numbers to be higher.  But since these numbers are kept 
in single-precision floats, there is a rather tight limit since these 
floats get less accurate than 1.0 when the numbers are more than 2**24 
or so.

Eric Greisen

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