[daip] [!5514]: aips - -SFL projection

[Eric Greisen]

Eric Greisen updated #5514
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                 Due: - Cleared - (was: 30 September 2014 06:34 PM)

-SFL projection 
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           Ticket ID: 5514
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/5514
           Full Name: Trisha L Ashley
               Email: trisha.ashley at gmail.com
             Creator: User
          Department: AIPS Data Processing
       Staff (Owner): Eric Greisen
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template Group: Default
             Created: 17 September 2014 11:35 PM
             Updated: 26 September 2014 07:30 PM
      Resolution Due: 03 October 2014 10:55 PM (7d 3h 24m)



1. The FFT routines that we use make the central pixel, N/2, N/2+1
     so 64,65 is habit.
2. That was a typo - it should have been 60.
3. CELGAL can work only on true projective geometries (-SIN and
-TAN are the most common of these) - CELGAL simply recomputes
the ref pixel value, plus a rotation.  It is quite accurate to use the
next to last image (in -TAN) rather than the last in -GLS - the routines
that return coordinates of things just have to know what they are doing.
If you load one to the TV and do a TVLABEL with GRCHAN 1 and
then load the other and do a TVLABEL with GRCHAN 2 (and set
DOCIRCLE to 1 also) you will see the differences in the projections.

Eric Greisen





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