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

[Eric Greisen]

Eric Greisen updated #5514
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              Status: Closed (was: Open)
                 Due: - Cleared - (was: 25 September 2014 08:55 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: Closed
            Priority: Default
      Template Group: Default
             Created: 17 September 2014 11:35 PM
             Updated: 25 September 2014 09:01 PM



I will not try to debug the -SFL header you were given.
Instead I would do the following:

1. Find the coordinate of pixel 50,50 in the Galactic image
(which has a correct ref latitude of 0)
GLON 127.836  GLAT 37.269

2. task='flatn'; 
Fix COORD returned by IMVAL (flatn insists in hours, minutes..
>for i=1:3; coord(i)=coord(i)/15; end
>inp
AIPS 1: FLATN: Re-grid multiple fields and pointings to one image
AIPS 1: Adverbs     Values                 Comments
AIPS 1: ----------------------------------------------------------------
AIPS 1:                                    Input images
AIPS 1: INNAME     'Test -SFL'                Image name (name)
AIPS 1: INCLASS    'orig'                     Image name (class)
AIPS 1: INSEQ         1                       Image name (seq. #)
AIPS 1:                                          (specify)
AIPS 1: INDISK        2                       Image disk drive #
AIPS 1: NFIELD        1                    Max number of fields per
AIPS 1:                                       pointing
AIPS 1: NMAPS         1                    Number of pointings
AIPS 1:                                    Output image
AIPS 1: OUTNAME    'Test -SFL'                Image name (name)
AIPS 1: OUTCLASS   ' '                        Image name (class)
AIPS 1: OUTSEQ        0                       Image name (seq. #)
AIPS 1: OUTDISK       2                       Image disk drive #
AIPS 1: IMSIZE      128         128        Output image size in pixels
AIPS 1: COORDINA      8.4667      3.3333   Central pixel coordinate
AIPS 1:               0.6561     37        all 0 => use observed
AIPS 1:              16           8.5959
AIPS 1: COOTYPE    '-TAN'                  Desired projection type
AIPS 1: COOINC     -180         180        Desired coordinate increment
AIPS 1: COOREF       64          65        Desired reference pixel
AIPS 1: ROTATE        0                    Rotation to be used (deg)
AIPS 1: REWEIGHT      1           0        (1) Interpolation halfwidth
AIPS 1:                                    (2) Minimum fraction of good
AIPS 1:                                        pixels required (0->1/3)
AIPS 1: WEIGHTIT      0                    Weight image down by WEIGHTIT
AIPS 1:                                    times radius from center in "
AIPS 1: EDGSKP        0                    Skip pixels around the edges
AIPS 1:                                    inscribed ellipse also used
AIPS 1: OPTYPE     ' '                     For mosaics only (NMAPS>1)
AIPS 1:                                    compute and output expected
AIPS 1:                                    noise ('NOIS') or weight
AIPS 1:                                    ('WEIG').
AIPS 1: APARM      *all 0                  (1) >0 => do 3-D corr.
AIPS 1:                                       ONLY for snapshots
AIPS 1:                                    (2) Parallactic angle (deg)
AIPS 1:                                    (3) Zenith angle (deg)
AIPS 1:                                    (4-8) radial scaling parms
AIPS 1:                                    (9) Linear scaling
AIPS 1: PBPARM     *all 0                  Beam parameters (NMAPS > 1)
AIPS 1:                                    (1) Cutoff; (2) Use (3)-(7)
AIPS 1:                                    (3)-(7) Beam shape
AIPS 1: NOISE      *all 0                  Relative uncertainties by
AIPS 1:                                    pointing: 0 -> image header
AIPS 1: BADDISK    *all 0                  Disks to avoid for scratch

go
getn n (of the output image)
celgal to make celestial coords, then

>keyw='crota2'
>geth
>typ keyv
AIPS 1: (  1)    -156.3930664     0
>tget flatn; rotate=-keyv(1)

>go
getn (new output image)
celgal
I prdict the rotation after celgal is zero
Now to get a -GLS or -SFL do
task 'flatn'
>pixxy 64,65
>imval
AIPS 1: Map pixel position:    64.00   65.00
AIPS 1: Skypos: RA 11 27 30.483  DEC 79 02 52.63
AIPS 1: Skypos: IPOL  -116.0 KM/S
AIPS 1: Image =   13.341 Kilo  K   *M/S
>y = (coord(4)*60 + coord(5) + coord(6)/20) / 3
>typ y
AIPS 1:   1581.5438232
>cooref(2) = 65 - y; coord(4)~ 0 0 0
>cooty '-gls'
outcl = cootyp
go

I hope this is clear.  It is amusing to
tvch = 1; grch 1; tvolo; tvla
getn last output image (-gls)
tvof 1; tvon 2; grch 2; tvch 2; tvlo; tvla
gron 3
tvbl

I tried with more accurate interpolation methods but they
have trouble at the edges (REWEIGH(1) parameter).

This will get you your image oriented in RA/Dec.

Cheers

Eric Greisen




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