AIPS HELP file for OGEOM in 31DEC21
As of Sun May 16 12:55:15 2021
OGEOM: Interpolate an image to the geometry of another.
INNAME Image name (name)
INCLASS Image name (class)
INSEQ 0.0 9999.0 Image name (seq. #)
INDISK 0.0 9.0 Image disk drive #
OUTNAME Image name (name)
OUTCLASS Image name (class)
OUTSEQ -1.0 9999.0 Image name (seq. #)
OUTDISK 0.0 9.0 Image disk drive #
BLC 0.0 4096.0 Bottom left corner of image
TRC 0.0 4096.0 Top right corner of image
IMSIZE 0.0 4096.0 Output image size in pixels
REWEIGHT 0.0 4.0 (1) Interpolation halfwidth
(2) Minimum fraction of good
pixels required (0->1/3)
APARM (1)=Delta X in pixels
(2)=Delta Y in pixels
(6)=shift X coordinates : ???
(7)=shift Y coordinates : ???
Use: OGEOM does an interpolation of an image to a rotated, shifted, and
scaled output image. It is assumed that the image geometry is
linear for these purposes. Use OHGEO for larger fields.
Interpolation is done only in the first 2 dimensions. Unlike
LGEOM, OGEOM will interpolate over blanked pixels so that it can
fill in small blanked regions and handle edges without having to
discard image area.
NOTE: the input subimage is read into dynamically allocated memory.
Very large input arrays may cause swapping on your computer.
This task does a straightforward interpolation from the input to
the output image grid. This process cannot be completely
accurate if, for example, one shifts and scales an image and
then reverses that process. Greater accuracy will be achieved on
images with more points per beam and with larger support sizes
for the interpolator.
INNAME......The input image name. Standard defaults.
INCLASS.....The input image class. Standard defaults.
INSEQ.......The input image sequence number. 0 => high
INDISK......The input image disk drive no. 0 => any
OUTNAME.....The output image name. blank => Standard
defaults based on INNAME.
OUTCLASS....The output image class. Standard behavior.
OUTSEQ......The output image seq. no., 0=> highest unique
If >0; image will be created if new, overwritten if image
OUTDISK.....Output disk drive no., 0=> highest with space
BLC.........The bottom left-hand pixel of the input image which
becomes the bottom left corner of the input subimage. The
value (0,0) means (1,1).
TRC.........The top right-hand pixel of the input image which becomes
the top right corner of the subimage. The value (0,0)
means take the top right hand corner of the image.
IMSIZE......Output image size in pixels [1=columns, 2=rows]. Default
is the input image size. If the output image size is
the same as the input size in both axes, then the
reference pixel is not changed other than by the
addition of APARM(1) and APARM(2).
REWEIGHT....Interpolation kernal parameters:
(1) Half width of the interpolating kernel
(1 - 4). Default = 1
Larger support sizes should produce more accurate
results at the cost of increased computation.
(2) Minimum fraction of pixels in interpolation kernal
area required for non-blanked output.
<= 0 or >= 1 => 0.333
1 & 2 = shift of coordinate reference point, expressed in
output pixels, for x & y relative to the center of the
subimage. Positive moves objects to the right and up
relative to center pixel.
3 = rotation in degrees (positive moves objects
counterclockwise relative to the image center as they
map from input image to output image).
4 = scale factor (greater than one moves objects outward
from the image center as they map from input to
output). This is applied wrt the image center
defined as Naxis(1)/2, Naxis(2)/2 + 1.
5 = 'differential scale'; this is an extra scale factor
applied to the y-axis AFTER the main transformation
has been done. This is useful to make spiral galaxies
appear face-on. Also, if it is negated the result is a
mirror-reflection in the y-axis.
6 & 7 = Coordinate shift in X and Y in arc seconds. The
measured right ascension and declination of objects
will change. Positive increases the RA and Dec. if
the image has the normal orientation (RA increasing to
the left, Dec. increasing upwards, no rotation). Note
that this option corrects the shift for the cos of the
latitude which only works correctly when there are no
rotations. THIS OPTION DESTROYS THE COORDINATES YOU
WENT TO A LOT OF TROUBLE TO MEASURE. Use it only in