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mFitplane - Use least squares to fit a plane to an image


mFitplane [-b border] [-d level] [-s statusfile] in.fits


Uses least squares to fit a plane (excluding outlier pixels) to an image. It is used on
the difference images generated using mDiff or mDiffExec.


-b border
Number of border pixels to ignore at edges of image.

-d level
Turns on debugging to the specified level (1-3).

-s statusfile
Output and errors are written to statusfile instead of stdout.


Input FITS file is a difference file between two other FITS files, as can be
generated using mDiff.


The plane fit to the image is of the form:

fit = A*x + B*y + C

where x is the "horizontal" pixel offset from CRPIX1 in the FITS header and y is the
"vertical" offset from CRPIX2. Since all reprojected images use the same reference pixel,
this is a uniform definition for x,y for the whole image set.

The fitting is a simple least squares, with an iterative loop to exclude points more than
2 sigma (sigma defined as the rms from the previous loop).

The rms output is the value computed above. The xmin, ... ymax output correspond to the
range of x,y values found while fitting. The rms is for information only but the xmin,
... ymax are used in the background fitting (mBgModel). crpix1 and crpix2 are the
reference pixels for each axis, as determined from the FITS header.


OK [struct stat="OK", a=A, b=B, c=C, crpix1=crpix1, crpix2=crpix2, xmin=xmin,
xmax=xmax, ymin=ymin, ymax=ymax, xcenter=xcenter, ycenter=ycenter, npixel=npixel,
rms=rms, boxx=boxx, boxy=boxy, boxwidth=boxwidth, boxheight=boxheight,

ERROR Argument to -b (string) cannot be interpreted as an integer

ERROR Cannot open status file: statusfile

ERROR Image file filename missing or invalid FITS

ERROR FITS library error

ERROR general error

Too few pixels to fit

Too few pixels for bounding box

Singular Matrix-1

Singular Matrix-2

allocation failure in ivector()


$ mFitplane 2mass-atlas-990322n-j0640266.fits
[struct stat="OK", a=-8.9198e-11, b=-2.54173e-10, c=5.24277e-05, crpix1=808,
crpix2=212.5, xmin=-808, xmax=167, ymin=-210.5, ymax=638.5, xcenter=-320.871,
ycenter=213.014, npixel=314299, rms=0.393003, boxx=-320.92, boxy=212.424,
boxwidth=835.421, boxheight=509.274, boxang=-29.5537]

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