Uses a minimisation
routine to determine the 2-D Gaussian profiles of multiple sources on an NDF format image. This will
be especially useful for those using JCMT data (see also JCMTDR
Source locations can be specified using a cursor or by text file. The user is allowed to restrain the
extent to which each minimisation iteration is allowed to modify the location, breadth or
position angle of the sources. This is essential when the package is used with overlapping
Input text files must contain the x and y coordinates of the source in the Current co-ordinates of the
NDF, and may in addition contain estimates for the position angle, Sa, Sb (std deviation of the
Gaussian functions in 2 directions - major axis then minor) and the peak value.
Output image options are for the generation of the complete whole image model or an image
containing the residuals in the regions surrounding the sources.
There are two separate fitting algorithms within GAUFIT, a non-linear least-squares routine
(selectable with parameter LSQFIT=true) or the original parameter-search routine. Some of the
parameters below have slightly different behaviour in the two modes, or are only available in one
mode or the other. These are indicated by prefacing the variant descriptions with either [PS:] for
parameter-search mode (lsqfit=false) or [LSQ:] for least-squares (lsqfit=true)
ANGCON = _LOGICAL (Read)
Angle rotation convention. Defines if clockwise or anticlockwise is considered positive.
ANGINC = _REAL (Read)
[PS:] The amount by which the angle of a
source may vary. Arbitrary range 0 to 1. 1 = free to move as required. 0 = unable to move.
ANGOFF = _REAL (Read)
Angular offset for position angles generated. Units degrees.
AUTOL = _LOGICAL (Read)
[PS:] Is the source origin provided to be refined?
The background value for the image. [LSQ:] You may give this as a negative
number, to have the routine obtain and report the best-fit background; in this case, the SIGMA
and NSIGMA parameters are ignored.
CALCSD = _LOGICAL (Read)
we calculate and display parameter uncertainties? A significant part of the calculation
is taken up with this calculation, so if you do not want the uncertainties, you will save
time by opting not to calculate them.
COLOUR = _INTEGER (Read)
Colour of the pen
used to mark source centres.
FWHM = _LOGICAL (Read)
Are the gaussian widths to
be read and written as FWHM or standard deviations?
IMGDEV = _DEVICE (Read)
Name of the graphics device on which the results graph should be displayed.
Name of a text file containing the co-ordinates of sources to be profiled.
Co-ordinates are in the Current co-ordinate system of the WCS component of IN.
IN = _NDF
The name of the source NDF data structure/file.
LSQFIT = _LOGICAL (Read)
Is the application to use the least-squares fitting routine, or the older parameter-search
MAXITER = _INTEGER (Read)
[LSQ:] Upper-bound on the iteration count
within the least-squares method (-1 indicates that you are happy with the default limit). The
default maximum count is large, and intended as an upper bound on the iteration count, to
stop it spinning its wheels uselessly on some pathological dataset. You should not need
to change this unless you suspect that the limit is genuinely being reached by a correct
MODE = _LOGICAL (Read)
Whether the application is to run in file input
mode or interactively. Interactive MODE=TRUE. File mode=FALSE.
MODEL = _NDF
The output NDF.
The type of output NDF file to be
created. MODTYP=R gives residuals near the sources. MODTYP=W gives the whole image
NITER = _INTEGER (Read)
[PS:] The number of iterations performed by the
NSIGMA = _REAL (Read)
Number of sigma above sky at which
pixels are considered to be significant. [LSQ:] If you give back=-1, then this is ignored.
OUT = _CHAR (Read)
File name for the output text file containing the profile data.
PINC = _REAL (Read)
[PS:] The amount by which the peak of a source may vary. 1
= free to move as required. 0 = unable to move.
PSIZE = _REAL (Read)
The size of
each pixel in arc seconds. If the image contains a SKY co-ordinate frame this value will be
SAINC = _REAL (Read)
[PS:] The amount by which the standard
deviation of a source may vary per iteration. Largest axis. 1 = free to move as required. 0
= unable to move.
SBINC = _REAL (Read)
[PS:] The amount by which the standard
deviation of a source may vary per iteration. Smallest axis.
SIGMA = _REAL (Read)
Standard deviation of the sky count. [LSQ:] If you give back=-1, then this is ignored.
[PS:] The amount by which the x coordinate of a source may vary per
iteration. 1 = free to move as required. 0 = unable to move.
YINC = _REAL (Read)
amount by which the x coordinate of a source may vary per iteration. 1 = free to move as
required. 0 = unable to move.