The clumps profiles are Gaussian, with elliptical isophotes. The values of each parameter defining the clump shape can be either fixed at a constant value or selected from a given probability distribution.
The coordinate system used to describe the peak and centroid positions is determined by the value supplied for parameter LIKE. If LIKE is null (!), then positions are specified in the pixel coordinate system. In addition, the clump sizes are specified in units of pixels, and the clump volume is specified in units of cubic pixels (square pixels for 2D data). If an NDF is supplied for LIKE, then positions are specified in the current coordinate system of the specified NDF. In addition, the clump sizes and volumes are specified in WCS units. Note, the sizes are still measured parallel to the pixel axes, but are recorded in WCS units rather than pixel units. Celestial coordinate positions are units of degrees, sizes are in units are arc-seconds, and areas in square arc-seconds. Spectral coordinates are in the units displayed by the KAPPA command "ndftrace".
If the data has less than 3 pixel axes, then the columns describing the missing axes will not be present in the catalogue.
The catalogue inherits any WCS information from the NDF supplied for parameter LIKE
The "size" of the clump on an axis is the RMS deviation of each pixel centre from the clump centroid, where each pixel is weighted by the correspinding pixel data value. This excludes the instrumental smoothing specified by BEAMFWHM and VELFWHM.
The KAPPA command "listshow" can be used to draw markers at the central positions of the clumps described in a catalogue. For instance, the command "listshow fred plot=mark" will draw markers identifying the positions of the clumps described in file fred.FIT, overlaying the markers on top of the currently displayed image. Specifying "plot=STCS" instead of "plot=mark" will cause the spatial outline of the clump to be drawn if it is present in the catalogue (see parameter SHAPE).