### G Inter-operability with PISA

PISA (Position, Intensity and Shape Analysis) is a Starlink package for detecting objects in two-dimensional image frames and determining the properties which characterise them (position, intensity, ellipticity, orientation etc). It is documented in SUN/109[13]. PISA lists the details of the objects which it has detected in simple text files. A limited degree of inter-operability with CURSA is possible by preparing a suitable description of these files so that they can be accessed as STL format catalogues (see Appendix C).

PISA generates two principal output files:

• the results file, containing details of the objects detected in the image frame (position, intensity etc). The default name of this file is pisafind.dat,
• the sizes file, containing a set of areal profiles (that is, the number of pixels detected within each of a set of intensity thresholds) for the objects detected in the image frame. The default name of this file is pisasize.dat.

Template STL description files for these two types of file are available respectively as files:

/star/share/cursa/pisaresults.TXT
/star/share/cursa/pisasizes.TXT

To access given PISA files simply take copies of the templates. If you have used the default file names for the PISA files then you will be able to simply use the templates without modification. However, if you specified your own file names you will need to edit your copies of the templates to refer to your files. Comments in the templates describe the changes, which are trivial; all that is needed is to change the FILE directive to specify your files.

Note that the columns in the PISA files do not change, so you should not need to alter the column definitions in the templates. If an object does not contain any pixels at a given intensity threshold (because it is too faint) then the corresponding field in the sizes file is set to -1.0.