PISA - Position Intensity and Shape Analysis

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Position Intensity and Shape Analysis

Welcome to the PISA home page. This document serves as a place to find out about the current status of PISA.

What is PISA?

PISA is a group of programs for automatically detecting and measuring objects on an astronomical image. It also provides the ability to display the shapes and positions of the detected objects over the image and convert its results into catalogues.

Current status

For a list of bugs and fixes in the current PISA see the news file in the latest EAO release.

Note that PISA should now be replaced by the EXTRACTOR package. New users are encouraged to use EXTRACTOR and old ones to switch.


A hypertext form of the PISA demonstration script is available. You can see this in action interactively by issuing the commands:

  % pisa
  % pisa_demo

if you have PISA installed on your system. It's best to do this in an empty directory as some files are created -- just delete this afterwards.

A hypertext version of the PISA glossy brochure is also available.

Problems and limitations

The PISA package has various in-built limitations (buffer sizes etc.), that are main cause of most of the "bugs" that people complain about. Have a look at these and if the problem cannot be fixed by applying an appreciation of its cause get in touch with me. I have an experimental version of PISAFIND that uses INTEGER images to get around the 32K limitation. Note that I have no time allocated to this particular project, so any support you get will be very limited.

    • The number of fragments per image (i.e. connected pixel groups) is limited to 200. Hence blends of objects cannot fragment into more than 200 pieces.
    • The number of pixels per image allowed during surface modelling is 10000.
    • The length of the first side of input image cannot be more than 10240 pixels.
    • The input data is processed using an HDS type of _WORD so the input data range must lie within the bounds -32768 to +32767, although PISAFIND itself only processes positive data up to the value 32766. This limitation is fundamental.
    • As in PISAFIND the length of first side of the input image has to be less than 10240 pixels.
    • The input data is processed using an HDS type of _WORD so the input data range must lie within the bounds -32768 to +32767.

Obtaining a copy of PISA

PISA is part of the EAO Starlink release.

Questions or comments to: p.w.draper@durham.ac.uk.

Copyright © 2005 Central Laboratory of the Research Councils
Copyright © 2006 Particle Physics and Astronomy Research Council
Copyright © 2008-2009 Science and Technlogy Facilities Council
Copyright © 2009-2013 Peter W. Draper
Last modified: 02-Jun-2016
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