The catalogue building is done in Leiden. In order to do this software had to be written to find sources in the maps and store these in a database. Because there are so many sources that we will detect (about 300.000 sources at 92 cm and 60.000 sources at 49 cm), the source finding procedure must be automated to the highest level. Only the very complicated sources will be done by hand.
When we started the project we had several choices for this part of the project: 1) write such a program from scratch, 2) take an existing package, 3) modify an existing routine. The first choice seemed not feasible, because this would take a lot of time (finding the appropriate algorithm, implementing it, debugging, etc.). There wasn't a package available which could do the job completely automated, but there was a routine available in AIPS called SAD (Search and Destroy, written by W. Jaffe).