Junction Commands

Another common job, using the catalogues, it is to merge the data of two or more data set. The user can have two catalogues, that contain some common objects, and he needs to write a new catalogue taking certain fields from the first catalogue and other fields from the second one, for the same object. DIRA2 can merge the fields of two catalogues when a common identifier (i.e. the object name) or a pointer that links the records between the two catalogues exists. Moreover when the user have a list of objects, with precise coordinates, he can try to identify these objects on target catalogues searching inside sky areas of given size.

The junction commands are:

DB_MERGE
merges the fields of two catalogues when a pointer to records position is present in one of these catalogues.

DB_JUNKEY
merges the fields of two catalogues when these have a common identification key.

DB_CROSS
Spatial cross correlation between a data set containing sky coordinates and a catalogues.

The DB_CROSS helps the user in the identification searching all the objects near a set of given center fields; the final object identification, meaning the decision, is an user concerning. This command is an extension of the DB_PLACO command. The other two procedures work using pointers and keywords already defined inside the catalogues.



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