tmatch1: Performs a crossmatch internal to a single table
tmatch1 performs efficient and flexible
crossmatching between the rows of a single table.
It can match rows on the basis of their relative position in the sky,
or alternatively using many other criteria such as separation in
in some isotropic or anisotropic Cartesian space,
identity of a key value, or some combination of these;
the full range of match criteria is dicussed in Section 7.1.
The basic task performed by the intra-table matcher is to identify
groups of rows within the table which match each other.
See Section 7.2 for an explanation of exactly what
consitutes a match group.
The result of identifying these groups is expressed as an output table
in one of a variety of ways, specified by the
These options include marking group membership in added columns
and eliminating some or all rows which form part of a match group.