Select vectors from a catalogue
using the bad pixels in a reference image to mask out unwanted vectors
using ARD or AST region specifications to select the required vectors
using an algebraic expression to select the required vectors on the basis of their column values
"
EXPRESSION"
. It should be set to a boolean
expression that uses column names from the input catalogue as variables. It should have
the format used by the CURSA ’
CATSELECT’
command (see sun/190). In general, the
arithmetic and boolean operators available in either C and Fortran can be used (e.g. ’
.ge.’
, ’
$>$=’
, ’
.and.’
, ’
&&’
, etc.), as can the usual mathematical functions (e.g. ’
abs’
, ’
tan’
, ’
pow’
, etc). A
vector is selected if the expression evaluates to TRUE (if using a Fortran-style expression) or a
non-zero value (if using a C-style expression). "
MASK"
. It specifies the two-dimensional NDF to be
used as a mask to select the required vectors. Vectors corresponding to good pixel values
in the mask are selected. The mask is assumed to be aligned with the catalogue in pixel
coordinates. "
MASK"
: The image specified by parameter MASK is used to select the vectors. If a vector has a
position that corresponds to a good pixel in MASK, then the vector is selected.
"
REGION"
: The ARD or AST region specified by parameter REGION is used to select the vectors. If
a vector falls within the region, then it is selected.
"
EXPRESSION"
: The boolean expression specified by parameter EXP is used to select the vectors. If
the boolean expression evaluates to TRUE for a vector, then the vector is selected.
"
REGION"
. It specifies the NDF to which the ARD description refers. It is used to
define the pixel coordinate system used by the ARD description. If null (!) is supplied, it is
assumed that the pixel coordinate system used by the ARD description is the pixel coordinate
system of the input catalogue. [!] "
REGION"
. It should be set to the name of a text file
containing a description of the region containing the vectors to be selected. This can either be in
the form of an ’
ARD description’
(see SUN/183), or an ’
AST Region’
(see SUN/210).