Values within the Pixel Mask

The ARD_WORK subroutine creates an array of integer values (the ``mask'') which holds the result of evaluating the entire logical expression at each pixel. Positive integers represent .TRUE. (i.e. included pixels) and zero represents .FALSE. (i.e. excluded pixels).

Each keyword included in an ARD description is represented by a different positive integer. This provides the possibility for applications to differentiate between the different regions within an ARD description on the basis of the pixel mask alone.