If this routine is not called prior to ARD_WORK (or if it is called with IWCS set AST__NULL), then the ARD description must provide (either directly or through a WCS statement) positions in pixel coordinates.
The FrameSet pointer supplied is simply stored by this routine. If any changes are subsequently made to the FrameSet by the calling routine, then these changes will be visible within ARD_WORK. In particular, if the calling routine annuls the FrameSet pointer, then ARD_WORK will fail.
The supplied FrameSet will be used by all subsequent calls to ARD_WORK until a new FrameSet is specified by calling ARD_WCS again.
ARD A Textual Language for Describing Regions within a Data Array