Using RA/DEC Information

Information describing spatial co-ordinate Frames can be stored within the WCS component of the standard NDF structure. All NDFs know about ``pixel co-ordinates'', but additional co-ordinate Frames can be added. In the context of POLPACK, the co-ordinate Frames most likely to be of interest are celestial co-ordinate systems such as RA/DEC. This information can be used in two ways:

1. To annotate the axes of vector maps produced using POLPLOT.
2. To align vector maps with other images obtained from elsewhere.