The routine creates a "similar section" from an array (whose ARY_
system identifier is supplied) using an existing NDF section as a
template. An identifier for the array section is returned and
this may subsequently be manipulated using the ARY_ system
routines (SUN/11). The new array section will bear the same
relationship to its base array as the NDF template does to its
own base NDF. Allowance is made for any pixel-index shifts which
may have been applied, so that the pixel-index system of the new
array section matches that of the NDF template.
This routine is intended for use when an array which must match
pixel-for-pixel with an NDF is stored in an NDF extension; if an
NDF section is obtained, then this routine may be used to obtain
a pixel-by-pixel matching section from the array.