If ISOCONT is called with two input images and IMAGE_1 (or IMAGE_2)
is stored in an IDL raster data structure, then the field of view of
each raster frame can be displayed by setting SCAN=1 (or SCAN=2). The
center of each raster frame is marked by a small square and a line
connecting each center indicates the direction of the scan. It is
possible not to display the color image by using the /NOCOLOR
keyword. One may suppress the contour plots using the /NOLEVEL level
keyword instead.
(See Fig. 16)