Help for CONTOUR


PURPOSE

	Create a graphics file of isolines.

TAE COMMAND LINE FORMAT

	contour INP=ELEVATION.IMG OUT=ELVLEVELS.CTR ZSTART=100  		ZEND=500 CONTINT=25 NUMPTS=3
EXAMPLES

	contour INP=SURFACE.IMG OUT=SURFACE.CTR CONTINT=5  		ZSTART=100 ZEND=200 NUMPTS=5

	In this example, contours will be generated starting at
100 and continuing through 200, at an interval of 5 units. Each
cell of 4 pixels (2 by 2) used to calculate the contours will be
devided into 5 small increments. This will increase the appearance
of a smooth contour line.

OPERATION

	The output graphics file coordinates will be in "pixel-space"
units. This means that a subwindow of a surface image contoured will
not start with values of 1,1 but in the approximate range of the
starting line, starting sample used in the SIZE parameter (assuming
there were pixels in the correct Z value range).

RESTRICTIONS

	Sized down surface images should be contoured as apposed to
contouring at the original resolution. Since the algorithm moves
accross and down the surface image there are a lot of pen ups, change
Z values, and pen downs. Typically a 1/5 scale image is sufficient
to generate a believable contour map of the surface.

NOTE

	The program MOD3DCTR can be run on the output of CONTOUR. This
process will sort the output of CONTOUR in Z order as well as allow
for scaling and offsets to the 3D graphics file. (Sorting is important
if a CALCOMP plot of the contours is needed. This allows for plotting
one entire Z value contour without the constant changes of pens, as would
be the case without the postprocess MOD3DCTR).

REVISIONS
	1-95   Meredith Cox  (CRI) - Made portable for UNIX