/* edges.aml
/*   makes HSV grids for a DEM, image emphasizes changes
/*   in slope in low-slope areas, with elevation color-coding 
/*   INPUT: a DEM (specify name in command line)
/*   OUTPUT: 3 grids, <DEMNAME>h, <DEMNAME>s, and <DEMNAME>v
/*     Ralph Haugerud, USGS Seattle
/*     last modified April 1998
/*       rhaugerud@usgs.gov
/*
/*  to be run from GRID

&arg ZGrid
&s slopeg = slopegrid
&s ElvStep = 5
&s HueStep = 15

%slopeg% = slope(%ZGrid%, DEGREE)

h0 = %ZGrid% div %ElvStep%
h1 = con(isnull(%ZGrid%), 0, %ZGrid% <= 0, 180, 170 - (h0 * %HueStep%))
/* sets Z < 0 to hue = 180 (cyan) 
%ZGrid%h = (h1 + 7200) mod 360

%ZGrid%s = con(isnull(%ZGrid%), 0, %ZGrid% < -200, 99, %ZGrid% < 1, int(50 - %ZGrid% / 4), 40)
/* if Z < 1, saturation = f(depth), else saturation = 40

%ZGrid%v = con(isnull(%ZGrid%), 99, %slopeg% > 10, 60, int(99 - 4 * %slopeg%))

kill slopegrid all
kill h0 all
kill h1 all
&return