From: "John E. Parks" <john@tang.uark.edu>
Subject: Re: How does 'd.rgb' work?
Date: Wed, 4 Mar 92 0:55:25 CST|while I am on the subject, I have a new derivative of blend.sh called
|intens.sh. While blend.sh combines two colors into one, intens.sh
|is designed to work with a color file, and a grayscale file, using the
|grayscale to vary the intensity of the colors. This avoids the
|'washed out' effect of you can get from blend.shI've heard that there is a script that will allow you to build 360
degree aspect maps instead of 24(15degree) maps. Is this true?
Sounds like it ought to be more than a script.__ __
/ ) / / ) Research Specialist
/ / _ /_ _ /__/ Ctr for Advanced Spatial Technologies
(__/_(_)_/ /_/ )_ / _ National Ctr for Resource Innovations
/ 12 Ozark Hall, Univ. of Arkansas
/ Fayetteville, AR 72701
John E. Parks phone: (501) 575-6159
[john@tang.uark.edu] Internet or: (501) 575-4575
Well, I am sure there is more than one, but here is one that I have. I
hope it is acurate. I threw it together from memory. The map looks
reasonable at least.
---------------------------- Rip here ------------------------------------
:
# Usage: 0 elevation aspect
# aspect is the output aspect file (0-360)
#
#
if test $# != 2
then
echo "Usage: `basename $0` elevation aspect" >&2
exit 1
fi
aspect=$2
elev=$1
r.mapcalc << EOF
$aspect = eval (\
root2 = 1.414213562, \
root3 = 1.732050808, \
A = ($elev[1,1]-$elev[1,-1]), \
B = ($elev[-1,-1]-$elev[1,-1]), \
U = (2*A), \
V = ((-2)*B), \
W = 2., \
mag = sqrt (1.*U*U+V*V+W*W), \
U = (U/mag), \
V = (V/mag), \
W = (W/mag), \
(((-U-V+W)/-root3) * 180 + 180 + 270) % 360)
EOF
# answer == -1 to 1
# * 180 == -180 to 180
# + 180 == 0 to 360
# + 270 % 360 == 0 to 360, except that 0 is rotated to SE for aspect color file
r.colors $aspect co=aspect
exit 0
---------------------------- Rip here too --------------------------------
--
Dave Gerdes
US Army Construction Engineering Research Lab
Spatial Analysis & Systems Team
dpgerdes@cerl.cecer.army.mil
(217) 352-6511 x591