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@@ -4,7 +4,8 @@ New raster map layers can be created which are arithmetic expressions
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involving existing raster map layers, integer or floating point constants,
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and functions.
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-<h3>PROGRAM USE</h3>
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+
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+<h3>Program use</h3>
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<em>r3.mapcalc</em> expression have the form:
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<p><b>result =</b><em> expression</em>
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@@ -38,7 +39,8 @@ r3.mapcalc 'foo=1'
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Sorry, <foo> is not a valid parameter
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</pre></div>
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-If no options are given, it manufactures "input=-" (which reads from
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+<!-- sync to r.mapcalc? -->
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+If no options are given, it manufactures "file=-" (which reads from
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stdin), so you can continue to use e.g.:
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<div class="code"><pre>
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@@ -50,15 +52,15 @@ r3.mapcalc <<EOF
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foo = 1
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EOF
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</pre></div>
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-But unless you need compatibility with previous versions, use input=
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+But unless you need compatibility with previous versions, use file=
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explicitly, e.g.:
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<div class="code"><pre>
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-r3.mapcalc input=file
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+r3.mapcalc file=file
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</pre></div>
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or:
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<div class="code"><pre>
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-r3.mapcalc input=- <<EOF
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+r3.mapcalc file=- <<EOF
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foo = 1
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EOF
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</pre></div>
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@@ -71,7 +73,8 @@ is entering input to <em>r3.mapcalc</em> on the command line, expressions
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should be enclosed within single quotes. See NOTES, below.
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-<h3>OPERATORS AND ORDER OF PRECEDENCE</h3>
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+<h3>Operators and order of precedence</h3>
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+
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The following operators are supported:
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<div class="code"><pre>
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Operator Meaning Type Precedence
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@@ -112,7 +115,9 @@ Division by 0 and modulus by 0 are acceptable and give a NULL result.
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The logical operators give a 1 result if the comparison is true, 0 otherwise.
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<p><p>
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-<h3>3D GRID NAMES</h3>
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+
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+<h3>3D Grid names</h3>
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+
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Anything in the expression which is not a number, operator, or function name
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is taken to be a 3D grid name.
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Examples:
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@@ -131,7 +136,7 @@ x = a-b
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<p><div class="code"><pre>
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x = "a-b"
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</pre></div>
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-<p>would be interpreted as: x equals the 3D grid named <em>a-b</em>
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+<p>would be interpreted as: x equals the 3D grid named <em>a-b</em>
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<p>Also
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<p><div class="code"><pre>
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x = 3107
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@@ -156,12 +161,13 @@ name@mapset
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<p><div class="code"><pre>
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result = x@PERMANENT / y@SOILS
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</pre></div>
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-<p>The mapset specified does not have to be in the mapset search path. (This
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-method of overriding the mapset search path is common to all GRASS commands,
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-not just <em>r3.mapcalc</em>.)
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+<p>The mapset specified does not have to be in the mapset search path.
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+(This method of overriding the mapset search path is common to all
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+GRASS commands, not just <em>r3.mapcalc</em>.)
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<p>
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-<h3>THE NEIGHBORHOOD MODIFIER</h3>
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+<h3>The neighborhood modifier</h3>
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+
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3D grids are data base files stored in voxel format, i.e., three-dimensional
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matrices of float/double values. In <em>r3.mapcalc</em>, 3D grids may be
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followed by a <em>neighborhood</em> modifier that specifies a relative offset
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@@ -176,18 +182,16 @@ refers to the cell one column to the right of the current cell. This syntax
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permits the development of neighborhood-type filters within a single 3D
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grid or across multiple 3D grids.
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-<p>
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-<h3>FUNCTIONS</h3>
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+<h3>Functions</h3>
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+
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The functions currently supported are listed in the table below.
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The type of the result is indicated in the last column.
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-<em>F</em>
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-means that the functions always results in a floating point value,
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-<em>I</em>
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-means that the function gives an integer result, and
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-<em>*</em>
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-indicates that the result is float if any of the arguments to the function
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-are floating point values and integer if all arguments are integer.
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+<em>F</em> means that the functions always results in a floating point value,
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+<em>I</em> means that the function gives an integer result, and
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+<em>*</em> indicates that the result is float if any of the arguments to the
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+function are floating point values and integer if all arguments are integer.
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+
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<p><div class="code"><pre>
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function description type
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---------------------------------------------------------------------------
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@@ -233,6 +237,7 @@ sqrt(x) square root of x F
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tan(x) tangent of x (x is in degrees) F
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xor(x,y) exclusive-or (XOR) of x and y I
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</pre></div>
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+
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<div class="code"><pre>
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Internal variables:
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row() current row of moving window
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@@ -249,7 +254,8 @@ Internal variables:
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Note, that the row(), col() and depth() indexing starts with 1.
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-<h3>FLOATING POINT VALUES IN THE EXPRESSION</h3>
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+<h3>Floating point values in the expression</h3>
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+
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Floating point numbers are allowed in the expression. A floating point
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number is a number which contains a decimal point:
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<div class="code"><pre>
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@@ -274,6 +280,7 @@ produce a floating-point result, as will using float():
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<h3>NULL support</h3>
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+
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<ul>
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<li>Division by zero should result in NULL.
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<li>Modulus by zero should result in NULL.
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@@ -381,7 +388,9 @@ values, the user doesn't know whether or not they both have the same value.
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Extra care must be taken if the expression is given on the command line.
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Some characters have special meaning to the UNIX shell.
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These include, among others:
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-<p>* ( ) > & |
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+<div class="code"><pre>
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+* ( ) > & |
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+</pre></div>
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<p>It is advisable to put single quotes around the expression; e.g.:
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<div class="code"><pre>
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'result = volume * 2'
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@@ -541,25 +550,36 @@ X (map) values supplied and y (newmap) values returned:
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<h2>KNOWN ISSUES</h2>
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-Continuation lines must end with a \ and have NO trailing white space
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-(blanks or tabs). If the user does leave white space at the end of
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+
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+Continuation lines must end with a <tt>\</tt> and have <em>no</em> trailing
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+white space (blanks or tabs). If the user does leave white space at the end of
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continuation lines, the error messages produced by <em>r3.mapcalc</em> will
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be meaningless and the equation will not work as the user intended.
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-This is important for the eval() function.
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+This is particularly important for the <tt>eval()</tt> function.
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<p><!-- STILL TRUE ??-->
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-Currently, there is no comment mechanism in <em>r3.mapcalc</em>. Perhaps
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-adding a capability that would cause the entire line to be ignored when
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-the user inserted a # at the start of a line as if it were not present,
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-would do the trick.
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+Currently, there is no comment mechanism in <em>r3.mapcalc</em>.
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+Perhaps adding a capability that would cause the entire line to be
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+ignored when the user inserted a # at the start of a line
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+as if it were not present, would do the trick.
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<p>The function should require the user to type "end" or "exit" instead
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of simply a blank line. This would make separation of multiple scripts
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separable by white space.
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-<p>r3.mapcalc does not print a warning in case of operations on NULL cells.
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-It is left to the user to utilize the isnull() function.
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+<p><em>r3.mapcalc</em> does not print a warning in case of operations on
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+NULL cells. It is left to the user to utilize the <tt>isnull()</tt> function.
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<h2>SEE ALSO</h2>
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-<b><a href="http://grass.osgeo.org/uploads/grass/history_docs/mapcalc-algebra.pdf">r3.mapcalc: An Algebra for GIS and Image
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+
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+<em>
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+<a href="g.region.html">g.region</a>,
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+<a href="r3.colors.html">r3.colors</a>,
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+<a href="r.mapcalc.html">r.mapcalc</a>
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+</em>
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+
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+
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+<h2>REFERENCES</h2>
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+
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+<b><a href="http://grass.osgeo.org/uploads/grass/history_docs/mapcalc-algebra.pdf">r.mapcalc: An Algebra for GIS and Image
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Processing</a></b>, by Michael Shapiro and Jim Westervelt, U.S. Army
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Construction Engineering Research Laboratory (March/1991).
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<p>
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@@ -572,13 +592,12 @@ Neteler, M. (2001): Volume modelling of soils using GRASS GIS 3D tools. - in:
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Brovelli, M. (ed.)(2001): The Geomatics Workbook N. 2. Politecnico di Milano,
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Italy (ISSN 1591-092X) (<a href="http://geomatica.como.polimi.it/workbooks/n2/articoli/mn2.pdf">PDF</a>)
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-<p><em><a href="r.mapcalc.html">r.mapcalc</a></em>
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-
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<h2>AUTHORS</h2>
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Tomas Paudits & Jaro Hofierka, funded by GeoModel s.r.o., Slovakia
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<br><a href="mailto:tpaudits@mailbox.sk">tpaudits@mailbox.sk</a>,
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<a href="MAILTO:hofierka@geomodel.sk">hofierka@geomodel.sk</a>
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+<p>Glynn Clements
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<p>
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<i>Last changed: $Date$</i>
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Markus Neteler