[GRASS-SVN] r64160 - grass/trunk/raster/r.terraflow
svn_grass at osgeo.org
svn_grass at osgeo.org
Wed Jan 14 00:26:25 PST 2015
Author: neteler
Date: 2015-01-14 00:26:25 -0800 (Wed, 14 Jan 2015)
New Revision: 64160
Modified:
grass/trunk/raster/r.terraflow/r.terraflow.html
Log:
r.terraflow manual: some cleanup; limit added
Modified: grass/trunk/raster/r.terraflow/r.terraflow.html
===================================================================
--- grass/trunk/raster/r.terraflow/r.terraflow.html 2015-01-14 07:54:14 UTC (rev 64159)
+++ grass/trunk/raster/r.terraflow/r.terraflow.html 2015-01-14 08:26:25 UTC (rev 64160)
@@ -3,8 +3,8 @@
<p><em>r.terraflow</em> takes as input a raster digital elevation
model (DEM) and computes the flow direction raster and the flow
accumulation raster, as well as the flooded elevation raster,
-sink-watershed raster (partition into watersheds around sinks) and tci
-(topographic convergence index) raster.
+sink-watershed raster (partition into watersheds around sinks) and TCI
+(topographic convergence index) raster maps.
<p><em>r.terraflow</em> computes these rasters using well-known
approaches, with the difference that its emphasis is on the
@@ -27,8 +27,8 @@
<p><table width="80%" align=center>
<tr>
- <th><img src="rterraflow_dir2.png" alt="[SFD]" border=0></th>
- <th><img src="rterraflow_dir3.png" alt="[MFD]" border=0></th>
+ <th><img src="rterraflow_dir2.png" alt="r.terraflow SFD"></th>
+ <th><img src="rterraflow_dir3.png" alt="r.terraflow MFD"></th>
</tr>
<tr>
<th>Flow direction to steepest<br> downslope neighbor (SFD).</th>
@@ -40,6 +40,7 @@
<p>The SFD and the MFD method cannot compute flow directions for
cells which have the same height as all their neighbors (flat areas)
or cells which do not have downslope neighbors (one-cell pits).
+
<ul>
<li>On plateaus (flat areas that spill out) <em>r.terraflow</em>
routes flow so that globally the flow goes towards the spill cells of
@@ -49,7 +50,6 @@
pits) <em>r.terraflow</em> assigns flow by flooding the terrain until
all the sinks are filled and assigning flow directions on the filled
terrain.
-
</ul>
<p>In order to flood the terrain, <em>r.terraflow</em> identifies all
@@ -83,7 +83,6 @@
<p>For more details on the algorithms see [1,2,3] below.
-
<h2>NOTES</h2>
One of the techniques used by <em>r.terraflow</em> is the
@@ -107,49 +106,48 @@
all times at most this much memory, and the virtual memory system
(swap space) will never be used. The default value is 300 MB.
+<p>The <b>stats</b> option defines the name of the file that contains the
+statistics (stats) of the run.
+
+<p><em>r.terraflow</em> has a limit on the number of rows and columns
+(max 32,767 each).
+
<p>The internal type used by <em>r.terraflow</em> to store elevations
-can be defined at compile-time. By default, <em>r.terraflow</em> is
-compiled to store elevations internally as floats.
-A version which is compiled to store elevations internally as
-shorts is available as <em>r.terraflow.short</em>. Other versions can
-be created by the user if needed.
+can be defined at compile-time. By default, <em>r.terraflow</em> is
+compiled to store elevations internally as floats. Other versions can be
+created by the user if needed.
-<p><em>r.terraflow.short</em> uses less space (up to 60B per cell, up
+<p>Hints concerning compilation with storage of elevations internally as
+shorts:
+<br>such a version uses less space (up to 60B per cell, up
to 60N intermediate file) and therefore is more space and time
-efficient. <em>r.terraflow</em> is intended for use with floating
-point raster data (FCELL), and <em>r.terraflow.short</em> with integer
+efficient. <em>r.terraflow</em> is intended for use with floating
+point raster data (FCELL), and <em>r.terraflow (short)</em> with integer
raster data (CELL) in which the maximum elevation does not exceed the
value of a short SHRT_MAX=32767 (this is not a constraint for any
terrain data of the Earth, if elevation is stored in meters).
-
-<p>Both <em>r.terraflow</em> and <em>r.terraflow.short</em> work with
+Both <em>r.terraflow</em> and <em>r.terraflow (short)</em> work with
input elevation rasters which can be either integer, floating point or
double (CELL, FCELL, DCELL). If the input raster contains a value that
exceeds the allowed internal range (short for
-<em>r.terraflow.short</em>, float for <em>r.terraflow</em>), the
+<em>r.terraflow (short)</em>, float for <em>r.terraflow</em>), the
program exits with a warning message. Otherwise, if all values in the
input elevation raster are in range, they will be converted
(truncated) to the internal elevation type (short for
-<em>r.terraflow.short</em>, float for <em>r.terraflow</em>). In this
+<em>r.terraflow (short)</em>, float for <em>r.terraflow</em>). In this
case precision may be lost and artificial flat areas may be created.
-
-<p>For instance, if <em>r.terraflow.short</em> is used with floating
+For instance, if <em>r.terraflow (short)</em> is used with floating
point raster data (FCELL or DCELL), the values of the elevation will
be truncated as shorts. This may create artificial flat areas, and the
-output of <em>r.terraflow.short</em> may be less realistic than those
+output of <em>r.terraflow (short)</em> may be less realistic than those
of <em>r.terraflow</em> on floating point raster data.
-
-The outputs of <em>r.terraflow.short</em> and <em>r.terraflow</em> are
+The outputs of <em>r.terraflow (short)</em> and <em>r.terraflow</em> are
identical for integer raster data (CELL maps).
-<p>The <b>stats</b> option defines the name of the file that contains the
-statistics (stats) of the run. The default name is <tt>stats.out</tt>
-(in the current directory).
-
<h2>EXAMPLES</h2>
-Example for small area in NC dataset:
+Example for small area in North Carolina sample dataset:
<div class="code"><pre>
g.region raster=elev_lid792_1m
r.terraflow elevation=elev_lid792_1m filled=elev_lid792_1m_filled \
@@ -172,6 +170,7 @@
some bounding box problems noticed when opening mogrify result in Gimp
-->
+<p>
Spearfish sample data set:
<div class="code"><pre>
@@ -194,7 +193,7 @@
<h2>SEE ALSO</h2>
<em>
-<a href=r.flow.html>r.flow</a>,
+<a href="r.flow.html">r.flow</a>,
<a href="r.basins.fill.html">r.basins.fill</a>,
<a href="r.drain.html">r.drain</a>,
<a href="r.topidx.html">r.topidx</a>,
@@ -208,8 +207,8 @@
<h2>AUTHORS</h2>
<dl>
- <dt>Original version of program: The <a
- href="http://www.cs.duke.edu/geo*/terraflow/">TerraFlow</a> project,
+ <dt>Original version of program: The
+ <a href="http://www.cs.duke.edu/geo*/terraflow/">TerraFlow</a> project,
1999, Duke University.
<dd><a href="http://www.daimi.au.dk/~large/">Lars Arge</a>,
<a href="http://www.cs.duke.edu/~chase/">Jeff Chase</a>,
@@ -219,7 +218,7 @@
<a href="http://www.science.purdue.edu/jsv/">Jeff Vitter</a>,
Rajiv Wickremesinghe.
- <dt>Porting for GRASS, 2002:
+ <dt>Porting to GRASS GIS, 2002:
<dd> <a href="http://www.daimi.au.dk/~large/">Lars Arge</a>,
<a href="http://www4.ncsu.edu/~hmitaso/index.html">Helena Mitasova,</a>
<a href="http://www.bowdoin.edu/~ltoma/">Laura Toma</a>.
@@ -255,7 +254,6 @@
In <em>GeoInformatica, International Journal on
Advances of Computer Science for Geographic Information
Systems</em>, 7(4):283-313, December 2003.
-
</ol>
<p><i>Last changed: $Date$</i>
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