[GRASS-SVN] r51333 - grass-addons/grass6/raster/r.stream.extract

[svn_grass at osgeo.org]

Author: mmetz
Date: 2012-04-09 12:11:22 -0700 (Mon, 09 Apr 2012)
New Revision: 51333

Modified:
   grass-addons/grass6/raster/r.stream.extract/description.html
Log:
r.stream.extract: update manual

Modified: grass-addons/grass6/raster/r.stream.extract/description.html
===================================================================
--- grass-addons/grass6/raster/r.stream.extract/description.html	2012-04-09 19:10:03 UTC (rev 51332)
+++ grass-addons/grass6/raster/r.stream.extract/description.html	2012-04-09 19:11:22 UTC (rev 51333)
@@ -21,12 +21,15 @@
 <em>elevation</em> must be exactly the same map used to calculate
 <em>accumulation</em>. If <em>accumulation</em> was calculated with
 <a href="r.terraflow.html">r.terraflow</a>, the filled elevation output
-of r.terraflow must be used. Further on, the current region's resolution
-should be identical to the <em>accumulation map</em>. Flow direction is
+of r.terraflow must be used. Further on, the current region should be 
+aligned to the <em>accumulation map</em>. Flow direction is
 first calculated from <em>elevation</em> and then adjusted to
 <em>accumulation</em>. It is not necessary to provide <em>accumulation</em>
 as the number of cells, it can also be the optionally adjusted or
 weighed total contributing area in square meters or any other unit. 
+When an original flow accumulation map is adjusted or weighed, the 
+adjustment or weighing should not convert valid accumulation values to 
+NULL (nodata) values.
 <p>
 <dt><em>depression</em> 
 <dd>Input map, optional: All non-NULL and non-zero cells will be regarded
@@ -130,6 +133,14 @@
 window determines whether narrow or broad valleys will be identified
 (See example below).
 
+<h4>Defining a region of interest</h4>
+The stream extraction procedure can be restricted to a certain region of 
+interest, e.g. a subbasin, by setting the computational region with 
+<em>g.region</em> and/or creating a MASK. Such region of interest should 
+be a complete catchment area, complete in the sense that the complete 
+area upstream of an outlet point is included and buffered with at least 
+one cell.
+
 <h4>Stream output</h4>
 The <em>stream_rast</em> output raster and vector contains stream
 segments with unique IDs. Note that these IDs are different from the IDs