[GRASS-SVN] r69583 - grass/trunk/raster3d/r3.in.lidar

[svn_grass at osgeo.org]

Author: wenzeslaus
Date: 2016-09-27 10:25:42 -0700 (Tue, 27 Sep 2016)
New Revision: 69583

Modified:
   grass/trunk/raster3d/r3.in.lidar/r3.in.lidar.html
Log:
r3.in.lidar: full workflow and updated notes in doc

Modified: grass/trunk/raster3d/r3.in.lidar/r3.in.lidar.html
===================================================================
--- grass/trunk/raster3d/r3.in.lidar/r3.in.lidar.html	2016-09-27 13:24:08 UTC (rev 69582)
+++ grass/trunk/raster3d/r3.in.lidar/r3.in.lidar.html	2016-09-27 17:25:42 UTC (rev 69583)
@@ -1,5 +1,9 @@
 <h2>DESCRIPTION</h2>
 
+The <em><a href="r.in.lidar.html">r.in.lidar</a></em> module
+is very similar to the <em>r3.in.lidar</em> module and many parts of
+its documentation apply also for <em>r3.in.lidar</em>.
+
 <p>
 <img src="r3_in_lidar.png">
 <p>
@@ -21,25 +25,28 @@
 
 <ul>
     <li>
-        This module is highly experimental. Don't rely on its
-        functionality or interface. Please report issues on the mailing
-        list or in the bug tracker.
+        This module is new and partially experimental. Please don't rely
+        on its interface and be critical towards its outputs.
+        Please report issues on the mailing list or in the bug tracker.
     <li>
-        No projection check or reprojection is performed, make sure you
-        are using data in the right projection for your GRASS Location.
+        No reprojection is performed, you need to reproject ahead or
+        use GRASS Location which has the right coordinate system
+        which fits with the data.
     <li>
-        Selection of points according to return or class is not yet
-        supported.
-    <li>All outputs are currently mandatory.
-    <li>Some temporary maps are created but not cleaned up.
+        Some temporary maps are created but not cleaned up. Use of
+        <b>--overwrite</b> might be necessary even when not desired.
     <li>
-        Expects points to have intensity (random result for related
-        outputs when they don't).
+        Expects points to have intensity and causing random (undefined)
+        result for related outputs (<b>sum, mean, proportional_sum</b>)
+        when the intensity is not present but the outputs were requested.
 </ul>
 
 
 <h2>EXAMPLES</h2>
 
+
+<h3>Basic import of the data</h3>
+
 Set the region according to a 2D raster and adding 3D minimum
 (bottom), maximum (top) and vertical (top-bottom) resolution.
 
@@ -56,6 +63,7 @@
     proportional_sum=points_sum_prop
 </pre></div>
 
+
 <h3>Point density vertical structure reduced to the terrain</h3>
 
 Create ground raster:
@@ -81,6 +89,90 @@
 </pre></div>
 
 
+<h3>Complete workflow for vertical structure analysis</h3>
+<!-- TODO: needs review and pictures -->
+Compute the point density of points in 2D while setting the output
+extent to be based on the data (<b>-e</b>) and the resolution set to
+a relatively high number (here 10 map units, i.e. meters for
+metric projections).
+
+<div class="code"><pre>
+r.in.lidar input=points.las output=points_n method=n -e resolution=10
+</pre></div>
+
+This step can be repeated with using different resolutions (and the
+<b>--overwrite</b> flag) to determine the resolution for the further
+analysis.
+
+<p>
+The <b>class_filter</b> option should be also provided if only part of
+the points is analyzed, for example <tt>class_filter=3,4,5</tt> would be
+used for low, medium, and high vegetation if the LAS file follows the
+usedstandard ASPRS class numbers.
+
+<p>
+The resolution should be suitable for computing digital elevation model
+which will be computed in the next steps.
+Once you decided on the resolution, you can use the 2D raster to set the
+computational region extent and resolution:
+
+<div class="code"><pre>
+g.region raster=points_n -p3
+</pre></div>
+
+<tt>class_filter=2</tt> is used to limit 
+
+<div class="code"><pre>
+r.in.lidar input=points.las output=ground_mean method=mean class_filter=2
+</pre></div>
+
+The following steps are not necessary if the point density is high
+enough to fill the raster continuously.
+
+<p>
+Convert the raster to vector point resulting in a decimated point cloud:
+
+<div class="code"><pre>
+v.to.rast input=ground_mean type=point output=ground_decimated use=z
+</pre></div>
+
+Interpolate the ground surface from the decimated ground points:
+
+<div class="code"><pre>
+v.surf.rst input=ground_decimated elevation=ground
+</pre></div>
+
+Now we need to determine upper vertical limit for the 3D raster
+(the top value from <tt>g.region -p3</tt>). This can be potentially
+done with lower resolution. The <b>-d</b> flag ensures that the ground
+raster will be used in its actual resolution regardless of the
+resolution of the output.
+
+<div class="code"><pre>
+r.in.lidar input=points.las method=max output=veg_max class_filter=3,4,5 base_raster=ground -d
+</pre></div>
+
+With that, we can finally set up the 3D extent and resolution:
+
+<div class="code"><pre>
+g.region rast=secref b=0 t=40 res=1 res3=1 -p3
+</pre></div>
+
+Note that the 2D and 3D resolutions are separate so that user can
+perform the 2D calculations on a finer resolution than the 3D
+calculations. The vertical resolution can be and often is set to a
+different value as well. Here we use the same value for all resolutions
+for simplicity.
+
+<p>
+Finally, we perform the 3D binning where we count number of points per
+cell (voxel):
+
+<div class="code"><pre>
+r3.in.lidar input=points.las n=n class_filter=3,4,5 base_raster=ground -d
+</pre></div>
+
+
 <h2>SEE ALSO</h2>
 
 <em>
@@ -92,6 +184,7 @@
 <a href="g.region.html">g.region</a>
 </em>
 
+
 <h2>REFERENCES</h2>
 
 <ul>