[GRASS-SVN] r55964 - grass-addons/grass7/raster/r.geomorphon

Tue Apr 23 19:59:59 PDT 2013

Author: hamish
Date: 2013-04-23 19:59:59 -0700 (Tue, 23 Apr 2013)
New Revision: 55964

Modified:
   grass-addons/grass7/raster/r.geomorphon/r.geomorphon.html
Log:
linewrap, 'last changed..'

Modified: grass-addons/grass7/raster/r.geomorphon/r.geomorphon.html
===================================================================

--- grass-addons/grass7/raster/r.geomorphon/r.geomorphon.html	2013-04-24 02:56:28 UTC (rev 55963)
+++ grass-addons/grass7/raster/r.geomorphon/r.geomorphon.html	2013-04-24 02:59:59 UTC (rev 55964)
@@ -1,3 +1,57 @@
+<h2>DESCRIPTION</h2>
+
+<center>
+<h3>What is geomorphon:</h3>
+<img src="geomorphon.png" border="1"><br>
+</center>
+
+<p> Geomorphon is a new concept of presentation and analysis of terrain
+forms. This concept utilises 8-tuple pattern of the visibility
+neighbourhood  and breaks well known limitation of standard calculus
+approach where all terrain forms cannot be detected in a single window
+size. The pattern arises from a comparison of a focus pixel with its eight
+neighbors starting from the one located to the east and continuing
+counterclockwise  producing ternary operator. For example, a tuple
+{+,-,-,-,0,+,+,+} describes one possible pattern of relative measures
+{higher, lower, lower, lower, equal, higher, higher, higher} for pixels
+surrounding the focus pixel. It is important to stress that the visibility
+neighbors are <b>not necessarily an immediate neighbors</b> of the focus
+pixel in the grid, but the pixels determined from <b>the line-of-sight</b>
+principle along the eight principal directions. This principle relates
+surface relief and horizontal distance by means of so-called zenith and
+nadir angles along the eight principal compass directions. The ternary
+operator converts the information contained in all the pairs of zenith and
+nadir angles into the ternary pattern (8-tuple). The result depends on the
+values of two parameters: search radius (L) and relief threshold (d). The
+search radius is the maximum allowable distance for calculation of zenith
+and nadir angles. The relief threshold is a minimum value of difference
+between  LOSs angle (zenith and nadir) that is considered significantly
+different from the horizon. Two lines-of-sight are necessary due to zenith
+LOS only, does not detect positive forms correctly.
+
+<p> There are 38 = 6561 possible ternary patterns (8-tuplets). However by
+eliminating all patterns that are results of either rotation or reflection
+of other patterns wa set of 498 patterns remain referred as geomorphons.
+This is a comprehensive and exhaustive set of idealized landforms that are
+independent of the size, relief, and orientation of the actual landform.
+
+<p> Form recognition depends on two free parameters: <b>Search radius</b>
+and <b>flatness threshold</b>. Using larger values of L and is tantamount
+to terrain classification from a higher and wider perspective, whereas
+using smaller values of L and is tantamount to terrain classification from
+a local point of view. A character of the map depends on the value of L.
+Using small value of L results in the map that correctly identifies
+landforms if their size is smaller than L; landforms having larger sizes
+are broken down into components. Using larger values of L allows
+simultaneous identification of landforms on variety of sizes in expense of
+recognition smaller, second-order forms. There are two addational
+parameters: <b>skip radius</b> used to eliminate impact of small
+irregularities. On the contrary <b>flatness distance</b> eliminates the
+impact of very high distance (in meters) of search radius which may not
+detect elevation difference if this is at very far distance. Important
+especially with low resolution DEMS.
+
+
 <h2>OPTIONS</h2>
 <DL>
 <DT><b>-m</b></DT>
@@ -42,25 +96,28 @@
 <DD>returns lenght of the shorter side of the bounding box rectangle calculated for geomorphon rotated to fit lest square line.</DD>
 
 
-<h2>DESCRIPTION</h2>
-<center>
-<h3>What is geomorphon:</h3>
-<img src="geomorphon.png" border="1"><br>
-</center>
-<p>Geomorphon is a new concept of presentation and analysis of terrain forms. This concept utilises 8-tuple pattern of the visibility neighbourhood  and breaks well known limitation of standard calculus approach where all terrain forms cannot be detected in a single window size. The pattern arises from a comparison of a focus pixel with its eight neighbors starting from the one located to the east and continuing counterclockwise  producing ternary operator. For example, a tuple {+,-,-,-,0,+,+,+} describes one possible pattern of relative measures {higher, lower, lower, lower, equal, higher, higher, higher} for pixels surrounding the focus pixel. It is important to stress that the visibility neighbors are <b>not necessarily an immediate neighbors</b> of the focus pixel in the grid, but the pixels determined from <b>the line-of-sight</b> principle along the eight principal directions. This principle relates surface relief and horizontal distance by means of so-called zenith an
 d nadir angles along the eight principal compass directions. The ternary operator converts the information contained in all the pairs of zenith and nadir angles into the ternary pattern (8-tuple). The result depends on the values of two parameters: search radius (L) and relief threshold (d). The search radius is the maximum allowable distance for calculation of zenith and nadir angles. The relief threshold is a minimum value of difference between  LOSs angle (zenith and nadir) that is considered significantly different from the horizon. Two lines-of-sight are necessary due to zenith LOS only, does not detect positive forms correctly.
-<p>There are 38 = 6561 possible ternary patterns (8-tuplets). However by eliminating all patterns that are results of either rotation or reflection of other patterns wa set of 498 patterns remain referred as geomorphons. This is a comprehensive and exhaustive set of idealized landforms that are independent of the size, relief, and orientation of the actual landform.
-<p>Form recognition depends on two free parameters: <b>Search radius</b> and <b>flatness threshold</b>. Using larger values of L and is tantamount to terrain classification from a higher and wider perspective, whereas using smaller values of L and is tantamount to terrain classification from a local point of view. A character of the map depends on the value of L. Using small value of L results in the map that correctly identifies landforms if their size is smaller than L; landforms having larger sizes are broken down into components. Using larger values of L allows simultaneous identification of landforms on variety of sizes in expense of recognition smaller, second-order forms. There are two addational parameters: <b>skip radius</b> used to eliminate impact of small irregularities. On the contrary <b>flatness distance</b> eliminates the impact of very high distance (in meters) of search radius which may not detect elevation difference if this is at very far distance. Import
 ant especially with low resolution DEMS.
-
 <h2>NOTES</h2>
 
-From computational point of view there are no limitations of input DEM and free parameters used in calculation. However in practice there are some issues on DEM resolution and search radius. Low resolution DEM especially above 1 km per cell requires smaller than default flatness threshold. On the other hand, only forms with high local elevation difference will be detected correctly. It results form fact that on very high distance (of order of kilometers or higher) even relatively high elevation difference will be recognized as flat. For example at the distance of 8 km (8 cells with 1 km resolution DEM) an relative elevation difference of at least 136 m is required to be noticed as non-flat. Flatness distance threshold may be helpful to avoid this problem.
+From computational point of view there are no limitations of input DEM and
+free parameters used in calculation. However in practice there are some
+issues on DEM resolution and search radius. Low resolution DEM especially
+above 1 km per cell requires smaller than default flatness threshold. On
+the other hand, only forms with high local elevation difference will be
+detected correctly. It results form fact that on very high distance (of
+order of kilometers or higher) even relatively high elevation difference
+will be recognized as flat. For example at the distance of 8 km (8 cells
+with 1 km resolution DEM) an relative elevation difference of at least 136
+m is required to be noticed as non-flat. Flatness distance threshold may
+be helpful to avoid this problem.
 
+
 <h2>SEE ALSO</h2>
 
 <em>
 <a href="r.param.scale.html">r.param.scale</a>
 </em>
 
+
 <h2>REFERENCES</h2>
 
 <ul>
@@ -68,5 +125,9 @@
 <li>Jasiewicz, J., Stepinski, T.,  2013, Geomorphons - a pattern recognition approach to classification and mapping of landforms, Geomorphology, vol. 182, 147-156</li>
 </ul>
 
-<h2>AUTHOR</h2>
+
+<h2>AUTHORS</h2>
 Jarek Jasiewicz, Tomek Stepinski (merit contribution)
+
+<p>
+<i>Last changed: $Date$</i>

