[GRASS-SVN] r31361 - grass/branches/develbranch_6/raster/r.flow
svn_grass at osgeo.org
svn_grass at osgeo.org
Thu May 15 15:30:26 EDT 2008
Author: epatton
Date: 2008-05-15 15:30:26 -0400 (Thu, 15 May 2008)
New Revision: 31361
Modified:
grass/branches/develbranch_6/raster/r.flow/description.html
Log:
Backported html edits from TRUNK; r31360
Modified: grass/branches/develbranch_6/raster/r.flow/description.html
===================================================================
--- grass/branches/develbranch_6/raster/r.flow/description.html 2008-05-15 19:28:51 UTC (rev 31360)
+++ grass/branches/develbranch_6/raster/r.flow/description.html 2008-05-15 19:30:26 UTC (rev 31361)
@@ -1,62 +1,64 @@
-<H2>DESCRIPTION</H2>
+<h2>DESCRIPTION</h2>
This program generates flowlines using a combined raster-vector
approach (see <a href="http://skagit.meas.ncsu.edu/~helena/gmslab/papers/hmg.rev1.ps">Mitasova and
-Hofierka 1993</A> and <a href="http://skagit.meas.ncsu.edu/~helena/gmslab/papers/ijgis.html">Mitasova et
-al. 1995)</A>) from an input elevation raster map <I>elevin</I>
+Hofierka 1993</a> and <a href="http://skagit.meas.ncsu.edu/~helena/gmslab/papers/ijgis.html">Mitasova et
+al. 1995</a>) from an input elevation raster map <b>elevin</b>
(integer or floating point), and optionally an input aspect raster map
-<I>aspin</I> and/or an input barrier raster map <I>barin</I>. There are
+<b>aspin</b> and/or an input barrier raster map <b>barin</b>. There are
three possible output maps which can be produced in any combination
-simultaneously: a vector map <I>flout</I> of flowlines, a raster map
-<I>lgout</I> of flowpath lengths, and a raster map <I>dsout</I> of flowline
+simultaneously: a vector map <b>flout</b> of flowlines, a raster map
+<b>lgout</b> of flowpath lengths, and a raster map <b>dsout</b> of flowline
densities (which are equal upslope contributed areas per unit width, when
multiplied by resolution).
+<p>
+Aspect used for input must follow the same rules as aspect computed
+in other GRASS programs (see <a href="v.surf.rst.html">v.surf.rst</a>
+or <a href="r.slope.aspect.html">r.slope.aspect</a>).
+<p>
-<P>Aspect used for input must follow the same rules as aspect computed
-in other GRASS programs (see <A HREF="v.surf.rst.html">v.surf.rst</A>
-or <A HREF="r.slope.aspect.html">r.slope.aspect</A>).
-
-<P>Flowline output is given in a vector map <I>flout</I>, (flowlines generated
+Flowline output is given in a vector map <b>flout</b>, (flowlines generated
downhill). The line segments of flowline vectors have endpoints on edges
of a grid formed by drawing imaginary lines through the centers of the
cells in the elevation map. Flowlines are generated from each cell downhill
-by default; they can be generated uphill using the flag <I>-u</I>. A flowline
+by default; they can be generated uphill using the flag <b>-u</b>. A flowline
stops if its next segment would reverse the direction of flow (from up
to down or vice-versa), cross a barrier, or arrive at a cell with undefined
-elevation or aspect. Another option, <I>skip</I>=val, indicates that only
-the flowlines from every val-th cell are to be included in <I>flout</I>.
-The default <I>skip</I> is max(1, <rows in elevin>/50, <cols in elevin>/50).
-A high <I>skip</I> usually speeds up processing time and often improves
-the readability of a visualization of <I>flout</I>.
+elevation or aspect. Another option, <b>skip</b>=val, indicates that only
+the flowlines from every val-th cell are to be included in <b>flout</b>.
+The default <b>skip</b> is max(1, <rows in elevin>/50, <cols in elevin>/50).
+A high <b>skip</b> usually speeds up processing time and often improves
+the readability of a visualization of <b>flout</b>.
+<p>
-<P>Flowpath length output is given in a raster map <I>lgout</I>. The value
+Flowpath length output is given in a raster map <b>lgout</b>. The value
in each grid cell is the sum of the planar lengths of all segments of the
-flowline generated from that cell. If the flag <I>-3</I> is given, elevation
+flowline generated from that cell. If the flag <b>-3</b> is given, elevation
is taken into account in calculating the length of each segment.
-<P>Flowline density downhill or uphill output is given in a raster map
-<I>dsout.</I> The value in each grid cell is the number of flowlines which
+<p>Flowline density downhill or uphill output is given in a raster map
+<b>dsout.</b> The value in each grid cell is the number of flowlines which
pass through that grid cell, that means the number of flowlines from the
entire map which have segment endpoints within that cell.
-With the <em>-m</em> flag less memory is used as aspect at each cell is computed
+With the <b>-m</b> flag less memory is used as aspect at each cell is computed
on the fly. This option incurs a severe performance penalty. If this flag is given,
the aspect input map (if any) will be ignored.
<!-- doesn't exist
-<P><B>-M</B> Use a fixed size memory and utilize page-swapping to handle
+<p><b>-M</b> Use a fixed size memory and utilize page-swapping to handle
large input files. This option incurs a severe performance penalty but
is the only way to handle arbitrarily-large data files. If this flag is
-given, the <B>-m</B> flag will be ignored.
+given, the <b>-m</b> flag will be ignored.
-->
-The <em>barin</em> parameter is a raster map name with non-zero
+The <b>barin</b> parameter is a raster map name with non-zero
values representing barriers as input.
-<H2>NOTES</H2>
+<h2>NOTES</h2>
For best results, use input elevation maps with high precision units (e.g.,
centimeters) so that flowlines do not terminate prematurely in flat areas.
To prevent the creation of tiny flowline segments with imperceivable changes
@@ -67,7 +69,7 @@
close" for that axis. Note that this distance (the so-called "quantization
error") is about 1-2% of the resolution on maps with square cells.
-<P>The values in length maps computed using the <B>-u</B> flag represent
+<p>The values in length maps computed using the <b>-u</b> flag represent
the distances from each cell to an upland flat or singular point. Such
distances are useful in water erosion modeling for computation of the LS
factor in the standard form of USLE. Uphill flowlines merge on ridge lines;
@@ -75,7 +77,7 @@
dispersed waterflow can be simulated. The density map can be used for the
extraction of ridge lines.
-<P>Computing the flowlines downhill simulates the actual flow (also known
+<p>Computing the flowlines downhill simulates the actual flow (also known
as the raindrop method). These flowlines tend to merge in valleys; they
can be used for localization of areas with waterflow accumulation and for
the extraction of channels. The downslope flowline density multiplied by
@@ -85,46 +87,44 @@
water erosion for the computation of the unit stream power based LS factor
or sediment transport capacity.
-<P>The program has been designed for modeling erosion on hillslopes and
+<p>The program has been designed for modeling erosion on hillslopes and
has rather strict conditions for ending flowlines. It is therefore not
very suitable for the extraction of stream networks or delineation of watersheds
unless a DEM without pits or flat areas is available
(<a href=r.fill.dir.html>r.fill.dir</a> can be used to fill pits).
-<P> To label the vector flowlines automatically, the user can use
+<p> To label the vector flowlines automatically, the user can use
<a href=v.category.html>v.category</a> (add categories).
-<H2>Algorithm background</H2>
+<h3>Algorithm background</h3>
-<P>1. Construction of flow-lines (slope-lines): <em>r.flow</em> uses an original
+<p>1. Construction of flow-lines (slope-lines): <em>r.flow</em> uses an original
vector-grid algorithm which uses an infinite number of directions between
0.0000... and 360.0000... and traces the flow as a line (vector) in the
direction of gradient (rather than from cell to cell in one of the 8
directions = D-infinity algorithm). They are traced in any direction using
aspect (so there is no limitation to 8 directions here). The D8 algorithm
produces zig-zag lines. The value in the outlet is very similar for both
-r.flow and r.flowmd (GRASS 5 only) algorithms (because it is
+<em>r.flow</em> and <em>r.flowmd</em> (GRASS 5 only) algorithms (because it is
essentially the watershed area), however the spatial distribution of flow,
especially on hillslopes is quite different. It is still a 1D flow routing
so the dispersal flow is not accurately described, but still better than D8.
-<P>2. Computation of contributing areas: <em>r.flow</em> uses a single flow
+<p>2. Computation of contributing areas: <em>r.flow</em> uses a single flow
algorithm, i.e. all flow is transported to a single cell downslope.
-<H2>FURTHER NOTES</H2>
-
-<b>Differences between <em>r.flow</em> and <em>r.flowmd</em></b>
+<h3><b>Differences between <em>r.flow</em> and <em>r.flowmd</em></b></h3>
<p>
<ol>
<li> <em>r.flow</em> has an option to compute slope and aspect internally thus making
-the program capable to process much larger data sets than r.flowmd. It has
+the program capable to process much larger data sets than <em>r.flowmd</em>. It has
also 2 additional options for handling of large data sets but it is not
known that they work properly.
<li> the programs handle the special cases when the flowline passes exactly
(or very close) through the grid vertices differently.
-<li> r.flowmd has the simplified multiple flow addition so the results are
+<li> <em>r.flowmd</em> has the simplified multiple flow addition so the results are
smoother.
</ol>
@@ -132,63 +132,62 @@
support as large data sets as <em>r.flow</em>.
-<H2>DIAGNOSTICS</H2>
+<h3>Diagnostics</h3>
-<P>"ERROR: r.flow: " input " file's resolution differs from current" region
+<p>"ERROR: r.flow: " input " file's resolution differs from current" region
resolution
-<P>The resolutions of all input files and the current region must match.
+<p>The resolutions of all input files and the current region must match.
-<P>"ERROR: r.flow: resolution too unbalanced (" val " x " val ")" The difference
+<p>"ERROR: r.flow: resolution too unbalanced (" val " x " val ")" The difference
in length between the two axes of a grid cell is so great that quantization
error is larger than one of the dimensions. Resample the map and try again.
+<h2>REFERENCES</h2>
-<H2>SEE ALSO</H2>
-
-<A HREF="r.basins.fill.html">r.basins.fill</A>,
-<A HREF="r.drain.html">r.drain</A>,
-<A HREF="r.fill.dir.html">r.fill.dir</A>,
-<A HREF="r.water.outlet.html">r.water.outlet</A>,
-<A HREF="r.watershed.html">r.watershed</A>,
-<A HREF="v.category.html">v.category</A>,
-<A HREF="v.to.rast.html">v.to.rast</A>
-
-
-<H2>AUTHORS</H2>
-
-<P><I>Original version of program:</I>
-<BR>Maros Zlocha and Jaroslav Hofierka, Comenius University, Bratislava,
-Slovakia,
-
-<P><I>The current version of the program (adapted for GRASS5.0)</I>:
-<BR>Joshua Caplan, Mark Ruesink, Helena Mitasova, University of Illinois
-at Urbana-Champaign with support from USA CERL.<br>
-<a href=http://skagit.meas.ncsu.edu/~helena/gmslab/>GMSL/University of Illinois at
-Urbana-Champaign</a>
-
-<H2>REFERENCES</H2>
-
-<P>Mitasova, H., L. Mitas, 1993, Interpolation by regularized spline with
+<p>Mitasova, H., L. Mitas, 1993, Interpolation by regularized spline with
tension : I. Theory and implementation. Mathematical Geology 25, p. 641-655.
-(<a href=http://skagit.meas.ncsu.edu/~helena/gmslab/papers/lmg.rev1.ps>online</A>)
+(<a href=http://skagit.meas.ncsu.edu/~helena/gmslab/papers/lmg.rev1.ps>online</a>)
-<P>Mitasova and Hofierka 1993 : Interpolation by Regularized Spline with
+<p>Mitasova and Hofierka 1993 : Interpolation by Regularized Spline with
Tension: II. Application to Terrain Modeling and Surface Geometry Analysis.
-Mathematical Geology 25(6), 657-669. (<a href=http://skagit.meas.ncsu.edu/~helena/gmslab/papers/hmg.rev1.ps>online</A>)
+Mathematical Geology 25(6), 657-669. (<a href=http://skagit.meas.ncsu.edu/~helena/gmslab/papers/hmg.rev1.ps>online</a>)
-<P>Mitasova, H., Mitas, L., Brown, W.M., Gerdes, D.P., Kosinovsky, I.,
+<p>Mitasova, H., Mitas, L., Brown, W.M., Gerdes, D.P., Kosinovsky, I.,
Baker, T., 1995: Modeling spatially and temporally distributed phenomena:
New methods and tools for GRASS GIS. International Journal of Geographical
Information Systems 9(4), 433-446.
-<P>Mitasova, H., J. Hofierka, M. Zlocha, L.R. Iverson, 1996, Modeling
+<p>Mitasova, H., J. Hofierka, M. Zlocha, L.R. Iverson, 1996, Modeling
topographic potential for erosion and deposition using GIS. Int. Journal of
Geographical Information Science, 10(5), 629-641. (reply to a comment to
this paper appears in 1997 in Int. Journal of Geographical Information
Science, Vol. 11, No. 6)
-<P>Mitasova, H.(1993): Surfaces and modeling. Grassclippings (winter and
+<p>Mitasova, H.(1993): Surfaces and modeling. Grassclippings (winter and
spring) p.18-19.
+<h2>SEE ALSO</h2>
+
+<a href="r.basins.fill.html">r.basins.fill</a>,
+<a href="r.drain.html">r.drain</a>,
+<a href="r.fill.dir.html">r.fill.dir</a>,
+<a href="r.water.outlet.html">r.water.outlet</a>,
+<a href="r.watershed.html">r.watershed</a>,
+<a href="v.category.html">v.category</a>,
+<a href="v.to.rast.html">v.to.rast</a>
+
+
+<h2>AUTHORS</h2>
+
+<p><i>Original version of program:</i>
+<br>Maros Zlocha and Jaroslav Hofierka, Comenius University, Bratislava,
+Slovakia,
+
+<p><i>The current version of the program (adapted for GRASS5.0)</i>:
+<br>Joshua Caplan, Mark Ruesink, Helena Mitasova, University of Illinois
+at Urbana-Champaign with support from USA CERL.<br>
+<a href=http://skagit.meas.ncsu.edu/~helena/gmslab/>GMSL/University of Illinois at
+Urbana-Champaign</a>
+
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