[GRASS-SVN] r37199 -
grass/branches/releasebranch_6_4/vector/v.vol.rst
svn_grass at osgeo.org
svn_grass at osgeo.org
Tue May 12 14:30:26 EDT 2009
Author: epatton
Date: 2009-05-12 14:30:26 -0400 (Tue, 12 May 2009)
New Revision: 37199
Modified:
grass/branches/releasebranch_6_4/vector/v.vol.rst/description.html
Log:
Added warning about lack of Lat/Long coordinate support; misc. cleanups, merge from devbr6: r37198
Modified: grass/branches/releasebranch_6_4/vector/v.vol.rst/description.html
===================================================================
--- grass/branches/releasebranch_6_4/vector/v.vol.rst/description.html 2009-05-12 18:11:26 UTC (rev 37198)
+++ grass/branches/releasebranch_6_4/vector/v.vol.rst/description.html 2009-05-12 18:30:26 UTC (rev 37199)
@@ -1,68 +1,68 @@
<h2>DESCRIPTION</h2>
-<p><i>v.vol.rst</i> interpolates values to a 3-dimensional raster map from
+<p><em>v.vol.rst</em> interpolates values to a 3-dimensional raster map from
3-dimensional point data (e.g. temperature, rainfall data from climatic
stations, concentrations from drill holes etc.) given in a 3-D vector
-point file named <i>input</i>. The size of the output
-3d raster map <i>elev</i> is given by the current 3D region. Sometimes, the
+point file named <b>input</b>. The size of the output
+3d raster map <b>elev</b> is given by the current 3D region. Sometimes, the
user
may want to get a 2-D map showing a modelled phenomenon at a
-crossection surface. In that case, <i>cellinp</i> and <i>cellout</i>
-options must be specified and then the output 2D raster map <i>cellout</i>
-contains crossection of the interpolated volume with a surface
-defined by <i>cellinp</i>
+crossection surface. In that case, <b>cellinp</b> and <b>cellout</b>
+options must be specified, with the output 2D raster map <b>cellout</b>
+containing the crossection of the interpolated volume with a surface
+defined by <b>cellinp</b>
2D raster map. As an option, simultaneously with interpolation,
geometric parameters of the interpolated
phenomenon can be computed (magnitude of gradient, direction of
gradient defined by horizontal and vertical angles), change of gradient,
Gauss-Kronecker curvature, or mean curvature). These geometric
parameteres are saved as
-3d raster maps <i>gradient, aspect1, aspect2, ncurv, gcurv, mcurv</i>,
+3d raster maps <b>gradient, aspect1, aspect2, ncurv, gcurv, mcurv</b>,
respectively.
</p>
-<p>At first, data points are checked for identical points and points
-that are closer to each other than given <i>dmin</i> are removed.
-Parameters <i>wmult</i> and <i>zmult</i> allow user to re-scale
+<p>At first, data points are checked for identical positions and points
+that are closer to each other than given <b>dmin</b> are removed.
+Parameters <b>wmult</b> and <b>zmult</b> allow the user to re-scale
the w-values and z-coordinates of the point data (useful e.g. for
transformation of elevations given in feet to meters, so that the
proper values of gradient and curvatures can be computed).
-Rescaling of z-coordinates (<i>zmult</i>) is also needed when the distances
+Rescaling of z-coordinates (<b>zmult</b>) is also needed when the distances
in vertical direction are much smaller than the horizontal
-distances, if that is the case, the value of <i>zmult</i>
+distances; if that is the case, the value of <b>zmult</b>
should be selected so that the vertical and horizontal distances
have about the same magnitude.
</p>
<p>Regularized spline with tension method is used in the interpolation.
-The <i>tension</i> parameter controls the distance over which
+The <b>tension</b> parameter controls the distance over which
each given point influences the resulting volume (with very high tension,
each point influences only its close neighborhood and the volume goes
rapidly to trend between the points).
Higher values of tension parameter reduce the overshoots that
can appear in volumes with rapid change of gradient. For noisy data, it
-is possible to define a global smoothing parameter, <i>smooth</i>.
+is possible to define a global smoothing parameter, <b>smooth</b>.
With the
-smoothing parameter set to zero (<i>smooth=0</i>) the resulting volume
+smoothing parameter set to zero (<b>smooth=0</b>) the resulting volume
passes exactly through the data points.
-When smoothing is used, it is possible to output a vector map <i>devi</i>
+When smoothing is used, it is possible to output a vector map <b>devi</b>
containing deviations of the resulting volume from the given data. </p>
-<p>User can define a 2D raster map named <i>maskmap</i>, which will
+<p>The user can define a 2D raster map named <b>maskmap</b>, which will
be used as a mask. The interpolation is skipped for 3-dimensional cells
-whose 2-dimensional projection has zero value in mask. Zero values will
+whose 2-dimensional projection has a zero value in the mask. Zero values will
be assigned to these cells in all output 3d raster maps. </p>
<p>If the number of given points is greater than 700, segmented
processing is used. The region is split into 3-dimensional "box"
-segments, each having less than <i>segmax</i> points and interpolation
+segments, each having less than <b>segmax</b> points and interpolation
is performed on each segment of the region. To ensure the smooth
-connection of segments the interpolation function for each segment is
-computed using the points in given segment
+connection of segments, the interpolation function for each segment is
+computed using the points in the given segment
and the points in its neighborhood. The minimum number of points taken
-for interpolation is controlled by <i>npmin</i> , the value of which
+for interpolation is controlled by <b>npmin</b> , the value of which
must
-be larger than <i>segmax</i> and less than 700. This limit of 700 was
+be larger than <b>segmax</b> and less than 700. This limit of 700 was
selected to ensure the numerical stability and efficiency of the
algorithm. </p>
-<h3>EXAMPLE</h3>
+<h2>EXAMPLES</h2>
<!-- TODO: find better data -->
Spearfish example (we simulate 3D soil range data):
@@ -116,7 +116,7 @@
<h3>SQL support</h3>
-Using the <em>where</em> parameter, the interpolation can be limited to use
+Using the <b>where</b> parameter, the interpolation can be limited to use
only a subset of the input vectors.
<div class="code"><pre>
@@ -129,7 +129,7 @@
Sometimes it can be difficult to figure out the proper values of
interpolation parameters. In this case, the user can use a
-crossvalidation procedure using <i>-c</i> flag (a.k.a. "jack-knife"
+crossvalidation procedure using <b>-c</b> flag (a.k.a. "jack-knife"
method) to find optimal parameters for given data. In this method,
every point in the input point file is temporarily excluded from the
computation and interpolation error for this point location is
@@ -140,7 +140,7 @@
<P>
<i>Example
- (<based on <a href="http://www.grassbook.org/data_menu2nd.phtml">Slovakia3d dataset</a>):</i>
+ (based on <a href="http://www.grassbook.org/data_menu2nd.phtml">Slovakia3d dataset</a>):</i>
<P>
<div class="code"><pre>
v.info -c precip3d
@@ -149,16 +149,16 @@
v.univar cvdevmap col=flt1 type=point
</pre></div>
-From the results, parameters have to be optimized. It is
+Based on these results, the parameters will have to be optimized. It is
recommended to plot the CV error as curve while modifying
the parameters.
<P>
-The best approach is to start with <em>tension</em>, <em>smooth</em>
-and <em>zmult</em> with rough steps, or to set <em>zmult</em> to a
+The best approach is to start with <b>tension</b>, <b>smooth</b>
+and <b>zmult</b> with rough steps, or to set <b>zmult</b> to a
constant somewhere between 30-60. This helps to find minimal RMSE
values while then finer steps can be used in all parameters. The
-reasonable range is <em>tension</em>=10...100,
-<em>smooth</em>=0.1...1.0, <em>zmult</em>=10...100.
+reasonable range is <b>tension</b>=10...100,
+<b>smooth</b>=0.1...1.0, <b>zmult</b>=10...100.
<p>
In <em>v.vol.rst</em> the tension parameter is much more sensitive to
changes than in <em>v.surf.rst</em>,
@@ -167,17 +167,24 @@
result, especially when the density of data are insufficient. Then
the optimal result found by CV is an oversmoothed surface.
+<h2>NOTES</h2>
+The vector points map must be a 3D vector map (x, y, z as geometry).
+The module <a href="v.in.db.html">v.in.db</a> can be used to generate
+a 3D vector map from a table containing x,y,z columns.
-<h3>Further notes</h3>
+Also, the input data should be in a projected coodinate system, such as
+Univeral Transverse Mercator. The module does not appear to have support for
+geographic (Lat/Long) coordinates as of May 2009.
+
<p><em>v.vol.rst</em> uses regularized spline with tension for
interpolation from point data (as described in Mitasova and Mitas,
1993). The implementation has an improved segmentation procedure based
-on Oct-trees which enhances
-the efficiency for large data sets. </p>
-<p>Geometric parameters - magnitude of gradient (<i>gradient</i>),
-horizontal (<i>aspect1</i>) and vertical (<i>aspect2) </i>aspects,
-change of gradient (<i>ncurv</i>), Gauss-Kronecker (<i>gcurv</i>) and
-mean curvatures (<i>mcurv</i>) are computed directly from the
+on Oct-trees which enhances the efficiency for large data sets. </p>
+
+<p>Geometric parameters - magnitude of gradient (<b>gradient</b>),
+horizontal (<b>aspect1</b>) and vertical (<b>aspect2) </b>aspects,
+change of gradient (<b>ncurv</b>), Gauss-Kronecker (<b>gcurv</b>) and
+mean curvatures (<b>mcurv</b>) are computed directly from the
interpolation function so that the important relationships between
these parameters are preserved. More information on these parameters
can be found in Mitasova et al., 1995 or Thorpe, 1979.</p>
@@ -185,64 +192,34 @@
<p>The program gives warning when significant overshoots appear and
higher tension should be used. However, with tension too high the
resulting volume will have local maximum in each given point
-and everywhere else the volume goes rapidly to trend. With smoothing
-parameter greater than zero the volume
-will not pass through the data points and the higher the parameter the
-closer
-the volume will be to the trend. For theory on smoothing with splines
-see Talmi and Gilat, 1977 or Wahba, 1990. </p>
+and everywhere else the volume goes rapidly to trend. With a smoothing
+parameter greater than zero, the volume will not pass through the data
+points and the higher the parameter the closer the volume will be to the
+trend. For theory on smoothing with splines see Talmi and Gilat, 1977 or Wahba, 1990. </p>
+
<p>If a visible connection of segments appears, the program should be
-rerun with higher <i>npmin</i> to get more points from the
+rerun with higher <b>npmin</b> to get more points from the
neighborhood of given segment. </p>
-<p>If the number of points in a vector map is less then 400, <i>segmax</i>
+
+<p>If the number of points in a vector map is less than 400, <b>segmax</b>
should be set to 400 so that segmentation is not performed when it is
not necessary. </p>
-<p>The program gives warning when user wants to interpolate outside the
-"box" given by minimum and maximum coordinates in vector map, zoom into
-the area where the points are is suggested in this case. </p>
-<p>For large data sets (thousands of data points) it is suggested to
+
+<p>The program gives a warning when the user wants to interpolate outside the
+"box" given by minimum and maximum coordinates in the input vector map.
+To remedy this, zoom into the area encompassing the input vector data points.
+</p>
+
+<p>For large data sets (thousands of data points), it is suggested to
zoom into a smaller representative area and test whether the parameters
chosen (e.g. defaults) are appropriate. </p>
-<p>The user must run <i>g.region</i> before the program to set the
+
+<p>The user must run <em>g.region</em> before the program to set the
3D region for interpolation. </p>
-<h2>NOTES</h2>
-The vector points map must be a 3D vector map (x, y, z as geometry).
-The module <a href="v.in.db.html">v.in.db</a> can be used to generate
-a 3D vector map from a table containing x,y,z columns.
-
<h2>BUGS</h2>
<b>devi</b> file is written as 2D and deviations are not written as attributes.
-<h2>SEE ALSO</h2>
-<a href="g.region.html">g.region</a>,
-<a href="v.in.ascii.html">v.in.ascii</a>,
-<a href="r3.mask.html">r3.mask</a>,
-<a href="v.in.db.html">v.in.db</a>,
-<a href="v.surf.rst.html">v.surf.rst</a>,
-<a href="v.univar.html">v.univar</a>
-
-<h2>AUTHOR</h2>
-<p>Original version of program (in FORTRAN) and GRASS enhancements: <br>
-Lubos Mitas, NCSA, University of Illinois at Urbana-Champaign,
-Illinois, USA, since 2000 at Department of Physics,
-North Carolina State University, Raleigh, USA
-<a href="mailto:lubos_mitas at ncsu.edu">lubos_mitas at ncsu.edu</a><br>
-Helena Mitasova, Department of Marine, Earth and Atmospheric Sciences,
-North Carolina State University, Raleigh, USA, <a
- href="mailto:hmitaso at unity.ncsu.edu">hmitaso at unity.ncsu.edu</a></p>
-<p>Modified program (translated to C, adapted for GRASS, new
-segmentation procedure): <br>
-Irina Kosinovsky, US Army CERL, Champaign, Illinois, USA <br>
-Dave Gerdes, US Army CERL, Champaign, Illinois, USA </p>
-<p>Modifications for g3d library, geometric parameters,
-cross-validation, deviations: <br>
-Jaro Hofierka, Department of Geography and Regional Development,
-University of Presov, Presov, Slovakia, <a
- href="MAILTO:hofierka at fhpv.unipo.sk">hofierka at fhpv.unipo.sk</a>, <a
- href="http://www.geomodel.sk">http://www.geomodel.sk</a> <br>
- </p>
-
<h2>REFERENCES</h2>
<p>Hofierka J., Parajka J., Mitasova H., Mitas L., 2002, Multivariate
Interpolation of Precipitation Using Regularized Spline with Tension.
@@ -291,4 +268,34 @@
<p>Thorpe, J. A. (1979): Elementary Topics in Differential Geometry.
Springer-Verlag, New York, pp. 6-94.</p>
+<h2>SEE ALSO</h2>
+<a href="g.region.html">g.region</a>,
+<a href="v.in.ascii.html">v.in.ascii</a>,
+<a href="r3.mask.html">r3.mask</a>,
+<a href="v.in.db.html">v.in.db</a>,
+<a href="v.surf.rst.html">v.surf.rst</a>,
+<a href="v.univar.html">v.univar</a>
+
+<h2>AUTHOR</h2>
+<p>Original version of program (in FORTRAN) and GRASS enhancements: <br>
+Lubos Mitas, NCSA, University of Illinois at Urbana-Champaign,
+Illinois, USA, since 2000 at Department of Physics,
+North Carolina State University, Raleigh, USA
+<a href="mailto:lubos_mitas at ncsu.edu">lubos_mitas at ncsu.edu</a><br>
+Helena Mitasova, Department of Marine, Earth and Atmospheric Sciences,
+North Carolina State University, Raleigh, USA, <a
+ href="mailto:hmitaso at unity.ncsu.edu">hmitaso at unity.ncsu.edu</a></p>
+<p>Modified program (translated to C, adapted for GRASS, new
+segmentation procedure): <br>
+Irina Kosinovsky, US Army CERL, Champaign, Illinois, USA <br>
+Dave Gerdes, US Army CERL, Champaign, Illinois, USA </p>
+<p>Modifications for g3d library, geometric parameters,
+cross-validation, deviations: <br>
+Jaro Hofierka, Department of Geography and Regional Development,
+University of Presov, Presov, Slovakia, <a
+ href="MAILTO:hofierka at fhpv.unipo.sk">hofierka at fhpv.unipo.sk</a>, <a
+ href="http://www.geomodel.sk">http://www.geomodel.sk</a> <br>
+ </p>
+
+
<p><i>Last changed: $Date$</i> </p>
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