[GRASS-SVN] r36583 - grass/branches/develbranch_6/vector/v.surf.idw
svn_grass at osgeo.org
svn_grass at osgeo.org
Fri Apr 3 12:40:07 EDT 2009
Author: neteler
Date: 2009-04-03 12:40:07 -0400 (Fri, 03 Apr 2009)
New Revision: 36583
Modified:
grass/branches/develbranch_6/vector/v.surf.idw/description.html
Log:
sites -> points; explain layer=o for z geometry
Modified: grass/branches/develbranch_6/vector/v.surf.idw/description.html
===================================================================
--- grass/branches/develbranch_6/vector/v.surf.idw/description.html 2009-04-03 16:39:24 UTC (rev 36582)
+++ grass/branches/develbranch_6/vector/v.surf.idw/description.html 2009-04-03 16:40:07 UTC (rev 36583)
@@ -21,36 +21,41 @@
<H2>NOTES</H2>
<p>
-The amount of memory used by this program is related to the
-number of sites in the current region. If the vector point map is
+The amount of memory used by this program is related to the number
+of vector points in the current region. If the vector point map is
very dense (i.e., contains many data points), the program may
not be able to get all the memory it needs from the
system. The time required to execute is related to the
resolution of the current region, after an initial delay
-determined by the time taken to read the input sites file.<p>
+determined by the time taken to read the input vector points map.</p>
+<p>
+To read and interpolate from the elevation co-ordinates as 3rd dimension
+of the vector geometry, use <em>layer=0</em>. In this case no <em>column</em>
+parameter has to be specified.</p>
+
<P>
If the user has a mask set, then interpolation is only done
for those cells that fall within the mask. However, all
-sites in the current region are used even
-if they fall outside the mask. Sites outside the current
+vector points in the current region are used even
+if they fall outside the mask. Vector points outside the current
region are not used in the interpolation. A larger region may
be set and a mask used to limit interpolation to a smaller area
-if it is desired to use sites from outside the region in the
+if it is desired to use vector points from outside the region in the
interpolation. The <em>-n</em> flag may also be used to
achieve a similar result.</p>
<p>
-If more than <EM>count</EM> sites fall into one target raster cell,
+If more than <EM>count</EM> points fall into one target raster cell,
the mean of all the site values will determine the cell value (unless
the -n flag is specifed, in which case only the <EM>count</EM>
-sites closest to the centre of the cell will be interpolated).</p>
+points closest to the centre of the cell will be interpolated).</p>
<P>
The <EM>power=</EM> parameter defines an exponential distance weight.
Greater values assign greater influence to values closer to the
point to be interpolated. The interpolation function peaks sharply over
-the given data points for 0 < <EM>p</EM> < 1 and more smoothly for
+the given data points for 0 < <EM>p</EM> < 1 and more smoothly for
larger values. The default value for the power parameter is 2.
</p>
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