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<div class="moz-cite-prefix">On 6/16/17 3:20 PM, Markus Metz wrote:<br>
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On Fri, Jun 16, 2017 at 11:28 AM, Paulo van Breugel <<a
href="mailto:p.vanbreugel@gmail.com"
moz-do-not-send="true">p.vanbreugel@gmail.com</a>>
wrote:<br>
><br>
> Hi devs, can anybody tell how v.surf.bspline computes
the point density and mean distance.<br>
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point density is the number of points divided by the size of
the bounding box of the points<br>
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mean distance is the square root of the size of the bounding box
divided by the number of points<br>
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> And what is the unit, pixels, as also used for length
spline steps or meters?<br>
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<div>the unit is map unit, you can then figure out a
reasonable resolution (in map units) for the current region
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I think it would be good to add your explanation to the manual page.
I was trying to come up with a text, but then I realized there is
still some ambiguity left.<br>
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According to the manual page, the ns_step and ew_step parameters are
in pixels (which I would interpret as 'number of pixels'). However,
the example of 'Basic interpolation and raster output with a longer
spline step' in the manual page talks about mapping units.<br>
<br>
<tt>v.surf.bspline input=point_vector raster=interpolate_surface
ew_step=25 ns_step=25</tt><tt><br>
</tt><tt>A bilinear spline interpolation will be done with a spline
step length of 25 map units. </tt><tt><br>
</tt><br>
So if the region's resolution is 100 meter, is the ns_step and
ew_step 2500 meter (25 pixels) or 25 meters? The former would be
more conform common practice in grass I think.<br>
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<div>Markus M<br>
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<div>><br>
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