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Hi Ari, <br>
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Interesting result. It looks roughly right: pixels with only dark points in their surrounding window are dark and pixels with only light point in the window are light.
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However, it does seem that the legend used for pixels uses different interval values than that for the pixels. Otherwise it would be hard to explain why pixels that have only a single point in their window do not have the same color as that point.
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The second thing that is concerning is the ragged edge of the apparent circles. It suggests that the distance calculation is not accurate. It shouldn't be more than a pixel off.
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You will always have these awkward edge effects in moving window analysis. However it can be reduced by 1) using a window radius considerably larger than the distance between points. 2) use a distance weighted kernel (my weapon of choice).
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Kind regards, Alex<br>
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<b><font color="#000000">From:</font></b><font color="#000000"> gdal-dev <gdal-dev-bounces@lists.osgeo.org> on behalf of Ari Jolma <ari.jolma@gmail.com></font><br>
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<font color="#000000"><b>Sent:</b></font><font color="#000000"> Saturday, March 10, 2018 10:00:00 AM</font><br>
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<font color="#000000"><b>To:</b></font><font color="#000000"> gdal-dev@lists.osgeo.org</font><br>
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<font color="#000000"><b>Subject:</b></font><font color="#000000"> [gdal-dev] Wondering gdal_grid moving average interpolation</font>
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I'm translating things on QGIS and now looking at GDAL tool rasterizing <br>
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point data set with moving average interpolation.<br>
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That's making a call to gdal_grid with -a average.<br>
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I've got the attached result from a point set (circles with red border <br>
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and inside inverse grayscale with interpolated value). The call was<br>
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gdal_grid -l INPUT -zfield suuntap -a <br>
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average:radius1=8000.0:radius2=8000.0:angle=0.0:min_points=0:nodata=0.0 <br>
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-ot Float32 -of GTiff INPUT.shp OUTPUT.tif<br>
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I'm wondering is that the expected since it looks like the raster cell <br>
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value is determined by point locations. I would have expected a much <br>
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more smooth surface without any obvious circular shapes. To me it looks <br>
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like the computation was not done cell by cell but instead point by point.<br>
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What am I missing or misunderstanding?<br>
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Ari<br>
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ps: This tool is in group 'Raster analysis'. In my opinion it should be <br>
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in a group 'Point data tools' or something.<br>
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