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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">At least I cannot resolve your issue on paper. Please share some test data.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">-Jukka-<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b>Lähettäjä:</b> gdal-dev <gdal-dev-bounces@lists.osgeo.org>
<b>Puolesta </b>Paul Meems via gdal-dev<br>
<b>Lähetetty:</b> keskiviikko 22. toukokuuta 2024 17.31<br>
<b>Vastaanottaja:</b> gdal-dev@lists.osgeo.org<br>
<b>Aihe:</b> [gdal-dev] Gdal_grid produces a lot of empty cells<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hello List,<o:p></o:p></p>
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<p class="MsoNormal"><br clear="all">
<o:p></o:p></p>
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<p class="MsoNormal">I have a CSV-file with sensor data and GPS coordinates in WGS84.<o:p></o:p></p>
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<p class="MsoNormal">I convert these GPS coordinates to a projected projection. Mostly a UTM zone, depending on the location.<o:p></o:p></p>
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<p class="MsoNormal">These X and Y values are added to the CSV-file and saved with a different name.<o:p></o:p></p>
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<p class="MsoNormal">Then I create a VRT-file to get the proper Z-column:<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""><OGRVRTDataSource><br>
<OGRVRTLayer name="01 field data-EPSG32634"><br>
<SrcDataSource>01 field data-EPSG32634.csv</SrcDataSource><br>
<GeometryType>wkbPoint</GeometryType><br>
<GeometryField encoding="PointFromColumns" x="X" y="Y" z="Countrate"/><br>
</OGRVRTLayer><br>
</OGRVRTDataSource></span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">This VRT file is sent to Gdal_grid to create a tiff-file using these arguments:<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-a invdist:power=2:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> smoothing=20:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> min_points=16:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> max_points=56:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> radius1=40:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> radius2=40:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> nodata=1.701410000000000071e+38 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-txe 273360 274940 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-tye 5559440 5561020 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-tr 12.5 12.5 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-a_srs EPSG:32634 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">"01 field data-EPSG32634-TC.vrt" "tmpmrmq4d.tiff"</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">This tiff-file looks like this: <a href="https://pasteboard.co/tKP1ZJ1cAY2r.png">https://pasteboard.co/tKP1ZJ1cAY2r.png</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">This process works fine and we've been using this for several years now.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Recently we added a process step to export one of the sensor data to a PostGIS database and with the help of Geoserver and OpenLayers we've created a very simple webpage.<o:p></o:p></p>
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<p class="MsoNormal">In this step, things are getting weird. The WebMap is in EPSG:3857 (Pseudo/Web-Mercator).<o:p></o:p></p>
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<p class="MsoNormal">I start with the original CSV-file with the sensor data and add the X and Y columns again, now in EPSG:3857. Then I create a similar vrt-file:<br>
<span style="font-family:"Courier New""><OGRVRTDataSource><br>
<OGRVRTLayer name="01 field data-EPSG3857"><br>
<SrcDataSource>01 field data-EPSG3857.csv</SrcDataSource><br>
<GeometryType>wkbPoint</GeometryType><br>
<GeometryField encoding="PointFromColumns" x="X" y="Y" z="Countrate"/><br>
</OGRVRTLayer><br>
</OGRVRTDataSource></span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">And call gdal_grid with similar arguments:<br>
<span style="font-family:"Courier New"">-a invdist:power=2:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> smoothing=20:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> min_points=16:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> max_points=56:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> radius1=40:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> radius2=40:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> nodata=1.701410000000000071e+38 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-txe 1984580 1987000 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-tye 6471320 6473740 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-tr 12.5 12.5 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-a_srs EPSG:3857 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">"01 field data-EPSG3857-TC.vrt" "tmpun25fo.tiff"</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">But now the result is: <a href="https://pasteboard.co/bcMp7rP5eyff.png">https://pasteboard.co/bcMp7rP5eyff.png</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">A huge amount of empty cells. I don't understand this. <o:p></o:p></p>
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<p class="MsoNormal">Both EPSG:32634 (WGS 84 / UTM zone 34N) and EPSG:3857 are in meters so I thought the same settings should work.<o:p></o:p></p>
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<p class="MsoNormal">But in fact only with very different settings I can get a proper grid:<br>
<span style="font-family:"Courier New"">-a invdist:power=2:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> smoothing=60:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> min_points=4:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> max_points=56:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> radius1=80:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> radius2=80:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> nodata=1.701410000000000071e+38 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-txe 1984580 1987000 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-tye 6471320 6473740</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-tr 20 20 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-a_srs EPSG:3857 </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">"01 field data-EPSG3857-TC.vrt" "tmpsvlhgy.tiff"</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I got these values through trial and error.<br>
<a href="https://pasteboard.co/7pypGsynS09K.png">https://pasteboard.co/7pypGsynS09K.png</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">But now we loose a lot of variation because the search radius and grid cell size are much higher.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">To make it even more weird. Other fields nearby don't have this problem and I also have this problem with other projections like:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Belgium (EPSG:3857): <a href="https://pasteboard.co/ZXLTsEuvpZ3s.png">https://pasteboard.co/ZXLTsEuvpZ3s.png</a><o:p></o:p></p>
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<p class="MsoNormal">Belgium (EPSG:31370): <a href="https://pasteboard.co/yNpF6yujF3tV.png">https://pasteboard.co/yNpF6yujF3tV.png</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">The Netherlands (EPSG:3857): <a href="https://pasteboard.co/8PpDJrDi1Wxq.png">https://pasteboard.co/8PpDJrDi1Wxq.png</a><o:p></o:p></p>
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<p class="MsoNormal">The Netherlands (EPSG:28992): <a href="https://pasteboard.co/38SlnHVCog4m.png">https://pasteboard.co/38SlnHVCog4m.png</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Norway (EPSG:3857): <a href="https://pasteboard.co/q69jQHRK40c6.png">https://pasteboard.co/q69jQHRK40c6.png</a><o:p></o:p></p>
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<p class="MsoNormal">Norway (EPSG: 25833): <a href="https://pasteboard.co/gs9HNAmnaxSJ.png">https://pasteboard.co/gs9HNAmnaxSJ.png</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">We do have enough data points: <a href="https://pasteboard.co/4CmBs7kgQGVO.png">
https://pasteboard.co/4CmBs7kgQGVO.png</a><o:p></o:p></p>
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<p class="MsoNormal"><a href="https://pasteboard.co/J8ZbMHKeErZu.png">https://pasteboard.co/J8ZbMHKeErZu.png</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Thanks if you made it all the way here ;)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">My questions are:<o:p></o:p></p>
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<li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level1 lfo1">
Am I using Gdal_Grid in the proper way or do I need to change one or more arguments?<o:p></o:p></li><li class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level1 lfo1">
What might be an explanation for the empty cells when using EPSG:3857?<o:p></o:p></li></ul>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Thanks,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Paul Meems<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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