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<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Ah, let me guess. The dem grid was interpolated from contour lines and you seeing the contours again.<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>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> gdal-dev <gdal-dev-bounces@lists.osgeo.org>
<b>On Behalf Of </b>Danilo da Rosa<br>
<b>Sent:</b> Monday, March 16, 2020 11:09 PM<br>
<b>To:</b> gdal-dev@lists.osgeo.org<br>
<b>Subject:</b> [gdal-dev] Slope obtained with GDAL has weird lines<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi!<o:p></o:p></p>
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<p class="MsoNormal">This may be a very basic question, but I can't find the answer anyware.<o:p></o:p></p>
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<p>I am working with this DEM obtained using <a href="https://pypi.org/project/terraincache/">
terraincache</a>, it uses mapzen data. The SRC is WGS 84.<o:p></o:p></p>
<p><a href="https://i.stack.imgur.com/Sp4Sg.jpg"><span style="text-decoration:none"><img border="0" width="822" height="539" style="width:8.5625in;height:5.6166in" id="_x0000_i1026" src="https://i.stack.imgur.com/Sp4Sg.jpg" alt="DEM File in QGIS"></span></a><o:p></o:p></p>
<p>I ran this GDAL command to get the slope:<o:p></o:p></p>
<p><code><span style="font-size:10.0pt">gdaldem slope -s 111120 dem.tif slope.tif</span></code> (I had to do scaling because of the SRC)<o:p></o:p></p>
<p>The resulting image looks fine but it's not smooth, it has weird lines over it, like contour lines.<o:p></o:p></p>
<p><a href="https://i.stack.imgur.com/POcHR.jpg"><span style="text-decoration:none"><img border="0" width="821" height="540" style="width:8.5541in;height:5.625in" id="_x0000_i1025" src="https://i.stack.imgur.com/POcHR.jpg" alt="Slope file on QGIS"></span></a><o:p></o:p></p>
<p>You can download the DEM file here: <a href="https://gofile.io/?c=Du7WnM">https://gofile.io/?c=Du7WnM</a><o:p></o:p></p>
<p>Does anyone have an idea of how to solve it? <o:p></o:p></p>
<p>Thanks in advance for your help,<o:p></o:p></p>
<p>Danilo<o:p></o:p></p>
<p>P.S. I made this question here too: <a href="https://gis.stackexchange.com/questions/353983/slope-obtained-with-gdal-has-weird-lines">
https://gis.stackexchange.com/questions/353983/slope-obtained-with-gdal-has-weird-lines</a><o:p></o:p></p>
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