[gdal-dev] Slope obtained with GDAL has weird lines

[Joaquim Manuel Freire Luís]

Ah, let me guess. The dem grid was interpolated from contour lines and you seeing the contours again.

From: gdal-dev <gdal-dev-bounces at lists.osgeo.org> On Behalf Of Danilo da Rosa
Sent: Monday, March 16, 2020 11:09 PM
To: gdal-dev at lists.osgeo.org
Subject: [gdal-dev] Slope obtained with GDAL has weird lines

Hi!

This may be a very basic question, but I can't find the answer anyware.

I am working with this DEM obtained using terraincache<https://pypi.org/project/terraincache/>, it uses mapzen data. The SRC is WGS 84.

[DEM File in QGIS]<https://i.stack.imgur.com/Sp4Sg.jpg>

I ran this GDAL command to get the slope:

gdaldem slope -s 111120 dem.tif slope.tif (I had to do scaling because of the SRC)

The resulting image looks fine but it's not smooth, it has weird lines over it, like contour lines.

[Slope file on QGIS]<https://i.stack.imgur.com/POcHR.jpg>

You can download the DEM file here: https://gofile.io/?c=Du7WnM

Does anyone have an idea of how to solve it?

Thanks in advance for your help,

Danilo

P.S. I made this question here too: https://gis.stackexchange.com/questions/353983/slope-obtained-with-gdal-has-weird-lines
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