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I am trying to make a map of a terraformed Mars in QGIS and as a part of that, I need to convert the Mars MOLA DEM into contour lines at an interval of 100m. However, the file is too big for QGIS to process the entire planet so at best I have roughly 55% of the elevation data I need. I can switch to a 500m interval for the time being but what I need to do is somehow split my DEM in half - something I have not been able to figure out.

Does anyone know how I go about this?

incomplete elevation data

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  • Create one or more polygons the size you want your cut raster to be. Than use menu raster > extraction > Clip raster by mask layer to get a clipped raster that has the size of your polygon. – Babel May 26 at 19:21
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You can try making two steps.It's faster using the console

Reduce the original file 11 Gb:

gdal_translate -co COMPRESS=DEFLATE -co PREDICTOR=2 Mars_HRSC_MOLA_BlendDEM_Global_200mp_v2.tif result.tif

Input file size is 106694, 53347
0...10...20...30...40...50...60...70...80...90...100 - done.

he result tif is only 2.7Gb and create contour lines 100 meters :

gdal_contour -b 1 -a ELEV -i 100.0 -f "GPKG" result.tif OUTPUT.gpkg

0...10...20...30...40...50...60...70...80...90...100 - done.

You can try to create the contour lines from the original file too, it will take longer but it should work

And the result is:

enter image description here

Contours Lines are also available thanks to OpenPlanetary,

https://openplanetary.carto.com/u/opmbuilder/tables/opm_499_mars_contours_200m_lines/public

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  • I get a syntax error when I run the compression – Cole Wintringham May 14 '20 at 20:08
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    What's the error? – Fran Raga May 20 '20 at 11:52

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