[GRASS-dev] [GRASS GIS] #3860: GRASS GIS producing different slope than GDAL

GRASS GIS trac at osgeo.org
Sun Jun 9 13:47:33 PDT 2019

#3860: GRASS GIS producing different slope than GDAL
 Reporter:  mazingaro  |      Owner:  grass-dev@…
     Type:  defect     |     Status:  new
 Priority:  major      |  Milestone:  7.6.2
Component:  Raster     |    Version:  unspecified
 Keywords:  slope      |        CPU:  x86-64
 Platform:  Linux      |

 When producing a slope in GRASS GIS 7.4 and 7.6 the results are different
 than with QGIS (GDAL) and ArcMap for the same input data and same
 parameter (Z ratio is 1.0 and degrees). QGIS and ArcMap generate almost
 the same output. In GRASS, I tried both for DCELL and FCELL and the
 results are same. The original layer has a resolution on 1 m and the GRASS
 region resolution is set to 0.5 m.

 Code GRASS: r.slope.aspect elevation=DMR at PERMANENT slope=slope

 Code GDAL: gdaldem slope .../DMR.tif .../slope.tif -of GTiff -b 1 -s 1.0

 Do I do something wrong or this can be a bug?
 Left - GRASS calculated slope and right - GDAL calculated one

Ticket URL: <https://trac.osgeo.org/grass/ticket/3860>
GRASS GIS <https://grass.osgeo.org>

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