Opened 2 years ago

Last modified 2 years ago

#6395 new defect

Artefacts appears on resampled Tiff DTED after performing an slope analysis

Reported by: poulet1212 Owned by: warmerdam
Priority: normal Milestone:
Component: GDAL_Raster Version: 1.11.3
Severity: normal Keywords:

Description (last modified by poulet1212)

As input file I use a single band 32 Float geotif file with elevation data. I reproject it using gdalwarp like: gdalwarp -ot Float32 -co "tfw=yes" -dstnodata 0 -s_srs EPSG:21781 -t_srs EPSG:4326 src dest

The result seem to be good as first glance, but problems appear as i perform a slope analysis on tjhe resulting file with either arcmap or QGis. Look the two attached file:

  • slope_analysis_without_artefact.PNG is the analysis performed one the original data
  • slope analysis with artefacts.PNG​ is the analysis performed on the reprojected data. You can clearly see some artefacts on the image.

The same problem also appears if if resample the data to a bigger cell size.

Attachments (2)

slope_analysis_without_artefact.PNG (366.6 KB) - added by poulet1212 2 years ago.
slope analysis with artefacts.PNG (293.8 KB) - added by poulet1212 2 years ago.

Download all attachments as: .zip

Change History (4)

Changed 2 years ago by poulet1212

Changed 2 years ago by poulet1212

comment:1 Changed 2 years ago by poulet1212

Component: defaultGDAL_Raster
Description: modified (diff)
Version: unspecified1.11.3

comment:2 Changed 2 years ago by Even Rouault

You might consider using another resampling kernel other than the default one that is nearest. For example -rb for bilinear resampling. EPSG:4326 is also probably not the best projection to get meaningful slopes if ArcMap? or QGIS are projection unaware when doing it, like gdaldem would be. Perhaps reprojecting the result of the slope analysis on the original projected raster would make more sense.

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