I have a DEM (.asc) file with a resolution of 1000 meters per pixel. Therefore the file has a lot of columns and rows.
I would like to chance the resolution per pixel from 1000 to 3000 meters per pixel. So i would like to resample it.
which gdal command do i use for this?
i know it's gdalwarp but how is the exact command line with the extra options?
if you know how to do it in QGIS I'm also happy with it.
Best Answer
The task could feel trivial by reading the gdalwarp documentation http://www.gdal.org/gdalwarp.html and GDAL AAIGrid -- Arc/Info ASCII Grid driver documentation http://www.gdal.org/frmt_various.html. The target pixel size is three times bigger than the native resolution 0.008333333333 degrees/pixel (not 1000 m/pixel, see the comments).
However, it is a bit more difficult than that.
Therefore the conversion must be done in two steps and with a better resampling method.
First step is to create an interim output as GDAL Virtual raster (.VRT) with "average" resampling
Second step is to convert the interim DEM into new ASCII Grid file with gdal_translate
Note:
The formats which are supported for output can be listed with gdalwarp --formats command. Formats which support direct output are marked with "+" character. However, all of them will not really work (NTv2 Datum Grid Shift file for example).
On Windows