I'm having a problem with resampling ETOPO NetCDF GRD to a bigger pixelsize for using it with Generic Mapping Tools.
I'm using gdal_warp for the resampling (just for testing with pixelsize of 1°):
gdalwarp -overwrite -s_srs EPSG:4326 -tr 1 1 -r near -of netCDF input_etopo.grd etopo_resampled.nc
but the output grd gets many null-values. If I use the geotiff of etopo the output is the same.
Does anybody had the same problem and knows how to prevent it? Different resampling methods doesn't solved the problem.