I am trying to process an elevation model in COG with GDAL using gdalwarp and gdal_translate, to change the height values from AHD (australian height datum aka sea level) to ellipsoid. The transformation works well using a geoid in the PROJ folder, however, the file size seem to double despite using the same lzw compression. Does anyone know why? What would the second file be carrying that the first one doesn't?
gdalwarp -s_srs "+proj=utm +zone=55 +south +ellps=GRS80 +units=m +no_defs +geoidgrids=au_ga_AUSGeoid2020_20180201.tif" -t_srs "+proj=utm +zone=54 +south +ellps=GRS80 +units=m +no_defs" input.tif output1.tif gdaladdo -r average output1.tif -ro gdal_translate output1.tif output2.tif -co COMPRESS=LZW -co BIGTIFF=YES -stats -co TILED=YES -co COPY_SRC_OVERVIEWS=YES -a_srs epsg:7855
original file is 169mo
output2 file is 324mo
I also get a funny message I never seen before when copying the overviews:
Warning 1: General options of gdal_translate make the COPY_SRC_OVERVIEWS creation option ineffective as they hide the overviews in the last command.