Convert raster from ellispoidal height to orthometric altitude

Differences between ellipsoidal height and orthometric altitude (or geoid height) are explained here

using gdalwarp to convert from UTM33N-WGS84 ellipsoidal height to UTM33N-EGM96 geoid height

gdalwarp -s_srs "+proj=utm +zone=33 +datum=WGS84 +units=m +no_defs" -t_srs "+proj=utm +zone=33 +datum=WGS84 +units=m +no_defs +geoidgrids=egm96_15.gtx" input.tif output.tif

The definition of the projection is the PROJ4 line that can be found on

Inversely, to convert from altitude to ellipsoidal height use such command (change srs and geoid grid if needed):

gdalwarp -s_srs "+proj=utm +zone=33 +datum=WGS84 +units=m +no_defs +geoidgrids=egm96_15.gtx" -t_srs "+proj=utm +zone=33 +datum=WGS84 +units=m +no_defs" input.tif output.tif

you can choose your input and output spatial reference using the proj4 syntax , and note the add of the geoid file with +geoidgrids=egm96_15.gtx in the command.

if you want to use EGM2008 geoid, get the file from and copy it to the proj directory. In Linux it’s


then you can simply change the geoid file in the command +geoidgrids=egm08_25.gtx