I have DEM data stored as RGF93 (Lambert-93) for lat/lon and NGF-IGN69 for altitude. I'm trying to change the reference ellipsoid for the elevation data (ultimately to NTF, but WGS84 would be fine to understand). I achieved to reproject the file using QGis or GDAL, but I can't find a way to change the altitude values. Shouldn't gdalwarp do the trick ?
Here's an example of a command I used :
gdalwarp -s_srs "+proj=lcc +towgs84=0.0000,0.0000,0.0000 +a=6378137.0000 +rf=298.2572221010000 +lat_0=46.500000000 +lon_0=3.000000000 +lat_1=44.000000000 +lat_2=49.000000000 +x_0=700000.000 +y_0=6600000.000 +units=m +no_defs" -t_srs "+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs +towgs84=0,0,0 +unit=m" input.tif output
What did I miss ?