Is it due to irregularity of geoid, we cannot convert the height between spherical datum and local datum (which uses locally defined geoid and height) by cs2cs?
What I mean is that, by using cs2cs, it only accepts x and y / lat and lon as input. The z / height data is not accepted for the conversion program. Does it mean that z / height cannot be directed converted?
What if I convert between spherical data, can it be converted directly by using projection formula?