Eeldades Maa referentspinnaks ellipsoidi, tähendaks loodimine, et me paneme oma instrumendi igas mõõtepunktis püsti ellipsoidi normaali (ellipsoidi pinnaga ristuva sirge) järgi.
High precision levelling, especially when conducted over long distances as used for the establishment and maintenance of vertical datums, is called geodetic levelling.
