That means that when traveling by ship, one does not notice the undulations of the geoid; the local vertical (plumb line) is always perpendicular to the geoid and the local horizon tangential to it.
Awen almăɣna net a fal issekel awădim daɣ Bato, war hin za egra a hin awădim imitikwiyan n geoid; teɣate net (iyaka wan ammas) hrkuk ozɣaɣ i geoid d edag wa id immuqăs diris