What does orthometric height refer to?

Orthometric height specifically refers to the vertical distance of a point above the geoid, which is an equipotential surface that represents the mean sea level of the Earth's gravity field. This definition is crucial for understanding how heights are measured in relation to the physical shape of the Earth and its gravitational anomalies. Orthometric height is significant in various applications, including geodesy and civil engineering, as it provides a true representation of elevation with respect to sea level.

The other choices pertain to different geographic concepts. The azimuth from one point to another relates to direction rather than vertical positioning. The shape of the Earth, which could refer to concepts like the geoid or ellipsoid, does not directly relate to orthometric height measurements. Lastly, the surface of the ocean, while relevant in terms of mean sea level reference, does not define orthometric height itself but serves as the basis for determining it. Thus, the correct understanding of orthometric height is firmly tied to its definition in relation to the geoid.