Orthometric vs ellipsoidal height

This article explains the difference between orthometirc (geoid) height and ellipsoidal height.

The orthometric (geoid) height of a point of the Earth Surface is the distance H_o from the point to the geoid.

The ellipsoidal height of a point of the Earth Surface is the distance H_e from the point to the ellipsoid.

Earth surface, ellipsoid and geoid

Orthometric height H _o and ellipsoidal height H _e

The geoid height above the ellipsoid (N) is the difference between the ellipsoidal height and orthometric (geoid) height.

N = H_e − H_o

Where:

N = geoid height above the ellipsoid
H_e = ellipsoidal height
H_o = orthometric (geoid) height

More information on this topic can be found in the following articles:

When to use the Geoid Height Above the Ellipsoid function

How to define Pix4D outputs with respect to a geoid model