What is ellipsoidal height h in relation to the reference ellipsoid?

• A. Ellipsoidal height is measured from the geoid.
• B. Ellipsoidal height is the distance above the reference ellipsoid.
• C. Ellipsoidal height is the distance below the reference ellipsoid.
• D. Ellipsoidal height equals orthometric height.

Answer: (B)

Ellipsoidal height h is the distance from the point to the reference ellipsoid measured along the normal to the ellipsoid, i.e., how far the point lies above the ellipsoid surface. This is a measurement tied to the mathematical reference surface (the ellipsoid) rather than to the geoid. It differs from orthometric height, which is height above the geoid, and from geoid-related concepts like N (geoid undulation) where h = H + N. So the correct idea is that h represents the height above the reference ellipsoid, not from the geoid or below it, and not equal to orthometric height.