Question

The height derived or deduced directly from the GPS observations is referred as

• A. The sensitive height
• B. The plyometric height
• C. The variable height
• D. The ellipsoidal height

Hint:

GPS positions are computed with reference to a mathematical reference surface called the ellipsoid (such as WGS-84).

Answer 1

The Correct Option is D

Concept:
GPS positions are computed with reference to a mathematical reference surface called the ellipsoid (such as WGS-84). So the vertical value that comes straight out of GPS measurements is measured relative to this ellipsoid.

Step 1:
The height measured perpendicular to the ellipsoid is called the ellipsoidal height (or geodetic height). It is what GPS gives directly.

Step 2:
To get the orthometric height (height above mean sea level / geoid) one must apply the geoid undulation as a correction. But the value obtained directly from GPS observations is the ellipsoidal height. The other options are not standard GPS height terms.

Answer: Option (4) — The ellipsoidal height.