If the GPS-derived height of a control point is 56.439 meters and the orthometric elevation is 8.795 meters, what is the separation between the ellipsoid and the geoid?

To find the separation between the ellipsoid and the geoid, you can use the formula:

Separation = GPS Height - Orthometric Elevation

In this case, the GPS-derived height, which is the height above the reference ellipsoid, is given as 56.439 meters. The orthometric elevation, representing the height above the geoid (which is used to represent mean sea level), is 8.795 meters.

Calculating the separation:

Separation = 56.439 meters - 8.795 meters
= 56.439 - 8.795
= 47.644 meters

This result indicates the height difference between the ellipsoidal surface and the geoidal surface. Since the geoid is generally lower than the ellipsoid in this context, the positive value indicates that the ellipsoid is above the geoid. Therefore, the separation is +47.644 meters, confirming that the correct choice reflects this positive height difference.