Fundamentals of Surveying (FS) Practice Exam

In an area where the geoid is considerably above the earth's surface, what is probably true?

1. the area has a significant deflection of the vertical

2. the area is mountainous or on a high plateau

3. the area is below sea level

4. the ellipsoid is above the geoid

The correct answer is: the area is below sea level

In areas where the geoid is considerably above the Earth's surface, it indicates that the gravitational potential is higher compared to the reference ellipsoid used in mapping and geodetic calculations. This situation often arises in regions that are below sea level. When land is below sea level, the geoid – which represents the shape of the Earth based on gravitational measurements – can indeed be situated above that land, as the geoid reflects the gravitational pull of the Earth and indicates how high the surface of the ocean would be if it extended into those areas. Other contexts could be relevant to the choices presented. For instance, significant deflections of the vertical typically occur in locations with heavy geological bodies nearby, which does not necessarily correlate directly with the position of the geoid. In mountainous regions or on high plateaus, the geoid is usually lower relative to the terrain due to the increased elevation and gravitational effects. As for the ellipsoid being above the geoid, this situation is not standard, as the ellipsoid is generally designed to average out the Earth's surface across a larger area and doesn't position itself above the geoid in the context of regional variations. Essentially, the relationship between the geoid and Earth's surface is primarily influenced by local elevation changes, making