orthometric correction

Orthometric correction is a surveying technique used to adjust height measurements to account for the Earth's irregular gravitational field. Surveying involves determining the relative positions of points on the Earth's surface. When conducting large-scale surveys, the Earth's curvature and gravitational anomalies must be considered.

The geoid is an imaginary surface representing mean sea level, used as a reference for elevations. Because gravity causes the geoid to be irregular, measured heights need correction. Orthometric corrections are specifically applied to long, north-south trending lines of levels at high altitudes to compensate for distortions caused by variations in centrifugal force and gravity. This ensures that height measurements accurately reflect the distance from the geoid, which is crucial for precise mapping and engineering projects.12