What are orthometric heights?
An orthometric height is the distance above or below the geoid to the earth’s surface, structure, or benchmark and is commonly called elevation. An ellipsoid height is the distance above or below the mathematical model of the earth (that best fit squashed sphere or GRS80). Note that the vector describing the orthometric height is parallel to the local gravity vector whereas the vector describing the ellipsoid height is normal to the ellipsoid surface. Back to top 5. What are tidal datums? A tidal datum is a surface defined by a particular phase of the tide. Examples of tidal datums are Mean Higher High Water (MHHW), Mean Tide Level (MTL), Mean Sea Level, and Mean Lower Low Water (MLLW). Tidal datums are computed using observations acquired at a specific tide station and are valid only at that particular station. A datum located in a water body is considered tidal if the variation in water level is sufficiently predictable based upon the phases of the moon and sun. Otherwise, it is cons
