Hoogtesystemen

Hoogtesystemen, also known as vertical datums or geodetic datums, are reference systems used to define the vertical position of points on or near the Earth's surface. They provide a common basis for measuring and comparing elevations, which is crucial for a wide range of applications including surveying, mapping, construction, and navigation.

A fundamental component of a heightsystem is its vertical reference surface. This can be based on various physical phenomena. Historically, mean sea level was a common reference, but this is problematic due to variations in sea level over time and geographical location. Modern heightsystems increasingly rely on gravity-based references or geoids. A geoid is a conceptual surface that represents the mean sea level extended through the continents and is defined by the equipotential surface of the Earth's gravity field.

There are different types of heightsystems. Orthometric heights, often referred to as "height above sea level," are the most intuitive and widely used. They represent the distance along the plumb line from a point to the geoid. Another type is ellipsoidal height, which is the distance from a point to the reference ellipsoid used in a geodetic system. The difference between orthometric and ellipsoidal height is due to the undulation of the geoid.

The establishment and maintenance of heightsystems are typically the responsibility of national mapping agencies. They conduct extensive geodetic surveys to determine precise height values for control points, which then serve as benchmarks for local surveying and engineering projects. Consistent use of a standardized heightsystem ensures accuracy and compatibility across different projects and datasets.