Höhenbezugsnetz

A Höhenbezugsnetz, or vertical datum network, is a fundamental concept in surveying and geodesy. It establishes a reference surface or system for measuring elevations and altitudes. Without a common reference, it would be impossible to consistently define and compare heights across different locations or projects.

There are two main types of vertical datum networks: those based on physical phenomena and those based on mathematical models. Physically based systems often rely on mean sea level (MSL) as a zero point. This is determined by averaging tidal observations over a significant period. However, MSL can vary geographically and over time, leading to inconsistencies. Mathematically based systems, on the other hand, use a defined geoid or a reference ellipsoid to establish a zero height. The geoid is an equipotential surface of the Earth's gravity field that approximates mean sea level.

In practice, national geodetic agencies establish and maintain these Höhenbezugsnetze. They consist of a network of permanent markers, known as benchmarks or control points, whose elevations are precisely determined relative to the chosen datum. These benchmarks are then used as starting points for local surveys, ensuring that all height measurements within a region are consistent and comparable. The accuracy and stability of a Höhenbezugsnetz are crucial for various applications, including civil engineering, infrastructure development, flood control, and mapping. Changes or updates to a national vertical datum can have significant implications for existing infrastructure and ongoing projects.