Korkeusmittaus

Korkeusmittaus, often translated as altimetry or height measurement, is the process of determining the vertical distance between a point and a reference level. This reference level can be sea level, the ground, or another defined datum. Various methods and instruments are employed for korkeusmittaus, depending on the required precision, scale, and application.

In surveying and geomatics, traditional methods include leveling using a leveling instrument and a graduated staff, which provides highly accurate height differences over relatively short distances. Trigonometric leveling, using an angle and a known horizontal distance, offers another approach, particularly useful for greater ranges. Modern techniques increasingly rely on GPS (Global Positioning System) and other GNSS (Global Navigation Satellite System) receivers, which can determine absolute heights by measuring the distance to satellites. However, GPS-based heights are typically ellipsoidal and require geoid models to be converted into orthometric heights, which represent height above sea level.

Remote sensing also plays a significant role in large-scale korkeusmittaus. Radar altimetry from satellites can measure the height of the ocean surface, ice sheets, and land surfaces. LiDAR (Light Detection and Ranging) systems, both airborne and terrestrial, use laser pulses to create detailed 3D elevation models of terrain and objects. Barometric altimeters, which measure atmospheric pressure, are used in aviation and for less precise, real-time altitude readings. The choice of method for korkeusmittaus is dictated by factors such as the need for absolute or relative heights, accuracy requirements, cost, and the area to be measured.