Reference area

This article deals with geometric objects in metrology and the concept from certification; for standardizations that relate to area, see reference value

A reference - or reference surface is an imaginary surface on which calculations or measurements relate. It is often an idealized , simplified model of real surfaces, the measurement or mathematical recording of which would be impossible, too complex or inadequate. An ellipsoid , a sphere or a plane is therefore used as a geometric reference surface .

Isosurface

→ Main article : Isosurface

An isosurface connects points with the same property or value:

• Isobars = areas of equal pressure, e.g. B. the atmospheric pressure to indicate flight altitudes
• Equipotential surface , e.g. B. the gravitational field of the earth and other celestial bodies

Height reference surface

Elevation reference surfaces of the earth take into account the deviation of the mean shape of the earth from a sphere or the deviation of the gravitational isosurface from an ellipsoid :

• Zero level
• Sea level (sea level)
• Reference ellipsoid (normal ellipsoid, earth ellipsoid, level ellipsoid)
• Geoid
• Quasigeoid
• Normal height zero (current height reference area in Germany)
• Equipotential surface , e.g. B. the gravitational field of the earth and other celestial bodies

Forest reference areas

The term reference area is also used in the field of ecological forestry , where a natural reference area with similar requirements serves as a comparison area for a cultivated area. This area should help to get information about the natural forest development in order to promote ecological forest use. The area should be at least 20 hectares. According to the FSC certification system for public forests, it is stipulated that 5% of the forest areas are not permanently under any forest management. In 2010, the German Forestry Council spoke out against adopting this standard because, in the opinion of the Council Chairman, it inhibits climate protection rather than promoting it:

“Neither the designation of reference areas, ie areas in which wood is no longer allowed to be used, nor the change in the choice of tree species due to the long-term reduction in the proportion of conifers from currently 45% to max. 20% are suitable criteria for countering climate change through the use of wood. Only through the increased use of sustainably produced wood can CO2 be bound in the long term and removed from the atmosphere. "

- Georg Schirmbeck

Web links

• Reference area In: Lexicon of Geosciences Spektrum.de (computing and reference area for geodetic calculations)
• Excursus: Earth's surface and reference areas nautisches-lexikon.de
• Kartenkunde - The earth and its depiction on maps oetk.at

Individual evidence

1. ↑ 9. Reference areas in: Naturland guidelines for ecological forest use. (PDF, as of May 2014, naturland.de ).
2. ↑ Reference area standard of FSC certification inhibits climate protection. proplanta.de, February 9, 2010, accessed on May 22, 2020 .