Abstract: Topographical measurements of surfaces yield a lot of data which are usually presented by tables of height coordinates or by contour maps. Here a method is described to characterize the surface geometry by just a few parameters which quantify the functional properties: sphericity, twist, and waviness. Examples of applications are given from the field of surface plate measurement. Some measurement techniques based on electronic levels, autocollimators and laserinterferometers are briefly discussed. A resulting accuracy of 0.1 $mu@m on a one square meter surface is claimed. With the characteristic parameters, even small geometrical changes due to the environmental conditions temperature and moisture could be recorded and explained. !5
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