Time Variation of Height and Gravity [antikvár]

1 IntroductionPrimitive instruments with intercommunicating tubes applied to the determination of heights and height differences are clearly manifesting that even surveyors of ancient times used to reference elevations to equilibrium water levels.In the course of science's development mankind has realized relations describing the form of the equilibrium liquid surface in the earth's gravity field, and so the concept of height e-volved spontaneously in the ancient wo rid could be exactly defined in a physico-mathematical form as the vertical distance between the equipotential surfaces of the earth's gravity field.Height determination has always had an important role in the cultural and economical development of human society. Without it the numerical and graphical representation of the earth's topography or today even that of other celestial bodies would be unimaginable. However, it is exactly this fact which underlies a number of scientific concepts, the direction of the economic life, the design and implementation of all kinds of technical projects, etc.The continuous progress of the methods and the instrumenta-tion of height measurements permits the precise determination of heiqhts to an ever increasing reliability. In the recent ' decades geodetic leveling has already reached such a degree of accuracy that for points on the earth's surface even the detection of elevation changes occurred during a relatively short period,as is human lifetime (some decades), has become possible. This technical facility and the realization found on the occasion of repeated height measurements met in the development of the geosciences with demand which claimed the urgent monitoring