Über die finnischen Arbeiten zum Problem der Isostasie

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General report on isostasy (General Assembly, Oslo, 1948) Part II Isostatic studies in various countries

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General report on isostasy (General Assembly, Oslo, 1948) Part II Isostatic studies in various countries

     

The practical significance of the geoid determinations

Summary By means of the increased gravity measurements it is possible to compute gravimetrically the undulationsN of the geoid with regard to the used reference ellipsoid as well as the «absolute» deflection of the vertical components _g and _g . The quantities _g and _g enable us to transfer the astronomically observed coordinates of any points from the geoid to the reference ellipsoid and in this way compute without any triangulations the distances along the reference ellipsoid. And still more. With the aid ofN, _g and _g we can obtain a general Geodetic World System and convert the existing many systems to it.—The geoid study is no more any academical pastime, it can solve the most important problems of the practical geodesy.     

On the gravimetric undulations of the geoid and the deflections of the vertical

Summary The author mentions the aims of the World-wide gravity project he established in the Ohio State University in Columbus, in 1950. He outlines the practical procedure of the gravimetric computations of the undulationsN and the vertical deflection components and and emphasizes that only by the global international cooperation and additional gravity observations at sea carried out during the last decade it has been possible to gather to Columbus the needed gravity material. Since there exist still large gravimetrically unsurveyed areas it is of vital significance to study what gravity anomalies are best to be used for these regions. The given figures concerning the accuracy of theN, and , estimated theoretically and obtained in practice, indicate that in the gravimetrically well surveyed parts of the world like in Europe and the United States we can get gravimetrically on basis of existing gravity material theN-values with accuracy of about 5–10 meters, and and with the accuracy of about 1. The geoid undulationsN are already computed in Columbus for more than 6000 points of the northern hemisphere. The sample maps show the interesting geoid of Europe and vicinity between the latitudes 60° and 30° and longitude 5° W and 30° E, drafted on basis of more than 1000N-values computed at the corners of 1°×1° squares. It is interesting to realize that the geoid undulations in all this area are positive, the extreme values being between 40 and 50 meters. The geophysical significance of the geoid maps of this kind is pointed out.