The international network of gravimeter bases here reported started out in 1948 as a field evaluation study of national gravity base values. It represented a preliminary step in undertaking a geodetic analysis of the international body of gravity data. However, it soon became apparent that more than an evaluation of national base values was required if a meaningful analysis was to be made. Connections were needed to the considerable body of commercial exploration data, much of which was on a floating datum. Many isolated surveys supposedly on the Potsdam datum appeared to be in error by several milligals. There was no uniformity in calibration standard being used to define the milligal. In most areas the gravity values for the existing control network of pendulum gravity bases were of poor quality (Â±3 mgal), and, furthermore, these bases were located at sites that were difficult to reoccupy.
Although the establishment of an international gravity standard defining the milligal only could be established through pendulum gravity measurements, an international network of superior, accessible gravity control bases could be established easily by using airports as observation sites that could be oc-cupied with a gravimeter during the ten to twenty minutes a plane was on the ground at each stop, as was demonstrated by the writer in 1948 (Woollard 1950). The final values for such a network of bases might have to wait until international agreement had been reached concerning a gravimeter calibration standard and the value of the reference datum firmly established, but there
Figures & Tables
International Gravity Measurements
“Originally established to test reliability of the world network of firstorder international gravity bases, the program was expanded to include establishment of a series of reliable pendulum gravity control measurements in North America to assure a potential accuracy of 1 mGal or better on any global series of measurements. Studies also expanded and standardized existing gravity surveys of the United States for reliable gravity anomaly maps, and evaluated reliability and gravity standards used for global work.”