Robertson, E.I. 1960 The New Zealand provisional gravity system. [s.l.]: [s.n.]. Report / Geophysics Division 27 43p.
Abstract: A large part of our knowledge of the earth's external form and internal structure is based on measurements of the forces of gravity. Since 1930 an increasing quantity of gravity data has been obtained by using modern gravity metres. Although geodetic gravity meters are capable of directly measuring gravity differences throughout the world, the most numerous and accurate observations are made with instruments with a range of about 100 mgal and a precision approaching 0.01 mgal, or 1 part in 108 of the earth's field. The scale factor of the gravity metre must first be accuratley determined, preferably by comparision with pendulum observations, the value of gravity at any point is then found by measuring the change of gravity from a control point at which the value is known. Since these control points must be frequently reoccupied to determine the drift of the gravity metre, there should be a sufficient number suitably distributed throughout the country in order to eliminate unnecessary travelling; and to ensure that gravity observations in different parts of the country are reduced to a common basis, the values of gravity at all control points should be accurately determined (auth)
