Precise gravity observations in Southern New Zealand 1977-1981

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Woodward, D.J. 1982 Precise gravity observations in Southern New Zealand 1977-1981. : . Report / Geophysics Division 188 25 p.

Abstract: Observations of gravity using LaCoste and Romberg model G and model D gravity meters at 133 points, that can be relocated accurately, in the Southern part of the South Island, New Zealand, are presented. These observations have been reduced to give estimates of the differences of gravity between the points. There are insufficient stations common to the different surveys to determine any significant changes of gravity with time in this region. The reductions have been made using least squares techniques to solve simultaneously for: (a) drift and base value, (b) tidal amplification factor, (c) relative scale factors between the instruments, and (d) the differences of gravity at the points. Attempts to solve at the same time for both the secular change of gravity at the observation points and the relative scale factors failed because the parameters are highly correlated. Readings made in different surveys and with each of the meters have been given different weights in the analysis to allow for the variable precision of the meters and the improvement in measurement technique over the period