Reduction Of Gravimetric Data Using An Integrated Computer Programme

Abstract

Gravimetric method of geophysical prospecting requires a methodical combination of both field techniques and data processing. For example drift correction in data processing cannot be successfully carried out without an a priori well-structured observational sequence during field observation that takes cognisance of both the instrumental and diurnal drift effects. The rigour of gravimetric data collection, and the non-availability of comprehensive data reduction software that takes care of local peculiarities, have always constituted hindrance to the application of the gravity method of geophysical studies. However, in recent time, the importance of the gravity method in mineral prospecting and geodynamic studies, has spurred researchers into the use of it. This programme is designed bearing in mind the need to include all the requirements for an all-embracing, up-to-date and exhaustive data reduction scheme. Therefore, the programme begins with systematic conversion of the gravimeter scale readings into an appropriate gravity unit, followed by a comprehensive drift correction routine, which employs the cascade model. The programme has a built-in mechanism, which automatically ties the survey to the international reference standard and computes the theoretical absolute gravity value at every station projected to the reference ellipsoid at the given latitude. In addition, the programme also calculates the observed absolute gravity value at every station, from which the various gravity anomalies are determined. A portion of the programme makes use of altimeter data, if available, to compute the elevation of the gravity station about the mean sea level, and return the result to an output data file. The programme is structured in modular form in order to enhance its flexibility, and with appropriate comment facilities in order to aid its comprehensibility.

Keywords: Gravimetric, data, reduction, computer, programme, sequence, modular, cascade, model

Nigerian Journal of Physics Vol. 19 (1) 2007: pp. 121-128