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This study investigates the development and testing of an approximation method for the Mine Surveyor to calculate meridian convergence. This study, a detailed review of experimental techniques, follows a statistical experimental approach to establish how accurate an alternative method performs against traditional methods of meridian convergence calculation used by the Mine Surveyor. The spatial study is defined by the geographical range of the existing Schreiber Geodetic Tables, ranging from 70 km south of Ndola (Zambia) to 10 km north of De Aar (South Africa). The sample size is established under the constraint of an infinite population. Linear regression in collaboration with the hold-out validation technique is adopted to statistically refine the alternative method of calculation. The computational outcomes of the refined alternative method in comparison to the unrefined method are predominantly closer to the traditional outcomes. Computational outcomes specific to the hold-out validation set demonstrate a maximum sub-{1^{\prime\prime }} variance of {0.650^{\prime\prime }}. A sub-variance of {0.650^{\prime\prime }} satisfies the South African Mine Survey limits of error. The subsequent clustering of variances at specific variance intervals are similar to comparative studies conducted by T. Soler and R.J. Fury with respect to meridian convergence.

Sinkholes are alarming and dangerous events, they have a worldwide occurrence, and are imposing a potential risk to urban communities and the widely developed built environment. Losses due to catastrophic sinkhole collapse, foundation, pavement and structural repairs, occur more often, due to the increased pressure to develop even on sinkhole prone land, and the aging of existing water supply infrastructure in the majority of cities. Remote sensing earth observation methods have proved to be valuable tools during the last two decades in long-term sinkhole hazard assessment. Satellite air borne and ground earth observation methods have primarily facilitated the wide detection of continuous displacement on the earth's crust. National sinkholes catalogues are necessary for town planers decision makers, and government authorities. In many instances the ground collapse is the result of water ingress from old poorly maintained leaking pipelines, or extensive dewatering activities. In the current study a comprehensive review of the current literature is presented in order to show experiences from South Africa and present recent mapping using PSInSAR methodology in Centurion South Africa.

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