An Investigation into the Stability of Some Selected Geodetic Controls in Lagos State of Nigeria Using Strain Analysis Technique

Abstract

Natural disasters are problems of global concern and may cause significant loss of lives, social, economic and environmental problems, it also sometimes threaten geopolitical stability. These disasters sometimes in the form of deformation have found application for its modeling and analyses in Geodesy and Geodynamics. Strain method was used to model the deformation. The strain deformation parameters (dilatancy, total shear strain and differential rotations) by finite element model were calculated, by using baseline ratios of coordinates of a classical traverse in Minna datum based on Clarke 1880 ellipsoid and Global Positioning System (space technique) based on WGS84. Programs and computation were carried out in the MATLAB. MONTE CARLO environment, haven eliminated the ill conditioned triangles. Statistical analysis was used to determine the significance in deformation parameters at 95%, 97.5% and 99.5% confidence interval. After the statistical testing of the deformation parameters, it was observed that some controls were unstable in terms of their computed dilatancy and total shear strain values. For network differential rotation, the significance at 95%, 97.5% and 99.5% confidence interval are 1.8743908, 0.9651796 and 0.4338522 respectively. While centroids or controls that did not respond to network rotation had values approximately -0.99999.The minimal and maximal principal strain occurs at centroid 11 and 36 with triangulated stations identities (36-12, 30-84, 43-34A) and (34-30A, 34-32A, 34-36A) respectively. The method adopted for this research proved very effective for deformation study and analysis.