REALIZATION OF THE LOCAL GEOID MODEL USING THE GPS/LEVELLING METHOD FOR NNAMDI AZIKIWE UNIVERSITY, AWKA, ANAMBRA STATE.

AUTHOR: ONWUZULIGBO CHUKWUBUEZE UZOCHUKWU

DEPARTMENT: SURVEYING AND GEOINFORMATICS

AFFILIATION: NNAMDI AZIKIWE UNIVERSITY, AWKA

Geodesy being the study of the shape and size of the earth and its gravity field concerns itself primarily with the business of positioning. Positions are defined by coordinates, which are determined using the geodetic surfaces. Coordinates consist of the horizontal and vertical coordinate systems. Whereas the horizontal coordinate systems have been well defined in Nigeria, the vertical coordinates system has suffered some major setbacks because of the difficulties in the realization of the surfaces. This work aims at the realization of a geoid model for Nnamdi Azikiwe university, Awka, through the determination of the geodetic surfaces in the area. Different methods for the determination of the geodetic surfaces exist, ranking between the Astro-geodetic methods (which has further been developed into Geometric method) and Gravimetric methods. The Geometric (GPS/Levelling) method of the geodetic surfaces determination was adopted for this project. It entails the establishment of the orthometric heights and the ellipsoidal heights. Due to the fact that the study area is not very undulating, sixty (60) stations were used for the establishment of this model and twelve (12) stations were used as test stations for the interpolation methods. The observed orthometric heights realized in this work were compared with different Global Geopotential Models (GGMs) derived orthometric heights. This comparison proved that the local orthometric heights have an identical height relationship with the GGMs derived orthometric heights. The Polynomial Regression Method Model D seen in Isioye and Youngu (2009) and Geometric Interpolation Techniques seen in Heiskanen and Moritz, 1967) methods of interpolation were adopted for the estimation of the orthometric heights of the test stations. The mean residual between the observed orthometric heights and the estimated orthometric heights were all found to be identical with the mean value of -0.038m. It was recommended, amongst others, that engineering firms, surveyors and all stakeholders should take the establishment of our local geoid model at both National and State levels seriously. The GPS/Levelling method of Geoid model establishment was further recommended to be used as a better alternative to the conventional Geodetic Spirit Levelling method of orthometric height determination because of its relatively cheaper cost, high accuracy and lower time consumption.

TO VIEW THE FULL CONTENT OF THIS DOCUMENT, PLEASE VISIT THE UNIZIK LIBRARY WEBSITE USING THIS LINK, http://naulibrary.org/dglibrary/admin/book_directory/Thesis/11059.pdf

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