Abstract
The improvement of the accuracy of a local geometric geoid model using the same data set (geoid heights) requires the fitting of a higher degree polynomial surface to the data set. Consequently, this paper presents improving the local geometric geoid model of FCT, Abuja accuracy by fitting a higher order polynomial surface. A fifth degree polynomial surface was fit to the existing geoid heights of 24 points used previously for the determination of the geometric geoid model of the study area to improve its accuracy. The least squares adjustment technique was applied to compute the model parameters, as well as the fit. The RMSE index was applied to compute the accuracy of the model. The computed accuracy (0.081m) of the model was compared with those of the previously determined geoid models (Multiquadratic, 0.110m and Bicubic, 0.136m models) of the study area to determine which of the models best fit the study area, as well as has the highest resolution. The comparison result shows that the fifth degree polynomial surface best fit the study area.
Highlights
The GNSS observation that uses the Global Positioning System (GPS)/Global Navigation Satellite System receivers gives the coordinates and elevations of stations at various points of measurements
This study presents improving the local geometric geoid model of Federal Capital Territory (FCT), Abuja accuracy by fitting a higher order polynomial surface
Data Acquisition The data used in this study included the existing UTM zone 32 coordinates, existing orthometric heights and GNSS observation ellipsoidal heights of 24 control stations within the Federal Capital Territory (FCT), Abuja
Summary
The GNSS observation that uses the Global Positioning System (GPS)/Global Navigation Satellite System receivers gives the coordinates and elevations of stations at various points of measurements. Geoid surface is used to approximate the physical shape of the Earth It is the equipotential surface of the Earth’s gravity field which more or less coincides with the mean sea level (Borge, 2013). Ubajekwe (2011) defined the geoid as the equipotential surface of the earth’s attraction and rotation which coincides on average with the mean sea level in the open Ocean. Moritz and Hofmann (2005) stated that the geoid coincides with that surface to which the oceans would conform over the entire earth if free to adjust to the combined effect of the earth mass attraction (gravitation) and the centrifugal force of the earth’s rotation They explained that the geoid is a surface along which the gravity potential is everywhere equal and to which the direction of gravity is always perpendicular when optical instruments containing gravity reference levelling devices are properly adjusted during observation coincides with the direction of gravity and are perpendicular to the geoid. It was as a result of the number of FUDMA Journal of Sciences (FJS) Vol 4 No 3, September, 2020, pp 114 - 120
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