A Gravimetric Approach for the Determination of Orthometric Heights in Akure Environs, Ondo State, Nigeria

An important component in position determination of any point is its height. Orthometric height determination has a significant role in geodesy, and it has wide-ranging application in numerous fields and activities. Orthometric height is the height above or below the geoid along the gravity plumb line. Orthometric height system is preferred to ellipsoidal height by many because of its relationship with the mean sea level (MSL). Determination of orthometric height for Akure environs was carried out using gravimetric approach by determining geoidal undulation via Stokes integral and ellipsoidal heights via GPS observations. A total of 59 stations within the study area were occupied for gravity observation using Lacoste and Romberg (G-512 series) and its complete accessories. South GNSS instrument was used for position and ellipsoidal height determination in static mode. In order to determine orthometric heights of the study area, the difference between the tailored geoid height (N Taylor ) and the ellipsoidal heights (h GPS ) were computed. The result shows that the determined orthometric height had an accuracy of 10.6121m standard deviation with a standard error of 1.38159m. The contour map and the 3D surface map of the computed orthometric heights were produced for the study area using kriging gridding method embedded in Surfer 11 software. The study recommends the use of gravimetric method in orthometric height determination when the tailored geoid height is computed. Keywords: Orthometric height, ellipsoidal height, Gravimetric approach, Gravity values, and geoidal height DOI : 10.7176/JEES/8-8-07