Comparison of the Positions Computed from DGPS/GNSS Observations Using the New/Unified and Various Old Transformation Parameters in Nigeria

Abstract

The accurate computation of positions of points from DGPS/GNSS observations acquired on the WGS84 ellipsoid in each country requires the application of transformation parameters. This is because, positions are determined with respect to the local datum/ellipsoid adopted for geodetic computation in each country. Prior to the derivation of the new/unified transformation parameters which were recently published by the Office of the Surveyor-General of the Federation, OSGOF, various sets of transformation parameters were determined by different multinational oil companies for use in Nigeria. Since the positions of reasonable number of points had been computed using these old sets of transformation parameters before the new/unified ones were derived and promulgated, there is need to verify which of the positions computed with the old sets of transformation parameters agree with the positions computed with the new/unified ones. Consequently, this paper compares the positions computed from DGPS/GNSS observations using the various, old sets and the unified transformation parameters. GNSS observations of four different points were processed with Compass post processing software using the various, old sets and the unified transformation parameters to obtain the positions of the points. The coordinates of each point obtained from the processing of the observations using the old sets of transformation parameters were compared with those obtained using the unified ones. The comparison results show that the positions computed using three different (SPDC, AGIP and DMA) sets of transformation parameters agree with those computed using the unified ones.