Developing a differential GPS (DGPS) Service in Ghana
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Date
2008
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Abstract
The prerequisite for successful execution of projects, applications, services or products reliant on surveys or geo-information, must be a uniform and reliable coordinate reference system. Provision of control points defining these reference frames by conventional methods are expensive, tedious, limited to intervisibility between beacons and the area of survey, thus reducing the effectiveness of networks at night and in poor weather conditions. Signals from Global Navigation Satellite Systems have proven to be fast, accurate and cheaper alternative to conventional methods, but performance indices for autonomous positioning are not satisfactory and as such for high precision assignments, relative or differential positioning techniques must be employed.
However, differential positioning does place additional operational demands (two GPS receivers are required with one on known point and a data link between them when DGPS is to be implemented in real-time). A base station has been established at KNUST to provide GPS logs, reference coordinates, and to disseminate differential corrections for post-processing computations. This base will serve as the second receiver required for differential operations. Using the base station, several observation sessions were conducted and processed to compute 2D transformation parameters to integrate GPS data into the National Mapping System. The parameters computed can be used within a maximum radial error of 0.58ft around campus.
Further investigations were carried-out on observation times and the solutions obtained showed that at least three hours was found to be optimum time to be spent when coordinating newly established base stations.
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A Thesis submitted to the Department of Geomatic Engineering,Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the Degree of Master of Philosophy.