Unification of Geodetic Datum in international boundaries a case study of Malawi, Mozambique and Zambian boundaries

Abstract

The diversity of datums in use today and the technological advancements that have made possible global positioning measurements with sub-meter accuracies, require careful datum selection and careful conversion between coordinates in different datums. This is due to different positional accuracies attributed to different datums. Zambia and Malawi’s coordinate system are based on Arc 1950 datum whereas Mozambique is based on 1960 Tete datum. Land Surveyors, Engineers and Planners require a unified datum or a known relationship to execute cross border projects between countries with different datums. The research was aimed at reviewing relevant literature, tying local coordinates of Zambia-Malawi and Zambia-Mozambique international boundaries to the World Geodetic System 1984 (WGS 84) positioned on the International Terrestrial Reference Frame 2008 (ITRF2008) and to establish the relationships between geodetic datums thereby unifying them. However, the unification of the vertical datum was beyond the scope of the research. Reviewed literature confirmed a lack of known relationship between Zambia and Mozambique datums under study and this posed a challenge to Land Surveyors in the execution of joint international boundary surveys. The Global Navigation Satellite System (GNSS) static observations were employed to collect primary data and secondary data was collected via internet, relevant organisations and archived books. The Online Positioning User Service was used to determine the WGS 84 coordinates of NYS 82 and ZP15. The raw data was analysed using Leica Geomatic Office software and the GNSS network was adjusted using three-dimensional minimally constrained network adjustment. The international boundary coordinates were tied to the WGS 84 datum which is homogeneous with ITRF2008. The transformation parameters from WGS84 to Arc 1950 datums were determined for Zambia-Malawi and Zambia-Mozambique boundaries based on twelve and seven well distributed common points respectively. The quality of fit of the Seven-Parameter transformation for the former boundary had been determined to be 0.3560m while for the latter it was 0.2724m. Keywords: geodetic datum, transformation parameters, adjustment, reference frame