Datum transformations using the NTv2 grid

June 29th, 2009, Published in Articles: PositionIT

by Julie Lovesay, Chief Directorate: National Geo-spatial Information (CD:NGI)

Prior to 1999, all geospatial data in South Africa was referenced to the Cape datum (Modified Clarke 1880 ellipsoid). Since the introduction of the Hartebeesthoek 94 datum (utilising the WGS84 ellipsoid) in 1999, GIS practitioners have faced challenges combining historical data in the Cape datum and more modern data in the Hartebeesthoek 94 datum. I have investigated an approach that can easily be used to transform data from the Cape datum to Hartebeesthoek 94. This is called the NTv2 grid which is software independent. However, it was tested within the ARC environment as this is one of the most widely used platforms.

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