Laborde projection in Madagascar cartography and its recovery in WGS84 datum

Abstract

The International Ellipsoid 1924 was adopted in Madagascar in 1925 for the definition of the Tananarive 1925 datum, while Laborde projection have been used for Madagascar cartography in 1926. Direct and inverse Laborde formulas are reviewed to convert cartographic and geodetic coordinates. The Hotine approximation of the Laborde projection is also discussed. From the geodetic point of view, there is the need to recover the Madagascar cartographic heritage in the WGS84 datum; datum transformations in the Molodensky form are known by literature, with the three dimensional accuracy of some meters. A new set of Helmert parameters has been estimated taking in account geoid correction and giving metric accuracy. © Società Italiana di Fotogrammetria e Topografia (SIFET) 2009.