conversion IGN Technical Note 74. 2018-04-20 true false Engineering survey, topographic mapping. 19861 Laborde Grid Longitude is referenced to the Paris meridian. See Laborde Grid (Greenwich) (projection code 8440) for equivalent in degrees referenced to Greenwich. Within a few hundred km of origin, may be approximated by Oblique Mercator method - see proj code 19911. 0 -21 49 21 0.9995 400000 800000