
Clarke 1880 Jamaica 

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The 1:12,500 series of Jamaica topo maps uses the Clarke 1880 spheroid (JAD69 uses Clarke 1866; JAD2001 uses WGS84), and Imperial units for the eastings and northings. The author does not have the datum parameters, but an arithmetic method to convert grid coordinates to JAD69, JAD2001, and WGS84 L/L  UTM, will be found lower on the page. JAMAICAN IMPERIAL GRID: Projection: Lambert Conical Orthomorphic (alternate name for Lambert Conformal Conic) with one standard parallel Spheroid: Clarke 1880 Unit of measurement: Foot Origin: 18 N, 77 W (unknown geocentric offset of spheroid, but located within 1m horizontal of JAD69 origin) False coordinates of origin: 550,000 feet Easting, 400,000 feet Northing REPROJECT METHODS: STEP ONE: Convert Imperial Eastings and Northings to JAD69: Short formula: jad69_E = (imp_E x 0.3048) + 82360 jad69_N = (imp_N x 0.3048) + 28080 Long formula: jad69_E = (imp_E x 0.304794369) + (imp_N x 0.000015417425) + 82357.457 jad69_N = (imp_N x 0.304794369) + (imp_E x 0.000015417425) + 28091.324 For both formulas, assume an accuracy of no better than one metre. STEP TWO: Use Geotrans to convert JAD69 to JAD2001 or WGS84 L/L using the methods on the JAD69 page, and JAD2001 page. A Geotrans file that includes the JAD69 datum can be downloaded at 3_param.dat. Replace the existing Geotrans file with that one, and use JAD_3 in the dropdown list. RS Stewart (with contributions by AG Fincham, and A Haiduk), June 8, 2009 
Maps, Georeferencing, and GIS in Jamaica 