Clarke 1880 Jamaica

 

Caving News Jamaican Caves Organisation JCO Main Page
Support Jamaican Caving   Contact the JCO

JAD69
JAD2001

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 drop-down list.


RS Stewart (with contributions by AG Fincham, and A Haiduk),
June 8, 2009


Maps, Georeferencing, and GIS in Jamaica