Antigua (1:25,000 scale)/Barbuda (1:10,000 scale)

St. Kitts/Nevis (1:25,000 scale)

The data listed above under 'basemap information I' and 'Digital Elevation Model' were developed from existing Ordinance Survey maps. The report on this DEM data development activity provides information on the data sources and procedures used to develop this digital DEM and ancillary data for Antigua/Barbuda and St. Kitts/Nevis (HTML 33k).

Georeferencing note*

Mapping of the Windward and Leeward Islands (i.e. from Anguilla to Grenada) is on British West Indies Grid, Local Astro Datums, Clarke 1880 (Modified) Ellipsoid. The exceptions are Barbuda and Barbados. The parameters of the British West Indies Grid are as follows:

Grid: British West Indies
Projection: Transverse Mercator
Latitude of Origin: Equator
Longitude of Origin: 62 deg 00 min West of Greenwich
Scale factor on central meridian: 0.9995
False co-ordinates of Origin: 400 000 metres East, nil North 
Unit of measurement: metre

The local datums for PGDM countries, and the approximate datum shifts from local datum to WGS84 Datum, are:

Antigua (but not Barbuda): USNHO Astro 1943, dX -270 m, dY +13 m, dZ +62 m
St Kitts and Nevis: K12 Astro 1955, dX +9 m, dY +183 m, dZ +236 m

Ellipsoidal definitions: British "Clarke 1880 (Modified)" = US "Clarke 1880" Semi major axis "a" = 6 378 249.145 m, semi minor axis "b" = 6 356 514.870m, flattening "f" = 1/293.465, da = -112.145 m, db = +237.444 m, df = -0.000 054 750 714, are the ellipsoidal differences between Clarke 1880 (Modified) and WGS84 Ellipsoids.

Barbuda mapping is on:

Grid: UTM Zone 20
Projection: Transverse Mercator
Latitude: Equator
Longitude: 63 deg 00 min West of Greenwich
Scale factor on central meridian: 0.9996
False co-ordinates of origin: 500 000 metres East, nil North
Unit of measurement: metre
Datum: North American 1927 (NAD27)
Ellipsoid: Clarke 1866  a 6 378 206.4 m, b 6 356 583.8 m , f 1/294.978 6982
Approx datum shift from NAD27 to WGS84: da -11, dY +175, dZ +188 metres

*Note: this georeferencing information was provided by David Lang, based on information obtained from the British Ordinance Survey.

USAID/OAS Post-Georges Disaster Mitigation:

Page last updated on 10 Sep 2001