Great Britain. Ministry of Overseas Development (Directorate of Overseas Surveys) Great Britain. Directorate of Overseas Surveys. North Decimal Degree 17.750000. South Decimal Degree 17.5000. East Decimal Degree -88.1667. West Decimal Degree -88.5000. Standard map series designation: series E755 ( D.O.S. 4499). Transverse Mercator projection. Grid: U.T.M. zone 16. Relief shown by 20 m. contour interval, shading and spot heights.