The maps used were produced by the Directorate of Overseas Surveys in the post-war years. The phase 1 area is covered by topographic mapping at 1:50 000 scale. Grid co-ordinates of sample sites were obtained by digitising locations marked on sampling maps, and are expressed in metres - one sample is from only 277m north of the equator, thus a Northing of 277. For some of the Phase 2 area the most detailed published maps available are at 1:250 000 scale. Aerial photographs were used to provide supplementary topographic and geological information. The map projection is UTM (Zone 37) and the Clarke 1880 spheroid is used (equatorial axis 6378249m, polar axis 6356515m). No locational data is available in the U.K. for the pan concentrates from sheet 105/3 (Area Code 53), but as they originate from a small area they have been retained for information.