Modern mapping of the Kingdom of Tonga was established in the decade after the islands gained independence from Britain in 1970. 1:25,000 scale coverage in 23 sheets was compiled by the Directorate of Overseas Surveys (DOS), (now Ordnance Survey International (OSI)). These line maps were on the Transverse Mercator projection, International ellipsoid, used the UTM grid and plotted relief with 10 m contour intervals. Other DOS coverage included 1:50,000 scale full-color photo maps of Tongatapu island. The Tonga Ministry of Lands Survey and Natural Resources (TMLSNR) acts as the national surveying authority and maintains some larger scale mapping, including a 1:2,500 scale map of the capital Nuku’alofa. Small scale coverage includes a 1:1,000,000 scale map of the group first published in 1969, a monochrome copy of DOS mapping republished at 1:900,000 by the Hawaii Geographical Society (HGS) and a map of the islands from Pacific Maps.
Soviet military topographic mapping of Tonga exists at the following scale: 1:1,000,000 (5 sheets, complete coverage, published 1965-1973). This product is available in print, digital raster and digital vector GIS formats from East View Geospatial.
1:25,000 scale soil maps of parts of the Vava’u, and Ha’apai groups and ‘Eua island has been published with sheet explanations by the New Zealand Soil Bureau (now Landcare Research). More recent 1:100,000 scale soil mapping of Tongatapu has also been published.
Thematic mapping of the Tonga group was compiled by New Zealand agencies in the 1980s.
Other recent mapping activity has been sponsored by the South Pacific Applied Geoscience Commission (SOPAC) which in 1995 issued a bathymetric chart of the islands’ Exclusive Economic Zone.