The country was initially mapped by the Tanganyika Geological Survey, based in Dodoma, and geological maps are available at a scale of 1:50,000. The sedimentary basins of Tanzania cover nearly 500,000 square km both onshore and offshore. Nearly fifty (50) wells have been drilled providing crucial subsurface geological information and knowledge on the petroleum prospectivity of the different basins. Gas has been discovered in numerous areas and is been produced from Songo Songo and Mnazi Bay. The whole country has been covered by topographic maps available in convenient scales of 1:100,000, 1:250,000 available from the Government mapping department.