Abstract
The purpose of this study is to determine the perimeter and depth of the Lagos lagoon bed located at Ilubirin, Ikoyi, Lagos Island Local Government Area, Lagos State, Nigeria for mapping of its floor topography for the purpose of dredging. The methodology and procedure involved are transferring of horizontal and vertical controls to the site, tidal observations, bathymetry survey (sounding), production of the chart, and Digital Terrain Model (DTM) of lagoon floor. All coordinates referred to Universal Transverse Mercator (UTM) Zone 31 origin. The total area of the site covered is 2.25 km2; the highest measured depth is 9.900 m from sounding line 51; and the lowest depth is 1.000 m from line 25. The DTM produced show the nature of the terrain of lagoon’s floor at Ilubirin. Therefore, it can be concluded that hydrographic survey (bathymetry) is required for the mapping of the Lagos lagoon floor at Ilubirin for determination of its topography for the purpose of dredging. It is recommended that Nigerian Government should collaborate with multinational companies to invest in hydrographic projects as such in order to explore the available underwater resources. This will also serve maritime trade, coastal zone management (CZM), tourism and Navy.

Key words: Sounding, Dredging, Lagoon, Mapping, Chart, Digital Terrain Model (DTM).