B.J. Irwin J.R. McCullough G.R. Driscoll C. F. Polloni D. W. Folger 1990 <p>This map is one of six in a series presenting marine gravity data off the western coast of Africa (fig. 1).&nbsp; The data, collected by the U.S. Geological Survey (USGS) in 1987 in response to a request from the Defense Mapping Agency, are intended to improve gravity coverage where it has been insufficient or inadequate.&nbsp; The information shown on this and the other three maps that cover the African coast represents a total of approximately 32,000 line kilometers of marine gravity data from Western Sahara south to Gabon.&nbsp; This map includes data collected off the coasts of Senegal, Gambia, Guinea-Bissau, Guinea, and Sierra Leone from July 22 to August 20, 1987.</p> application/pdf 10.3133/mf2098D en U.S. Geological Survey Map showing free-air gravity anomalies off the western coast of Africa Senegal (south of 15° north latitude) to Sierra Leone reports