This layer is a georeferenced raster image of the United States Aerospace Center's Operational Navigation Chart (ONC) 1:1,000,000 map series sheet entitled: ONC J-4 : Algeria, Chad, Libya, Niger, Sudan. Edition: 6. Revision date: 1998. Printed in: 2000. Covers all or portions of: Algeria, Chad, Libya, Niger, Sudan.
The image inside the map neatline is georeferenced to the surface of the earth and fit to World Geodetic System (1984) coordinates. All map collar information is also available as part of the raster image. Series source sheets are of varying revision dates (1979-1998) and editions, published by the U.S. Defense Mapping Agency/U.S. National Imagery and Mapping Agency (later the National Geospatial-Intelligence Agency).
The source map was scanned and georeferenced for Harvard University's Center for Geographic Analysis' AfricaMap project by East View Cartographic. Individual ONC sheets covering Africa (47 sheets in total) were selected from the worldwide ONC series.
The ONC is the standard worldwide small-scale aeronautical chart series, and contains cartographic data with an aeronautical overprint depicting obstructions, aerodromes, special use airspace, navigational aids, Maximum Elevation Figures (MEFs), and related data.
ONC's also show selected topographic, cultural and hydrographic features such as: city outlines, towns and villages, rivers, lakes, landmark features (labeled), roads, railroads, towers, transmission lines, vegetation areas, clearings, and more. Ground elevation is indicated by contours (1000-foot intervals with 250-foot auxiliary contours), shading, tints, and spot heights.
Please pay close attention to map collar information for original projection information, keys and legends to grid and chart numbering and other numbers, elevations, aeronautical information, vertical obstacles, ground cover, cultural features, and other data which appear inside the neatline.