Part of an occasional Sahara A to Z series
Hang around long enough and you’ll get the full set

See also:
Old Saharan Trade Routes Map
‘V’ is for Vintage Sahara Maps
Sahara – blanks on the map
Maps of the Sahara

Here a fascinating 1960s vintage film (45 mins; French) on the work it took IGN to produce their brilliant 1:200,000 scale Sahara maps from thousands of aerial photos, sonar readings and laborious ground surveys.
Loads more in Yves R’s Sahara website and some stills below.