Desert Erg Iguidi, Algeria, True Colour Satellite Image. True colour satellite image of Erg Iguidi, a sand desert between Algeria and Mauritania. The 250m wide dunes lay in the South on a sand plain, and in the North on a blakek sandstone area. The light blue areas are calcareous and salt crusts left out from the evaporation of the oueds' water. Image taken on 29 March 1987 using LANDSAT data.