Abstract
Space-borne Synthetic Aperture Radar (SAR) has the capability to image subsurface features down to several meters in arid regions. A first demonstration of this capability was performed in the Egyptian desert during the early eighties, thanks to the first Shuttle Imaging Radar mission. Global coverage provided by recent SARs, such as the Japanese ALOS/PALSAR sensor, allowed the mapping of vast ancient hydrographic systems in Northern Africa. We present a summary of palaeohydrography results obtained using PALSAR data over large deserts such as the Sahara and the Gobi. An ancient river system was discovered in eastern Lybia, connecting in the past the Kufrah oasis to the Mediterranean Sea, and the terminal part of the Tamanrasett river was mapped in western Mauritania, ending with a large submarine canyon. In southern Mongolia, PALSAR images combined with topography analysis allowed the mapping of the ancient Ulaan Nuur lake. We finally show the potentials of future low frequency SAR sensors by comparing L-band (1.25 GHz) and P-band (435 MHz) airborne SAR acquisitions over a desert site in southern Tunisia.
Highlights
Space-borne Synthetic Aperture Radar (SAR) allows the mapping of continental surfaces at centimetre-scale wavelengths
SAR is able to probe the subsurface down to several meters: it was shown that L-band (1.25 GHz) radar is able to penetrate meters of low electrical loss material such as sand [2,3]
The end of the Kufrah River disperses as a network of small shallow channels across the surface of the about 300 km away to the northwest and emerging from beneath the Calanscio Sand Sea, lies the broad Sarir Dalmah alluvial fan, that covers more than 15,000 km2, possibly constituting an inland major, 2 to 4 km-wide, alluvium-filled Wadi Sahabi palaeochannel that incised more than 300 m into bedrock
Summary
Space-borne Synthetic Aperture Radar (SAR) allows the mapping of continental surfaces at centimetre-scale wavelengths. The whole dataset is managed with the help of a web map server, allowing the import and 1 × 1 SRTM squares, covering latitudes between 17◦ N and 37◦ N and longitudes between 17◦ W display of PALSAR data using Google Earth It is freely accessible through a dedicated web site [14]. The PALSAR dataset was palaeo-environment and palaeoclimate of North Africa and Arabia It helps in the building of extended to the Gobi Desert in Central Asia, covering latitudes between 34° N and 52° N and longitudes more complete geological maps and in support of future water prospecting in arid and semi-arid between 73° E and 120° E. regions [15].
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