Earth & Environmental Science Journalism:

Science Research Project

Assessing the utility of combined studies of Synthetic Aperture Radar and ASTER in the Dakhla Oasis of the Western Desert of Egypt.

Laura Wright


The work discussed here is a case study in the utility of combined studies of optical and radar imagery in desert regions using Advanced Space Thermal Emission and Reflection Radiometer (ASTER), Shuttle Imaging Radar-C (SIR-C) and X-band Synthetic Aperture Radar (X-SAR) data. The purpose is to determine whether or not useful information about the paleoenvironment of an area can be obtained from combined radar and optical imagery investigations that cannot be obtained by studying a single set of data, using the Dakhla Oasis in the Western Desert of Egypt as a test site. Dakhla was chosen as the site for this study because it is home to the large-scale archaeological investigation that began in 2001 at Amheida (25.65 N, 28.75 E), the site believed to be the Roman city of Trimithus. Research Systems' ENVI 3.5 software was used for image processing. For the purposes of comparison, three scenes of X-SAR imagery were digitally mosaicked together to cover the whole of the study area covered by the SIR-C and ASTER images. The data sets were then co-registered and analyzed at 15-meter resolution. Analysis of the data revealed several paleochannels that were classified according to McCauley's 1982 paleodrainage classification scheme. Superposed drainage features revealed by radar that were not visible in ASTER suggest that there were several pluvial phases in the Dakhla Oasis, the last of which probably occurred near the end of the African Humid Period (AHP). The results of this study show that there is utility in comparative studies of radar and optical imagery in the Dakhla Oasis. Through comparison with archaeological records, it appears that the hyperarid conditions that exist in the region today probably also existed by the time Amheida was settled around 330 BC.

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Last updated: 23 May 2003, KAK.