Abstract
Abstract. Sand dunes can change location, form or dimensions depending on wind direction and strength. Sand dune movements can be effectively monitored through the comparison of multi-temporal satellite images. However, not all remote sensing platforms are suitable to study sand dunes. This study compares coarse (Landsat) and fine (Worldview) resolution platforms, specifically focussing on sand dunes within the Ubari Sand Sea (Libya). Sand dune features (crest line, dune ridge basal outlines) were extracted from Landsat and Worldview 2 imagery in order to construct geomorphic maps. These geomorphic maps were then compared using image overlay and differencing, and the Root Mean Squared Error (RMSE) was used to determine if the mapped dune patterns were significantly different. It was found that Landsat is a sufficient data source when studying dune patterns within a regional sand sea, but smaller dunes identified from Worldview data were not capable of being extracted in the data sourced from Landsat. This means that for studies concerned with the dune patterns and movements within sand seas, Landsat is sufficient. But in studies where the specific dynamics of specific dunes are required, a finer resolution is required; platforms such as Worldview are needed in order to gain more detailed insight and to link the past and present day climate and environmental change.
Highlights
Sand dunes are one the most significant features created by wind driven deposition (Blumberg, 2006)
After Hugenholtz et al (2012), the aim of this study is to compare Landsat and Worldview 2 imagery to determine if similar dune patterns can be detected at the two different spatial resolutions (Landsat vs. Worldview 2), and to study dune migration within the Ubari Sand Sea
The unsupervised classification (Figure 5) gives a general idea of the dune features but is not able to separate the slopes from the crest and interdune areas successfully
Summary
Sand dunes (and draa or mega dunes) are one the most significant features created by wind driven deposition (Blumberg, 2006). Sand dune formation requires an ample supply of loose sand, little or no vegetation cover, strong winds (above the grain size threshold velocity), and topographic context that favour in sand deposition (Tsoar, 2001). Dunes within inland sand seas can change location, extend or grow (in length and height), or change form depending on wind direction and strength (Levin et al, 2004; Blumberg, 2006; Howari et al, 2007). Changes in climate can either reactivate stable dunes or stabilize active dunes (through changes in wind power, precipitation, evapotranspiration and changes in vegetation cover) and can lead to desertification (Yizhaq et al, 2009)
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