Sand Dune Attributes Estimated from SAR Images

Dunes (such as linear dunes oriented in a constant direction), their size, and interdune spacing are very regular in the deserts. Therefore, they manifest a periodic pattern in terms of spatial distribution. There are several modulation transfer functions between SAR images and the actual periodic surface parameters, and the image brightness is sensitive to the local incidence angle. According to previous studies, a linear mapping process can describe these modulation processes. This study proposes an algorithm for estimating the linear dune features including linear dune direction (the prevailing wind direction), interdune spacing, and rms slope and dune height from SAR images. To estimate rms slope, two algorithms were developed, a local incidence angle method and a modulation transfer function method. The linear dune height was then calculated based on the rms slope of the surface. Finally, the obtained results were compared with the truth data from field investigations. The estimated physical quantities did not completely agree with the truth data, and possible error sources are discussed.