ISLA Federico Ignacio
congresos y reuniones científicas
Coastal-dune bodies recognised by SAR images
ISLA, F; CORTIZO, L
Congreso; XIV RAS; 2014
SAR (Synthetic Aperture Radar) images were conceived to monitor areas where passive remote sensing did not apply. The European Remote Sensing Satellites (ERS 1 and 2) were planned with specific periods for monitoring sea-ice contacts. However, band C (5.6 cm) can only penetrate clouds and fogs (Purkis and Klemas, 2011). Polarimetric techniques were applied to deal with different kind of forests and crops. The application of longer bands has been envisaged as a promising tool for sedimentologic purposes (Henderson and Lewis, 1998). Band L (23 cm) were applied satisfactorily to survey ground-water flows beneath sand deserts of uniform grain sizes. Images of ?radar rivers? have been reported from the Sahara, Lybia, China, Mojave, Yuma, Kara-Kum and Israel deserts (Abdelsalam et al., 2000). Performances depend on grain size, subsurface water content, and the dielectric constant of the sand (Daniels et al., 2003). Some of these techniques have been applied to coastal barriers, although they are more subject to groundwater variations, and their bedforms can change in relation to dry-sand availability and wind variations at the coastal area (Cortizo and Isla 2007, 2012). In forested or urbanised areas the diffuse reflection (also known as volume reflection) or the double-bounce effects should be considered (Fig.1). The penetration in sand diminishes with the rise of the water table. The brightness due to a high content in quartz can play against the application of images in the visible spectra (Fig.2A). The L band is a better choice to define dune bodies, or the scars of the migration of parabolic dunes (Fig.2B). The scars of transverse dunes of Mar Chiquita highlights profiles of the nucleus with large-scale crossbeds dipping to the north (Fig. 2 C and D).