Investigating the use of the dual-polarized and large incident angle of SAR data for mapping the fluvial and aeolian deposits

Abstract

a b s t r a c tMapping the spatial distributions of the fluvial deposits in terms of particles size as well as imaging the near-surface features along the non-vegetated aeolian sand-sheets, provides valuable geological information. Thus this work aims at investigating the contribution of the dual-polarization SAR data in classifying and mapping the surface sediments as well as investigating the effect of the radar incident-angle on improving the images of the hidden features under the desert sand cover. For mapping the fluvial deposits, the covariance matrix ([C 2 ]) using four dual-polarized ALOS/PALSAR-1 scenes cover the Wadi El Matulla, East Qena, Egypt were generated. This [C 2 ] matrix was used to generate a supervised classification map with three main classes (gravel, gravel/sand and sand). The polarimetric scattering response, spectral reflectance and temperatures brightness of these 3 classes were extracted. However for the aeolian deposits investigation, two Radarsat-1 and three full-polarimetric ALOS/PALSAR-1 images, which cover the northwestern sandy part of Sinai, Egypt were calibrated, filtered, geocoded and ingested in a GIS database to image the near-surface features. The fluvial mapping results show that the values of the radar backscattered coefficient (r°) and the degree of randomness of the obtained three classes are increasing respectively by increasing their grain size. Moreover, the large incident angle (h i = 39.7) of the Radarsat-1 image has revealed a meandering buried stream under the sand sheet of the northwestern part of Sinai. Such buried stream does not appear in the other optical, SRTM and SAR dataset. The main reason is the enhanced contrast between the low backscattered return from the revealed meandering stream and the surroundings as a result of the increased backscattering intensity, which is related to the relatively large incident angle along the undulated surface of the study area. All archaeological observations support the existence of paleo-fresh water lagoon at the northwestern corner of the study area, which might have been the discharge lagoon of the revealed hidden stream.

Using InSAR Coherence for Investigating the Interplay of Fluvial and Aeolian Features in Arid Lands: Implications for Groundwater Potential in Egypt

“…Radar images have been utilized in previous works along the Eastern Sahara to reveal locations of sand-buried courses of ancient rivers and streams [30,[53][54][55]. However, in this work, four Sentinel-1 radar images with the Vertical-Vertical (VV) polarization covering the study areas (two for each) were selected to match the same acquisition dates as the optical Sentinel-2 images (16 September 2016, and 28 December 2017, for Wadi El-Matulla and 28 September 2016, and 28 December 2017, for El-Gallaba Plain).…”

“…Starting in the 1980s, space shuttle missions have been used for exploring large-scale and difficult-to-access areas along the eastern Sahara [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Space-borne images of the earth provide different levels of information that can be interpreted into considerable information of geomorphological, geological, and hydrological features.…”

“…Space-borne images of the earth provide different levels of information that can be interpreted into considerable information of geomorphological, geological, and hydrological features. Radar sensors, such as the ones onboard of the space shuttle missions, have the ability to penetrate the dry sand sheet of the deserts and provide valuable information about the near-surface features, which is used as complementary information to that provided by visible and infrared sensors [14,[28][29][30]. The Great Sahara, including the Egyptian deserts, are considered by many researchers as a type locality, which exemplifies the driest Earth environment.…”

Recognizing the Wadi Fluvial Structure and Stream Network in the Qena Bend of the Nile River, Egypt, on Landsat 8-9 OLI Images

“…Hamdan and Khozyem [33] applied the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and Geographic Information System (GIS) techniques to delineate drainage networks in the Wadi El-Mathula watershed in the Central Eastern Desert. Various methods of geomorphometric modeling exist and can be applied to detect the spatial patterns of fluvial systems, or for hydrogeological modeling aimed at the analysis of groundwater potential [34][35][36]. The geometry and morphology of the relief and the characteristics of topographic parameters such as slope, aspect, and hillshade can be extracted as morphometric characteristics for the analysis of watersheds using 3D mapping [37].…”

Enhanced lithological mapping of Durba-Araba basement blocks, along the eastern margin of the Central Gulf of Suez Rift, Egypt, using Landsat-8 Data

“…The digital format of remote sensing data enables advanced image processing techniques, which, in turn, enhance the extraction of information for mapping (Ghrefat et al 2021). Remote sensing is a significant tool for tracing lithological boundaries, and it is widely used in regional and detailed mapping, geomorphological and structural interpretation, and mineral prospecting (Crosta 1989;Hassan et al 2015;Hassan and Sadek 2017;Zakeri et al 2017;Gaber et al 2017;Beiranvand Pour et al 2018;Abu El-Leil et al 2019;Rajan Girija and Mayappan 2019;Hamimi et al 2020;Abdelkareem et al 2021). The progress made so far in the optical Landsat-8 (OLI) data is appropriate for remote lithological mapping and reducing the cost and time of field surveys and displays an array of multispectral data spanning a large area (Zhu and Abdelkareem 2021).…”