Characterization of different landscape surfaces in arid environments by the use of Sentinel-1 SAR data

 

The earth's arid regions were and are particularly vulnerable to climatic changes. At the same time, they are the habitat for more than 2 billion people. Due to the size of the areas, the poor infrastructure in many parts and the often adverse environmental conditions, the state of research on the rates of landscape change still has large gaps. Remote sensing data have been used intensively for monitoring drylands for several decades. But especially with regard to geomorphological processes and process rates, optical remote sensing methods often reach their limits. Within the framework of this project, the suitability of radar data for the characterisation of surfaces is therefore investigated. With the two satellites of the Sentinel-1 series of ESA (European Space Agency), a modern SAR (Synthetic Aperture Radar) with a spatial resolution of less than 15 m per pixel is available free of charge. Dry areas are particularly suitable for the use of radar remote sensing due to the low vegetation cover, as vegetation leads to volume scattering of the signal and thus distorts it. Within the scope of the investigations, both SAR intensities and interferometric coherences for the spatiotemporal characterisation of land surfaces are to be tested. The Orog-Nuur basin in southern Mongolia was selected as the test area. The region is characterised by a variety of different land surfaces and geomorphological processes. These include former lake sediments, which are modified by current periglacial processes, dunes, large beach walls of gravel and especially a variety of different alluvial fan surfaces. The different surfaces are recorded and described in detail geomorphologically on site. One focus of the work is the creation of highly accurate orthophotos and digital terrain models from drone images. Since the surface roughness strongly influences the backscatter signal of the SAR system, detailed roughness analyses for different spatial scales can be carried out with the help of the terrain models. Finally, the terrain findings and the morphometric analyses are compared with the radar data to achieve an accurate characterisation of the different surfaces from remote sensing data. If the radar data prove to be suitable for a detailed characterisation of the surfaces in dry areas, this will offer a new method for a detailed monitoring of these sensitive landscape areas. Especially in areas with a high variability, a detailed and temporally dense observation series, as offered by the Sentinel system, is of great importance.

 

Duration	09/2019 - 03/2020
Funding	DFG – Dr. G. Stauch
Project partners	Dr. T. Ullmann, Uni Würzburg