SAR-datasets

The radar observations are derived from synthetic aperture radar (SAR) observations captured by Sentinel-1A, Sentinel-1B, and Sentinel-1C, part of the Copernicus Sentinel-1 -mission. These SAR images have been continuously acquired since April 2014, but Sentinel-1B only contributed data between April 2016 and December 2021 before ending data transmission. The primary imaging mode employed is the Interferometric Wide-swath (IW). These images undergo baseline processing in the Ground-Range Detected High Resolution (GRDH) mode, which contains only the amplitude information of the backscatter observation.

The SAR visualizations present the VV (Vertical–Vertical) and VH (Vertical–Horizontal) -polarized C-band backscatter from the Earth’s land surface. Each pixel within the scene is spaced at 10 meters, providing detailed information about the surface characteristics. The data are orthorectified with Copernicus 10 m digital elevation model (DEM) inside 39 European states (including islands), while elsewhere they are processed with the 30 m DEM. Radiometric terrain correction is applied, resulting in gamma zero backscatter coefficients.

The SAR visualization layers offered in Tarkka are:

‘Enhanced’. This visualization style combines VV and VH, and shows water areas in shades of blue and black, and land areas in shades of green to ochre. It is original design by Pierre Markuse for Sentinel-Hub and released under CC BY 4.0 International.

‘Linear VV’. A grayscale visualization of VV backscatter, sensitive to surface roughness. It can also capture multiple reflections from structures and features with vertical alignment such as urban areas.

‘Decibel VV’. Same as above but with a logarithmic transformation, allowing for a dynamic representation of radar reflectivity and making it easier to identify subtle changes in the Earth’s surface.

‘Decibel VH’. Same as above but based on VH backscatter, sensitive to volumetric scattering and surface properties such as vegetation.

The processing of the radar imagery utilizes the data and processing capabilities of Sentinel-Hub by Sinergise Ltd. These radar products are not available as a WMS service but can be accessed for analysis and interpretation through Tarkka web application.