3D SAR imaging of the snowpack in presence of propagation velocity changes: Results from the AlpSAR campaign
In this paper we present results relative to the 3D GBSAR surveys acquired in february 2013 on the Austrian Alps as a part of the ESA campaign AlpSAR. The GBSAR was operated at X- and Ku-Band with a bandwidth of 4 GHz and employing a 2D synthetic aperture, resulting in 3D resolution capabilities at a resolution of few centimeters. Images produced at two different sites reveal the presence of multiple layers within the snowpack. The strongest backscatter contributions have been observed to correspond to bottom layers, that dominate the ones from the snow/air interface and the near subsurface. GBSAR data are observed to provide sensitivity to the propagation velocity into the snowpack, as revealed by the apparent depth variation with respect to the incidence angle.
Forest Biomass Retrieval From L-Band SAR Using Tomographic Ground Backscatter Removal
A tomographic synthetic aperture radar (TomoSAR) represents a possible route to improved retrievals of forest parameters. Simulated orbital L-band TomoSAR data corresponding to the proposed Satellites for Observation and Communications-Companion Satellite (SAOCOM-CS) mission (1.275 GHz) are evaluated for retrieval of above-ground biomass in boreal forest. L-band data and biomass measurements, collected at the Krycklan test site in northern Sweden as part of the BioSAR 2008 campaign, are used to compare biomass retrievals from SAOCOM-CS to those based on SAOCOM SAR data. Both data sets are in turn compared with the corresponding airborne case, as represented by experimental airborne SAR through processing of the original SAR data. TomoSAR retrievals use a model involving a logarithmic transform of the volumetric backscatter intensity, <inline-formula> <tex-math notation="LaTeX">$I_{\mathrm{ vol}}$ </tex-math></inline-formula>, defined as the total backscatter originating between 10 and 30 m above ground. SAR retrievals are obtained with slope-compensated intensity <inline-formula> <tex-math notation="LaTeX">$\gamma ^{0}$ </tex-math></inline-formula> using the same model. It is concluded that tomography using SAOCOM-CS represents an improvement over an airborne SAR imagery, resulting in biomass retrievals from a single polarization (HH) having a 26%–30% root-mean-square error with a little to no impact from the look direction or the local topography.
The laws of Cnut and the history of Anglo-Saxon royal promises
The ‘first’ and ‘second’ law codes of Cnut are the last surviving codes issued in the name of an Anglo-Saxon king.They are the final fruit of the interest in kingship and law and in the inter-relationship of the two which characterized the period following the monastic revival in England and which is especially associated with the name of Wulfstan, archbishop of York. Although they are far from being complete codifications of Anglo-Saxon law, they draw extensively on earlier legislation. They are different in kind from much tenth-century law, which is usually more limited and administrative in content and character, and their nature and purpose invite further consideration.