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.
Single and Multipolarimetric P-Band SAR Tomography of Subsurface Ice Structure
In this paper, first results concerning the characterization of the subsurface of ice sheets and glaciers through single and multipolarization synthetic aperture radar (SAR) tomography (TomoSAR) are illustrated. To this aim, the processing of data acquired in the framework of the European Space Agency IceSAR 2012 campaign is discussed. IceSAR 2012 was conceived so as to support the secondary objectives of the future Earth Explorer mission BIOMASS, which will be a SAR instrument with media penetration capabilities due to the use of the P-band frequency. In this regard, a tomographic study of ice was motivated by the fact that cryospheric remote sensing is of fundamental importance in order to understand more in depth the morphology and the dynamic processes regulating ice sheets. The main objective of the tomographic experiment of the campaign herein discussed was indeed to assess the capability of P-band SAR to retrieve any information about ice subsurface structure. Imaging has been achieved through TomoSAR techniques, applied to airborne multibaseline data acquired in the southwest of Greenland. Different imaging approaches are compared, and the main results achieved are presented: It is found that scattering in the upper layers of glacial subsurface can be achieved up to an extent of about 20-60 m, conditional on the different types of glaciological zone observed. Moreover, clear morphological structures have been found beneath the ice surface at one of the investigated sites.
Geographic And Environmental Influence On Maya Settlement Patterns Of The Northwest Yucatan: An Explanation For The Sparsely Settled Western Cenote Zone
Most settlement pattern research and GIS analysis of the ancient Maya of the Northern Yucatan have focused on water availability in a dry landscape where cenotes are often the only water source. While water is of paramount importance, permanent settlement secondarily requires farmable soil, a resource often as precious as water in many parts of the Yucatan. The dynamics between these resources reveal areas of ideal settlement and more challenging landscapes for which the Maya developed strategies to overcome environmental conditions. A region of the southwest "Cenote Zone", however, appears to have presented the ancient Maya with insurmountably poor environmental conditions despite abundant water resources. The lack of dense population and stone architecture in this area emphasizes the lack of a simple correlation between cenotes and settlement. This thesis uses GIS analysis to identify and explore such problematic settlement areas to better understand the factors and complexities involved in the more successful settlements of neighboring regions. iv This work is dedicated to my late father, who first introduced me to the Mundo Maya through a visit to the ruins of Tikal at the age of nine, and who instilled in me strength, curiosity, and a love for exploring the world. v ACKLOWLEDGEMENTS I'd like to acknowledge Dr. Arlen Chase and Dr. Diane Chase for providing such outstanding opportunities and instruction, and for leading by example both in the field and in the classroom. Dr. John Walker for his eye-opening perspectives, GIS instruction, inspiring hard-working attitude, and patience in the field. Dr. Clifford Brown and Dr. Walter Witschey for their invaluable correspondence and for their contributions to mapping and GIS data of Maya sites.