Development of virtual morphometric globes using Blender

Virtual globes - programs implementing interactive three-dimensional (3D) models of planets - are increasingly used in geosciences. Global morphometric models can be useful for tectonic and planetary studies. We describe the development of the first testing version of the system of virtual morphometric globes for the Earth, Mars, and the Moon. As the initial data, we used three 15'-gridded global digital elevation models (DEMs) extracted from SRTM30_PLUS, the Mars Orbiter Laser Altimeter, and the Lunar Orbiter Laser Altimeter gridded archives. For three planetary bodies, we derived global digital models and maps of several morphometric attributes (i.e., horizontal curvature, vertical curvature, minimal curvature, maximal curvature, and catchment area). To develop the system, we used Blender, the open-source software for 3D modeling and visualization. First, a 3D sphere model was generated. Second, the global morphometric maps as textures were imposed to the sphere surface. Finally, the real-time 3D graphics Blender engine was used to implement globe rotation and zooming. The testing of the developed system demonstrated its good performance. Morphometric globes clearly represent peculiarities of planetary topography, according to the physical and mathematical sense of a particular morphometric variable.Comment: 14 pages, 7 figures (references corrected

Spectral filtering as a method of visualising and removing striped artefacts in digital elevation data

Spectral filtering was compared with traditional mean spatial filters to assess their ability to identify and remove striped artefacts in digital elevation data. The techniques were applied to two datasets: a 100 m contour derived digital elevation model (DEM) of southern Norway and a 2 m LiDAR DSM of the Lake District, UK. Both datasets contained diagonal data artefacts that were found to propagate into subsequent terrain analysis. Spectral filtering used fast Fourier transformation (FFT) frequency data to identify these data artefacts in both datasets. These were removed from the data by applying a cut filter, prior to the inverse transform. Spectral filtering showed considerable advantages over mean spatial filters, when both the absolute and spatial distribution of elevation changes made were examined. Elevation changes from the spectral filtering were restricted to frequencies removed by the cut filter, were small in magnitude and consequently avoided any global smoothing. Spectral filtering was found to avoid the smoothing of kernel based data editing, and provided a more informative measure of data artefacts present in the FFT frequency domain. Artefacts were found to be heterogeneous through the surfaces, a result of their strong correlations with spatially autocorrelated variables: landcover and landsurface geometry. Spectral filtering performed better on the 100 m DEM, where signal and artefact were clearly distinguishable in the frequency data. Spectrally filtered digital elevation datasets were found to provide a superior and more precise representation of the landsurface and be a more appropriate dataset for any subsequent geomorphological applications

Geomorphometric modeling and mapping of Antarctic oases

Geomorphometric modeling is widely used in geosciences. However, geomorphometric modeling and mapping of Antarctic oases has not been performed so far. This article presents the first results of our work on geomorphometric modeling and mapping of several Antarctic oases including the Larsemann Hills, Thala Hills, Schirmacher oasis, and Fildes Peninsula. As input data, we used fragments of the Reference Elevation Model of Antarctica. For each territory, we derived digital models of the following 17 morphometric variables from the extracted and edited digital elevation models: slope, aspect, horizontal curvature, vertical curvature, mean curvature, Gaussian curvature, minimal curvature, maximal curvature, unsphericity curvature, difference curvature, vertical excess curvature, horizontal excess curvature, ring curvature, accumulation curvature, catchment area, topographic index, and stream power index. Derived geomorphometric maps can be useful for structural geological and process-oriented hydrological studies. The ultimate goal of the ongoing work is to create a digital large-scale geomorphometric atlas of Antarctic oases and other ice-free Antarctic territories.Comment: 84 pages, 72 figure

EARTHQUAKE LIGHTS IN LEGENDS OF THE GREEK ORTHODOXY

Local legends may contain information about real geological events of the past. Earthquake lights (EQL) can occur in the atmosphere over earthquake epicenter areas and adjacent faults before and during quakes. They may look like diffuse airglow, flashes, fiery pillars, and luminous balls. EQL may cause a mystical experience probably due to the influence of their electromagnetic fields on the brain. Subjective perception and interpretation of EQL depend on religious and cultural traditions. We study a stereotype of EQL interpretation in the legends of the Greek Orthodoxy exemplified by the legends about the foundation of two shrines: St. George Monastery near the Cape Fiolent, Crimea and the Panagia Tripiti Church in Aigion, Peloponnese. It is argued that the similar interpretation of EQL observation in the Crimean and Peloponnesian legends were caused by similar natural and economic living conditions of the Greek population in the both regions in the Middle Ages. We also consider some examples of EQL observation took place in other regions and their interpretation in other denominations. Differences and relations between EQL of mechanoelectrical and degassing origin are discussed. Finally, we consider the role of active faults in the production of a mystical experience and sacralization of an affected landscape

The structure of the hydrodynamic plasma flow near the heliopause stagnation point

The plasma flow in the vicinity of the heliopause stagnation point in the presence of the H atom flow is studied. The plasma at both sides of the heliopause is considered to be a single fluid. The back reaction of the plasma flow on the H atom flow is neglected, and the density, temperature and velocity of the H atom flow are taken to be constant. The solution describing the plasma flow is obtained in the form of power series expansions with respect to the radial distance from the symmetry axis. The main conclusion made on the basis of the obtained solution is that the heliopause is not the surface of discontinuity anymore. Rather, it is the surface separating the flows of the solar wind and interstellar medium with all plasma parameters continuous at this surface

Global digital elevation models for terrain morphology analysis in mountain environments: insights on Copernicus GLO-30 and ALOS AW3D30 for a large Alpine area

This study focuses on the quality evaluation of two of the best 1 arc-second public global digital elevation models (DEMs), Copernicus GLO-30 DEM and ALOS AW3D30 DSM, from the perspective of their capability to represent the terrain fine-scale morphology of a complex alpine landscape, located in the Italian Trentino Province. The analysis is performed on an area of 6210 km(2), considering a reference DEM derived from a high resolution and accurate airborne Lidar survey. The quality assessment goes beyond a conventional approach based on elevation differences statistics, computed on a pixels-by-pixel basis. An ad hoc approach for evaluating the capability to represent fine-scale morphology, including surface roughness, is adopted. Moreover, the quality analysis is performed considering the influence of local morphology and of the different land covers. The findings show that although the two global DEMs have comparable overall quality, their relative performances change according to local landscape characteristics. Copernicus DEM performance is on average better than ALOS in correspondence of urbanized areas as well as in areas without vegetation cover, with gentle slopes and relatively low short-range roughness. Meanwhile, ALOS DEM performance is slightly better than Copernicus in rougher terrain and steeper slopes. In general, both DEMs have poor performances in steep slopes, with a limited capability to describe fine-scale morphology. The adoption of these global DEMs for terrain analysis and modelling of earth surface processes should be performed carefully, considering the impact of different land covers and of local morphology, including surface roughness

Vegetation and Topographic Control on Spatial Variability of Soil Organic Carbon

Soil organic carbon (SOC) is one of the most important parameters affecting the hydraulic characteristics of natural soils. Despite being rather easy to measure, SOC is known to be highly variable in space. In this study, vegetation, climate, and morphology factors were used to reproduce the spatial distribution of SOC in the mineral horizons of forest and grassland areas in north-western Italy and the feasibility of the approach was evaluated. When the overall sample (114 samples) was analyzed, average annual rainfall and elevation were significant descriptors of the SOC variability. However, a large part of the variability remains unexplained. Two stratification criteria were then adopted, based on vegetation and topographic properties. We obtained an improvement of the quality of the estimates, particularly for grasslands and forests in the absence of local curvatures. These results indicate that the spatial variability of soil organic matter is scarcely reproducible at the regional scale, unless an a-priori reduction of the heterogeneity is applied. A discussion on the feasibility of applying stratification criteria to deal with heterogeneous samples closes the pape