Wavelets applied to simplification of digital terrain models

Wavelet thresholding is used to generate simplified terrain models. This non-linear filtering technique is adaptive in the sense that the large wavelet coefficients in areas of high relief are kept, whereas all coefficients smaller than a threshold value, representing smooth areas, are thrown away. The degree of detail in the simplified model is controlled by the number of wavelet coefficients retained. Two different areas are analysed using this method. The experiments show the smoothing effect of the thresholding, and how the main terrain features survive as the threshold value increases. At large threshold values the method introduces blocking artifacts in the model.     

Measuring the significance of a divide to local drainage patterns

This article presents a framework for estimating a new topographic attribute derived from digital elevation models (DEMs) called maximum branch length (B _max). Branch length is defined as the distance travelled along a flow path initiated at one grid cell to the confluence with the flow path passing through a second cell. B _max is the longest branch length measured for a grid cell and its eight neighbours. The index provides a physically meaningful method for assessing the relative significance of drainage divides to the dispersion of materials and energy across a landscape, that is, it is a measure of ‘divide size’. B _max is particularly useful for studying divide network structure, for mapping drainage divides, and in landform classification applications. Sensitivity analyses were performed to evaluate the robustness of estimates of B _max to the algorithm used to estimate flow lengths and the prevalence of edge effects resulting from inadequate DEM extent. The findings suggest that the index is insensitive to the specific flow algorithm used but that edge effects can result in significant underestimation along major divides. Edge contamination can, however, be avoided by using an appropriately extensive DEM.     

Catalyzed Reactions on Mineral Plaster Materials Used for Indoor Air Purification

Zeolites have been used for a long time for purification and catalytical purposes. Recently, first products appeared on the market using zeolites also for improving the indoor air quality so far volatile organic compounds (VOC) are concerned. However, porous compounds like zeolites can be found also in plaster material. Therefore, it was manifest to evaluate the capability of plaster with regard to air cleaning. In this article, the contribution of plaster compounds toward adsorption and catalytical decomposition of VOCs is evaluated using α‐pinene, chlorobenzene, 2‐ethoxyethylacetate, and pentanal as target substances under standard conditions (23°C, 50% r.H.). These compounds were chosen because of their VOC typical physicochemical properties like molecular dimensions, density, boiling point, vapor pressure, and octanol–water distribution coefficient (logk_ow). Hydrated lime and metakaolin were found out to have good adsorption properties under these circumstances. Also natural zeolites showed good results especially on pentanal. By investigations in environmental chambers the reduction potential of test plasters on chlorobenzene and 2‐ethoxyethylacetate concentrations could be shown. Application of coatings had no or only temporary influence on the performance of the plaster. Additional tests in small chambers demonstrated the possibility to improve the properties of plasters with help of FAU‐ or MFI‐type zeolites but the experiments also showed that α‐pinene and pentanal undergo chemical reactions. Further effort should be made on investigations also toward other compounds, especially more volatile ones like formaldehyde. Also additional building materials like insulation material or boards should be taken into account.     

On the influence of DC railway noise on variation data from Belsk and Lviv geomagnetic observatories

Geomagnetic variation data from the observatories in Belsk (BEL, Poland) and Lviv (LVV, Ukraine) significantly suffer from disturbances caused by direct current (DC) electric railways. The aim of this study is to quantify the impact of these disturbances on quantities derived from such data, as the K index of magnetic activity and the induction arrow used in the geomagnetic deep sounding method to indicate lateral contrasts of electric conductivity in the solid earth. Therefore, undisturbed data have been reconstructed by means of a frequency-domain transfer function that relates the horizontal magnetic field components of the observatory to the ones synchronously recorded at a noise-free reference station. The comparison of the K index derived from original and reconstructed data shows an increase of quiet time segments by 29% for LVV and by 14% for BEL due to our noise removal procedure. Furthermore, the distribution of the corrected K indices agrees well with the one from the Niemegk observatory in Germany.     

Modeling of deep magnetovariation soundings on the rotating earth

Induced magnetic fields in the Earth arise due to two phenomena: induction generated by the time-variable exciting field and the motional induction caused by movement of the conductive planet in the outer magnetic fields. The comparison of both approaches on the spherical Earth has been analyzed in the present work for two sources in the ionosphere and magnetosphere. For this aim, both sources with their natural sizes and positions have been modeled analytically to obtain the fields on the layered sphere at the middle latitudes. The conditions when the steady ring current field is not influenced by the Earth’s rotation have been established theoretically. The synthetic diurnal magnetograms were used for the deep sounding by the magnetovariation spatial gradient method and the result was compared with the one obtained on the nonrotating sphere. Sounding results using both approaches were found different above the 2D inhomogeneous mantle. The precessions of the magnetospheric belt current pole for daily sampling frequency were presented using several geomagnetic observatory data in the northern hemisphere.     

Analysis and farmers’ perception of climate change in the Kashmir Valley,India

Theoretical and Applied Climatology - Analysis of climatic variables is important for the detection and attribution of climate change trends and has received considerable attention from researchers...     

Automated mapping of rock slope geometry,kinematics and stability with RSS-GIS

A GIS-implemented, deterministic approach for the automated spatial evaluation of geometrical and kinematical properties of rock slope terrains is presented. Based on spatially distributed directional information on planar geological fabrics and DEM-derived topographic attribute data, the internal geometry of rock slopes can be characterized on a grid cell basis. For such computations, different approaches for the analysis and regionalization of available structural directional information applicable in specific tectonic settings are demonstrated and implemented in a GIS environment. Simple kinematical testing procedures based on feasibility criteria can be conducted on a pixel basis to determine which failure mechanisms are likely to occur at particular terrain locations. In combination with hydraulic and strength data on geological discontinuities, scenario-based rock slope stability evaluations can be performed. For conceptual investigations on rock slope failure processes, a GIS-based specification tool for a 2-D distinct element code (UDEC) was designed to operate with the GIS-encoded spatially distributed rock slope data. The concepts of the proposed methodology for rock slope hazard assessments are demonstrated at three different test sites in Germany.