Vertical and horizontal spheroidal boundary-value problems

Vertical and horizontal spheroidal boundary-value problems (BVPs), i.e., determination of the external gravitational potential from the components of the gravitational gradient on the spheroid, are discussed in this article. The gravitational gradient is decomposed into the series of the vertical and horizontal vector spheroidal harmonics, before being orthogonalized in a weighted sense by two different approaches. The vertical and horizontal spheroidal BVPs are then formulated and solved in the spectral and spatial domains. Both orthogonalization methods provide the same analytical solutions for the vertical spheroidal BVP, and give distinct, but equivalent, analytical solutions for the horizontal spheroidal BVP. A closed-loop simulation is performed to test the correctness of the analytical solutions, and we investigate analytical properties of the sub-integral kernels. The systematic treatment of the spheroidal BVPs and the resulting mathematical equations extend the theoretical apparatus of geodesy and of the potential theory.     

The origin of shallow landslides in Moravia (Czech Republic) in the spring of 2006

At the end of March 2006, the Czech Republic (CZ) witnessed a fast thawing of an unusually thick snow cover in conjunction with massive rainfall. Most watercourses suffered floods, and more than 90 shallow landslides occurred in the Moravian region of Eastern CZ, primarily in non-forested areas. This region, geologically part of the Outer Western Carpathians, is prone to landslides because the bedrock is highly erodible Mesozoic and Tertiary flysch.The available meteorological data (depth of snow, water equivalent of the snow, cumulative rainfall, air and soil temperatures) from five local weather stations were used to construct indices quantitatively describing the snow thaw. Among these, the Total Cumulative Precipitation (TCP) combines the amount of water from both thawing snow and rainfall. This concurrence of rain and runoff from snow melt was the decisive factor in triggering the landslides in the spring.The TCP index was applied to data of snow thaw periods for the last 20 years, when no landslides were recorded. This was to establish the safe threshold of TCP without landslides. The calculated safe threshold value for the region is ca. 100 mm of water delivered to the soil during the spring thaw (corresponding to ca. 11 mm day^− 1). In 2006, 10% of the landslides occurred under or at 100 mm of TCP. The upper value of 155 mm covered all of the landslides.     

KLENOT Project 2002–2008 contribution to NEO astrometric follow‐up

Abstract— Near‐Earth object (NEO) research plays an increasingly important role not only in solar system science but also in protecting our planetary environment as well as human society from the asteroid and comet hazard. Consequently, interest in detecting, tracking, cataloguing, and the physical characterizing of these bodies has steadily grown. The discovery rate of current NEO surveys reflects progressive improvement in a number of technical areas. An integral part of NEO discovery is astrometric follow‐up crucial for precise orbit computation and for the reasonable judging of future close encounters with the Earth, including possible impact solutions. The KLENOT Project of the Klet Observatory (South Bohemia, Czech Republic) is aimed especially at the confirmation, early follow‐up, long‐arc follow‐up, and recovery of near‐Earth objects. It ranks among the world's most prolific professional NEO follow‐up programs. The 1.06 m KLENOT telescope, put into regular operation in 2002, is the largest telescope in Europe used exclusively for observations of minor planets and comets, and full observing time is dedicated to the KLENOT team. In this paper, we present the equipment, technology, software, observing strategy, and results of the KLENOT Project obtained during its first phase from March 2002 to September 2008. The results consist of thousands of precise astrometric measurements of NEOs and also three newly discovered near‐Earth asteroids. Finally, we also discuss future plans reflecting also the role of astrometric follow‐up in connection with the modus operandi of the next generation surveys.     

Efficient road geometry identification from digital vector data

A new method for the automatic identification of road geometry from digital vector data is presented. The method is capable of efficiently identifying circular curves with their radii and tangents (straight sections). The average error of identification ranged from 0.01 to 1.30 % for precisely drawn data and 4.81 % in the case of actual road data with noise in the location of vertices. The results demonstrate that the proposed method is faster and more precise than commonly used techniques. This approach can be used by road administrators to complete their databases with information concerning the geometry of roads. It can also be utilized by transport engineers or traffic safety analysts to investigate the possible dependence of traffic accidents on road geometries. The method presented is applicable as well to railroads and rivers or other line features.     

Local quasigeoid model creation from astrogeodetic measurements

This article describes the process of creation and testing of a local quasigeoid model using the astrogeodetic method known as astronomical levelling. The process used here was based on astronomical levelling principles combined with the least square adjustment in a triangular network and a common method of surface generation. Using this method, the authors have created a quasigeoid model of a small portion of the city of Brno. This model covers an area of approximately 1 × 2 km and is based on the astronomically determined vertical deflection at 11 stations. The average distance between the astrogeodetic stations was 500 m, which is an unusually high density (5.5 stations per km²). This high geo-spatial data density input made it possible to generate a quasigeoid model of height difference precision at mm-level over few km. Tests described in this article document the suitability of our methods for creating local quasigeoid models of high precision and resolution. Employing the least square adjustment in a planar network offers the possibility to easily compute standard deviations of both input and result values. This is a great advantage in comparison with more common astrogeodetic quasigeoid profiles, which are not suitable for simple adjustment and require more complex methods to be used for evaluation of their precision. The model described here serves the authors as a technological example, from which they learn more about the potential of the astrogeodetic method. Astrogeodetic models of a much greater extent are planned to be used for validation purposes of models generated by other independent methods (gravimetric, satellite, combined, etc.).     

Effects of vegetation on channel morphodynamics: results and insights from laboratory experiments

A series of laboratory experiments demonstrates that riparian vegetation can cause a braided channel to self‐organize to, and maintain, a dynamic, single‐thread channel. The initial condition for the experiments was steady‐state braiding in non‐cohesive sand under uniform discharge. From here, an experiment consisted of repeated cycles alternating a short duration high flow with a long duration low flow, and uniform dispersal of alfalfa seeds over the bed at the end of each high flow. Plants established on freshly deposited bars and areas of braidplain that were unoccupied during low flow. The presence of the plants had the effect of progressively focusing the high flow so that a single dominant channel developed. The single‐thread channel self‐adjusted to carry the high flow. Vegetation also slowed the rate of bank erosion. Matching of deposition along the point bar with erosion along the outer bend enabled the channel to develop sinuosity and migrate laterally while suppressing channel splitting and the creation of new channel width. The experimental channels spontaneously reproduced many of the mechanisms by which natural meandering channels migrate and maintain a single dominant channel, in particular bend growth and channel cutoff. In contrast with the braided system, where channel switching is a nearly continuous process, vegetation maintained a coherent channel until wholesale diversion of flow via cutoff and/or avulsion occurred, by which point the previous channel tended to be highly unfavorable for flow. Thus vegetation discouraged the coexistence of multiple channels. Varying discharge was key to allowing expression of feedbacks between the plants and the flow and promoting the transition from braiding to a single‐thread channel that was then dynamically maintained. Copyright © 2010 John Wiley & Sons, Ltd.     

European glacial relict snails and plants: environmental context of their modern refugial occurrence in southern Siberia

Knowledge of present‐day communities and ecosystems resembling those reconstructed from the fossil record can help improve our understanding of historical distribution patterns and species composition of past communities. Here, we use a unique data set of 570 plots explored for vascular plant and 315 for land‐snail assemblages located along a 650‐km‐long transect running across a steep climatic gradient in the Russian Altai Mountains and their foothills in southern Siberia. We analysed climatic and habitat requirements of modern populations for eight land‐snail and 16 vascular plant species that are considered characteristic of the full‐glacial environment of central Europe based on (i) fossil evidence from loess deposits (snails) or (ii) refugial patterns of their modern distributions (plants). The analysis yielded consistent predictions of the full‐glacial central European climate derived from both snail and plant populations. We found that the distribution of these 24 species was limited to the areas with mean annual temperature varying from ?6.7 to 3.4 °C (median ?2.5 °C) and with total annual precipitation varying from 137 to 593 mm (median 283 mm). In both groups there were species limited to areas with colder and drier macroclimates (e.g. snails Columella columella and Pupilla loessica, and plants Kobresia myosuroides and Krascheninnikovia ceratoides), whereas other species preferred areas with relatively warmer and/or moister macroclimates (e.g. snails Pupilla turcmenica and P. alpicola, and plants Artemisia laciniata and Carex capillaris). Analysis of climatic conditions also indicated that distributional shifts of the studied species during the Pleistocene/Holocene transition were closely related to their climatic tolerances. Our results suggest that the habitat requirements of southern Siberian populations can provide realistic insights into the reconstruction of Eurasian, especially central European, glacial environments. Data obtained from modern populations also highlight the importance of wet habitats as refugia in the generally dry full‐glacial landscape.