Terrain generalization with line integral convolution     

Bernhard Jenny 《制图学和地理信息科学》2021,48(1):78-92

ABSTRACT

Line integral convolution is a technique originally developed for visualizing vector fields, such as wind or water directions, that places densely packed lines following the direction of movement. Geisthövel and Hurni adapted line integral convolution to terrain generalization in 2018. Their method successfully removes details and retains sharp mountain ridges; it is particularly suited for creating generalized shaded relief. This paper extends line integral convolution generalization with a series of enhancements to reduce spurious artifacts, accentuate mountain ridges, control the level of detail in mountain slopes, and preserve sharp transitions to flat areas. The enhanced line integral convolution generalization effectively removes excessive terrain details without changing the position of terrain features. Sharp mountain ridgelines are accentuated, and transitions to flat waterbodies and valley bottoms are preserved. Shaded relief imagery derived from generalized elevation models is visually pleasing and resembles manually produced shaded relief.  相似文献   

Neoproterozoic to Early-Palaeozoic magmatic evolution in the Gondwana-derived Austroalpine basement to the south of the Tauern Window (Eastern Alps)   总被引：1，自引：0，他引：1  

Bernhard?SchulzEmail author  Klaus?Bombach  Sabine?Pawlig  Helene?Br?tz 《International Journal of Earth Sciences》2004,93(5):824-843

In the Austroalpine Basement to the south of the Tauern Window, distinct suites of metabasites occur with orthogneisses in pre-Early-Ordovician units. Tholeiitic and alkaline within-plate basalt-type metabasites are associated with acid meta-porphyroids in the post-Early-Ordovician Thurntaler Phyllite Group. According to their correlated trace element abundances, metabasite zircons crystallized with their host rocks. Protolith Pb–Pb zircon ages, whole-rock Ta/Yb–Th/Yb and oxygen, Sr, Nd isotope data define two principal evolution lines. An older evolution at elevated Th/Yb typical of subduction-related magmatism, started by 590-Ma N-MORB-type and 550–530 Ma volcanic arc basalt type basic suites, which mainly involved depleted mantle sources. It finished with mainly crustal-source 470–450-Ma acid magmatites. An other evolution line by tholeiitic and 430-Ma alkaline within-plate basalt-type suites in both pre- and post-Early-Ordovician units is characterized by an intraplate mantle metasomatism and enrichment trend along multicomponent sources. These magmatic evolution lines can be related to a plate tectonic scenario that involved terranes in a progressively mature Neoproterozoic to Ordovician active margin, and a subsequent Palaeo-Tethys passive margin along the north Gondwanan periphery.  相似文献   

Combining field and modelling techniques to assess rockfall dynamics on a protection forest hillslope in the European Alps   总被引：4，自引：0，他引：4  

Luuk K. A. Dorren  Bernhard Maier  Uif S. Putters  Arie C. Seijmonsbergen 《Geomorphology》2004,57(3-4):151-167

Adequate management of a mountain forest that protects downslope areas against impacts of rockfall requires insight into the dynamics of the hillslope environment. Therefore, we applied a combined approach, using field and modelling techniques, to assess the determining factors for rockfall source areas, rockfall tracks and rockfall runout zones on a forested slope in mountainous terrain. The first objective of this study was to understand why rockfall occurs in the study area. The second objective was to translate the knowledge obtained in the field into a model that simulates rockfall dynamics on a forested slope realistically. The third objective was to assess which hillslope characteristics primarily determine the distribution of active rockfall tracks. To achieve these objectives, we made a geomorphological map of the whole study area, and we measured the major discontinuity planes in the bedrock that are exposed in the rockfall source areas. Furthermore, a test site for simulation modelling within the larger study area was defined in which both a forest and a hillslope inventory were carried out. The available data and our developed rockfall simulation model allowed us to assess the slope characteristics that mainly determine the distribution of areas affected by rockfall. We found that in decreasing order of importance, both standing and felled trees, the surface roughness and rockfall resistant shrubs primarily determine the distribution of rockfall-affected areas. Simulation tests without a forest cover produced similar rockfall runout zones as fossil rockfall events identified in the field. We believe that the combined field and modelling approach is a prerequisite for understanding how forests can protect against rockfall.  相似文献   

Hydrochemistry of urban groundwater in Seoul, South Korea: effects of land-use and pollutant recharge   总被引：1，自引：0，他引：1  

Byoung-Young Choi  Seong-Taek Yun  Soon-Young Yu  Pyeong-Koo Lee  Seong-Sook Park  Gi-Tak Chae  Bernhard Mayer 《Environmental Geology》2005,48(8):979-990

The ionic and isotopic compositions (δD, δ¹⁸O, and ³H) of urban groundwaters have been monitored in Seoul to examine the water quality in relation to land-use. High tritium contents (6.1–12.0 TU) and the absence of spatial/seasonal change of O–H isotope data indicate that groundwaters are well mixed within aquifers with recently recharged waters of high contamination susceptibility. Statistical analyses show a spatial variation of major ions in relation to land-use type. The major ion concentrations tend to increase with anthropogenic contamination, due to the local pollutants recharge. The TDS concentration appears to be a useful contamination indicator, as it generally increases by the order of forested green zone (average 151 mg/l), agricultural area, residential area, traffic area, and industrialized area (average 585 mg/l). With the increased anthropogenic contamination, the groundwater chemistry changes from a Ca–HCO₃ type toward a Ca–Cl(+NO₃) type. The source and behavior of major ions are discussed and the hydrochemical backgrounds are proposed as the basis of a groundwater management plan.  相似文献   

Modelling transport dynamics of contaminated sediments in the headwater of a hydropower plant at the Upper Rhine River     

George Jacoub  Bernhard Westrich 《洁净——土壤、空气、水》2006,34(3):279-286

Sediments are an essential habitat compartment in rivers, which is a subject to dynamic transport processes. In many rivers, the fine deposited sediments are contaminated with heavy metals and organic compounds. Contaminated deposits are considered as potential hot spots because of the risk of the mobilization under erosive hydraulic conditions. Numerical models for particulate contaminant transport are then necessary and can be applied to estimate and predict the potential impact of mobilized contaminants as an important contribution to sediment management. This paper focuses on the quantification of the amount of contaminated sediments resuspended during the extreme flood event in 1999 and the prediction of deposition one year after the flood event. To assess such erosive flood event, a 2D numerical transport model was developed to analyse the dynamics of erosion and sedimentation processes in the headwater of a cross dam at the Upper Rhine River. The dam consists of a weir, a hydropower plant, and a navigation lock. As the weir is operating only for flood management, a huge amount of sediment highly contaminated with the hexachlorobenzene (HCB) was deposited in the weir zone. Therefore, numerical simulations were performed to determine the spatial and temporal distribution of deposited contaminated sediments as depending on the river discharge and its distribution to the hydraulic structures. The numerical investigation presented here is taken as a retrospective analysis of the contaminated sediment dynamics in the headwater to improve future sediment management.  相似文献   

中德联合冬给措纳湖地区寒区环境变迁研究进展     

杨思忠  金会军  Bernd Wünnemann  Steffen Mischke  吉延峻  陈建辉  杨奇丽 《冰川冻土》2006,28(6):850-853

青藏高原腹地的内陆湖及其湖相沉积物能够较真实地反映气候变化特征,在高原环境变迁研究中备受中外科学家的关注.2006年8月15日~9月10日,中德联合考察小组对青藏高原东北部的冬给措纳湖一带进行了第四纪冻土、地貌和地质学考察,并对湖岸阶地做了初步的数字高程分析.调查了冬给措纳湖底地形、地貌,采集了湖相沉积物样本.在湖的东岸和西岸发现多年冻土,湖泊西北山谷观察到古冰川活动遗迹.初步推测该湖是由断陷沉降形成.为进一步分析湖区气候和环境变迁,联合小组拟定2007年3月份钻取湖芯.  相似文献   

Advection of plumes in mantle flow: implications for hotspot motion, mantle viscosity and plume distribution   总被引：8，自引：0，他引：8  

Bernhard Steinberger  & Richard J. O'Connell 《Geophysical Journal International》1998,132(2):412-434

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Remediating Ground Water with Zero-Valent Metals: Chemical Considerations in Barrier Design   总被引：2，自引：0，他引：2  

Paul G. Tratnyek  Timothy L. Johnson  Michelle M. Scherer  Gerald R. Eykholt 《Ground Water Monitoring & Remediation》1997,17(4):108-114

To gain perspective and insight into the performance of permeable reactive barriers containing granular iron metal, it is useful to compare the degradation kinetics of individual chlorinated solvents over a range of operating conditions. Pseudo first-order disappearance rate constants normalized to iron surface area concentration (k_SA) recently have been reported for this purpose. This paper presents the results of further exploratory data analysis showing the extent to which variation in k_SA is due to initial halocarbon concentration, iron type, and other factors. To aid in preliminary design calculations, representative values of k_SA and a reactive transport model have been used to calculate the minimum barrier width needed for different ground water flow velocities and degrees of halocarbon conversion. Complete dechlorination of all degradation intermediates requires a wider treatment zone, but the effect is not simply additive because degradation occurs by sequential and parallel reaction pathways.  相似文献   

Editorial     

Bernhard Wehrli 《Aquatic Sciences - Research Across Boundaries》1997,59(4):193-283

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Reconstructing the iron cycle from the horizontal distribution of metals in the sediment of Baldeggersee     

Tobias Schaller  H. Christoph Moor  Bernhard Wehrli 《Aquatic Sciences - Research Across Boundaries》1997,59(4):326-344

In Baldeggersee, the distributions of solid phase Fe, Mn, V, Cr, As and Mo were determined in different sediment strata, deposited under various deep-water oxygen conditions. Iron concentrations are correlated with water depth when an anoxic sediment is in contact with an oxic water column. Benthic redox gradients trigger iron transport towards the deepest site (geochemical focusing) and loss of iron from the shallower parts through the outflow. Fe cycling in the lake is inhibited by oxygen penetration into the sediment. Vanadium and arsenic can be used as tracers for the internal Fe cycle. Their distribution patterns are highly correlated with iron. In case of a stable oxycline in the deep water, Mo is enriched in the sediment and correlates with Mn. The horizontal distribution patterns of Fe, V, As and the correlation of Fe and Mn with trace metals are promising proxy indicators for the reconstruction of deep-water oxygen conditions during deposition.  相似文献