Cartography-Oriented Design of 3D Geospatial Information Visualization – Overview and Techniques

In economy, society and personal life map-based interactive geospatial visualization becomes a natural element of a growing number of applications and systems. The visualization of 3D geospatial information, however, raises the question how to represent the information in an effective way. Considerable research has been done in technology-driven directions in the fields of cartography and computer graphics (e.g., design principles, visualization techniques). Here, non-photorealistic rendering (NPR) represents a promising visualization category – situated between both fields – that offers a large number of degrees for the cartography-oriented visual design of complex 2D and 3D geospatial information for a given application context. Still today, however, specifications and techniques for mapping cartographic design principles to the state-of-the-art rendering pipeline of 3D computer graphics remain to be explored. This paper revisits cartographic design principles for 3D geospatial visualization and introduces an extended 3D semiotic model that complies with the general, interactive visualization pipeline. Based on this model, we propose NPR techniques to interactively synthesize cartographic renditions of basic feature types, such as terrain, water, and buildings. In particular, it includes a novel iconification concept to seamlessly interpolate between photorealistic and cartographic representations of 3D landmarks. Our work concludes with a discussion of open challenges in this field of research, including topics, such as user interaction and evaluation.     

Measurements of meteor smoke particles during the ECOMA-2006 campaign: 1. Particle detection by active photoionization

We present a new design of an in situ detector for the study of meteor smoke particles (MSPs) in the middle atmosphere. This detector combines a classical Faraday cup with a xenon-flashlamp for the active photoionization/photodetachment of MSPs and the subsequent detection of corresponding photoelectrons. This instrument was successfully launched in September 2006 from the Andøya Rocket Range in Northern Norway. A comparison of photocurrents measured during this rocket flight and measurements performed in the laboratory proves that observed signatures are truly due to photoelectrons. In addition, the observed altitude cut-off at 60 km (i.e., no signals were observed below this altitude) is fully understood in terms of the mean free path of the photoelectrons in the ambient atmosphere. This interpretation is also proven by a corresponding laboratory experiment. Consideration of all conceivable species which can be ionized by the photons of the xenon-flashlamp demonstrates that only MSPs can quantitatively explain the measured currents below an altitude of 90 km. Above this altitude, measured photocurrents are most likely due to photoionization of nitric oxide. In conclusion, our results demonstrate that the active photoionization and subsequent detection of photoelectrons provides a promising new tool for the study of MSPs in the middle atmosphere. Importantly, this new technique does not rely on the a priori charge of the particles, neither is the accessible particle size range severely limited by aerodynamical effects. Based on the analysis described in this study, the geophysical interpretation of our measurements is presented in the companion paper by Strelnikova, I., et al. [2008. Measurements of meteor smoke particles during the ECOMA-2006 campaign: 2. results. Journal of Atmospheric and Solar-Terrestrial Physics, this issue, doi:10.1016/j.jastp.2008.07.011].     

An infiltration model based on flow variability in macropores: development, sensitivity analysis and applications

Simulating infiltration in soils containing macropores still provides unsatisfactory results, as existing models seem not to capture all relevant processes. Recent studies of macropore flow initiation in natural soils containing earthworm channels revealed a distinct flow rate variability in the macropores depending on the initiation process. When macropore flow was initiated at the soil surface, most of the macropores received very little water while a few macropores received a large proportion of the total inflow. In contrast, when macropore flow was initiated from a saturated or nearly saturated soil layer, macropore flow rate variation was much lower. The objective of this study was to develop, evaluate, and test a model, which combines macropore flow variability with several established approaches to model dual permeability soils. We then evaluate the INfiltration–INitiation–INteraction Model (IN³M) to explore the influence of macropore flow variability on infiltration behavior by performing a sensitivity analysis and applying IN³M to sprinkling and dye tracer experiments at three field sites with different macropore and soil matrix properties. The sensitivity analysis showed that the flow variability in macropores reduces interaction between the macropores and the surrounding soil matrix and thus increases bypass flow, especially for surface initiation of macropore flow and at higher rainfall intensities. The model application shows reasonable agreement between IN³M simulations and field data in terms of water balance, water content change, and dye patterns. The influence of macropore flow variability on the hydrological response of the soil was considerable and especially pronounced for soils where initiation occurs at the soil surface. In future, the model could be applied to explore other types of preferential flow and hence to get a generally better understanding of macropore flow.     

Climate and relief-induced controls on the temporal variability of denudation rates in a granitic upland

How soil erosion rates evolved over the last about 100 ka and how they relate to environmental and climate variability is largely unknown. This is due to a lack of suitable archives that help to trace this evolution. We determined in situ cosmogenic beryllium-10 (¹⁰Be) along vertical landforms (tors, boulders and scarps) on the Sila Massif to unravel their local exhumation patterns to develop a surface denudation model over millennia. Due to the physical resistance of tors, their rate of exhumation may be used to derive surface and, thus, soil denudation rates over time. We derived soil denudation rates that varied in the range 0–0.40 mm yr^-1. The investigated boulders, however, appear to have experienced repositioning processes about ~20–25 ka bp and were therefore a less reliable archive. The scarps of the Sila upland showed a rapid bedrock exposure within the last 8–15 ka. Overall, the denudation rates increased steadily after 75 ka bp but remained low until about 17 ka bp . The exhumation rates indicate a denudation pulse that occurred about 17–5 ka bp . Since then the rates have continuously decreased. We identify three key factors for these developments – climate, topography and vegetation. Between 75 and 17 ka bp , climate was colder and drier than today. The rapid changes towards warmer and humid conditions at the Pleistocene–Holocene transition apparently increased denudation rates. A denser vegetation cover with time counteracted denudation. Topography also determined the extent of denudation rates in the upland regime. On slopes, denudation rates were generally higher than on planar surfaces. By determining the exhumation rates of tors and scarps, soil erosion rates could be determined over long timescales and be related to topography and particularly to climate. This is key for understanding geomorphic dynamics under current environmental settings and future climate change. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

Higher and lowest order mixed finite element approximation of subsurface flow problems with solutions of low regularity

In this work we study mixed finite element approximations of Richards’ equation for simulating variably saturated subsurface flow and simultaneous reactive solute transport. Whereas higher order schemes have proved their ability to approximate reliably reactive solute transport (cf., e.g. [Bause M, Knabner P. Numerical simulation of contaminant biodegradation by higher order methods and adaptive time stepping. Comput Visual Sci 7;2004:61–78]), the Raviart–Thomas mixed finite element method (RT₀) with a first order accurate flux approximation is popular for computing the underlying water flow field (cf. [Bause M, Knabner P. Computation of variably saturated subsurface flow by adaptive mixed hybrid finite element methods. Adv Water Resour 27;2004:565–581, Farthing MW, Kees CE, Miller CT. Mixed finite element methods and higher order temporal approximations for variably saturated groundwater flow. Adv Water Resour 26;2003:373–394, Starke G. Least-squares mixed finite element solution of variably saturated subsurface flow problems. SIAM J Sci Comput 21;2000:1869–1885, Younes A, Mosé R, Ackerer P, Chavent G. A new formulation of the mixed finite element method for solving elliptic and parabolic PDE with triangular elements. J Comp Phys 149;1999:148–167, Woodward CS, Dawson CN. Analysis of expanded mixed finite element methods for a nonlinear parabolic equation modeling flow into variably saturated porous media. SIAM J Numer Anal 37;2000:701–724]). This combination might be non-optimal. Higher order techniques could increase the accuracy of the flow field calculation and thereby improve the prediction of the solute transport. Here, we analyse the application of the Brezzi-Douglas-Marini element (BDM₁) with a second order accurate flux approximation to elliptic, parabolic and degenerate problems whose solutions lack the regularity that is assumed in optimal order error analyses. For the flow field calculation a superiority of the BDM₁ approach to the RT₀ one is observed, which however is less significant for the accompanying solute transport.     

The effect of forcing and landscape distribution on performance and consistency of model structures

It is often challenging to determine the appropriate level of spatial model forcing and model distribution in conceptual rainfall‐runoff modelling. This paper compares the value of incorporating both spatially distributed forcing data and spatially distributed model conceptualisations based on landscape heterogeneity, applied to the Ourthe catchment in Belgium. Distributed forcing data were used to create a spatial distribution of model states. Eight different configurations were tested: a lumped and distributed model structure, each with four levels of model state distribution. The results show that in the study catchment the distributed model structure can in general better reproduce the dynamics of the hydrograph, and furthermore, that the differences in performance and consistency between calibration and validation are smallest for the distributed model structure with distributed model states. For the Ourthe catchment, it can be concluded that the positive effect of incorporating a distributed model structure is larger than that of incorporating distributed model states. Distribution of model structure increases both model performance and consistency. Copyright © 2015 John Wiley & Sons, Ltd.     

Arsenic in seawater and brown algae of the Baltic and the North Sea

A long-term study within the pilot environmental specimen bank programme of the Federal Republic of Germany on arsenic levels in coastal and open seawater and their reflection in the brown seaweed (Fucus vesiculosus) has been performed. Dissolved arsenic was on average 0.76 (range 0.45–1.11) μgl⁻¹ for 17 sampling stations in the Baltic Sea, whereas contents of dissolved arsenic are somewhat higher in shallow waters of the coastal zone of the North Sea. Total arsenic levels in algae ranged up to 40 mg kg⁻¹ (dry weight) and showed for the four locations studied obvious seasonal variations for comparatively nonpolluted or nondisturbed locations only. However, probably due to biological influences, the results obtained so far indicate that composite samples integrating a one year period are supposed to be the best strategy for future environmental specimen banking. Using a new efficient speciation technique the percentage of chemically stable organoarsenic compounds in the investigated algae has been found to be 95% of the total arsenic content and thus somewhat lower than in teleost fish. For comparison, typical data for a few other algae species from the Baltic and the Mediterranean Sea are also shown.     

Meso- and bathy-pelagic fish parasites at the Mid-Atlantic Ridge (MAR): Low host specificity and restricted parasite diversity

Seven meso- and bathy-pelagic fish species from the Mid-Atlantic Ridge (MAR) were firstly studied for fish parasites and feeding ecology. With a total of seven parasite species, the 247 meso- and bathy-pelagic deep-sea fish specimens belonging to the families Melamphaidae (3 spp.), Myctophidae (3 spp.) and Stomiidae (1 sp.) revealed low parasite diversity. The genetically identified nematodes Anisakis simplex (s.s.) and Anisakis pegreffii from the body cavity, liver and muscles of Myctophum punctatum were the most abundant parasites, reaching a prevalence of 91.4% and mean intensity of 3.1 (1–14). Anisakis sp. (unidentified) infected Chauliodus sloani and Poromitra crassiceps. Bothriocephalidean and tetraphyllidean cestode larvae infected Benthosema glaciale, the latter also occurring in C. sloani and Scopelogadus beanii, at low prevalences. Adult parasites at low infection rates included the digenean Lethadena sp. (2.9%), and the two copepod species Sarcotretes scopeli (5.7%) and Tautochondria dolichoura (5.3–11.4%). The myctophid Lampanyctus macdonaldi and the melamphaid Scopelogadus mizolepis mizolepis were free of parasites. Analyses of the stomach contents revealed crustaceans, especially copepods and euphausiids for the myctophids and also amphipods for the melamphaids as predominant prey items. While all stomachs showing distinct content comprising often unidentified ‘tissue’ (possibly gelatinous zooplankton), only C. sloani preyed upon fish. Though this feeding habit would enable transfer of a variety of crustacean-transmitted parasites into the fish, the parasite fauna in the meso- and bathy-pelagic fish was species poor. All observed parasites showed low host specificity, demonstrating no distinct pattern of host–parasite co-evolution. The MAR is no barrier for the parasite distribution in the North Atlantic meso- and bathy-pelagial.