The number of web services providing cartographic data is increasing. A main challenge is to enable a user to combine these services, not only from a technical perspective, but also from a cartographic one. One common use case for these services is to create mashups based on thematic polygons on top of background maps. In this study we compare four cartographic designs of thematic polygons: only boundaries, transparencies, hatches and icons. The aim of the comparison is to investigate whether the designs are good for identifying the extent of the polygons and if the design disturbs the reading of the background map. The comparison is based on an eye-tracking study, where 24 participants performed polygon identification tasks as well as background search tasks. The study revealed that hatches were more efficient than the other designs for polygon identification. Hatches had significantly shorter total fixation times as well as scanpath lengths, possibly since the participants were able to identify the extent of the polygon solely based on the interior (i.e. the hatches), while for the other designs the participants were extensively reliant on the boundaries. However, the results also indicate that the hatches design disturbs the reading of the background map more than the other designs; hatches also appear visually unpleasant for many users. Since each design had its strengths and weaknesses, we recommend producers of services for thematic data to provide several designs so users can select an appropriate design for their own use cases. 相似文献
AbstractDetecting and describing movement of vehicles in established transportation infrastructures is an important task. It helps to predict periodical traffic patterns for optimizing traffic regulations and extending the functions of established transportation infrastructures. The detection of traffic patterns consists not only of analyses of arrangement patterns of multiple vehicle trajectories, but also of the inspection of the embedded geographical context. In this paper, we introduce a method for intersecting vehicle trajectories and extracting their intersection points for selected rush hours in urban environments. Those vehicle trajectory intersection points (TIP) are frequently visited locations within urban road networks and are subsequently formed into density-connected clusters, which are then represented as polygons. For representing temporal variations of the created polygons, we enrich these with vehicle trajectories of other times of the day and additional road network information. In a case study, we test our approach on massive taxi Floating Car Data (FCD) from Shanghai and road network data from the OpenStreetMap (OSM) project. The first test results show strong correlations with periodical traffic events in Shanghai. Based on these results, we reason out the usefulness of polygons representing frequently visited locations for analyses in urban planning and traffic engineering. 相似文献
In this study a 2D basin model has been built along a transect crossing the Horn Graben in WNW-ESE direction. The aim of the investigation was to improve the understanding of the thermal evolution of the basin and its influence on possible petroleum systems. The 2D model of the subsurface is based on one seismic line and data from two exploration wells. Both wells TD’ed in Triassic sediments. The updoming of the Ringkøbing-Fyn High began during Late Carboniferous–Early Permian. At the end of the Permian the Horn Graben became active due to regional extension. The subsequent sedimentation history from Triassic to date is well recorded by well reports. A matter of debate has been whether or not significant amounts of Pre-Permian sediments exist in this area of the North Sea. Since organic material rich Paleozoic sediments serve as source rocks in widespread areas of North Germany and the southern North Sea it would be of great importance to know whether the same deposits exist in the Horn Graben. Nielsen et al. (Bull Geol Soc Denmark Copenhagen 45:1–10, 1998) introduced a model, which shows Paleozoic sediments covering the basement at a maximum depth of 6.5 km. Assuming, Paleozoic sediments are underlying the Permian salt deposits there should be an active petroleum system present. The 2D model includes the Paleozoic source rock and tries to explain why two exploration wells have not found petroleum. 相似文献
The purpose of this paper is to present a simple methodology to improve the evaluation of the human-biometeorological benefits of open spaces. It is based on two groups of new indices using as basis the well-known PET index. This simple methodology along with the accompanying indices allows a qualitative and quantitative evaluation of the climatic behavior of the selected sites. The proposed methodology was applied in a human-biometeorology research in the city of Athens, Greece. The results of this study are in line with the results of other related studies indicating the considerable influence of the sky view factor (SVF), the existence of the vegetation and the building material on human-biometeorological conditions. The proposed methodology may provide new insights in the decision-making process related to urban open spaces’ best configuration.
The speed of calculating sensitivities for 3-D conductivity structures for time- domain electromagnetic methods is significantly improved by applying the reciprocity theorem directly in the time domain. The sensitivities are obtained by convolving the electric field in the subsurface due to a transmitter at the surface with the electric field impulse response due to another transmitter, which replaces the original receiver. The acceleration compared to the classical perturbation method is approximately P/R , where P is the number of model parameters and R is the number of receiver positions. If the sensitivity has to be calculated very close to the receiver, approximate sensitivities can be obtained using an integral condition. Comparisons with the classical perturbation approach show that the method gives accurate results. Examples using transmitter–receiver configurations from a long-offset transient electromagnetics survey demonstrate the usefulness of sensitivities for the evaluation of resolution properties. 相似文献
Gabbroic and ultramafic xenoliths and olivine and clinopyroxene phenocrysts in basaltic rocks from Gran Canaria, La Palma,
El Hierro, Lanzarote and La Gomera (Canary Islands) contain abundant CO2-dominated fluid inclusions. Inclusion densities are strikingly similar on a regional scale. Histogram maxima correspond to
one or more of the following pressures: (1) minimum 0.55 to 1.0 GPa (within the upper mantle); (2) between 0.2 and 0.4 GPa
(the Moho or the lower crust); (3) at about 0.1 GPa (upper crust). Fluid inclusions in several rocks show a bimodal density
distribution, the lower-density maximum comprising both texturally early and late inclusions. This is taken as evidence for
an incomplete resetting of inclusion densities, and simultaneous formation of young inclusions, at well-defined magma stagnation
levels. For Gran Canaria, pressure estimates for early inclusions in harzburgite and dunite xenoliths and olivine phenocrysts
in the host basanites overlap at 0.9 to 1.0 GPa, indicating that such magma reservoir depths coincide with levels of xenolith
entrainment into the magmas. Magma chamber pressures within the mantle, inferred to represent levels of mantle xenolith entrainment,
are 0.65–0.95 GPa for El Hierro, 0.60–0.68 GPa for La Palma, and 0.55–0.75 GPa for Lanzarote. The highest-density fluid inclusions
in many Canary Island mantle xenoliths have probably survived in-situ near-isobaric heating at the depth of xenolith entrainment.
Inclusion data from all islands indicate ponding of basaltic magmas at Moho or lower crustal depths, and possibly at an additional
higher level, strongly suggestive of two main crustal accumulation levels beneath each island. We emphasize that repeated
magmatic underplating of primitive magmas, and therefore intrusive accretion, are important growth mechanisms for the Canary
Islands, and by analogy, for other ocean islands. Comparable fluid inclusion data from primitive rocks in other tectonic settings,
including Iceland, Etna and continental rift systems (Hungary, South Norway), indicate that magma accumulation close to Moho
depths shortly before eruption is not, however, restricted to oceanic intraplate volcanoes. Lower crustal ponding and crystallization
prior to eruption may be the rule rather than the exception, independent of the tectonic setting.
Received: 30 May 1997 / Accepted: 6 February 1998 相似文献
Liquidus phase relations have been experimentally determined in the systems Qz-Ab-Or-(H2O), Qz-Ab-(H2O) and Qz-Or-(H2O) at H2O-undersaturated conditions (aH2O = 0.07) and P = 5 kbar. Starting materials were homogeneous synthetic glasses containing 1 wt% H2O. The liquidus temperatures were bracketed by crystallization and dissolution experiments. The results of kinetic studies
showed that crushed glasses are the best starting materials to overcome undercooling and to minimize the temperature difference
between the lowest temperature of complete dissolution (melting) and the highest temperature at which crystallization can
be observed. At P = 5 kbar and aH2O = 0.07, the Qz-Ab eutectic composition is Qz32Ab68 at 1095 °C (±10 °C) and the Qz-Or eutectic is Qz38Or62 at 1030 °C (±10 °C). The minimum temperature of the ternary system Qz-Ab-Or is 990 °C (±10 °C) and the minimum composition
is Qz32Ab35‐ Or33. The Qz content of the minimum composition in the system Qz-Ab-Or-H2O remains constant with changing aH2O. The normative Or content, however, increases by approximately 10 wt% with decreasing aH2O from 1 to 0.07. Such an increase has already been observed in the system Qz-Ab-Or-H2O-CO2 at high aH2O and it is concluded that the use of CO2 to reduce water activities does not influence the composition of the minima in quartz-feldspar systems. The determined liquidus
temperature in melts with 1 wt% H2O is very similar to that obtained in previous nominally “dry” experiments. This discrepancy is interpreted to be due to problems
in obtaining absolutely dry conditions. Thus, the hitherto published solidus and liquidus temperatures for “dry” conditions
are probably underestimated.
Received: 27 March 1997 / Accepted: 1 October 1997 相似文献
The state-of-the-art in modelling the marine ecosystem of the greater North Sea is reviewed, providing an overview especially about three-dimensional models that describe and predict how the marine ecosystem of the greater North Sea area functions and how concentrations and fluxes of biologically important elements vary in space and time, throughout the shelf and over years, in response to physical forcing. Articles with a strong concentration on modelling were selected from the available literature, and all articles around the existing “ecological modelling groups” dealing with the area of the North Sea were sorted in chronological order of their appearance in the literature. We found eleven of such groups and described their different modelling efforts. Selecting the seven three-dimensional models (NORWECOM, GHER, ECOHAM, ERSEM, ELISE, COHERENS and POL3dERSEM), we characterized the complexity of the models, by comparing the resolution in time and space, and the resolution of the trophic structure by discussing the number and kind of state variables and of the processes relating these state variables to each other.The review of biogeochemical/ecological modelling for the greater North Sea shows that important findings by model simulations have either confirmed existing knowledge derived from field work or have given new insight into the mechanisms of the functioning of the North Sea system: the temporal and spatial development and magnitude of primary production, its spreading from the coasts to the north-west over the open North Sea, its mechanisms of limitation, the functioning of the pelagic small food web and of the benthic web, the mechanisms of nutrient regeneration, the effects of riverine and atmospheric nutrient inputs causing eutrophication of coastal waters, the extent of eutrophication in the North Sea, and the budgets for nitrogen, phosphorus, and silicon. The three-dimensional ecological models of the greater North Sea have provided consistent distributions and dynamics of the lower trophic levels on their regional, annual and decadal scales which cannot be derived to this degree of coverage by observations.The state-of-the-art in validation for these models is presented in part 2 相似文献