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1.
Open source, spatial analysis, and activity-travel behaviour research: capabilities of the aspace package 总被引：2，自引：0，他引：2
This paper reports on recent experience with the development of aspace, an Open Source (OS) library for the geographic visualization and analysis of activity-travel behaviour. The paper begins
with an overview of recent progress with respect to the convergence of Open Source technology, spatial analysis, and travel
behaviour research. The remainder of the paper focuses on aspace; a collection of functions that, when combined with data describing the geographical location of daily activities, can be
used to visualize and describe spatial properties of individual and household activity spaces. These properties include: size,
orientation, shape, and the geographical dispersion of activity locations contained within the activity space. Several planar
geometries are used to transform measurable spatial properties into intuitive objects for visualizing spatial patterns of
activity participation. Experiments are conducted, using data from the first wave of the 2003 Toronto Travel Activity Panel
Survey, to demonstrate the potential application of aspace for basic and applied policy-based research into activity-travel behaviour. The toolkit is distributed as a downloadable
‘package’ from the Open Source R Project for Statistical Computing.
相似文献
2.
Seija Kultti Minna Vliranta Kaarina Sarmaja‐Korjonen Nadia Solovieva Tarmo Virtanen Tommi Kauppila Matti Eronen 《第四纪科学杂志》2003,18(6):503-520
This study investigated Holocene tree‐line history and climatic change in the pre‐Polar Urals, northeast European Russia. A sediment core from Mezhgornoe Lake situated at the present‐day alpine tree‐line was studied for pollen, plant macrofossils, Cladocera and diatoms. A peat section from Vangyr Mire in the nearby mixed mountain taiga zone was analysed for pollen. The results suggest that the study area experienced a climatic optimum in the early Holocene and that summer temperatures were at least 2°C warmer than today. Tree birch immigrated to the Mezhgornoe Lake area at the onset of the Holocene. Mixed spruce forests followed at ca. 9500–9000 14C yr BP. Climate was moist and the water level of Mezhgornoe Lake rose rapidly. The hypsithermal phase lasted until ca. 5500–4500 14C yr BP, after which the mixed forest withdrew from the Mezhgornoe catchment as a result of the climate cooling. The gradual altitudinal downward shift of vegetation zones resulted in the present situation, with larch forming the tree‐line. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
3.
Wildfires are frequent boreal forest disturbances in Canada, and emulating their patterns with forest harvesting has emerged as a common forest management goal. Wildfires contain many patches of residual vegetation of various size, shape, and composition; understanding their characteristics provides insights for improved emulation criteria. We studied the occurrence of residual vegetation within eleven boreal wildfire events in a natural setting; fires ignited by lightning, no suppression efforts, and no prior anthropogenic disturbances. Relative importance of the measurable geo-environmental factors and their marginal effects on residual presence are studied using Random Forests. These factors included distance from natural firebreaks (wetland, bedrock and non-vegetated areas, and water), land cover, and topographic variables (elevation, slope, and ruggedness index). We present results at spatial resolutions ranging from four to 64 m while emphasizing four and 32 m since they mimic IKONOS- and Landsat-type images. Natural firebreak features, especially the proximity to wetlands, are among the most important variables that explain the likelihood residual occurrence. The majority of residual vegetation areas are concentrated within 100 m of wetlands. Topographic variables, typically important in rugged terrain, are less important in explaining the presence of residuals within our study fires. 相似文献
4.
Ülo Suursaar Tarmo Kall Holger Steffen Hannes Tnisson 《Boreas: An International Journal of Quaternary Research》2019,48(4):913-928
Recent LiDAR surveys have revealed that on postglacially uplifting coasts of Estonia rhythmic coastal landforms (beach ridge sequences and foredune plains) occur to a considerable extent. We studied four of them to reveal age and periodicity in these multiple ridge systems and discussed their genesis in the Subatlantic (semi‐continental) conditions of the Baltic Sea area. Using recent models of Fennoscandian uplift due to glacial isostatic adjustment (GIA), we constructed Holocene apparent sea level curves for the study sites at Õngu, Mänspe, Haldi and Keibu; converted distance–height shore profiles into time series (including corrections on shore profile non‐linearity and variations in GIA‐eustasy balance); and analysed the patterns using spectral analysis. It was suggested that due to non‐tidal conditions, relatively low‐energy hydrodynamic forcing and small aeolian contribution, the ridges mark ancient shorelines. They are relatively modest in height (mostly 0.2–1 m), form regular and extensive (up to 150 ridges) patterns, and date back to ~9000 years before present. We studied <5‐ka‐old sections. The mean ridge spacing varied, depending also on coastal slope, between 21 and 39 m. Both simple counting and spectral analysis involved some specific limitations, yet the estimates for typical spacing were alike, at 32 (±5) years. The regular nature of the low‐ridge patterns originated from relative sea level lowering and gradual sediment accretion/erosion. However, the progradation was rather uplift‐ than accretion‐driven and the stepwise process in ridge formation was probably not autocyclic. It was governed or modulated by quasi‐periodic 25–40 year cyclicity in local wave forcing, relative sea level variations and wind conditions. Being most likely connected to the North Atlantic Oscillation, the quasi‐regular, decadal‐scale, similarly phased variations may magnify each other's effect on the westerly exposed coasts of Estonia. Additionally, some other (e.g. event‐driven) mechanisms may also be present. 相似文献
5.
Anisotropy of wind and wave regimes in the Baltic proper 总被引：1，自引：0，他引：1
Tarmo Soomere 《Journal of Sea Research》2003,49(4):305
The directional distribution of moderate and strong winds in the Baltic Sea region is shown to be strongly anisotropic. The dominating wind direction is south-west and a secondary peak corresponds to north winds. North-west storms are relatively infrequent and north-east storms are extremely rare. Angular distribution of extreme wind speed also has a two-peaked shape with maxima corresponding to south-west and north winds, and a deep minimum for easterly winds. The primary properties of the anisotropy such as prevailing winds, frequency of their occurrence, directional distribution of mean and maximum wind speeds coincide on both sides of the Baltic proper. The specific wind regime penetrates neither into the mainland nor into the Gulf of Finland or the Gulf of Riga.Properties of the saturated wave field in the neighbourhood of proposed sites of the Saaremaa (Ösel) deep harbour are analysed on the basis of the wave model WAM forced by steady winds. The directional distribution of wave heights in typical and extreme storms is highly anisotropic. Remarkable wave height anomalies may occur in the neighbourhood of the harbour sites. 相似文献
6.
The two-dimensional spectrum of large-scale motions in the upper layer of the south-eastern Atlantic has been estimated using surface buoy observations. The derived spectrum is compared with the theoretical spectra of weakly non-linear Rossby waves. In thein situ data-based spectrum, one can trace such characteristic peculiarities of the theoretically derived spectra as symmetry relative to the parallels and energy concentration in a nearly zonal flow.Translated by Vladimir A. Puchkin. 相似文献
7.
Predicted global changes can be studied effectively by combining spatially explicit data sets on vegetation and other landscape properties with process models. However, detailed knowledge of the vegetation distribution of remote Arctic areas is relatively scarce. This paper shows how a mesoscale vegetation and land cover classification of a large, remote Arctic area can be conducted at a fine spatial resolution (30 m cell size) using a limited ground reference data set. The study area is the catchment of the River Usa (93 500 km2 ) in north-eastern European Russia. Vegetation zones in the Usa Basin range from taiga in the south to forest-tundra and tundra in the north, and to alpine in the Ural mountains in the east. Classification was done using a mosaic of spectrally adjusted Landsat TM5 images from five different dates and a semi-supervised method. Ground reference data were collected during the summers of 1998, 1999 and 2000. Accuracy of the 21-class vegetation type/land cover classification produced was tested against test points interpreted from oblique aerial photographs taken from a helicopter (logistic limitations prohibited the collection of representative ground reference data). The main vegetation types (forests, willow dominated stands and meadows, peatlands, tundra heaths, mainly unvegetated areas, and water bodies) were distinguished with relatively high accuracy: 84% of the test points were classified correctly. Spatially detailed land cover data sets like the one described here allow detailed landscape-level analysis and process modelling on many different subjects. 相似文献
8.
9.
The use of Lagrangian trajectories for the identification of the environmentally safe fairways 总被引：1，自引：0，他引：1
We propose and test a method for the optimisation of marine fairways to minimise the risk to high-value areas, based on statistical analysis of Lagrangian trajectories of current-driven pollution transport. The offshore areas are quantified according to the probability of pollution released in these areas to reach vulnerable regions. The method contains an eddy-resolving circulation model, a scheme for tracking of Lagrangian trajectories, a technique for the calculation of quantities characterising the potential of different sea areas to supply adverse impacts, and routines to construct the optimum fairway. The gain is expressed in terms of the probability of pollution transport to the nearshore and the associated time (particle age). The use of the optimum fairway would decrease the probability of coastal pollution by 40% or increase the average time of reaching the pollution to the coast from 5.3 to about 9 days in the Gulf of Finland, the Baltic Sea. 相似文献
10.
Extraordinarily low and high sea level events are analysed on the basis of historical data and their mechanisms of occurrence are studied with the 1 km grid size 2D hydrodynamic model in the two almost tideless semi-enclosed sub-basins of the Baltic Sea, the Gulf of Riga and the Väinameri. The sea level is modelled with realistic meteorological forcing and comparison data from 1999 and 2001. Resonance properties of the sub-basins are studied and their possible role in the formation of extraordinary sea level events is discussed. While the extremely low levels (−1.23 m below the mean sea level) in the Estonian coastal waters do not generally originate locally, the high levels (up to 2.53 m above the mean as measured in the Pärnu Bay) are short-term and local. They occur in combination with several forcing and morphometrical factors and are localised in the shallow and narrow bays exposed to the direction of the strongest possible storm winds, SW and W. Model simulations show that extremely high and low sea levels in some small bays of western Estonia can exceed the corresponding values in the Pärnu Bay. 相似文献