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1.
One of the simplest location models in terms of its constraint structure in location‐allocation modeling is the location set‐covering problem (LSCP). Although there have been a variety of geographic applications of the set‐covering problem (SCP), the use of the SCP as a facility location model is one of the most common. In the early applications of the LSCP, both potential facility sites as well as demand were represented by points discretely located in geographic space. The advent of geographic information systems (GIS), however, has made possible a greater range of object representations that can reduce representation error. The purpose of this article is to outline a methodology using GIS and K = 3 central place lattices to solve the LSCP when demand is continuously distributed over a bounded area and potential facility sites have not been defined a priori. Although, demand is assumed to exist over an area, it is shown how area coverage can be accomplished by the coverage of a point pattern. Potential facility site distributions based on spacings that are powers of one‐third the coverage distance are also shown to provide more efficient coverage than arbitrarily chosen spacings. Using GIS to make interactive adjustments to an incomplete coverage also provides an efficient alternative to smaller spacings between potential facility sites for reducing the number of facilities necessary for complete coverage. 相似文献
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Online representations of places are becoming pivotal in informing our understanding of urban life. Content production on online platforms is grounded in the geography of their users and their digital infrastructure. These constraints shape place representation, that is, the amount, quality, and type of digital information available in a geographic area. In this article we study the place representation of user‐generated content (UGC) in Los Angeles County, relating the spatial distribution of the data to its geo‐demographic context. Adopting a comparative and multi‐platform approach, this quantitative analysis investigates the spatial relationship between four diverse UGC datasets and their context at the census tract level (about 685,000 geo‐located tweets, 9,700 Wikipedia pages, 4 million OpenStreetMap objects, and 180,000 Foursquare venues). The context includes the ethnicity, age, income, education, and deprivation of residents, as well as public infrastructure. An exploratory spatial analysis and regression‐based models indicate that the four UGC platforms possess distinct geographies of place representation. To a moderate extent, the presence of Twitter, OpenStreetMap, and Foursquare data is influenced by population density, ethnicity, education, and income. However, each platform responds to different socio‐economic factors and clusters emerge in disparate hotspots. Unexpectedly, Twitter data tend to be located in denser, more deprived areas, and the geography of Wikipedia appears peculiar and harder to explain. These trends are compared with previous findings for the area of Greater London. 相似文献
3.
Geoffrey M. Jacquez 《Journal of Geographical Systems》2000,2(1):91-97
This paper summarizes contributions of GIS in epidemiology, and identifies needs required to support spatial epidemiology
as science. The objective of spatial epidemiology is to identify disease causes and correlates by relating spatial disease
patterns to geographic variation in health risks. GIS supports disease mapping, location analysis, the characterization of
populations, and spatial statistics and modeling. Although laudable, these accomplishments are not sufficient to fully identify
disease causes and correlates. One reason is the failure of present-day GIS to provide tools appropriate for epidemiology.
Two needs are most pressing. First, we must reject the static view: meaningful inference about the causes of disease is impossible
without both spatial and temporal information. Second, we need models that translate space-time data on health outcomes and putative exposures into
epidemiologically meaningful measures. The first need will be met by the design and implementation of space-time information
systems for epidemiology; the second by process-based disease models. 相似文献
4.
A model that emphasizes possible alternative sequences of events that occur over time is presented in this article. Representing alternative or branching events captures additional semantics unrealized by linear or non‐branching approaches. Two basic elements of branching, divergence and convergence are discussed. From these elements, many complex branching models can be built capturing a perspective of events that will take place in the future or have occurred in the past. This produces likely sequences of events that a user may compare and analyze using spatial or temporal criteria. The branching events model is especially useful for spatiotemporal decision support systems, as decision‐makers are able to identify alternative locations and times of events and, depending on the context, also identify regions of multiple possible events. A branching events viewer application is presented illustrating a case study based on a tornado response. 相似文献
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The emergence of Geographical Information Systems (GIS) as an important tool in the analysis of spatial phenomena has been mirrored by the evolution of the data models underpinning such systems. When considering vector‐based solutions, such developments have seen a migration from single‐user, file‐based, topological hybrid models to multi‐user database management system (DBMS) based integrated formats, often with no inherent topology. With all these solutions still being readily available, the decision of which to employ for a given application is a complicated one. This study analyses the performance of a number of vector data storage formats for use with ESRI's ArcGIS, with the aim to facilitate the ‘intelligent selection’ of an appropriate solution. Such a solution will depend upon the application domain and both single‐user and multi‐user (corporate) scenarios are considered. Findings indicate that single‐user ESRI coverages and multi‐user ArSDE/Oracle strategies perform better when considering the range of GIS operations used to evaluate data store performance. 相似文献
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Joni Downs Mark Horner Rebecca Loraamm James Anderson Hyun Kim Dave Onorato 《Transactions in GIS》2014,18(1):46-65
Crossing structures are an effective method for mitigating habitat fragmentation and reducing wildlife‐vehicle collisions, although high construction costs limit the number that can be implemented in practice. Therefore, optimizing the placement of crossing structures in road networks is suggested as a strategic conservation planning method. This research explores two approaches for using the maximal covering location problem (MCLP) to determine optimal sites to install new wildlife crossing structures. The first approach is based on records of traffic mortality, while the second uses animal tracking data for the species of interest. The objective of the first is to cover the maximum number of collision sites, given a specified number of proposed structures to build, while the second covers as many animal tracking locations as possible under a similar scenario. These two approaches were used to locate potential wildlife crossing structures for endangered Florida panthers (Puma concolor coryi) in Collier, Lee, and Hendry Counties, Florida, a population whose survival is threatened by excessive traffic mortality. Historical traffic mortality records and an extensive radio‐tracking dataset were used in the analyses. Although the two approaches largely select different sites for crossing structures, both models highlight key locations in the landscape where these structures can remedy traffic mortality and habitat fragmentation. These applications demonstrate how the MCLP can serve as a useful conservation planning tool when traffic mortality or animal tracking data are available to researchers. 相似文献
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Smart card-automated fare collection systems now routinely record large volumes of data comprising the origins and destinations of travelers. Processing and analyzing these data open new opportunities in urban modeling and travel behavior research. This study seeks to develop an accurate framework for the study of urban mobility from smart card data by developing a heuristic primary location model to identify the home and work locations. The model uses journey counts as an indicator of usage regularity, visit-frequency to identify activity locations for regular commuters, and stay-time for the classification of work and home locations and activities. London is taken as a case study, and the model results were validated against survey data from the London Travel Demand Survey and volunteer survey. Results demonstrate that the proposed model is able to detect meaningful home and work places with high precision. This study offers a new and cost-effective approach to travel behavior and demand research. 相似文献
9.
现有的几种地基导航伪卫星布局优化算法时间复杂度过高,无法满足应急场景下的伪卫星导航系统布设需求,为此提出了基于最大凸多面体准则的快速优化算法。该算法利用最大凸多面体准则,对所有可能布设伪卫星的位置进行评估,评估依据为能否对降低多用户几何精度因子加权均值产生较大贡献,评估结果将可布设伪卫星位置分为高贡献度顶星位置、高贡献度底星位置和低贡献度可剔除位置3类。评估后穷举高贡献度的顶星、底星组合,找到最优伪卫星布局。将该算法应用于常见不规则地形的伪卫星布设问题中,仿真结果表明,该算法能够得到全局最优解,且解算耗时较现有算法大幅减少,能够满足应急场景下伪卫星导航系统布设的实际应用需求。 相似文献
10.
Much effort has been applied to the study of land use multi‐objective optimization. However, most of these studies have focused on the final land use scenarios in the projected year, without considering how to reach the final optimized land use scenario. To fill this gap, a spatio‐temporal land use multi‐objective optimization (STLU‐MOO) model is innovatively proposed in this research to determine possible spatial land use solutions over time. The STLU‐MOO is an extension of a genetic land use multi‐objective optimization model (LU‐MOO) in which the LU‐MOO is generally carried out in different years, and the solutions at year T will affect the solutions at year T + 1. We used the Wuhan agglomeration (WHA) as our case study area. The STLU‐MOO model was employed separately for the nine cities in the WHA, and social, economic, and environmental objectives have been considered. The success of the experiments in the case study demonstrated the value and novelty of our proposed STLU‐MOO model. In addition, the results also indicated that the objectives considered in the case study were in conflict. According to the results, the optimal land use plan in 2050 can be traced back to 2040, 2030, and 2020, providing a series of Pareto solutions over the years which can provide spatio‐temporal land use multi‐objective optimization solutions to support the land use planning process. 相似文献
11.
Kevin M. Curtin Gabriela Voicu Matthew T. Rice Anthony Stefanidis 《Transactions in GIS》2014,18(2):286-301
The Traveling Salesman Problem is one of the most prominent problems in combinatorial optimization, and is regularly employed in a wide variety of applications. The objective of this article is to demonstrate the extent of sub‐optimality produced by Traveling Salesman solution procedures implemented in the context of Geographic Information Systems and to discuss the consequences that such solutions have for practice. Toward that end, an analysis is made of Traveling Salesman solutions from implementations in four Geographic Information System packages. These implementations are tested against the optimal solution for a range of problem sizes. Computational results are presented in the context of a school bus routing application. This analysis concludes that no Traveling Salesman implementation in GIS is likely to find the optimal solution when problems exceed 10 stops. In contrast, optimal solutions can be generated with desktop linear programming software for up to 25 cities. Moreover, one GIS implementation consistently found solutions that were closer to optimal than its competitors. This research strongly suggests that for applications with fewer than 25 stops, the use of an optimal solution procedure is advised, and that GIS implementations can benefit from the integration of more robust optimization techniques. 相似文献
12.
Carsten Keßler 《Transactions in GIS》2017,21(3):488-502
Explicit information about places is captured in an increasing number of geospatial datasets. This article presents evidence that relationships between places can also be captured implicitly. It demonstrates that the hierarchy of central places in Germany is reflected in the link structure of the German language edition of Wikipedia. The official upper and middle centers declared, based on German spatial laws, are used as a reference dataset. The characteristics of the link structure around their Wikipedia pages, which link to each other or mention each other, and how often, are used to develop a bottom‐up method for extracting central places from Wikipedia. The method relies solely on the structure and number of links and mentions between the corresponding Wikipedia pages; no spatial information is used in the extraction process. The output of this method shows significant overlap with the official central place structure, especially for the upper centers. The results indicate that real‐world relationships are in fact reflected in the link structure on the web in the case of Wikipedia. 相似文献
13.
Progress toward developing a GIS of place can only follow from an understanding of what place is, and this understanding draws on geographical theory. Here—following Agnew, Tuan, and others—we consider place as being made up of three components—location, locale, and sense of place—which are recognizable at multiple scales and vary historically as a product of social and political processes. Using the testimonies of two survivors of the Holocaust, we sketch the components of a model for a GIS of place that allows for this theory of place to be visualized and analyzed. The model is, crucially, both multi‐scalar and sensitive to uncertainty, as a GIS of place needs to be able to zoom in and out of the different scales at which place is experienced, as well as capture both uncertain data and uncertainty as data. We see potential in the representations proposed for scaling up from the anecdotal to the general in the sense that any narrative can be grouped and classified according to places and scales as shown here. The challenge in developing a GIS of place along the lines we propose here is to design a new set of functionalities that can do so. 相似文献
14.
Alternative method for angular rate determination within the GOCE gradiometer processing 总被引：2，自引：1，他引：1
The most crucial part of the GOCE gradiometer processing is, besides the internal calibration of the gradiometer, the determination
of the satellite’s inertial angular rate. This paper describes a new method for the angular rate determination. It is based
on the stochastic properties of the GOCE star sensors and the gradiometer. The attitude information of both instrument types
is combined at the level of angular rates. The combination is done in the spectral domain by Wiener filtering, and thus using
an optimal relative weighting of the star sensor and gradiometer attitude information. Since the complete processing chain
from raw measurements to gravity field solutions is performed, the results are not only analyzed at the level of gravity gradients,
but also of gravity field solutions. Compared to the nominal method, already the resulting gravity gradients show a significantly
improved performance for the frequencies (mainly) below the gradiometer measurement bandwidth. This can be verified by analysis
of the gravity gradient trace. The improvement is propagated to the level of gravity field models, where a better accuracy
can be observed for selected groups of coefficients at characteristic bands at orders k × 16, with integer k, up to high harmonic degrees. 相似文献
15.
Mostafizur Rahaman Laskar Suman Chatterjee Aniruddha Das 《Journal of the Indian Society of Remote Sensing》2018,46(6):873-883
Air pollution is a major problem, conscious both for health and surroundings. This is a novel approach for the design & development of a system for the monitoring of different air pollutants especially at remote places where it is difficult to install any conventional air quality monitoring stations as well as for the cities. In this research work, a framework of Functional air quality index which is an indicator of susceptibility to respiratory illness has been built using the Bayesian neural network to provide the random real-time data about a location through wireless communication. The monitoring system is integrated with different types of sensors to measure the level of different air pollutants or air quality parameters such as Suspended particulate matters, (PM2.5), Nitrogen dioxide, Sulphur dioxide, Ozone which are directly associated with airways inflammatory diseases such as Asthma, Bronchitis, COPD. Each location in Map (GPS) can be updated automatically with fAQI to the user through mobile computing and satellite commutation. The user gets information about the neighborhood location with health-related information such as- whether a particular location is sensitive to respiratory diseases such as Bronchitis, asthma, COPD etc. due to suspended allergen/pollutants in the ambient air. This novel approach is designed with its’ own prototype and an application of Inter of Things in Health GIS for the benefit of humanity. 相似文献
16.
A. K. Mitra Sankar Nath A. K. Sharma 《Journal of the Indian Society of Remote Sensing》2008,36(3):243-253
Operational meteorology is perceived as a fuzzy environment in which information is vaguely defined. The mesoscale processes
such as fog, stratus and convection are generally dependent on the topography of the place and has always been difficult to
forecast for the meteorologists. The main objective of the present study is to introduce the concept of fuzzy inference system (FIS) in the prediction of fog. This approach uses the concept of a pure fuzzy logic system where the fuzzy rule base
consists of a collection of fuzzy IF-THEN rules. The fuzzy inference engine uses these fuzzy IF-THEN rules to determine a mapping from fuzzy sets in the input universe of discourse to fuzzy sets in the output universe of discourse
based on fuzzy logic principles. Basic weather elements, which affect weather characteristics of fog, are fuzzified. These
are then used in fuzzy weather prediction models based on fuzzy inferences. These models are simulated and the crisp results
obtained using developed defuzzification strategies are compared with the actual weather data. The basis of methodology is
to construct the fuzzy rule base domain from the available daily current weather observations in winter season over New Delhi.
The results reveal that dew point spread and rate of change of dew point spread are the most important parameters for the
formation of fog. The results further indicate that fog formation over New Delhi are dominant when (i) dew point is greater
then 7°C along with dew point spread between 1 and 3°C. (ii) rate of change of dew point spread must be negative and wind
speed should be less than 4 knots. This study presents a technique for predicting the probability of fog over New Delhi for
5–6 hours in advance. The skill score indicates that the performance of FIS is appreciably good. The method is found to be
promising for operational application. 相似文献
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Although most GIS-based planning support have the capacity to show the location and attributes of different places, very few GIS-based systems are able to describe adequately the degree of spatial interaction, or the geographic accessibility, between places. The Faculty of Geographical Sciences of the Utrecht University (The Netherlands) and the South African Council for Scientific and Industrial Research (CSIR), are developing a methodology to address the problem of measuring accessibility by integrating specialised GIS software (FlowMap) that measures the geographic accessibility between locations within a spatial decision support system (AccessMap). The resulting GIS-tool is applied to the Wild Coast area in South Africa. In this region a lack of accessibility to market centres is perceived as one of the major constraints of economic development in the region. 相似文献