Showing papers in "International Journal of Geographic Information Systems in 1994"
TL;DR: In this article, the 4-intersection model is extended to cover topological relations between 2-dimensional objects with arbitrary holes, called regions with holes, where each region with holes is represented by its generalized region, the union of the object and its holes and the closure of each hole.
Abstract: The 4-intersection, a model for the representation of topological relations between 2-dimensional objects with connected boundaries and connected interiors, is extended to cover topological relations between 2-dimensional objects with arbitrary holes, called regions with holes. Each region with holes is represented by its generalized region—the union of the object and its holes — and the closure of each hole. The topological relation between two regions with holes, A and B, is described by the set of all individual topological relations between (1) A ’s generalized region and B’s generalized region, (2) A ’s generalized region and each of B’s holes, (3) B’s generalized region with each of A ’s holes, and (4) each of A ’s holes with each of B’s holes. As a side product, the same formalism applies to the description of topological relations between 1-spheres. An algorithm is developed that minimizes the number of individual topological relations necessary to describe a configuration completely. This model of representing complex topological relations is suitable for a multi-level treatment of topological relations, at the least detailed level of which the relation between the generalized regions prevails. It is shown how this model applies to the assessment of consistency in multiple representations when, at a coarser level of less detail, regions are generalized by dropping holes.
233 citations
TL;DR: Methods for modelling imprecision in the definition, analysis and synthesis of two-dimensional features and fuzzy sets are presented, intended to have applications in geographical information systems, but is equally applicable to other types of spatial information systems or spatial database applications.
Abstract: This paper presents methodologies for modelling imprecision in the definition, analysis and synthesis of two-dimensional features. The imprecision may arise through incomplete information, the presence of varying concentrations of attributes, or the use of qualitative descriptions of spatial features or their relationships. The work is intended to have applications in geographical information systems (GIS), but is equally applicable to other types of spatial information systems or spatial database applications. Fuzzy sets are used as a representational and reasoning device. The paper contains definitions of an imprecisely defined spatial feature or fuzzy region; definitions of distance and directional metrics between two such regions; a methodology for analysis of the spatial relationship between two regions; and a methodology for synthesis of new regions that are subject to the presence of imprecise spatial constraints.
209 citations
TL;DR: The author argues that object-oriented approaches can be taken at each of these layers of any computerized system, with a high-level system-independent conceptual model of the application domain supported by increasingly system-oriented models beneath.
Abstract: This paper surveys the current state of the object-oriented paradigm as it applies to the handling of geo-referenced information. The model of any computerized system is multi-layered, with a high-level system-independent conceptual model of the application domain supported by increasingly system-oriented models beneath. The author argues that object-oriented approaches can be taken at each of these layers. The major constructs of object-orientation are discussed from this layered viewpoint and in the context of geo-information handling.
163 citations
TL;DR: In this paper, a framework for embedding urban models within GIS is proposed, which is based upon using the display capabilities of GIS as the user interface to the conventional modelling process, beginning with data selection and analysis, moving to model specification and calibration, and thence to prediction.
Abstract: This is the first of two papers elaborating a framework for embedding urban models within GIS. This framework is based upon using the display capabilities of GIS as the user interface to the conventional modelling process, beginning with data selection and analysis, moving to model specification and calibration, and thence to prediction. In this paper, we outline how various stages in this process based on purpose-built software outside the system, are accessed and operated through the GIS. We first deal with display based on thematic maps, surfaces, graphs and linked windows, standard to any data from whatever source, be it observations, model estimates or predictions. We then describe how various datasets are selected, how the spatial system can be partitioned or aggregated, and how rudimentary exploratory spatial data analysis enables scatterplots to be associated with thematic maps. We illustrate all these functions and operations using the proprietary GIS ARC-INFO applied to population data ...
121 citations
TL;DR: This paper study the problem of linking a set of transceiver stations in a visibility-connected communication network, by placing a minimum number of relays on the terrain surface, and proposes a practical approximate solution based on a Steiner heuristic.
Abstract: Line-of-sight communication on topographic surfaces has relevance for several applications of Geographical Information Systems. In this paper, we study the problem of linking a set of transceiver stations in a visibility-connected communication network, by placing a minimum number of relays on the terrain surface. The problem is studied in the framework of a discrete visibility model, where the mutual visibility of a finite set of sites on the terrain is represented through a graph, called the visibility graph. While in the special case of only two transceivers an optimal solution can be found in polynomial time, by computing a minimum path on the visibility graph, the general problem is equivalent to a Steiner problem on the visibility graph, and, thus, it is untractable in practice. In the latter case, we propose a practical approximate solution based on a Steiner heuristic. For both the special and the general case, we propose both a static and a dynamic algorithm that allow computation of a s...
118 citations
TL;DR: A survey of the state-of-the-art of the algorithms for computing the different kinds of visibility information is presented, according to the previous classification, and a new algorithm for Computing the horizon on a digital terrain model is described.
Abstract: In this paper, we address the problem of computing visibility information on triangulated digital terrain models. We present first a general introduction to digital terrain models. Visibility problems on terrains are classified, according to the kind of visibility information they compute, into point visibility, line visibility and region visibility. A survey of the state-of-the-art of the algorithms for computing the different kinds of visibility information is presented, according to the previous classification. A new algorithm for computing the horizon on a digital terrain model is also described.
101 citations
TL;DR: An ordinary geographical information system has a collection of nearest neighbourhood operations, such as generating a buffer zone and searching for the nearest facility from a given location, and this collection serves as a useful tool box for spatial analysis.
Abstract: An ordinary geographical information system has a collection of nearest neighbourhood operations, such as generating a buffer zone and searching for the nearest facility from a given location, and this collection serves as a useful tool box for spatial analysis. Computationally, these operations are undertaken through the ordinary Voronoi diagram. This paper extends this tool box by generalizing the ordinary Voronoi diagram. The tool box consists of 35 nearest neighbourhood operations based upon twelve generalized Voronoi diagrams: the order-fe Voronoi diagram, the ordered order-fc Voronoi diagram, the farthest-point Voronoi diagram, the kth-nearest-point Voronoi diagram, the weighted Voronoi diagram, the line Voronoi diagram, the area Voronoi diagram, the Manhattan Voronoi diagram, the spherical Voronoi diagram, the Voronoi diagram in a river, the polyhedral Voronoi diagram, and the network Voronoi diagram. Each operation is illustrated with examples and the literature of computational methods.
100 citations
TL;DR: This paper begins by reviewing residential location models based on population density theory, stating continuous and discrete model forms, and calibration methods, and presents ways in which the system can be used to explore and fit a variety of models to different zoning systems.
Abstract: This is the second of two papers which elaborates a framework for embedding urban models within GIS. In the first paper (Batty and Xie 1994), we outlined how the display functions of a proprietary GIS could be used to organize a series of external software modules which contained the central elements of the modelling process, namely dataset selection and analysis, and model specification, calibration, and prediction. In that paper, we dwelt on display and data analysis functions whereas here we outline the model-based functions of the system. We begin by reviewing residential location models based on population density theory, stating continuous and discrete model forms, and calibration methods. We then illustrate a pass through the software using data for the Buffalo urban region, showing how observed data and model estimates can be evaluated through graphic display. We present ways in which the system can be used to explore and fit a variety of models to different zoning systems and in so doing...
83 citations
TL;DR: The systems integration problem, defined as coupling GIS and other systems, is analysed by the use of two models based on database and federated database reference models, including a three-schema model of a system.
Abstract: The systems integration problem, defined as coupling GIS and other systems, is analysed by the use of two models based on database and federated database reference models. A three-schema model of a system enables the classification of incompatibilities between systems in terms of differences in external, conceptual and internal schemas. A systems reference model identifies transformation, constructor and accessor operations as the basic mechanisms to overcome these differences. The possible architectures of integrated systems are defined in terms of the presence of these operations and their general strengths and weaknesses are assessed.
79 citations
TL;DR: An evaluation of the findings of twelve case studies which were undertaken in a variety of British local government contexts during 1991 and 1992 suggests that some organizational cultures are inherently receptive and able to sustain the effective implementation of GIS in local government.
Abstract: GIS have received increasing attention in recent years, particularly in local government. Despite the claims in the literature about the potential of the technology, to date there is still little information on the impact GIS applications are having on the organizations in which they are being implemented. With these considerations in mind this paper presents an evaluation of the findings of twelve case studies which were undertaken in a variety of British local government contexts during 1991 and 1992. The evaluation of the findings of the case studies is divided into two parts. The first part indicates the limited impact GIS has had on the local authorities investigated even after at least two years experience. Given these findings the second part seeks to identify the issues which appear to be responsible for inhibiting the effective implementation of GIS in British local government. Overall it is suggested that some organizational cultures are inherently receptive and able to sustain the deve...
57 citations
TL;DR: The literature on spatial databases is also substantial; the bibliography of Samet's landmark book on spatial data structures lists 823 references as discussed by the authors and some 350 papers in temporal databases have appeared, authored by almost 300 researchers.
Abstract: Spatial and temporal databases are important and well-established sub-disciplines of database research. Some 350 papers in temporal databases have appeared, authored by almost 300 researchers. The literature on spatial databases is also substantial; the bibliography of Samet's landmark book on spatial data structures lists 823 references.
TL;DR: This paper presents a methodology which provides a practicable solution to a specific class of areal interpolation problems, and three alternative procedures, based on least squares criteria, are suggested for estimation of the land use mix in each land class.
Abstract: This paper presents a methodology which provides a practicable solution to a specific class of areal interpolation problems. The method allows for the transformation of the areal basis of land use data from a set of reporting units to a set of land capability classes within each of which land use mix is assumed to be homogeneous. Three alternative procedures, based on least squares criteria, are suggested for estimation of the land use mix in each land class. Although these are shown to produce similar and broadly plausible results in an empirical application, choice of procedure may be guided by consideration of the particular application and computational ease.
TL;DR: The results of a case study indicate that the new method, compared to current methods, may lead to different evaluations of the level of opportunitie, as it is assumed that the probability of successfully visiting a specific facility is a function of the diversity of supply provided.
Abstract: The opportunities available at a demand location are usually measured as the costs of reaching a specified critical number of facilities from that location. This method does not however, account for multistop trips nor for differences in the diversity of supply at the level of individual facilities. In this paper we introduce an alternative measurement method that overcomes these shortcomings. In this method the probability of successfully visiting a specific facility is assumed to be a function of the diversity of supply provided. Trip routes are constructed that have an acceptable probability of success. Then, the expected costs of travelling the optimum route are determined as an indicator of spatial opportunities. The proposed method has been implemented in a GIS environment, using typical GIS data and GIS tools for spatial analysis and display. The results of a case study indicate that the new method, compared to current methods, may lead to different evaluations of the level of opportunitie...
TL;DR: Findings of apostal survey of users of various GIS products, in a wide variety of organizations and countries are reported, which have practical implications for improving future GIS design.
Abstract: The complex functionality of GIS makes it difficult to present a simple interface to the end-user. What problems does this create for users? How does it affect the uptake and use of GIS to its full potential?This paper reports some findings of apostal survey of users of various GIS products, in a wide variety of organizations and countries. The level of investigation of the present study is discussed in the context of previous surveys of GIS users, and the paper focuses on selected findings and resulting recommendations which have practical implications for improving future GIS design.
TL;DR: Simulated vector coastlines of known and varied complexity are rasterized at various levels by the quadtree method and a method of selecting the most appropriate raster size based on the complexity of the source data and the required level of accuracy is presented.
Abstract: Simulated vector coastlines of known and varied complexity are rasterized at various levels by the quadtree method. The rasterizing error for each combination of coastline and raster size is calculated by a simple Boolean overlay method. The relationship between line complexity, raster size and rasterizing error is investigated and a method of selecting the most appropriate raster size based on the complexity of the source data and the required level of accuracy is presented.
Journal Article•
TL;DR: It is posits that a geographical model embedded within a GIS provides an alternative means of devising credible capital values, and anticipates some of the prospects for the use of GIS in local revenue-raising.
Abstract: GIS is a technology which is ideally suited to analysis of the market values of properties, since such values are based upon spatial comparisons as well as individual property attributes. Great Britain now has a new mechanism of local taxation, the council tax, which is based upon the capital values of properties. Central to the implementation of this tax has been the potentially controversial assignment of properties to valuation 'bands'. This paper posits that a geographical model embedded within a GIS provides an alternative means of devising credible capital values, and anticipates some of the prospects for the use of GIS in local revenue-raising.
TL;DR: Kriging is an optimal method of spatial interpolation that produces an error for each interpolated value, which has the advantage of increasing spatial resolution in many regions, and reducing it in others where maintaining a constant size of block is unjustified.
Abstract: Kriging is an optimal method of spatial interpolation that produces an error for each interpolated value. Block kriging is a form of kriging that computes averaged estimates over blocks (areas or volumes) within the interpolation space. If this space is sampled sparsely, and divided into blocks of a constant size, a variable estimation error is obtained for each block, with blocks near to sample points having smaller errors than blocks farther away. An alternative strategy for sparsely sampled spaces is to vary the sizes of blocks in such away that a block's interpolated value is just sufficiently different from that of an adjacent block given the errors on both blocks. This has the advantage of increasing spatial resolution in many regions, and conversely reducing it in others where maintaining a constant size of block is unjustified (hence achieving data compression). Such a variable subdivision of space can be achieved by regular recursive decomposition using a hierarchical data structure. An ...
TL;DR: The potential use of cost-benefit analysis is reviewed to explore tangible and intangible benefits, to identify the costs involved, and to explore the effect that a robust GIS strategy can have on the relationship between costs and benefits.
Abstract: Justifying GIS in local government is a complex task for two main reasons: first, a GIS implementation can range from a single, well-defined application in one department to a corporate multi-purpose GIS; and, second, local authorities are complex organizations currently facing major pressures for change, and considerable uncertainty about their future structure and role. The purpose of this paper is to review the potential use of cost-benefit analysis, to explore tangible and intangible benefits, to identify the costs involved, to explore the effect that a robust GIS strategy can have on the relationship between costs and benefits, and to review some of the published material on the cost-justification of GIS in local government.
TL;DR: It is shown how complex topologic relations among spatial objects can be analysed through standard SQL operations, and the implementation of the 3-D formal data structure (FDS) is given by querying a test database.
Abstract: The conceptual Formal Data Structure of Molenaar (1990, 1992) for describing 3-dimensional (3-D) representations of terrain was implemented in a relational database model. It is shown how complex topologic relations among spatial objects can be analysed through standard SQL operations. Topics like consistency rules and updating operations will not be handled, they should be dealt with separately. The emphasis is here on topologic queries, so that no attention will be paid to a thematic structure. The geometric data set has been structured so that information on topology, shape and size, and position can be retrieved. A demonstration of the implementation of the 3-D formal data structure (FDS) is given by querying a test database.
TL;DR: Fractal analysis is used to suggest that real world data lie on a continuum between the simple and the random, and that a major GIS challenge is the scientific representation and understanding of rapidly changing multi-scale fields.
Abstract: A central problem in spatial analysis is the mapping of data for complex spatial fields using relatively simple data structures, such as those of a conventional GIS. This complexity can be measured using such indices as multi-scale variance, which reflects spatial autocorrelation, and multi-fractal dimension, which characterizes the values of fields. These indices are computed for three spatial processes: Gaussian noise, a simple mathematical function, and data for a random walk. Fractal analysis is then used to produce a vegetation map of the central region of California based on a satellite image. This analysis suggests that real world data lie on a continuum between the simple and the random, and that a major GIS challenge is the scientific representation and understanding of rapidly changing multi-scale fields.
TL;DR: A parallel algorithm for computing the visible region of an observation point located on the terrain is proposed, based on a sequential triangle-sorting visibility approach proposed by De Floriani et al. (1989).
Abstract: In this paper we address the problem of computing visibility information on digital terrain models in parallel. We propose a parallel algorithm for computing the visible region of an observation point located on the terrain. The algorithm is based on a sequential triangle-sorting visibility approach proposed by De Floriani et al. (1989). Static and dynamic parallelization strategies, both in terms of partitioning criteria and scheduling policies, are discussed. The different parallelization strategies are implemented on an MIMD multicomputer and evaluated through experimental results.
TL;DR: The development of probability-based spatial-temporal models for more than two classes is demonstrated using discriminant function analysis, a significant departure from other probabilistic approaches which have largely been confined to modelling the outcome of a single binary event.
Abstract: The development of probability-based spatial-temporal models for more than two classes is demonstrated using discriminant function analysis. This represents a significant departure from other probabilistic approaches which have largely been confined to modelling the outcome of a single binary event. It also represents a significant departure from conventional deterministic overlay analysis. Procedures for calibrating and validating such models are presented and discussed. The validation procedures discussed implicate both aspatial consideration, i.e., the amount of each cover type estimated, and spatial factors, i.e., the location of each cover type and the spatial dependence of model residuals (spatial autocorrelation).
TL;DR: A method for inducing compact rule-sets whose classification accuracy can, at least in some domains, compare favourably with that achieved by larger less succinct rule- sets produced by alternative methods is described.
Abstract: Rule-based classifiers are used regularly with geographical information systems to map categorical attributes on the basis of a set of numeric or unordered categorical attributes Although a variety of methods exist for inducing rule-based classifiers from training data, these tend to produce large numbers of rules when the data has noise This paper describes a method for inducing compact rule-sets whose classification accuracy can, at least in some domains, compare favourably with that achieved by larger less succinct rule-sets produced by alternative methods One rule is induced for each output class The condition list for this rule represents a box in n-dimensional attribute space, formed by intersecting conditions which exclude other classes Despite this simplicity, the classifier performed well in the test application prediction of soil classes in the Port Hills, New Zealand, on the basis of regolith type and topographic attributes obtained from a digital terrain model
TL;DR: A unique method for plotting field bearing locations, of the kind typically taken by wildlife biologists on free ranging species, directly on a computer-compatible habitat map is proposed, and is especially useful for habitat preference studies.
Abstract: This paper proposes a unique method for plotting field bearing locations, of the kind typically taken by wildlife biologists on free ranging species, directly on a computer-compatible habitat map. We show how to use a GIS data base to identify differential habitat use directly from the polygon formed by each set of bearings. A geometric algorithm is developed to interpret the bearings accurately. The technique avoids the most difficult errors associated with using point locations, namely those due to animal movement, and distance from receiver to transmitter, and is especially useful for habitat preference studies.
TL;DR: Structural properties are presented as well as algorithms which yield optimal or near-optimal references for some of the optimality notions and several of the algorithms are shown to be efficient.
Abstract: Several notions of optimality are introduced for two-dimensional geometric versioning of polygons. The storage required for a series of versions is minimized by determining references and restating versions from the references. Structural properties are presented as well as algorithms which yield optimal or near-optimal references for some of the optimality notions. Several of the algorithms are shown to be efficient.
TL;DR: The present state of GIS in Bulgaria is described, some problems with its development are pointed to, and several ideas about ways to improve the implementation and use of G IS in the country are put forward.
Abstract: The paper describes the present state of GIS in Bulgaria, points to some problems with its development, and puts forward several ideas about ways to improve the implementation and use of GIS in the country. Special stress is placed on the danger of centralizing GIS functions within the planning institutions of the national state, on the importance of GIS education, training and pilot projects for the future development of GIS, and the necessity to reduce the technological and informational gap between Western countries and Bulgaria.