摘要:

This study examines the effects of line simplification on the positional accuracy of linear features. The goal is to quantify the relation between the level of simplification and the degree of positional error, so that users can choose appropriate levels of simplification that will yield results meeting specific accuracy criteria. The study focuses on the Douglas-Peucker line simplification algorithm and examines both natural and anthropogenic features (streams and roads) derived from United States Geological Survey Digital Line Graphs. Results show that error can be modelled at an aggregate level using cumulative frequency curves and their confidence limits. This makes it possible to identify the level of simplification that eliminates the largest number of vertices while still attaining a specific positional accuracy standard. A simple implementation strategy is described in which an optimal level of simplification is identified and simplification is applied selectively for different lines. The study shows that management of simplification induced error is possible using simple tools well within the reach of GIS users.

ISSN:1365-8816    

DOI:10.1080/136588100240877

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Cellular Automata (CA) have attracted growing attention in urban simulation because their capability in spatial modelling is not fully developed in GIS. This paper discusses how cellular automata (CA) can be extended and integrated with GIS to help planners to search for better urban forms for sustainable development. The cellular automata model is built within a grid-GIS system to facilitate easy access to GIS databases for constructing the constraints. The essence of the model is that constraint space is used to regulate cellular space. Local, regional and global constraints play important roles in affecting modelling results. In addition, 'grey' cells are defined to represent the degrees or percentages of urban land development during the iterations of modelling for more accurate results. The model can be easily controlled by the parameter k using a power transformation function for calculating the constraint scores. It can be used as a useful planning tool to test the effects of different urban development scenarios.

ISSN:1365-8816    

DOI:10.1080/136588100240886

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Traditionally, the classes in thematic maps have been treated as crisp sets, using classical set theory. In this formulation, map classes are assumed to be mutually exclusive and exhaustive. This approach limits the ability of thematic maps to represent the continuum of variation found in most landscapes. Substitution of fuzzy sets allows more flexibility for treatment of map classes in the areas of accuracy assessment and area estimation. Accuracy assessment methods based on fuzzy sets allow consideration of the magnitude of errors and assessment of the frequency of ambiguity in map classes. An example of an accuracy assessment from a vegetation map of the Plumas National Forest illustrates the implementation of these methods. Area estimation based on fuzzy sets and using accuracy assessment data allows estimation of the area of classes as a function of levels of class membership. The fuzzy area estimation methods are an extension of previous methods presented by Card (1982). One interesting result is that the sum of the areas of the classes in a map need not be unity. This approach allows a wider range of queries within a GIS.

ISSN:1365-8816    

DOI:10.1080/136588100240895

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Multi-criteria evaluation (MCE) is perhaps the most fundamental of decision support operations in geographical information systems (GIS). This paper reviews two main MCE approaches employed in GIS, namely Boolean and Weighted Linear Combination (WLC), and discusses issues and problems associated with both. To resolve the conceptual differences between the two approaches, this paper proposes the application of fuzzy measures, a concept that is broader but that includes fuzzy set membership, and argues that the standardized factors of MCE belong to a general class of fuzzy measures and the more specific instance of fuzzy set membership. This perspective provides a strong theoretical basis for the standardization of factors and their subsequent aggregation. In this context, a new aggregation operator that accommodates and extends the Boolean and WLC approaches is discussed: the Ordered Weighted Average. A case study of industrial allocation in Nakuru, Kenya is employed to illustrate the different approaches.

ISSN:1365-8816    

DOI:10.1080/136588100240903

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This paper presents a replicable methodology to assess the extent of fragmentation in forests induced by natural and man-made features and disturbances. The analysis is presented in the context of conservation ecology research and its relevance to the development of environmental protection policy is discussed. Methodologically, the approach utilizes Geographical Information Systems (GIS), Relational Database Management Systems (DBMS), symbolic mathematics software, spatial autocorrelation statistics and graph data structures. The intersection of these technologies and techniques offers a potentially fertile area to extend the meaningful definition of natural forested areas and their management as well as our understanding of how these areas can be preserved through conservation policy. The paper concludes with suggestions for further extensions of the research.

ISSN:1365-8816    

DOI:10.1080/136588100240912

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:1365-8816    

DOI:10.1080/136588100240921

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor