摘要:

Categorical coverages are popular for the presentation of thematic data in cartographic form and have gained widespread use. Routines for their preparation are included in most GIS software. Categorical coverages are simple to implement and easy to understand. The popularity of the categorical coverage is closely related to the intuitive rules that determine its behaviour. This paper presents a formalization of these rules based on the concepts of a partition of space and the refinement of such partitions of space. A family of categorical coverages is defined as all categorical coverages that can be produced from a data set through aggregations of categories. It is shown that categorical coverages are partially ordered by refinement of partitions. This ordering is preserved in the mapping from the ordering of the partition of the attribute domain to the partition of space. This formalization is not only useful for implementors of GIS, but the list of possible operations and their properties is the base for the design of a user interface to produce and manipulate categorical coverages. The thematic definition of categorical coverages is directly related to the cartographic rendering. Changes in the thematic definition, i.e., changes of the map legend, can be automatically propagated to the rendering. Limitation of cartographic rendering, e.g., resolution of the screen, limits the presentation of the result. These influences from the rendering cannot automatically be translated into changes in the subdivisions of the categories. This may explain why good graphical presentation is still an art and the production of thematic maps is not fully automated.

ISSN:1365-8816    

DOI:10.1080/136588197242365

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Generalization is a fundamental function in GIS. It has been an important research theme for many years in cartography and GIS. A number of generalization operations have been identified, however most of them, especially those rule-based operations, remain at the conceptual level. This paper describes a set of mathematical (algebraic) models for area aggregation based on the operators developed in mathematical morphology. In this paper, the process of area aggregation is decomposed into two components, viz., combination and shape refinement, and algebraic models for both components are developed. These are demonstrated using various examples. The models provide a mathematical basis for area aggregation in digital generalization of map and other spatial data. The results show that these algebraic models have the potential for successful application.

ISSN:1365-8816    

DOI:10.1080/136588197242374

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Adaptive Recursive Tessellations (ART) is a conceptual and generalized framework for a series of hierarchical tessellation models characterized by a variable decomposition ratio and rectangular cells. ART offers more flexibility in cell size and shape than the quadtree which is constrained by its fixed 1:4 decomposition ratio and square cells. Thus the variable resolution storage characteristic of the hierarchical tessellations can be fully utilized. A data structure for the implementation of the ART, called Adaptive Recursive Run-Encoding (ARRE), is proposed. Then a spatial database management system specially for ART, the Tessellation Manager, is constructed based on the ARRE. Space efficiency analysis of three ART models are conducted using the Tessellation Manager. The result shows that ART models have similar space efficiency with the quadtree model. ART also has many potential applications in GIS and is suitable as a spatial data model for raster GIS.

ISSN:1365-8816    

DOI:10.1080/136588197242383

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Regression equations between a response variable and candidate explanatory variables are often estimated using a training set of data from closely observed locations but are then applied using covariate data held in a GIS to predict the response variable at locations throughout a region. When the regression assumptions hold and the GIS data are free from error, this procedure gives unbiased estimates of the response variable and minimizes the prediction mean squared error. However, when the explanatory variables in the GIS are recorded with substantially greater errors than were present in the training set, this procedure does not minimize the prediction mean squared error. A theoretical argument leads to the proposal of an adaptation for regression equations to minimize the prediction mean squared error. The effectiveness of this adaptation is demonstrated by a simulation study and by its application to an equation for tree growth rate.

ISSN:1365-8816    

DOI:10.1080/136588197242392

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The methods and advantages of integrating knowledge-based and geographical information system techniques for the analysis of provenance and diagenesis in sedimentary basins are demonstrated by examples from the Cheshire Basin located in north-west England. Approximate reasoning techniques to handle the vagueness and uncertainty inherent in a large amount of geological data, knowledge and reasoning are reviewed with particular emphasis on provenance analysis using subjective probability theory, Dempster-Shafer theory and fuzzy logic techniques. Object-oriented methods for analysing diagenetic history in user specified volumes of the basin are discussed.

ISSN:1365-8816    

DOI:10.1080/136588197242400

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In this paper we propose a simple technique for assessing the positional accuracy of digitized linear features. The approach relies on a comparison with a representation of higher accuracy, and estimates the percentage of the total length of the low accuracy representation that is within a specified distance of the high accuracy representation. The approach deals successfully with three deficiencies of other methods: it is statistically based; is relatively insensitive to extreme outliers; and does not require matching of points between representations. It can be implemented using standard functions and a standard scripting language in any raster or vector GIS. We present the results of a test using data from the Digital Chart of the World.

ISSN:1365-8816    

DOI:10.1080/136588197242419

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor