摘要:

Wildfire provides a good example to study spatio-temporal representations for GIS applications because of its spatio-temporal variability. One of the salient features ofa GIS is itsbuilt-in capability to calculate and maintain centroid, length, area, and topological relations among spatial objects. Likewise, a competent temporal GIS should be able to support queries about temporal measures, such as rate, frequency, life expectancy, and temporal relations. In doing so, temporal GIS need well-designed representations to structure spatiotemporal constructs and their relations. While temporal information is often incorporated into GIS by time-stamping attributes or layers, this research applies knowledge acquisition techniques of written materials analysis and unstructured interviews with wildfire professionals to elicit conceptual models for wildfire representation. Four elicited conceptual models form a wildfire information cycle which presents a continuum in wildfire conceptualization across different types of wildfire studies. Current GIS layer models can support three of the four conceptual models: locational snapshots (as raster layers), entity snapshots (as features on vector layers), and fire mosaics (as vector layers). The support of layer-based models for representing fire processes is, however, inadequate. With the wildfire information cycle and its four conceptual models, this study shows (1) spatio-temporal information dependency among human's conceptual models, (2) the missing process-oriented data model (fire entities) in GIS, and (3) a three-domain model of semantics, time, and space as a generic GIS representation to support all the four conceptual models. Follow-up studies are undertaken in formulating the three-domain model to implement the wildfire information cycle.

ISSN:1365-8816    

DOI:10.1080/136588197242059

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Many scientific applications employ computer graphics as a means of interactively visualizing two-dimensional geophysical data sets. This paper presents an algorithm for improving rendering performance by using an image segmentation approach to reduce the number of rendered polygons while maintaining complete display fidelity. Though applied here specifically to the output from a numerical ionosphere model, the algorithm is broadly applicable to many other two-dimensional cellular data sets, geophysical and otherwise. In an ionospheric context, this algorithm demonstrates the ability to reduce the number of rendered polygons by 95 per cent or more with a corresponding reduction in rendering time.

ISSN:1365-8816    

DOI:10.1080/136588197242068

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We present a method for systematically identifying neighbourhoods that may face transportation difficulties during an evacuation. A classification of this nature offers a unique approach to assessing community vulnerability in regions subject to fast-moving hazards of uncertain spatial impact (e.g., urban firestorms and toxic spills on highways). The approach is founded on an integer programming (IP) model called the critical cluster model (CCM). An heuristic algorithm is described which is capable of producing efficient, high-quality solutions to this model in a GIS context. The paper concludes with an application of the method to Santa Barbara, California.

ISSN:1365-8816    

DOI:10.1080/136588197242077

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A prototype spatial graphic landscape system for use in PC-based micro-computers was developed. Spatial characteristics and attributes of a landscape were entered into a geographical information system to create a data base. A grazing pressure index was modelled using an algorithm which sequentially adjusts grazing capacity of response units for percentage lost to brush density, slope, and distance from water. The grazing pressure model was verified on a poorly watered homogeneous pasture (1302ha) and well watered complex pasture (2959ha). Response units were highly correlated to observed grazing (r 0.92-0.94) in the poorly watered, homogeneous pasture. However, correlations were poor in the complex, well-watered pasture. Circular barrier effects of slopes, intermittent watering sources and relative differences in ecological condition of adjacent response units were identified as the primary factors reducing model performance.

ISSN:1365-8816    

DOI:10.1080/136588197242086

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A linkage was developed between a spatial graphic landscape system and a bioeconomic analysis model for grazingland. User interactive models were described. The first model evaluated potential water sites based on potential grazing land harvest.The second modelevaluated potential water sites by comparing the annualized net present values of two different water facility developments. The third identified optimal areas of a landscape for woody brush treatment using a linear optimizing procedure. Example analyses are described and recommendations for improvements to future models made.

ISSN:1365-8816    

DOI:10.1080/136588197242095

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1365-8816    

DOI:10.1080/136588197242103

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor