摘要:

Currently, farmcrops temporal arrangement is constrained by the generally inadequate treatment of spatial simulation in terms of socioeconomic and ecological information, resulting in artificially deflected planning. For farming in the future, positional information is of particular importance. In this paper, a description is given of the farmcrops temporal arrangement method, to reduce errors and time in precision farming, based on GPS/GIS/RS and planning techniques currently being used in many institutions together with respective approaches, usability, and trends. The system, being presented here, appears to be particularly suited to data processing and data analysis incorporating image segmentation with location sensing, which will help to combine the advantage of small field sample locations with large-scale, cost-efficient image processing methods.

ISSN:1082-4006    

DOI:10.1080/10824009709480488

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A decomposition model is described to model linear features sampled by manual digitization or field survey. The model consists of three components, original data, systematic pattern, and random error. Least squares and moving least squares techniques are introduced for polynomial curve fitting. Polynomial functions are proposed to represent linear features. The position deviation between sampled points and the polynomial function is used as an approximation of the random error. Experimental results are presented to show the effectiveness of the decomposition model. Potential applications of the model have been discussed including estimation of errors associated with points sampled along linear features, digital representation and mapping of linear features.

ISSN:1082-4006    

DOI:10.1080/10824009709480489

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Managing highway incidents involving gaseous hazardous spills requires accurate assessment of potential risks to both the population and environment. Further, quick decisions must be made on how to effectively carry out emergency rescue and evacuation. In this paper we demonstrate that a Geographic Information System (GIS) provides an ideal tool to perform risk analysis and to assist emergency response. We have built a prototype GIS that integrates a dispersion model with Arc/Info to simulate gaseous hazardous spills under different circumstances. A case study is conducted based on the highway network and 1990 census data of the Greater Cincinnati Metropolitan area.

ISSN:1082-4006    

DOI:10.1080/10824009709480490

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The effect of scale on spatial analysis has long, but sporadically, been recognized in human geography and more recently and acutely in landscape ecology. As the number of studies directly and systematically addressing scale effects is still limited, it remains unclear how results of different statistical analyses are affected by changing scale for different landscapes, or whether or not such effects can be predicted and, if so, in what situations. However, it is certain that erroneous conclusions may result if scale effects are not considered explicitly in spatial analysis with area-based data. With widespread use of remote sensing data and GIS, a better understanding of the issue of scale effects is much needed. The main purpose of this study, therefore, was to examine how results of statistical analysis respond to a systematic change in the scale of analysis. Specifically, we investigated how the relationship between landscape metrics (local landcover diversity and richness indices) and independent variables (TM bands and vegetation indices) would change with different sample sizes and mathematical representations of variables. The landscape under study is the Minden area of Nevada in the western Great Basin. Four different sample sizes (19×19, 15×15, 11×11, and 5×5 pixels) and four different representation forms (variance, mean, variance-mean ratio, and coefficient of variation) of the variables were used in all statistical analyses. We systematically examined the effects of changing sample size and representations of variables on the results of regression, analysis of variance, and correlation analysis. The results indicated that the relationship between landscape metrics and TM bands and vegetation indices was affected considerably by the change of sample size. Both the R2value and the level of statistical significance of the relationship tended to increase as sample size increased. In addition, the results of ANOVA showed that the relative importance of the TM bands and vegetation indices in the relationship varied with sample size as well. Although the spatial pattern of local-scale (or “neighborhood”) diversity and richness of land-cover types in this Great Basin landscape could be adequately quantified using spectral information-based variables, the results and accuracy of such a analysis depended on both landscape composition and sample size. The linear response of the statistical relationship to the change in sample size over some range of scales indicated that scale effects could be readily predicted in certain cases. However, in general, because scale effects can further be complicated by the choice of variables and the idiosyncrasy of particular landscapes, the predictability of scale effects seems to be confined only to certain domains of scale. To find these domains multiple-scale or hierarchical analysis must be performed. This study further supports that the modifiable areal unit problem is a common one across the disciplinary boundaries of geography, ecology and other earth sciences. Unraveling the problem not only will improve our understanding of pattern and process in nature, but also will have important implications for appropriate use of remote sensing data and GIS.

ISSN:1082-4006    

DOI:10.1080/10824009709480491

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper presents an approach to designing a spatial query language, called GeoSQL, in terms of the conventional spatial query and implementation process. A critical factor to the design is how to accommodate spatial operators in an appropriate form, while being compatible with the Structured Query Language (SQL) standard. To achieve this, the FROM clause of SQL is restructured to contain spatial operators via a subquery so that the results of spatial operations can be easily fed into both the SELECT and WHERE clauses. The subquery in the FROM clause creates an intermediate relation, on which the selection in terms of certain criteria is conducted. This is a distinct characteristic of GeoSQL. The syntax and semantics of GeoSQL are described, and a set of examples for testing the expressiveness of the language is given. The interface of the language is also designed with the introduction of visual constructs (e.g., icons and ListBoxes) to aid the entry of query text. This distinguishes GeoSQL's interface from the previous extended SQLs, which only employ pure text for constructing a query. After this, an implementation of GeoSQL is discussed. This paper finally suggests further extending GeoSQL for temporal and fuzzy queries.

ISSN:1082-4006    

DOI:10.1080/10824009709480492

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Most road network extraction algorithms developed are based on linear analysis methods. These methods involve search of edges through edge filtering, morphological filtering, or gradient modelling. As image resolution increases from 10–30 m to 0.5–2 m, road networks will appear to be narrow areas rather than thin lines. This becomes a challenge for traditional linear analysis methods based on mask operations but creates an opportunity for classification based methods. We experimented with an advanced linear analysis, gradient direction profile analysis, and a few classification algorithms including a maximum likelihood classification, clustering and a contextual classifier for road network extraction using airborne digital camera data acquired over Livermore, California with approximately 1.6 m spatial resolution.

ISSN:1082-4006    

DOI:10.1080/10824009709480493

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1082-4006    

DOI:10.1080/10824009709480494

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In order to better manage large quantity of environmental and spatial information, US EPA has built up Spatial Data Library Systems (ESDLS), Envirofacts and Spatial Data Clearinghouse, ESDLS is a repository for the Agency's new and legacy geospatial data holdings. It enables Agency access to its geospatial data in ARC/INFO format, integrates these data in a standardized, framework. Environfacts was developed as an enterprise data repository for Agency data systems. It is a relational database implemented in the Oracle Relational Database Management System and contains seven EPA's program system databases. Geospatial Data Clearinghouse provides a pathway to find information about geospatial data used at EPA. Although ESDLS can be accessed through several GIS applications, it is mainly for EPA internal uses. Meanwhile, Environfacts can be accessed by the public through Internet. Spatial Data Clearinghouse currently provides public access to its metadata. However, it is promised that public can access its geospatial data via the Internet in the future.

ISSN:1082-4006    

DOI:10.1080/10824009709480495

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor