摘要:

The size and complexity of modern geographical datasets continues to grow and with that growth comes an increased difficulty in assessing the usefulness of a particular dataset for a particular problem. The task of browsing through a large database is rapidly becoming impractical because of the shear volume of the data, therefore, the information potential of the database is lost because the scope of the database is beyond comprehension. This article promotes new methodologies beyond the use of descriptive metadata to support a user's desire to find a dataset suitable for his or her analysis.

ISSN:1365-8816    

DOI:10.1080/136588199241427

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This paper outlines an approach in applying artificial intelligence techniques to solve spatial problems. The approach consists of combining casebased reasoning with geographical information systems to form a hybrid system to solve spatial problems. In this paper, the hybrid is applied to the problem of soil classification which is solved by searching the case base for other spatial cases similar to the problem case. The knowledge from the retrieved case is used to formulate an answer to the problem case. The paper compares the results from this new approach with a traditional method of soil classification.

ISSN:1365-8816    

DOI:10.1080/136588199241436

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A method for quantitative assessments of spatial accuracy and completeness for line data sets is suggested and explored. Data sets of higher accuracy are used for the assessments. The method utilizes only generally available GIS operations. It works by establishing a number of buffers of increasing width around the lines. For each width, the maps are overlaid, and statistics are computed. By plotting the results in graphs, the usefulness of the method is demonstrated. The method is explored using the Digital Chart of the World (DCW), with theNorwegian mapping authority'snationalN250 mapseries as referencedataset.

ISSN:1365-8816    

DOI:10.1080/136588199241445

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

SRAD, a spatially-distributed solar radiation model, was applied to a Canadian boreal forest environment in north-western Ontario. SRAD is grid based, and factors in both topo- and meso-scaled processes using a digital elevation model (DEM) and local monthly atmospheric parameters as inputs. SRAD generates estimates of incident, outgoing, and net irradiance, as well as surface and air temperatures for each point in the DEM, over any time period ranging from one day to one year. Cloudiness and other atmospheric conditions are factored into the shortwave irradiance estimates. From the DEM, the terrain effects of slope angle, aspect, and topographic shading are calculated and used to modify the estimates of shortwave irradiance. The SRAD-generated irradiance estimates for the study region were found to be consistent with irradiance data from other sources. Estimates of irradiance were most sensitive to the parameters of sunshine fraction and cloudiness. Radiation estimates were generated and compared using both a 20 m and a 100 m resolution DEM. Extremely low irradiance estimates generated at the fine scale were absent at the coarser scale. However the mean value of irradiance at both scales was estimated to be the same at 12.4 MJm-2 day-1 annually. Radiation estimates were also determined at the two scales for a series of forest research plots. For 91% of the plots, the irradiance estimates during the growing season differed by less than 0.5 MJm-2 day-1 between the two scales. Results presented here suggest that SRAD can provide useful input for predictive spatial models in boreal forest ecosystems.

ISSN:1365-8816    

DOI:10.1080/136588199241454

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

GIS technology has transformed spatial data handling capabilities and made it necessary for governments to re-examine their roles with respect to the supply and availability ofgeographicalinformation. This paper reviews the experiences of eleven national initiatives which together constitute the first generation of national spatial data infrastructures and it also considers what lessons might be learnt for the next generation that will come into being over the next ten years. The presentation is divided into three sections. The first of these consists of a short profile of each of the eleven strategies for Australia, Canada, Indonesia, Japan, Korea, Malaysia, Netherlands, Portugal, Qatar, United Kingdom and United States. These are evaluated in the second section in relation to the driving forces behind them and their main features in terms of status, scope, access, approach to implementation and resources. The last section considers what lessons might be learnt from this experience and discusses the changing context within which the next generation of national spatial data infrastructures are likely to be formulated. It concludes with some thoughts on which countries are most likely to be candidates for the next generation of national spatial data infrastructures.

ISSN:1365-8816    

DOI:10.1080/136588199241463

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:1365-8816    

DOI:10.1080/136588199241472

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:1365-8816    

DOI:10.1080/136588199241481

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor