GML is becoming the de facto standard for electronic data exchange among the applications of Web and distributed geographic information systems. However, the conventional query languages （e. g. SQL and its extended v...GML is becoming the de facto standard for electronic data exchange among the applications of Web and distributed geographic information systems. However, the conventional query languages （e. g. SQL and its extended versions） are not suitable for direct querying and updating of GML documents. Even the effective approaches working well with XML could not guarantee good results when applied to GML documents. Although XQuery is a powerful standard query language for XML, it is not proposed for querying spatial features, which constitute the most important components in GML documents. We propose GQL, a query language specification to support spatial queries over GML documents by extending XQuery. The data model, algebra, and formal semantics as well as various spatial Junctions and operations of GQL are presented in detail.展开更多
Constrained Delaunay triangulated irregular network is one kind of dynamic data structures used in geosciences. The research on point and edges insertion in CD-TIN is the basis of its application. Comparing with the a...Constrained Delaunay triangulated irregular network is one kind of dynamic data structures used in geosciences. The research on point and edges insertion in CD-TIN is the basis of its application. Comparing with the algorithms of points and constrained edge insertion, there are very a few researches on constrained edge deletion in CD-TIN. Based on the analysis of the polymorphism of constrained edge, virtual points are used to describe the intersection of constrained edges. A new algorithm is presented, called as influence domain retriangulating for virtual point （IDRVP）, to delete constrained edges with virtual points. The algorithm is complete in topology. Finally, the algorithm is tested by some applications cases.展开更多
Resettlement is considered a major policy measure in two major Chinese policy programs,the "Great Development of the West" and poverty alleviation in the new century,and the "New Countryside Development...Resettlement is considered a major policy measure in two major Chinese policy programs,the "Great Development of the West" and poverty alleviation in the new century,and the "New Countryside Development".The selection of the target location of resettlement sites for poverty-stricken villages is of critical importance to the success of resettlement projects,yet the selection process is challenged by the need for analyzing a variety of contributing factors,and the need for many rounds of tedious data processing.So in this paper we present an in-depth analysis of the major factors and data processing model concerning mountainous povertystricken villages,which also takes a major part of China's poor villages.Our analysis shows the following factors bear the most importance in resettlement selection:1) topography:candidate areas should have slope less than 25 degrees and altitude less than 2400 meters.2) accessibility:close to market conventions places and transportation facilities.3) farming resources:with abundant land and water resources.4) non-intrusiveness:interests of receiving villages should be considered and negative impact minimized.A simple measure could be having the candidate area 1000 m away from the receiving residents.5) Minimal ecological and political footprint:candidate areas shall not conflict with nature conservation areas or nationally planned key land use projects.6) Social and cultural compatibility:residents will better off if relocated in the same county,considering language,religion,ethnic culture and other factors.Taking Makuadi,Lushui County of Nujiang Prefecture as a case study,we demonstrate how GIS analysis and modeling tools can be used in the selection process of resettlement projects in mountainous areas.展开更多
基金Funded by the Youth Chengguang Project of Science and Technology of Wuhan City of China(No.20045006071-16)
文摘GML is becoming the de facto standard for electronic data exchange among the applications of Web and distributed geographic information systems. However, the conventional query languages （e. g. SQL and its extended versions） are not suitable for direct querying and updating of GML documents. Even the effective approaches working well with XML could not guarantee good results when applied to GML documents. Although XQuery is a powerful standard query language for XML, it is not proposed for querying spatial features, which constitute the most important components in GML documents. We propose GQL, a query language specification to support spatial queries over GML documents by extending XQuery. The data model, algebra, and formal semantics as well as various spatial Junctions and operations of GQL are presented in detail.
文摘Constrained Delaunay triangulated irregular network is one kind of dynamic data structures used in geosciences. The research on point and edges insertion in CD-TIN is the basis of its application. Comparing with the algorithms of points and constrained edge insertion, there are very a few researches on constrained edge deletion in CD-TIN. Based on the analysis of the polymorphism of constrained edge, virtual points are used to describe the intersection of constrained edges. A new algorithm is presented, called as influence domain retriangulating for virtual point （IDRVP）, to delete constrained edges with virtual points. The algorithm is complete in topology. Finally, the algorithm is tested by some applications cases.
基金supported by the National Natural Science Foundation of China (Grant No.40761019)National Natural Science Foundation of Yunnan (Grant No.2007D157M)
文摘Resettlement is considered a major policy measure in two major Chinese policy programs,the "Great Development of the West" and poverty alleviation in the new century,and the "New Countryside Development".The selection of the target location of resettlement sites for poverty-stricken villages is of critical importance to the success of resettlement projects,yet the selection process is challenged by the need for analyzing a variety of contributing factors,and the need for many rounds of tedious data processing.So in this paper we present an in-depth analysis of the major factors and data processing model concerning mountainous povertystricken villages,which also takes a major part of China's poor villages.Our analysis shows the following factors bear the most importance in resettlement selection:1) topography:candidate areas should have slope less than 25 degrees and altitude less than 2400 meters.2) accessibility:close to market conventions places and transportation facilities.3) farming resources:with abundant land and water resources.4) non-intrusiveness:interests of receiving villages should be considered and negative impact minimized.A simple measure could be having the candidate area 1000 m away from the receiving residents.5) Minimal ecological and political footprint:candidate areas shall not conflict with nature conservation areas or nationally planned key land use projects.6) Social and cultural compatibility:residents will better off if relocated in the same county,considering language,religion,ethnic culture and other factors.Taking Makuadi,Lushui County of Nujiang Prefecture as a case study,we demonstrate how GIS analysis and modeling tools can be used in the selection process of resettlement projects in mountainous areas.
