An algorithm of multi-model spatial overlay based on three-dimensional terrain model TIN and its application

D GIS spatial overlay analysis is being broadly concerned about in international academe and is a research focus. It is one of the important functions of spatial analysis using GIS technology. An algorithm of multi model spatial overlay based on three dimensional terrain model TIN is introduced in this paper which can be used to solve the TIN based three dimensional overlay operation in spatial analysis. The feasibility and validity of this algorithm is identified. This algorithm is used successfully in three dimensional overlay and region variation overlay analysis.

Remote sensing monitoring of the recent rapid increase in cultivation activities and its effects on desertification in the Mu Us Desert, China

The recent ecological improvement in the Mu Us Desert of China, largely attributed to large-scale afforestation projects, has created new opportunities for cultivation activities. However, the subsequent rapid increase in reclamation on desertification land and its impact on desertification have raised concerns. In this study, we first extracted data on cultivated land and desertification land in 1975,1990, 2000, 2005, 2010, 2015, and 2020 through the human-computer interaction visual interpretation method. By overlaying the cultivated land dynamics and desertification land, we subsequently explored the effect of cultivation activities on desertification in the Mu Us Desert during the six periods from 1975 to 2020(1975–1990, 1990–2000, 2000–2005, 2005–2010, 2010–2015, and 2015–2020). The results showed that cultivated land in the Mu Us Desert showed a fluctuating and increasing trend from 3769.26 km~2 in 1975 to 4865.73 km~2 in 2020, with 2010 as the turning point for the recent rapid increase. The main contributors included the large and regular patches distributed in Yuyang District and Shenmu of Shaanxi Province, and relatively smaller patches concentrated in Inner Mongolia Autonomous Region. The increased cultivated land from the reclamation on desertification land was dominated by moderate and severe desertification lands, and the decreased cultivated land that was transferred into desertification land as abandoned cultivated land was dominated by slight and moderate desertification lands. The effect of cultivation activities on desertification reversal(average area proportion of 10.61% for reversed desertification land) was greater than that of the development of desertification(average area proportion of 5.82% for developed desertification land). Nevertheless, compared to reversed desertification land,both the significant increase of developed desertification land during the periods of 2000–2005 and 2005–2010 and the insignificant decrease during the periods of 2005–2010, 2010–2015, and 2015–2020 implied a potential remobilization risk. Therefore, this study provides a significant theoretical reference for the formulation of ecological restoration projects and regional macroeconomic development policies by considering the influence of cultivation activities, to ensure the overall environmental stability and sustainability in desertification land where reclamation and abandonment activities have taken place.

Research on the Relationship between Active Faults and Earthquakes in the Junction Area of the China North-South Seismic Belt and Central Orogenic Belt Based on GIS

Research on the relationship between faults and seismicity in the junction area of China's north-south seismic belt and central orogenic belt based on the Geography Information System (GIS) has been done.For each of the 16 faults in this area,we build a 25km buffer zone and use overlay analysis to investigate the seismicity and its characteristics on each fault.The results unveil the main seismic faults as follows:the western segment of the northern-edge of the west Qinling fault,the southwestern segment of the Lixian-Luojiabao fault,the southeastern segment of the Lintan-Dangchang fault,the southwestern segment of the Wenxian fault,the Huya fault,and the Xueshan fault.The most active faults are the Huya and Xueshan faults,then the Tazang fault,the Lixian-Luojiabao fault and the northern piedmont of the Guanggaishan-Dieshan fault.The research zone can be divided into four areas according to focal depth,which gets deeper from north to south.The profile of focal depth indicates the geometry and mechanical property of faults,and further reveals the movement model of eastward extrusion of the Tibetan plateau and southeastward escape of masses,thus providing basis for the protection against earthquakes and hazard mitigation in this area.

Key issues in the strategic environmental assessment of the middle reaches of the Yangtze River

The middle reaches of the Yangtze River were the key areas of central China emphasized in many strategic plans.It was also an important ecological and fragile area,because there are many wetlands,lakes,rivers and soil erosion area.And it linked the ecological fragile upper reaches of the Yangtze River with the most developed Yangtze River Delta in China.It is urgent to figure out the key industries,key areas and key ecological and environmental problems for the strategic environmental assessment of the middle reaches of the Yangtze River.The important regions consisted of the economic key region,the planning key region,the ecological key region,and the fragile ecological region.The key industries consisted of the ones contributed to economic growth,or affecting the environment,or preferred by the local government.Besides,the ecological and environmental problems involved the water environment,the atmosphere environment,and the ecological environment.The key regions were identified through word frequency statistics of many plans by ROST Word Parser.And it was spatially overlaid by ArcGIS9.2.The key industries were calculated based on the economic statistics data,the environmental pollution census and the word frequency statistics.Based on SCI-EXPANDED,CPCI-S,CCR-EXPANDED,IC database and Chinese CNKI periodical database,the ecological and environmental problems of the middle reaches of the Yangtze River were analyzed by Citespace software according to the keywords and abstract of every paper.The results show that the important regions of the middle reaches of the Yangtze River concentrated in the central urban region,along the river and lake,surrounding mountains,and the wetland.The equipment manufacturing,chemical industry,mining industry,energy supply industry,food industry,textile and garment industry were the key industries need to be focused on.The urgent ecological and environmental problems in the middle reaches of the Yangtze River were the water environment pollution,water ecosystem,heavy metal pollution,soil and wetlands destruction,organic pollution and biodiversity decrease issues..