A spatial decomposition approach for accelerating buffer analysis of vector data

Parallel vector buffer analysis approaches can be classified into 2 types:algorithm-oriented parallel strategy and the data-oriented parallel strategy.These methods do not take its applicability on the existing geographic information systems(GIS)platforms into consideration.In order to address the problem,a spatial decomposition approach for accelerating buffer analysis of vector data is proposed.The relationship between the number of vertices of each feature and the buffer analysis computing time is analyzed to generate computational intensity transformation functions(CITFs).Then,computational intensity grids(CIGs)of polyline and polygon are constructed based on the relative CITFs.Using the corresponding CIGs,a spatial decomposition method for parallel buffer analysis is developed.Based on the computational intensity of the features and the sub-domains generated in the decomposition,the features are averagely assigned within the sub-domains into parallel buffer analysis tasks for load balance.Compared with typical regular domain decomposition methods,the new approach accomplishes greater balanced decomposition of computational intensity for parallel buffer analysis and achieves near-linear speedups.

Effects of Forest Roads on Habitat Pattern for Sables in Da Hinggan Mountains, Northeasten China

The anthropogenic managements of forest have created a network of roads resulting in the loss and alternation of habitat. To better understand road′s impact on animal habitats, we assessed the habitat pattern of sables(Martes zibellina), one of rodents within national first-class protected species, when roads are considered in Huzhong area in Da Hinggan Mountains, northeastern China. Employing published literatures about behavior ecology, aerial photographs and forest stand maps, we classified the study area into three habitat types including best-suitable, suitable and unsuitable habitats based on sable habitat requirements at the landscape scale including four variables derived from forest source map with attribute database. Results indicated the loss and significant fragmentation of best-suitable habitat and home range habitat when roads, especially 150 m avoidance distance of roads, were considered. The roads reduced and fragmented highly suitable habitats more significantly during earlier development period than the later development period. Additionally, the suitable area percentage increased with increasing distance to roads. This study helped to identify the suitable area for sables and location of sable population. Also, this study suggested the passage construction and road management involving road closure and removal will reduce the fragmentation functionally and benefit the sable population.

GIS-BASED STUDY ON THE RELATIONSHIP BETWEEN EARTHQUAKES AND ACTIVE FAULTS IN SHANGHAI AND ITS ADJACENT OFFSHORE REGION, EAST CHINA

The relation between earthquakes and active faults in Shanghai and its adjacent offshore region is quantitatively evaluated using GIS-based buffer and overlay analysis techniques. Statistics on the distance from the epicenter of an earthquake to its nearest active fault suggest that most earthquakes in the study area occurred within 10 to 20 km of major active faults. The strikes of active faults have significant influences on the occurrence of earthquakes. The NE-NNE-striked faults are less active than NW-NNW- or EW-striked faults. Along the NW-NNW- or EW-striked faults, the frequency of earthquakes is much higher than that along NE-NNE-striked faults. The time of fault activity has some degree of influence on the earthquakes. The newer the faults, the higher the frequency of earthquakes within the zone of the faults.

The Study of Spatial Distribution of Land Use in the Yellow River Delta in China

In this paper, Land at 8 OLI image data from 2013 to 2017 was interpreted by visual interpretation combined with supervised classification to extract the information of land use distribution in the Yellow River Delta in China. The characteristics of Land Use Cover Change (LUCC) in the past five years which were analyzed by land use spatial analysis method based on buffer zone were discussed to obtain the land use index trend of five land types in buffer zones at different distance. The land use transfer maps of 2013 and 2017 were made by using the geo-information mapping method. The spatial-temporal change rules and the development process of land use in the Yellow River Delta during the past five years were analyzed. According to the analysis results, the comprehensive index of land use degree in the study area was in the middle level. The land use transfer maps were mainly consisted of farmland and grassland. The change rate of bare land to vegetation was 20.21% and that of vegetation to bare land was 14.15%. This study can provide effective basis for the scientific management of land and rational guidance for planning in this area.

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.

Impact analysis of expressway construction on ecological carrying capacity in the Three-River Headwater Region

The construction of expressways has a variety of impacts on the ecologically fragile and sensitive Three-River Headwater Region and causes changes in the structure and carrying capacity of the ecosystem. To assess the impact of expressway construction on the ecological carrying capacity of the regional natural system, net primary productivity(NPP)was used as the quantitative index to indicate the efficiency of the regional ecological environment to fix and transform photosynthesis products. In this study, trend analysis and buffer zone analysis were used to quantitatively analyze the spatial and temporal characteristics of NPP in the study area from 2006 to 2015 based on the MOD17A3/NPP dataset. In addition, the spatial-temporal effects of expressway and interchange construction on NPP in buffer zones were studied using GIS spatial analysis. The summarized results are as follows.(1) The multi-year average NPP in the study area is 137.9 gC/m^2,indicating a slight downward trend;spatially, the overall NPP shows a downward trend from east to west.(2) The impact of expressway construction on NPP in buffer zones will last for more than two years, generally presenting greater NPP further from the expressway.(3) After completion of the interchange, the NPP decreases significantly within its radiation radius;at a distance of 6 km, the NPP gradually stabilizes.(4) The influence law of expressway construction and interchange construction on NPP is approximately the same in the respective buffer zones.

Spatiotemporal evolution of national development zones and their impact on urban land growth in China

Development zones are important growth poles for promoting regional economic development. However, the spatiotemporal relationship between development zone construction and urban land growth is still unclear. This paper analyzes the spatiotemporal changes of national-level development zones(NDZs), approximately 219 national economic development zones, and 156 high-tech development zones during 1990–2018 in China. The impact of development zone establishment on the growth of surrounding urban land was quantitatively explored using circle buffering analysis and time series comparative analysis. The results show that China's NDZs spread from the southeast coast to the inland area from 1990 to 2018, and the establishment of the development zones has an obvious promoting effect on the surrounding urban land growth. The scope and intensity of influences of the development zone established in different periods present distinct nonstationarity in space and time. Overall, the impact on urban land(IU) of China's NDZs established in different years was mostly highest at the 100 m buffer zone radius, while the slope of the IU was mostly negative, which meant that the 100 m buffer zone radius of the development zone center was the most efficient scale to promote urban land growth. In the meantime, the curve of IU of NDZs established before 1990, during 1996–2000 and 2001–2005 has a clear inflection point, which indicates that the most efficient scales of NDZs established before 1990, during 1996–2000, and 2001–2005 are 1300 m, 900–1000 m, and 800 m, respectively. NDZs established in other periods do not have the most obvious efficient scale. The development zone played the greatest role in promoting urban land growth from 2000 to 2010. Three association modes, including post-growth, pre-growth and steady-growth, were identified based on the differences in geographical location, establishment time, and type of development zones. We quantitatively identify the impact of the growth pole of NDZs on urban land growth from the perspective of spatiotemporal evolution. The findings would provide decision-making support for optimizing the spatial relationship between development zone construction and urban land growth.

A comparative study of spatiotemporal patterns of urban expansion in six major cities of the Yangtze River Delta from 1980 to 2015

Introduction:China has been experiencing dramatic urbanization in parallel with its eco-nomic boom over the past three to four decades.The Yangtze River Delta(YRD),as the most important engine in the Chinese economy,has pioneered in the rapid urbanization road of China since the late 19705.We quantifed and compared the spatiotemporal patterns of urban expansion in six major cities in the YRD urban agglomeration between 1980 and 2015.Outcomes:We found that Sha nghai,Nanjing,Hangzhou,Wuxi,Suzhou and Ningbo expanded by an annual rate of 5.4%,5.9%,9.6%,7.4%,6.3%and 8.1%from 1980 to 2015,suggesting larger cities generally possess lower growth rates.Spatiotemporal patterns of urban expansion are defined by multiple forces including physical conditions and urban planning and policy.The urbanization processes in Shanghai,Nanjing and Hangzhou gen-erally conformed with the difusion-coales cence theory as the number of patches(NP)and patch density(PD)of urbanized land peaked and the proportion of leapfrogging urban growth type began to decrease around 2005,which separating their urbanization processes into difusion phase before and coalescence phase after.In contrast,Suzhou,Wuxi and Ningbo is either in the diffusion or in the transition phase from diffusion to coalescence,not showing temporal dynamics of diffusion-coalescence phase across the study period,which might be related to the fact that the urban areas in these three cities were more dispersive in space than that of other cities.Conclusions:These spatially explicit findings are the fundamental cornerstone to understand the characteristics,drivers and consequences of urban expansion in the urban agglomera-tions,and then detect the feasibility of general urbanization theories and further advance in-depth theoretical understanding to support a sustainable urban future.