An appearance‐preserving simplification method for complex 3D building models

The simplification of 3D building models to effectively reduce model complexity and improve rendering efficiency is an important component of 3D GIS. To reduce the data volume while preserving the model appearance, this article proposes a novel simplification method for complex 3D building models. Texture discontinuities are addressed by developing a new data model that records the mapping relation between the texture coordinates of each vertex and its neighboring triangles. The surface mesh of the building model is then segmented into regions, guided by topology and appearance. Finally, the mesh segmentation information is used to derive an improved error metric that considers both geometric and texture errors, and the texture coordinates are adjusted after each simplification operation. A series of comparative experiments alongside traditional methods demonstrates that our approach achieves a good balance between geometric fidelity and texture preservation, and produces simplified 3D building models with better visual quality.     

1：100万图号中行号、列号正误的快速判断方法

针对多个县(市)、区土地调查文字材料将1:100万图号中的行、列号用错而产生严重缺陷的事实,本人认真学习了"国家基本比例尺地形图分幅和编号"的基础知识,并总结归纳出简易的快速判断正误的方法,以杜绝类似差错的发生.     

Landscape Effects of Land Consolidation Projects in Central China——A Case Study of Tianmen City,Hubei Province

The goal of land consolidation in China is still to develop agricultural production. The study of landscape effects of land consolidation projects （LCPs） faces many difficulties because of the lack of government＇s interest and data. This paper, taking Tianmen City of Hubei Province in Central China as an example, presents a methodology for analyzing landscape effects of LCPs by GIS and Fragstats3.3. It describes landscape effects with indexes of Patch Density （PD）, Largest Patch Index （LPI）, Landscape Shape Index （LSI）, Interspersion and Juxtaposition Index （IJI）, Aggregation Index （AI）, and Shannon＇s Diversity Index （SHDI）, showing more regular shape, simpler structure and less habitat diversity after LCPs. It computes ten landscape indexes of four categories of patches including Cultivated Land, Road, Water Channel, and River and Pond. The indexes show that 1） cultivated land becomes more fragmental in patch area, less irregular in patch shape and more concentrated in block; 2） the transport capacity of roads and irrigation and drainage capacity of water channels have been improved; 3） the landscape change of river and pond can be summarized as decreasing scale, more regular shape, reducing connectivity and diversity of the class. LCPs can facilitate agricultural production as well as protect cultivated land and food security. However, it is doubted that the increase of cultivated land from LCPs results from the reducing in landscape diversity of water area.     

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长江口外高盐水入侵分析

本文根据１９７５～１９８２，１９８７～１９９０年东海海洋调查、１９８２～１９８３年上海市海岸带海洋水文调查和１９８８～１９８９年长江口河口锋调查资料，分析了高盐水入侵长江口外的特征和规律，结果表明，高盐水入侵边界的多年平均位置与长江水下三角洲的东边界大致一致，入侵长江口外的高盐水主要源于台湾暖水，冬季尚有黄海混合水入侵的迹象。文中还探讨了高盐水的入侵机理，并阐述了高盐水入侵对入海泥沙输移和长江水下三角洲的发育起着控制作用。     

黄海溶解氧垂直分布的最大值

海洋溶解氧垂直分布中的最大值,正如最小值一样,亦为溶解氧垂直分布中的一个突出的现象.对于这一现象,不同的研究者作出了不同的解释.Thompson在太平洋北部及东北部25-50M处观测到氧最大值层,他们认为这一氧最大值层,是与光合带相适应的.对鄂霍次克海中氧的最大值的形成,绘出了一个假设的图,认为夏季氧垂直分布中的最大值,是由于在跃层形成时期,浮游植物光合作用时,大量的氧从上面渗入到稍下的层内,随着增温时该处稳定密度层的形成,垂直交换困难,因而氧即被保持下耒,形成了夏季最大值.Ichiye认为,密度跃层中的氧最大值,是由于氧的涡动扩散,要进行得比热的涡动传导为慢的缘故.     

城市GIS数据多级共享交换平台系统

针对目前城市众多管理部门对城市GIS数据共享交换平台不同层次的共享需求,在分析文件级、数据平台级、系统功能级以及Web服务级四种共享交换模式特点的基础上,本文采用业务流技术设计了一种集成多级共享交换模式的数据模型。结合无锡市地理信息共享交换平台项目的建设,给出了模型在城市GIS数据交换平台系统中的具体应用过程,以期对其他城市同类系统的建设提供一定的参考价值。     

山东省上古生界页岩气资源潜力评价

以山东省上古生界海陆过渡相富有机质泥页岩为研究对象,对泥页岩的沉积环境、厚度及分布、有机质类型及含量、有机质演化程度等资料进行分析,认为石炭-二叠纪山西组和太原组泥页岩发育厚度大而稳定,有机质类型以Ⅲ型为主,镜质体反射率一般在0.7%~1.7%之间,有机碳含量一般在1.5%~9.0%之间,是页岩气主要富集层位。以含气量不小于0.5m3/t、镜质体反射率不小于0.5%、有机碳含量平均不小于2.0%等为资源量评价标准,建立有机碳含量与含气量关系模型,估算山东省上古生界页岩气潜在地质资源总量为5 736.75×108 m~3,明确了具有勘查价值的区域有鲁西南含煤区、黄河北含煤区、阳谷-茌平含煤区和临清坳陷,为山东省上古生界页岩气下一步勘查指明了方向。     

Influence of Headland Breakwaters on Morphological Processes at Longfengtou Beach in Haitan Bay,Facing the Taiwan Strait

Breakwaters can be used as artificial headlands in beach nourishment to mitigate coastal erosion. Longfengtou Beach, located on the southwest coast of Haitan Bay facing the Taiwan Strait on the northeast, suffers severe erosion, where the monsoon causes significant season hydrodynamic variations. Headland breakwaters are intended to be employed to mitigate coastal erosion. A 2D sediment transport model is established using MIKE21 based on current-wave coupling and calibrated by measured data. Summer and winter wave conditions are chosen as characteristic weak and strong waves respectively. The numerical results of suspended sediment concentration and seasonal morphological evolution are compared under the conditions with and without the headland breakwaters. Sediment transport in summer can be regarded as mainly determined by current field, while in winter wave effect is strong enough to change current field. The northern breakwater, nearly perpendicular to the ebb current direction, obstructs the currents and decreases velocity of the ebb currents, and confines the water carrying sediments within the protection area during the flood period. The southern breakwater also breaks the waves in advance and significantly reduces the hydrodynamic effects during the flood period and maintains high suspended sediment concentration in the protection area. In general, two headland breakwaters decrease the erosion near the beach and enlarge the deposition area, which play a significant role in prevention of sediment loss in nearshore area and mitigate coastal erosion.