基于邻近四点法的建筑物多边形化简   总被引：1，自引：1，他引：0  

许文帅  龙毅  周侗  陈林 《测绘学报》2013,(6):929-936

对早期的局部线化简算法进行拓展和改善,提出一种以建筑物多边形上邻近四点组合为基本处理单元,以最小可视长度阈值为综合指标,通过对其凹凸结构的类型判别及区别处理,实现建筑物多边形快速化简的方法。将线化简中对三点或多点进行局部处理拓展为邻近四点,较好地保持了建筑物形态特征;有针对性地采取全局检查消除自相交现象,并探讨了起始点的选择问题。选取1∶10 000居民地数据进行多组地图综合试验,结果表明该方法可有效地保持多边形的轮廓特征与面积大小。  相似文献   

地图水系综合中等高线簇与河网协同的汇水区域提取方法     

舒方国  龙毅  周侗  曹阳 《测绘学报》2013,42(5):774-781

在地图水系自动综合中河流选取需要建立对不同河流重要性程度的有效判别。由于河流汇水区域直接反映河流的作用空间,因而其面积大小成为关键性的量化指标。目前基于河流的汇水区域自动提取方法主要从河流单一要素出发,按“空间均衡竞争”思想平分河流之间的区域,由于未考虑地形因素使得提取的汇水区域往往存在偏差,而传统基于DEM的汇水区域提取虽然考虑了地形,但没有与河流目标建立显性的对应关系。河流是一种天然的沟谷地性线,与山脊线具有对生互补的空间耦合关系,本文提出了一种等高线簇与河网双要素协同的河流汇水区域提取方法,该方法对河流与等高线的目标集合构建约束Delaunay三角网(CD-TIN)并将三角形分类,对不同类型的三角形分别采用骨架线提取规则与梯度向量引导的分水线搜索规则提取分水线段,连接形成网络结构并依此计算各河段的汇水区域。实验结果表明,本算法能更准确地提取河流汇水区域,从而为河流综合选取提供有效支持。  相似文献   

基于FY2G卫星的宁夏空中云水资源特征研究     

常倬林  党张利  孙艳桥  林彤 《气象研究与应用》2022,43(1):47-52

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IPCC AR6解读：全球和区域海平面变化的监测和预估     

张通  俞永强  效存德  华莉娟  闫展 《气候变化研究进展》2022,18(1):12-18

IPCC第六次评估报告第一工作组报告第九章综合评估了与海平面相关的最新监测和数值模拟结果,指出目前（2006—2018年）的海平面上升速率处于加速状态（3.7 mm/a),并会在未来持续上升,且呈现不可逆的趋势。其中低排放情景（SSP1-1.9）和高排放情景（SSP5-8.5）下,到2050年,预估全球平均海平面（GMSL）分别上升0.15~0.23 m和0.20~0.30 m;到2100年,预估GMSL分别上升0.28~0.55 m和0.63~1.02 m。南极冰盖不稳定性是影响未来海平面上升预估的最大不确定性来源之一。区域海平面变化是影响沿海极端静水位的重要因素。  相似文献   

Differential signal of change among multiple components of West African rainfall     

Obarein  Omon A.  Lee  Cameron C. 《Theoretical and Applied Climatology》2022,149(1-2):379-399

Theoretical and Applied Climatology - Rainfall components likely differ in the magnitude and direction of their long-term changes for any given location, and some rainfall components may carry a...  相似文献   

全球沉积盆地动态分类方法:从原型盆地及其叠加发展过程讨论          下载免费PDF全文

温志新  童晓光  张光亚  王兆明  宋成鹏 《地学前缘》2012,19(1):239-252

沉积盆地是油气生成和聚集的基本地质单元,其形成和发展为板块构造演化所控制,主要表现在两个方面,一是板块从分离到汇聚的不同阶段、板块的不同位置,产生不同的原型盆地,形成了特定的构造-沉积体系,决定了其生、储、盖等基本含油气条件;二是后期叠加的原型盆地不但本身具有新的油气地质特征,还能够改变早期原型盆地的成藏条件及油气分布规律。以板块构造演化历史为时间线索,通过对现今盆地早期原型及其后期叠加改造过程的系统解剖,用动态方法将全球处于一个威尔逊旋回的现今盆地划分为12种类型。在此基础上,总结了各类盆地的基本属性及含油气条件,为科学预测各类盆地的含油气远景奠定了基础。  相似文献   

Single-grain OSL dating of glaciofluvial quartz constrains Reid glaciation in NW Canada to MIS 6     

Martina Demuro  Duane G. Froese  Lee J. Arnold  Richard G. Roberts 《Quaternary Research》2012,77(2):305-316

Improved chronological control on the penultimate advance of the Cordilleran Ice Sheet in northwest Canada (the Reid glaciation) is required for a better understanding of late Quaternary palaeoclimatic and palaeoenvironmental change in eastern Beringia. However, reliable dating of glaciation events beyond the last glacial maximum is commonly hindered by a lack of directly dateable material. In this study we (i) provide the first combined minimum and maximum age constraint on the Reid glaciation at Ash Bend, its reference locale in the Stewart River valley, northwestern Canadian Cordillera, using single-grain optically stimulated luminescence dating of quartz; and (ii) compare the timing of the Reid glaciation with other penultimate ice sheet advances in the region with the aim of establishing improved glacial reconstructions in eastern Beringia. We obtain ages of 158 ± 18 ka and 132 ± 18 ka for glaciofluvial sands overlying and underlying the Reid till, respectively. These ages indicate that the Reid advance, at its reference locale, occurred during MIS 6. This precludes an earlier MIS 8 age, and suggests that the Reid advance may have been synchronous with the Delta glaciation of central Alaska, and is likely correlative with the Mirror Creek glaciation in southern Yukon.  相似文献   

Climate disaster resilience of the education sector in Thua Thien Hue Province, Central Vietnam   总被引：2，自引：2，他引：0  

Thi My Thi Tong  Rajib Shaw  Yukiko Takeuchi 《Natural Hazards》2012,63(2):685-709

Recognizing the importance of building disaster resilience for education sector, this study aims to develop a methodology to measure the level of educational resilience to cope with natural disasters and is then applied in Central Vietnam. The assessment tool in this paper is developed through a combination of climate disaster resilience indexes and the 16 tasks of Hyogo framework for action designed for education sector. It looks at five dimensions namely physical conditions, human resources, institutional issues, external relationships, and natural conditions, with each dimension characterized by three parameters and five variables. Findings from this study provide important insights into enhancing resilience of the education system in Thua Thien Hue at the provincial, local, and school levels. By giving the overall resilience situation, it can help policy-makers and practitioners in developing an effective plan to increase the level of educational resilience. In addition, it provides the School Management Board with a means to assess the school??s resilience level and set out priorities that need to be focused on with regard to the improvement of school safety and disaster risk reduction education.  相似文献   

GIS-based multi-dimensional risk assessment of the grassland fire in northern China     

Xing-peng Liu  Ji-quan Zhang  Zhi-jun Tong  Yulong Bao 《Natural Hazards》2012,64(1):381-395

This study presents a methodology for risk analysis and assessment to manage grassland fire in northern China based on the Geographical Information Systems from the viewpoints of climatology, geography, disaster science, and environmental science and so on. Using natural disaster and risk assessment theory, a multi-dimensional grassland fire risk index (MGFRI) was proposed by integrating weighted comprehensive method, analytic hierarchy process, and fuzzy gamma method into natural disaster risk index. The developed MGFRI will be an easily understandable tool to manage grassland fire by comparing the risk of regions in the northern China and relative contributions of various factors, for example, hazard, exposure, vulnerability, and management ability. A scale of one to five was derived to measure the risk degree. It shows that 4.4?% of grassland falls in the category of ??very high?? risk, followed by 9.6, 19.1, 60.9, and 5.9?%, respectively, in the categories ??high??, ??middle??, ??low??, and ??very low??. The assessment results show reliability by test. The results in this study are intended to support local, provincial, and national government agencies to: (1) make resource allocation decisions; (2) make high-level planning decisions; and (3) raise public awareness of grassland fire risk, its causes, and ways to manage it.  相似文献   

Sequence Stratigraphy of the Jurassic Coal Measures in Northwestern China   总被引：1，自引：0，他引：1  

WANG Tong  SHAO Longyi  TIAN Ye  LU Jing  WANG Wenlong 《《地质学报》英文版》2012,86(3):769-778

The sequence stratigraphy of the Jurassic coal measures of northwestern China has been studied based on data from outcrop and borehole sections. Because of the geological background and the diversity of basin types, such as isochronisms of coal seams and recognition of key sequence boundaries, it is rare to summarize and correlate sequence structure and framework. The types and recognition characteristics of the sequence boundaries of the Jurassic coal measures are revealed by comparing climatic characteristics, structural styles and the base level cycle. A total of five third-order sequences and 15 systems tracts have been subdivided and the sequence stratigraphic framework has been reconstructed confirming that the thick coals accumulated in the late stage of transgression system tracts of sequence I (SQ I) and sequence III (SQ III). This idea is of important academic significance for instructing coal resources exploration, and enhancing geological effects of prospecting engineering. It is also of practical significance for guaranteeing construction of the large-scale coal production base in northwestern China, accelerating the westward development of the coal industry stratagem.  相似文献