过去百年青海和西藏耕地空间格局重建及其时空变化   总被引：7，自引：1，他引：6  

李士成  张镱锂  何凡能 《地理科学进展》2015,34(2)

网格化的历史土地利用/覆被数据集,可为历史气候变化和碳循环研究提供基础数据。本文估算了1910年,并订正了1950-2000年青海和西藏的省域耕地面积数据;基于现代耕地空间格局,量化了海拔高程和地面坡度与耕地空间分布之间的关系,构建了历史耕地网格化重建模型。将1910、1960、1980和2000年的省域耕地面积数据带入网格化重建模型,得到了4个时间断面的耕地空间格局。结果表明:青藏两省耕地面积1910-1950年稳定,1950-1980年快速增加,1980-2000年基本稳定,略有降低。就空间格局而言,1960-1980年,河湟谷地和"一江两河"地区土地开垦范围的扩张和垦殖强度的增长在过去百年最为明显。模型检验表明,模型重建的2000年耕地空间格局与2000年遥感数据相关系数达0.92。  相似文献   

水汽层析代数重构算法   总被引：1，自引：0，他引：1  

何林  柳林涛  苏晓庆  许超钤  段鹏硕 《测绘学报》2015,44(1):32-38

讨论了代数重构算法在水汽层析应用中的各种问题,包括约束条件的构造、层析初值的选择、松弛因子的计算、终止条件的确定等,给出了计算最优松弛因子的黄金分割搜索法和确定终止条件的NCP规则,对比分析了Kaczmarz、Randkaczmarz、Symkaczmarz、SART、Landweber、Cimmino、CAV、DROP等8种常见的代数重构算法,并以香港SatRef的观测数据进行了试验。试验结果表明,以上8种代数重构技术都能够满足水汽层析的要求;迭代终止条件比松弛因子更为重要;采用文中计算最优松弛因子的黄金分割搜索法和NCP迭代终止条件,CAV算法结果最优,其次为Cimmino算法。  相似文献   

利用小波变换进行遥感多光谱图像融合的算法及实现   总被引：3，自引：0，他引：3  

林卉  杜培军  肖剑平 《地球科学与环境学报》2006,28(1):75-78,100

在分析了小波变换的分解与重建方法后,提出了一种基于区域的图像增强算法。先提取出源图的边缘,以图像的边缘为参考,围绕边缘建立融合窗口,然后结合区域内的图像信息,应用基于窗口的融合规则进行融合处理。实验结果显示,融合后的图像综合了3幅源图像的不同特征,处理后的图像变得容易识别了。表明该方法保持了尽可能多的原始信息,算法简单,稳定性好,适合于多光谱遥感图像识别、医学成像等领域。  相似文献   

THE SATELLITE TOWNS OF METROPOLIS GUANGZHOU：EVOLUTION， INHERENT LINKS WITH THE CENTRAL CITY AND TENDENCIES──A CASE STUDY OFRENHE TOWN     

阎小培 《中国地理科学(英文版)》1994,(1)

ＴＨＥＳＡＴＥＬＬＩＴＥＴＯＷＮＳＯＦＭＥＴＲＯＰＯＬＩＳＧＵＡＮＧＺＨＯＵ：ＥＶＯＬＵＴＩＯＮ，ＩＮＨＥＲＥＮＴＬＩＮＫＳＷＩＴＨＴＨＥＣＥＮＴＲＡＬＣＩＴＹＡＮＤＴＥＮＤＥＮＣＩＥＳ──ＡＣＡＳＥＳＴＵＤＹＯＦＲＥＮＨＥＴＯＷＮＹａｎＸｉａｏｐｅ...  相似文献   

Critical Approach to Methods of Glacier Reconstruction in High Asia and Discussion of the Probability of a Qinghai-Xizang （Tibetan） Inland Ice     

Matthias Kuhle 《山地科学学报》2007,4(2):91-124

This overview discusses old and new results as to the controversy on the past glacier extension in High Asia, which has been debated for 35 years now. This paper makes an attempt to come closer to a solution. H.v. Wissmann's interpretation (1959) of a small-scale glaciation contrasts with M. Kuhle's reconstruction (1974) of a large-scale glaciation with a 2.4 million km2 extended Qinghai-Xizang (Tibetan) inland glaciation and a Himalaya-Karakorum icestream network. Both opinions find support but also contradiction in the International and Chinese literature (Academia Sinica). The solution of this question is of supraregional importance because of the subtropical position of the concerned areas. In case of large albedo-intensive ice surfaces, a global cooling would be the energetical consequence and, furthermore, a breakdown of the summer monsoon. The current and interglacial heat-low above the very effective heating panel of the Qinghai-Xizang (Tibetan) Plateau exceeding 4000 m, which gives rise to this monsoon circulation, would be replaced by the cold-high of an inland ice. In addition, the plate-tectonically created Pleistocene history of the uplift of High Asia — should the occasion arise up to beyond the snowline (ELA) —would attain a paleoclimatically great, perhaps global importance. In case of a heavy superimposed ice load, the question would come up as to the glacio-isostatic interruption of this primary uplift. The production of the loesses sedimentated in NE-China and their very probable glacial genesis as well as an eustatic lowering of the sea-level by 5 to 7 m in the maximum case of glaciation are immediately tied up with the question of glaciation we want to discuss. Not the least, the problems of biotopes of the sanctuary-centres of flora and fauna, i.e., interglacial re-settlement, are also dependent on it. On the basis of this Quaternary- geomorphological-glaciological connection, future contributions are requested on the past glaciation, the current and glacial permafrost table and periglacial development, the history of uplift, and the development of Ice Age lakes and loess, but also on the development of vegetation and fauna in High Asia.  相似文献   

深源远震波形反演介质层状结构     

宫培谦  高锡铭  李幼铭  束沛镒 《大地测量与地球动力学》1995,(4)

在远场正演计算的基础上，运用３０°～９０°的四个不同深源远震记录波形，通过试错法选取台站下方的结构，借助波场反向重建算法，反演确定宜昌台站下方的速度结构。这一算法的实现有助于提高用试错法所得结果的可靠性和精确度，对于利用天然地震资料研究地球深部构造有一定的实用价值。  相似文献   

Subbottom acoustic and sedimentary records of past surface water–groundwater exchange through sinkhole lakes in south Georgia,U.S.A     

J.?A.?HyattEmail author  R.?Gilbert 《Environmental Geology》2004,46(1):32-46

Lake Balboa is a deep sinkhole lake in south Georgia. Subbottom acoustic profiling and long sediment cores reveal four stratigraphic units within >20 m of lacustrine fill above acoustically stratified and faulted Miocene/Pliocene overburden and basement Eocene limestone which hosts the Floridan Aquifer system (FAS). Fill consists of thin, rhythmically bedded, peaty sediments (Unit I), indicative of slow sedimentation in a shallow swamp until 13,110–12,680 cal BP, a mix of desiccated and over-consolidated clay and silty sand (Unit II) implying periodic subaerial exposure of the lake bed until 9470–9025 cal BP, and gyttja associated with a rapid 8 m rise in water level by 9120–9020 cal BP (Unit III), as well as an additional rise of 10 m to modern lake levels (Unit IV). Accumulation of nearly 4.5 m of low permeability gyttja, and higher lake levels have fundamentally changed exchange between surface water and groundwater, reducing by 40% or more the rate of vertical leakage to the FAS and increasing shallow aquifer discharge to the lake.  相似文献   

面向分类的高光谱影像局部线性嵌入算法研究     

杨明  余旭初  吴翰书  王超  林斌 《测绘科学》2012,(4):29-31

局部线性嵌入算法(LLE)能很好保存数据点的局部性质,因此有很好的数据可视化效果,但它不是一种很好的面向分类的特征提取方法。因为它存在样本外点学习能力差和忽略了样本类别信息的缺点。对此,本文提出一种分类型局部线性嵌入算法。所提方法通过计算重构误差来判定样本类别,并引进平移向量和缩放因子对距离修正,显著提高类别可分性。在对高光谱影像进行分类的试验中验证了该方法的有效性。  相似文献   

结构光系统结合数码相机的小物体高质量纹理重建   总被引：1，自引：0，他引：1  

郑顺义  周漾 《武汉大学学报(信息科学版)》2012,37(5):529-533,633

针对双鸟饕餮纹夔神鼍鼓等小文物或其他小型物体,提出了基于结构光扫描系统结合普通高分辨率单反数码相机的纹理重建方法。该方法具有自动化程度高、效率和质量高的特点,其中主要解决了单张高分辨率影像与物体几何模型的自动配准,以及配准后从多张影像生成无缝纹理模型的问题。实验证明了本文方法的可行性和有效性。  相似文献   

北宋中期耕地面积及其空间分布格局重建(英文)   总被引：3，自引：1，他引：2  

何凡能  李士成  张学珍 《地理学报(英文版)》2012,22(2):359-370

To understand historical human-induced land cover change and its climatic effects, it is necessary to create historical land use datasets with explicit spatial information. Using the taxes-cropland area and number of families compiled from historical documents, we esti-mated the real cropland area and populations within each Lu (a province-level political region in the Northern Song Dynasty) in the mid-Northern Song Dynasty (AD1004-1085). The es-timations were accomplished through analyzing the contemporary policies of tax, population and agricultural development. Then, we converted the political region-based cropland area to geographically explicit grid cell-based fractional cropland at the cell size of 60 km by 60 km. The conversion was based on calculating cultivation suitability of each grid cell using the topographic slope, altitude and population density as the independent variables. As a result, the total area of cropland within the Northern Song territory in the 1070s was estimated to be about 720 million mu (Chinese area unit, 1 mu = 666.7 m2), of which 40.1% and 59.9% oc-curred in the north and south respectively. The population was estimated to be about 87.2 million, of which 38.7% and 61.3% were in the north and south respectively, and per capita cropland area was about 8.2 mu. The national mean reclamation ratio (i.e. ratio of cropland area to total land area; RRA hereafter for short) was bout 16.6%. The plain areas, such as the North China Plain, the middle and lower reaches of the Yangtze River, Guanzhong Plain, plains surrounding the Dongting Lake and Poyang Lake and Sichuan Basin, had a higher RRA, being mostly over 40%; while the hilly and mountainous areas, such as south of Nanling Mountains, the southwest regions (excluding the Chengdu Plain), Loess Plateau and south-east coastal regions, had a lower RRA, being less than 20%. Moreover, RRA varied with topographic slope and altitude. In the areas of low altitude (≤250 m), middle altitude (250-100 m) and high altitude (1000-3500 m), there were 443 million, 215 million and 64 million mu of cropland respectively and their regional mean RRAs were 27.5%, 12.6% and 7.2% respectively. In the areas of flat slope, gentle slope, medium slope and steep slope, there were 116 million, 456 million, 144 million and 2 million mu of cropland respectively and their regional mean RRAs were 34.6%, 20.7%, 8.5% and 2.3% respectively.  相似文献