基于双张影像的城市建筑物高度提取方法     

宋仁波  李文慧  王细元  王月香 《测绘工程》2014,23(9):66-69

针对现有城市建筑物高度提取方法存在的问题,提出一种基于双张影像的城市建筑物高度简易提取方法。利用高分辨率遥感影像和建筑物立面影像,分别提取样本建筑物的阴影长度和高度,采用最小二乘法解算出影像阴影和建筑物高度的相关公式,通过阴影长度反算出建筑物的高度,从而实现大批量建筑物高度数据的获取。通过建模实例和测量对比实验表明,方法具有操作简单、快速的特点,能满足较高的精度要求,具有一定的应用价值。  相似文献   

A shadow- eliminated vegetation index (SEVI) for removal of self and cast shadow effects on vegetation in rugged terrains     

《International Journal of Digital Earth》2013,6(9):1013-1029

ABSTRACT

The effect of terrain shadow, including the self and cast shadows, is one of the main obstacles for accurate retrieval of vegetation parameters by remote sensing in rugged terrains. A shadow- eliminated vegetation index (SEVI) was developed, which was computed from only red and near-infrared top-of-atmosphere reflectance without other heterogeneous data and topographic correction. After introduction of the conceptual model and feature analysis of conventional wavebands, the SEVI was constructed by ratio vegetation index (RVI), shadow vegetation index (SVI) and adjustment factor (f (Δ)). Then three methods were used to validate the SEVI accuracy in elimination of terrain shadow effects, including relative error analysis, correlation analysis between the cosine of solar incidence angle (cosi) and vegetation indices, and comparison analysis between SEVI and conventional vegetation indices with topographic correction. The validation results based on 532 samples showed that the SEVI relative errors for self and cast shadows were 4.32% and 1.51% respectively. The coefficient of determination between cosi and SEVI was only 0.032 and the coefficient of variation (std/mean) for SEVI was 12.59%. The results indicate that the proposed SEVI effectively eliminated the effect of terrain shadows and achieved similar or better results than conventional vegetation indices with topographic correction.  相似文献   

扎龙湿地水体遥感提取过程中云阴影去除方法研究   总被引：2，自引：1，他引：1  

郑晓燕  张艳红  刘万崧 《湿地科学》2010,8(1):21-27

以扎龙湿地为研究区,利用空间分辨率高、纹理信息丰富、定位精度高和购买价格相对低廉的ALOS遥感影像,测定了研究区水体等5种典型地物和云阴影的波谱亮度值;根据水体和云阴影的光谱特征,利用阈值法对近红外波段ALOS影像进行阈值处理,将包含云阴影信息的水体信息提取出来;基于ALOS彩色影像,再采用决策树方法自动提取湿地水体信息,同时将云阴影信息去除,并再补充提取因去除云阴影而损失的水体信息;与目视解译结果相比,用本研究方法得到的研究区湿地水体信息精度高于85%。近红外波段阈值法和彩色影像决策树法相结合的方法是一种能有效去除云阴影而高精度获取湿地水体信息的方法。  相似文献   

婴幼儿X线胸片对胸腺增大的分析诊断   总被引：1，自引：0，他引：1  

代燕增  冯建明  张巧权 《CT理论与应用研究》2010,19(2):69-74

目的:探讨婴幼儿胸腺影增大的X线表现。方法:收集我院近年婴幼儿X线胸片观察到增大的胸腺影300例,主要讨论婴幼儿胸腺的影像表现、诊断与鉴别诊断。结果:对X线胸片上显示的300例增大的胸腺影在性别、年龄、形态、位置等方面进行分析总结。其中右上纵隔旁僧帽状90例,双侧纵隔旁杯形90例,右上纵隔旁船帆状75例,右肺尖圆块状30例,左上纵隔旁椭圆形15例。结论:X线胸片对婴幼儿胸腺影增大的诊断与鉴别具有一定作用,定性诊断最后尚需依靠穿刺活检及结合临床综合分析。  相似文献   

多光谱遥感影像中云影区域的检测与修复     

周伟  关键  姜涛  何友 《遥感学报》2012,16(1):132-142

提出了一种有效针对多光谱遥感影像的云影检测与阴影区域修复方法。基于同一地区时相相近的两幅影像,充分利用碎云及阴影的光谱特性分别对云影区域进行融合增强,然后采用Otsu算法求解最佳阈值自动检测出云及阴影区域,根据云影的出现会引起两幅影像局部相应区域明显的亮度变化,可排除亮地物和水体的影响,建立归一化的云影密度图,在此基础上,采用线性加权组合与光谱直方图匹配相结合的方法对其加以修复,利用SPOT 4影像进行的实验表明其修复效果完全能够满足应用需要。  相似文献   

Roles of financial innovation and information technology: Lessons from US sub-prime mortgage crisis and its implications for China     

James H LENZER JR  Simon Xiaobin ZHAO 《中国地理科学(英文版)》2012,22(3):343-355

The mortgage loan has evolved from a local lending instrument into a major global security and its role is unparallel to other financial instruments in the process of financial globalization.This paper explains how technology and financial innovation transformed the mortgage loan from a local security into a premier global security traded worldwide.It examines the fundamental flaws of this process and why it does not work in regards to mortgage lending and the re-securitization products that were created through financial innovation.The findings show that regulation was unable to keep pace with financial innovation,which created an environment where actors in the financial service sector were able to behave geographically irresponsibly by using information asymmetries to their advantage by participating in moral hazard activities and engaging in other immoral and unethical business practices that were centered around localized geography,which ultimately contributed to the global financial crisis.It also examines the roll of financial innovation in regard to the Lehman Brothers Mini-Bond in Hong and its role as a driving force behind China’s newly emerging shadow banking sector.It concludes with a policy recommendation and its implication for China’s continued economic development.  相似文献   

Improvement of glacial lakes detection under shadow environment using ASTER data in Himalayas, Nepal     

CHEN Wenbo  FUKUI Hiromichi  DOKO Tomoko  GU Xingfa 《中国地理科学(英文版)》2013,23(2):216-226

The detection of glacial lake change in the Himalayas, Nepal is extremely significant since the glacial lake change is one of the crucial indicators of global climate change in this area, where is the most sensitive area of the global climate changes. In the Himalayas, some of glacial lakes are covered by the dark mountains′ shadow because of their location. Therefore, these lakes can not be detected by conventional method such as Normalized Difference Water Index (NDWI), because the reflectance feature of shadowed glacial lake is different comparing to the ones which are located in the open flat area. The shadow causes two major problems: 1) glacial lakes which are covered by shadow completely result in underestimation of the number of glacial lakes; 2) glacial lakes which are partly identified are considered to undervalue the area of glacial lakes. The aim of this study is to develop a new model, named Detection of Shadowed Glacial Lakes (DSGL) model, to identify glacial lakes under the shadow environment by using Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) data in the Himalayas, Nepal. The DSGL model is based on integration of two different modifications of NDWI, namely NDWIs model and NDWI she model. NDWIs is defined as integration of the NDWI and slope analysis and used for detecting non-shadowed lake in the mountain area. The NDWIshe is proposed as a new methodology to overcome the weakness of NDWIs on identifying shadowed lakes in highly elevated mountainous area such as the Himalayas. The first step of the NDWIshe is to enhance the data from ASTER 1B using the histogram equalization (HE) method, and its outcome product is named ASTER he . We used the ASTER he for calculating the NDWI he and the NDWIshe . Integrated with terrain analysis using Digital Elevation Model (DEM) data, the NDWI she can be used to identify the shadowed glacial lakes in the Himalayas. NDWIs value of 0.41 is used to identify the glacier lake (NDWIs≥0.41), and 0.3 of NDWIshe is used to identify the shadowed glacier lake (NDWIshe≤0.3). The DSGL model was proved to be able to classify the glacial lakes more accurately, while the NDWI model had tendency to underestimate the presence of actual glacial lakes. Correct classification rate regarding the products from NDWI model and DSGL model were 57% and 99%, respectively. The results of this paper demonstrated that the DSGL model is promising to detect glacial lakes in the shadowed environment at high mountains.  相似文献   

Review of shadow detection and de-shadowing methods in remote sensing     

AmirReza SHAHTAHMASSEBI  YANG Ning  WANG Ke  Nathan MOORE  SHEN Zhangquan 《中国地理科学(英文版)》2013,23(4):403-420

Shadow is one of the major problems in remotely sensed imagery which hampers the accuracy of information extraction and change detection.In these images,shadow is generally produced by different objects,namely,cloud,mountain and urban materials.The shadow correction process consists of two steps:detection and de-shadowing.This paper reviews a range of techniques for both steps,focusing on urban regions(urban shadows),mountainous areas(topographic shadow),cloud shadows and composite shadows.Several issues including the problems and the advantages of those algorithms are discussed.In recent years,thresholding and recovery techniques have become important for shadow detection and de-shadowing,respectively.Research on shadow correction is still an important topic,particularly for urban regions(in high spatial resolution data) and mountainous forest(in high and medium spatial resolution data).Moreover,new algorithms are needed for shadow correction,especially given the advent of new satellite images.  相似文献   

台特玛湖干涸湖盆区植物风影沙丘的形态特征   总被引：1，自引：0，他引：1  

蔡东旭  李生宇  刘耀中  俞祥祥  王海峰  雷加强  雷加强  武新成  彭琴  屈磊 《干旱区地理》2017,40(5):1020-1028

对台特玛湖干涸湖盆区盐穗木、柽柳和碱蓬3种植物风影沙丘的形态参数进行野外了测定,应用统计学方法,分析对比了不同植物风影沙丘的形态特征及阻沙能力。结果表明：（1）风影沙丘处于由沙嘴向沙堆演化阶段,沙丘形态参数间相关性显著（P<0.01）,其中沙丘高度与水平尺度相关性较好,沙丘垂向发育速度快于水平扩展。（2）风影沙丘与植物形态参数间亦存在相关性,受植物生物特性的影响,不同植物的相关性差异较大,其中碱蓬呈高度正相关（R>0.85,沙丘背风坡坡度除外）,盐穗木次之,柽柳灌丛相关性微弱。（3）在相同的区域环境下,3种植物的单株阻沙能力呈柽柳 > 盐穗木 > 碱蓬,盐穗木、碱蓬积沙量受株高影响较大,两者呈二次函数关系;柽柳积沙量主要取决于灌丛迎风剖面的面积。  相似文献   

云南金沙江流域水土流失直接经济损失测算方法与区域特征分析   总被引：4，自引：0，他引：4  

李云辉  贺一梅  杨子生 《山地学报》2002,(Z1)

应用环境经济评价理论与方法,定量地测算了云南金沙江流域水土流失(包括坡面侵蚀和重力侵蚀2个方 面)的直接经济损失,包括养分流失损失、水分流失损失和泥沙流失损失3项内容,并分析了水土流失直接经济损失 的区域特征,为该流域水土流失防治提供了基础依据。  相似文献