Spectral Filtering and Classification of Terrestrial Laser Scanner Point Clouds   总被引：1，自引：0，他引：1  

Derek D.  Lichti 《The Photogrammetric Record》2005,20(111):218-240

A method is presented for filtering and classification of terrestrial laser scanner point clouds. The algorithm exploits the four-channel (blue, green, red and near infrared) multispectral imaging capability of some terrestrial scanners using supervised, parametric classification to assign thematic class labels to all scan cloud points. Its principal advantage is that it is a completely data-driven algorithm and is independent of spatial sampling resolution since the processing is performed in four-dimensional spectral feature space. Its application to two data-sets of different spatial extent and spatial and spectral complexity is reported, for which respective overall classification accuracies of 87·0% and 82·0% were achieved. Analysis of the input data with emphasis on the characteristics pertinent to the anticipated outcomes precedes detailed analysis of the classification results and error sources and their causes. Erroneously classified points are attributed to radiometric errors stemming from both detector hardware and physical effects.  相似文献   

用940 nm通道遥感水汽总量的可行性试验   总被引：7，自引：2，他引：7       下载免费PDF全文

黄意玢  董超华 《应用气象学报》2002,13(2):184-192

在940 nm水汽弱吸收带和其附近窗区选取若干探测通道, 采取不同通道组合, 模拟计算通道反射率比值, 并建立了该比值与水汽含量之间的统计关系。用探空观测独立样本检验水汽含量模拟计算结果, 相对误差小于6%。  相似文献   

A satellite-based climatology of fog and low-level stratus in Germany and adjacent areas   总被引：1，自引：0，他引：1  

Jrg Bendix 《Atmospheric Research》2002,64(1-4)

A 10-year fog climatology of Germany and adjacent areas, based on NOAA-Advanced Very High-Resolution Radiometer (AVHRR) data, is presented. Maximum fog frequency is obtained for the Lake Constance area; minimum fog occurrence, accounting for basins and river valleys, is located in the Lower Rhine area. This is a transition zone between coastal advection fog and the more continental radiation fog of the lower mountain range. Fog persistence is estimated by a comparison of night and day maps. Using the bispectral approach of Nakajima and Nakajima [J. Atmos. Sci. 52, (1995) 4043], the potential of weather satellite data for climatologies of fog's optical and microphysical properties is examined. Maps of fog optical depth, effective radius and liquid water path (LWP) are computed from well-illuminated noon images and the resulting data set is statistically evaluated. Typical features of advection fog are obtained for the coastal areas of the North and Baltic Seas, while the fog of the pre-Alpine basins reveals characteristics of continental radiation fog. The results are in general accordance with field observations of various sources.  相似文献   

基于空间信息技术的城市应急救援联动系统研究   总被引：26，自引：0，他引：26  

陈秀万  杨凯欣  方裕  陈斌 《地理与地理信息科学》2003,19(4):49-52

该文分析国内外城市现代救援体系及其发展趋势，对基于统一的空间信息基础设施平台分布式城市应急救援联动系统(体系结构与系统实现)的关键技术进行研究，以成都市城市应急救援联动系统为例，探讨了城市应急救援联动系统的构成、功能、业务流程、系统平台、用户界面等。  相似文献   

Fire Severity,Water Repellency Characteristics and Hydrogeomorphological Changes Following the Christmas 2001 Sydney Forest Fires     

R. A. SHAKESBY  C. J. CHAFER  S. H. DOERR  W. H. BLAKE  P. WALLBRINK  G. S. HUMPHREYS 《The Australian geographer》2003,34(2):147-175

Soil water repellency can enhance overland flow and erosion and may be altered by fire. The Christmas 2001 bushfires near Sydney allowed investigation of the relationship between fire severity, water repellency and hydrogeomorphological changes. For two sub-catchments with differences in fire severities in Nattai National Park, south-west of Sydney, this paper considers: (1) the links between fire severity based on SPOT image analysis and ground observation of fire severity and repellency; (2) the textural and organic/minerogenic characteristics of eroded sediment; and (3) erodibility, erosion and deposition of soils in both catchments. Ground surveys show that image analysis reflects well the degree of vegetation consumption by fire, but cannot adequately predict the degree of ground litter consumption, associated soil heating and repellency effects. Fire had varying effects on repellency, leaving it unchanged, destroying it or enhancing it, depending on the soil temperature reached. The main post-fire hydrogeomorphological changes have been widespread erosion and colluvial and alluvial deposition of topsoil in foot-slope locations and river systems, but only localised redistribution of the highly erodible, repellent sandy subsurface layer. The fire did not trigger major geomorphological change in the study area, but fires probably cause important topsoil and nutrient depletion and may also affect water quality.  相似文献   

图像处理技术在地质灾害监测中的应用   总被引：1，自引：0，他引：1  

冯苍旭  史云  陈实 《中国地质灾害与防治学报》2003,14(2):84-86

三维激光微位移监测技术是一种对地质灾害进行长期监测的新方法。该技术用激光作为光源，用CCD摄像器作为镜头，通过图象采集卡把视频信号采入计算机中，用与该仪器配套的专门软件对采集到的光斑图像进行处理，计算出光斑的三维中心坐标值，把该值和原点坐标值进行比较，就可以算出灾害体滑动的距离。该系统可以对灾害体进行长期、非接触监测，监测时间、监测频率可以任意设定。文章概括介绍该监测的原理，各个组成部分，重点介绍软件部分，即采集的视频信号进入计算机后的图像处理过程和数据库结构。该监测系统已在三块地区试运行了3个月，效果较好。  相似文献   

机载激光测深中的波浪改正技术   总被引：3，自引：0，他引：3  

黄谟涛  翟国君  欧阳永忠  陆秀平 《武汉大学学报(信息科学版)》2003,28(4):389-392

基于我国新研制的机载激光测深系统基本配置，提出了3种可供选择的波浪改正计算方案(也称为深度值归算方案)，具体分析了3种方案的适用条件和应用范围，并从理论上对3种改正模型的计算精度进行了估算。  相似文献   

TRMM PR雷达与阜阳雷达降水资料的对比研究   总被引：8，自引：0，他引：8  

王成刚  葛文忠  魏鸣 《遥感学报》2003,7(4):332-336

选取了1998年与1999年HUBEX观测资料，将TRMM卫星上的星载降雨雷达PR与阜阳的713数字化天气雷达资料在以下3个方面做了比较：(1)强度场的分布；(2)平均反射率廓线；(3)灵敏度。分析、比较结果可知阜阳雷达在探测灵敏度和水平方向的分辨率要高于PR，但由于波束宽度、衰减和资料转化过程计算误差的原因，其远距离处的观测值与真实值有一定偏差。PR波长短，对衰减敏感，尤其是在垂直方向上经过强衰减后，订正值仍偏小。但由于探测方式的不同PR在水平方向上不存在衰减的问题，且其资料分布均匀，因此提出一种用PR资料来订正地基雷达资料的方法用以提高地基雷达探测的精确度。  相似文献   

从激光扫描数据中进行建筑物特征提取研究   总被引：42，自引：4，他引：42  

李必军  方志祥  任娟 《武汉大学学报(信息科学版)》2003,28(1):65-70

提出了一套基于建筑物几何特征的信息挖掘方案，并具体介绍了研究中采用的一些原理、方法与实用算法，从而可以直接从激光扫描数据中提取建筑物的平面外轮廓信息。利用本方案对车载激光扫描系统获取的城市建筑物试验数据进行了具体的处理，并给出了三维建模和可视化表达结果。  相似文献   

Preliminary Results from a New 157 nm Laser Ablation ICP-MS Instrument: New Opportunities in the Analysis of Solid Samples     

Philippe Telouk  Estelle F. Rose-Koga  Francis Albarede 《Geostandards and Geoanalytical Research》2003,27(1):5-11

Preliminary results are given from an excimer 157 nm laser ablation multiple-collector inductively coupled plasma-mass spectrometer (LA-MC-ICP-MS), used for the isotopic measurements of solid materials. Elements of geological interest with different volatilities such as Pb and U (e.g. zircon geochronology) and Cu and Zn (as examples of geochemical/biochemical tracers) were analysed. The range of ablation rates of 20-150 nm s^-1 enabled us to ablate the sample down to a depth of 45 μm for a 50 μm diameter pit. The Cu and Zn isotopic measurements gave values that were very stable with, on average, a 0.01 % standard error, comparable with that achieved in liquid mode measurements.  相似文献