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林隙主被动遥感协同自动识别

林业科学 2017年第11期53卷 94-103页

作者：毛学刚侯吉宇范文义东北林业大学林学院哈尔滨150040

【目的】研究林隙主被动遥感协同自动识别方法,为进一步量化林隙特征提供技术支持。【方法】以真彩色航空正射影像(0.2 m)和机载Li dar(3.7点·m-2)为主被动遥感数据源,选取东北典型天然次生林——帽儿山实验林场东林施业区为研究区进... 详细信息

【目的】研究林隙主被动遥感协同自动识别方法,为进一步量化林隙特征提供技术支持。【方法】以真彩色航空正射影像(0.2 m)和机载Li dar(3.7点·m-2)为主被动遥感数据源,选取东北典型天然次生林——帽儿山实验林场东林施业区为研究区进行面向对象林隙识别。在面向对象分类过程中,通过对比3种分割方案(航空影像分割、Li dar数据分割、航空影像&Li dar协同分割)、10种尺度(10~100,步长为10)确定最优分割方案及尺度参数。在最优分割结果基础上应用航空影像的光谱特征、Li dar数据提取的高度特征及共同特征,应用支持向量机分类器(SVM)进行林隙识别。【结果】3种分割方案的最优尺度均为20;所有尺度均是基于Li dar数据分割ED3modified(0.52±0.11)低于基于航空影像分割(0.58±0.07)与航空影像&Li dar协同数据分割(0.58±0.07)。在Li dar数据最优尺度(20)下,采用光谱和高度共同特征的主被动识别与单独采用光谱特征的主动识别及单独使用高度特征的被动识别相比,分类精度分别提高36.71%和8.17%。【结论】3种分割方案中,基于Li dar数据分割结果最好;使用主被动遥感协同自动识别进行林隙分类时精度最高(OA=87.73%,Kappa=0.81)。

关键词：林隙尺度分割分类特征 Li dar 航空影像 CHM 支持向量机

基于机载Lidar数据的林木冠层投影面积与体积测量

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农业机械学报 2016年第1期47卷 304-309页

作者：张卫正董寿银王国飞裘正军吴翔何勇浙江大学生物系统工程与食品科学学院杭州310058 浙江省第二测绘院航测与遥感三分院杭州310012 星际空间(天津)科技发展有限公司天津300384

机载激光雷达系统能够采集反映林木三维结构的点云,利用点云分类及林木冠层投影面积和体积计算方法获得林木信息。通过不规则三角网法和平面拟合过滤算法分别提取地面和建筑物点云,并将建筑物点云过滤得到林木点云,将树冠点云投影到x-y... 详细信息

机载激光雷达系统能够采集反映林木三维结构的点云,利用点云分类及林木冠层投影面积和体积计算方法获得林木信息。通过不规则三角网法和平面拟合过滤算法分别提取地面和建筑物点云,并将建筑物点云过滤得到林木点云,将树冠点云投影到x-y平面,采用角度法搜索边界,提取林木点云边缘,并在与其相对应的CCD影像上显示。利用任意多边形面积算法计算各个连通区域的面积,将它们求和得到冠层投影面积,通过台体的体积计算得到冠层体积。在研究区域随机选出10个外业样地进行传统的人工测量,实验结果表明,基于Li dar的激光测量与人工测量测得的投影面积和体积的相关系数分别为0.957和0.944。本文提出的方法准确有效,为高精度定量估算林木冠层生物量提供了依据。

关键词：林木机载Li dar 投影面积体积不规则三角网平面拟合过滤算法

基于变尺度格网索引与机器学习的行道树靶标点云识别

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农业机械学报 2018年第6期49卷 32-37页

作者：李秋洁郑加强周宏平陶冉束义平南京林业大学机械电子工程学院南京210037

针对行道树连续喷雾施药方式严重污染环境,果园对靶施药技术难以推广至复杂城区环境等问题,应用车载2D Lidar获取街道三维点云数据,研究行道树靶标识别方法。构建变尺度格网点云索引结构,实现邻域快速搜索及点云在线处理;提取高程、深... 详细信息

针对行道树连续喷雾施药方式严重污染环境,果园对靶施药技术难以推广至复杂城区环境等问题,应用车载2D Lidar获取街道三维点云数据,研究行道树靶标识别方法。构建变尺度格网点云索引结构,实现邻域快速搜索及点云在线处理;提取高程、深度、密度、协方差矩阵等11个点云球域特征,分析特征分布特性,采用基于径向基核函数的支持向量机算法融合特征,学习树冠点云分类器;采用FIFO缓冲区保存点云帧序列,实现行道树靶标在线识别。实验结果表明,该方法能够实现行道树靶标精确识别,在测试集上的分类错误率小于0.8%,检出率大于99.4%,虚警率小于0.9%,鉴别力最强的4个特征从高到低依次是高程均值、深度均值、高程范围和高程方差。

关键词：对靶喷雾行道树识别 2D Li dar 点云索引点云分类

基于Lidar的海原断裂松山段断错地貌分析与古地震探槽选址实例

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地质通报 2016年第1期35卷 104-116页

作者：李占飞刘静邵延秀张金玉袁兆德王鹏唐茂云王朋涛中国地震局地质研究所北京100029 中国地震局兰州地震研究所甘肃兰州730000 中国地震灾害防御中心北京100029

基于高精度机载Li dar数据在GIS平台的地貌因子渲染分析,对海原断裂老虎山段松山地区古地震研究点进行高精度大比例尺(1∶1000)地貌填图,勾勒出研究点微地貌空间展布和断裂高精度几何形态。通过对松山古地震研究点2个新探槽的开挖,结合... 详细信息

基于高精度机载Li dar数据在GIS平台的地貌因子渲染分析,对海原断裂老虎山段松山地区古地震研究点进行高精度大比例尺(1∶1000)地貌填图,勾勒出研究点微地貌空间展布和断裂高精度几何形态。通过对松山古地震研究点2个新探槽的开挖,结合细致的探槽解译、地震事件识别与分期、年代学样品测试,得出5次37380±880BP以内的不连续古地震序列。通过对比此处已经开挖的各自相距不足150m、分布于断裂同一段落的4个古地震探槽的微地貌位置、沉积特征和地震事件信号强弱,发现即使相距不远,不同微地貌位置古地震探槽揭示的古地震现象也会有显著差别。这种差别凸显了古地震研究结果,如揭示的事件证据和个数等与探槽点位置的选取有较强的依赖性。综合对比分析表明,较低的地势、低能静水环境、高沉积速率、细粒的沉积物源区及连续的沉积环境是走滑断裂上开展古地震研究的优选地貌位置。实例表明,基于高精度地形数据对研究点开展精细地貌填图揭示微地貌时空演化,从而在探槽开挖前对古地震研究点的构造地貌优劣进行充分评价是提高古地震研究质量的必要程序,同时也显示出高精度机载Li dar数据在活动构造研究中的重要新应用。

关键词：机载Li dar GIS分析古地震微地貌填图最佳探槽点新机遇

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关键点检测的复杂建筑物模型自动重建

遥感学报 2014年第6期18卷 1237-1246页

作者：李鹏程邢帅徐青周杨刘志青张艳耿迅信息工程大学地理空间信息学院河南郑州450052

利用机载Li dar点云数据进行建筑物重建是当今摄影测量与遥感领域的一个热点问题,特别是复杂形状建筑物模型的精确自动构建一直是一个难题。本文提出一种基于关键点检测的复杂建筑物模型自动重建方法,采用RANSAC法与距离法相结合的分割... 详细信息

利用机载Li dar点云数据进行建筑物重建是当今摄影测量与遥感领域的一个热点问题,特别是复杂形状建筑物模型的精确自动构建一直是一个难题。本文提出一种基于关键点检测的复杂建筑物模型自动重建方法,采用RANSAC法与距离法相结合的分割方法自动提取建筑物屋顶各个平面的点云,并利用Alpha Shape算法提取出各个平面的精确轮廓,根据屋顶平面之间的空间拓扑关系分析建筑物的公共交线特征,在此特征约束下对提取的初始关键点进行修正,最终重建出精确的建筑物3维模型。选取不同类型复杂建筑物与包含复杂建筑物的城市区域点云进行实验,结果表明该算法具有较强实用价值。

关键词：建筑物重建机载Li dar 点云分割轮廓提取关键点检测

Analysis of Ground Level Ozone and Nitrogen Oxides in the City of dar es Salaam and the Rural Area of Bagamoyo, Tanzania

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Open Journal of Air Pollution 2015年第4期4卷 224-238页

作者： Asha Mansour Hamdun Takemitsu Arakaki Department of Aquatic Science and Fisheries College of Natural and Applied Science University of Dar es Salaam Dar es Salaam Tanzania Department of Chemistry Biology and Marine Science Faculty of Science University of the Ryukyus Okinawa Japan

From 2012 to 2015, we measured surface ozone, NOx, NO2, and NO levels at three urban sites (Mapipa, Ubungo, and Posta) and two suburban sites (Kunduchi and Vijibweni) in the city of dar es Salaam and in the village of Mwetemo, a rural area of Bagamoyo, Tanzania. The average hourly O3 concentrations at all sites were between 9 ppb and 30 ppb during our sampling periods. O3 levels at suburban sites were generally higher than at urban sites. The average hourly concentrations in dar es Salaam were 10 - 32 ppb, while in Bagamoyo they were 9 - 15 ppb. We observed a strong diurnal variation in dar es Salaam while measurements from Bagamoyo showed little variation. At dar es Salaam, the surface O3 concentrations increased from their minimum level at sunrise (around 6:00 a.m.) to a maximum in the late afternoon (around 4:00 p.m.), and then decreased toward 11:00 p.m. Another secondary ozone peak appeared between midnight and ~4:00 a.m., after which the surface ozone concentrations decreased to a minimum around 7:00 a.m. NO2 concentrations were higher at the urban sites of Ubungo and Posta, and their weekly average NO2 concentrations were 246 ppb and 118 ppb, respectively. Weekly average NOx concentrations ranged from 39.4 ppb at the Kunduchi site (suburban) to 738 ppb at the Ubungo site (urban). To our knowledge, there were few continuous measurements of ozone and nitrogen oxides concentrations in Tanzania. Since high NOx concentrations were observed, continuous air quality monitoring and effective air pollution control measures are required in dar es Salaam to prevent further deterioration of air quality and limit the possible negative impacts on humans and vegetation.

关键词： Ozone NOx Daily Variation Bagamoyo dar es Salaam

Prevalence and associated factors of sexual violence among private college female students in Bahir dar city, North Western Ethiopia

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Health 2013年第6期5卷 1069-1075页

作者： Bizuayhu Shimekaw Berihun Megabiaw Zelalem Alamrew Department of Epidemiology and Biostatistics School of Public Health College of Medicine and Health Sciences University of Gondar Gondar Ethiopia Department of Public Health College of Medicine and Health Sciences Bahir Dar University Bahir Dar Ethiopia Department of Public health Faculty of Health Sciences Andenet Medical College Dangila Ethiopia

Background: Despite the higher risk victimization of young women in Ethiopia, the prevalence of sexual violence and its determinants among college students were scarce, particularly in the study area. This study was undertaken to determine the prevalence and associated factors of sexual violence among female private college students in Bahir dar city. Methods: A cross sectional study was conducted in April 2012 among 541 female college students in Bahir dar city using multistage sampling technique. A pretested self-administered questionnaire was used. The data were analyzed in bivariate and multivariate logistic regression analysis with SPSS version 16 soft ware package. Result: The study revealed that the prevalence of sexual violence among female college students was 37.3%. Respondents whose childhood background from rural areas were more than four times likely to have had sexual violence (AOR = 4.51, 95%CI: 1.67 - 12.16). The odds of sexual violence were higher for those respondents who had a close friend who drank alcohol (AOR = 3.13, 95%CI: 1.09 - 8.97). Besides, respondents who had never discussed on reproductive health issues with their parents were more than four times likely to have had sexual violence (AOR = 4.36, 95%CI: 1.40 -13.56). Conclusion: This study shows that sexual violence among female college students is higher. Sexual violence is associated with certain variables such as rural childhood residence, having a close friend who drank alcohol, and not discussing reproductive issues with parents. Therefore, it is recommend ed that sexual violence needs due attention and remedial action from policy makers, college officials, parents, students and other concerned bodies.

关键词： Sexual Violence Female College Students Bahir dar City and Ethiopia

Assessing Weather Research and Forecasting (WRF) Model Parameterization Schemes Skill to Simulate Extreme Rainfall Events over dar es Salaam on 21 December 2011

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Journal of Geoscience and Environment Protection 2018年第1期6卷 36-54页

作者： Triphonia Jacob Ngailo Nyimvua Shaban Joachim Reuder Michel D. S. Mesquita Edwin Rutalebwa Isaac Mugume Chiku Sangalungembe Department of Mathematics University of Tanzania Dar es Salaam Tanzania Geophysical Institute University of Bergen Bergen Norway Uni Research Climate Bjerknes Centre for Climate Studies University of Bergen Bergen Norway General studies Department Dar es Salaam Institute of Technology Dar es Salaam Tanzania Department of Geography Geoinformatics and Climate Sciences Makerere University Kampala Uganda Modelling Section Tanzania Meteorological Agency Dar es Salaam Tanzania

This paper evaluates the skills of physical Parameterization schemes in simulating extreme rainfall events over dar es Salaam Region, Tanzania using the Weather Research and Forecasting (WRF) model. The model skill is determined during the 21 December 2011 flooding event. Ten sensitivity experiments have been conducted using Cumulus, Convective and Planetary boundary layer schemes to find the best combination and optimize the WRF model for the study area for heavy rainfall events. Model simulation results were verified against observed data using standard statistical tests. The model simulations show encouraging and better statistical results with the combination of Kain-Fritsch cumulus parameterization scheme, Lin microphysics scheme and Asymmetric Convection Model 2 (ACM2) planetary boundary scheme than any other combinations of physical parameterization schemes over dar es Salaam region.

关键词： WRF dar es Salaam Extreme Rainfall Events Physical Parameterization Schemes

Estimation of Aquifer Transmissivity Using dar Zarrouk Parameters Derived from Surface Resistivity Measurements: A Case History from Parts of Enugu Town (Nigeria)

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Journal of Water Resource and Protection 2012年第12期4卷 993-1000页

作者： Ahamefula U. Utom Benard I. Odoh Anthony U. Okoro Department of Geological Sciences Nnamdi Azikiwe University Awka Nigeria

Many investigation techniques are commonly employed with the aim of estimating the spatial distribution of transmissivity. Unfortunately, the conventional methods for the determination of hydraulic parameters such as pumping tests, permeameter measurements and grain size analysis are invasive and relatively expensive. A geoelectric investigation involving vertical electrical sounding was carried in parts of Enugu town, Enugu state, Nigeria. The survey was aimed at extrapolating the result of pumping tests over an area. Using the dar Zarrouk parameter, a β constant of 0.32 was found to translate resistivity to transmissivity with clay content as the primary factor controlling the hydraulic conductivity. Results of the study show a strong correlation between aquifer transmissivity and longitudinal conductance (R2 = 0.82). Estimation of aquifer transmissivity values based on the results of the resistivity measurements also made it possible to demarcate area with good groundwater potential in parts of Enugu town, Nigeria.

关键词： Resistivity Transmissivity dar Zarrouk Parameters Longitudinal Conductance Pumping Tests