顾及地形起伏的无人机影像覆盖分析方法     

张衡  李骁  叶朋飞 《测绘通报》2020,(1):102-106

使用无人机实施测绘航空摄影时，由于无人机相对航高较低，地面起伏会对无人机影像的分辨率、覆盖范围、重叠度造成较大的影响，影像成果会出现分辨率不足、重叠度不够、覆盖漏洞等缺陷。针对这一情况，本文提出了一种利用数字微分正解法的计算方法，借助DEM准确计算每张影像的覆盖范围，并使用FME软件高效生成全部影像的覆盖范围。经过实际使用，验证了该方法可以在航线设计阶段准确预测并分析全部影像的覆盖范围、重叠度，因此可及时发现设计问题并调整航线。该方法可以有效减少因地形起伏造成的影像覆盖缺陷，减少返工现象，从整体上提高了作业效率。  相似文献   

低空无人机的倾斜摄影测量技术在城市轨道交通建设中的应用     

冯增文  李珂  李梓豪  任传斌 《测绘通报》2020,(9):42-45

智慧地铁的建设需要三维模型的支撑，运用倾斜摄影测量技术，结合三维可视化技术，为智慧地铁提供了三维数据支撑，推动了全生命周期智慧地铁建设的全面发展。本文旨在以雄安新区城市轨道交通R1线为研究区，对其沿线85 km进行了无人机航飞工作，通过数据处理获取了沿线三维实景模型，并对模型成果精度进行了详细对比。结果表明，此次倾斜摄影测量成果满足1：500比例尺要求。此外，还对倾斜摄影测量技术在城市轨道交通建设中的相关应用进行了介绍，为城市轨道交通建设工作由二维向三维转变开拓了新的方向。  相似文献   

Environmental impact of fluidized solidified silt casting on surrounding water bodies     

Yunquan Li  Silin Wu  Shi Shu  Yiyan Lv  Yan Cui 《Marine Georesources & Geotechnology》2020,38(5):604-610

Abstract

With the growing demand for underwater refill engineering, the construction technology of implementing fluidized solidification in underwater pouring has recently received increased attention. However, the environmental impact of underwater casting on surrounding water bodies, especially when the silt is polluted, is still unclear. In this study, a simulated underwater pouring test and a static immersion release test were conducted separately to study the quality of the surrounding water during and after pouring. The results showed that fluidized-solidified silt casting could increase the pH of the surrounding water, even after the pouring had stopped, by approximately 1.0 and the turbidity could reach 200 NTU. No diffusion of Zn and Cu into the surrounding water was observed and while Ni and Cr exhibited slight diffusion, this was at a level well below international water quality standard. During construction, reducing the distance from the seafloor to the bottom of the pouring catheter could reduce the level of pollution. After construction, the use of neutral solidified materials can effectively reduce the pH of the surrounding water and the potential risk of heavy metal dissolution.  相似文献   

倒置显微镜拍照法对浮游植物计数的稳定性分析     

陈明华  史康佳  李志杰  蔡菲  张浩  张建辉  胡文涛 《湖泊科学》2020,32(5):1564-1574

准确定量分析湖泊河流中浮游植物群落结构对评价湖泊河流健康和保障人类饮水安全至关重要.显微镜镜检法是定量分析浮游植物群落结构的唯一方法,但不能满足浮游植物计数分析要求.在Utermhl倒置计数管视野法基础上提出倒置显微镜拍照法,使用拍照法对小球藻、四尾栅藻、斜生栅藻3种纯藻样品和鄱阳湖野外样品计数得到:1)在5、10倍物镜下拍照因浮游植物个体太小导致计数不准确,在20、40倍物镜下拍照计数准确,增加拍照次数可较好地避免计数偏差,拍照次数是影响拍照法计数分析的主要因素; 2)小球藻、四尾栅藻、斜生栅藻在20和40倍物镜下分别拍摄5和10张照片时每升浮游植物计数稳定;鄱阳湖野外样品在20和40物镜倍下分别拍摄5、10张照片时每升浮游植物计数稳定; 3)倒置显微镜拍照法比计数框行格法、目镜视野法、目镜行格法和Utermhl倒置计数管视野法计数稳定,变异系数最小为0.812.  相似文献   

A smoothed particle hydrodynamics modelling of soil–water mixing and resulting changes in average strength     

Wangcheng Zhang  Mark F. Randolph 《国际地质力学数值与分析法杂志》2020,44(11):1548-1569

Soil–water interaction is a pivotal process in many underwater geohazards such as underwater landslides where soil sediments gradually evolve into turbidity currents after interactions with ambient water. Due to the large deformations, multiphase interactions and phase changes this involves, investigations from numerical modelling of the transition process have been limited so far. This study explores a simple numerical replication of such soil–water mixing with respect to changes in average strength using smoothed particle hydrodynamics (SPH). A uniform viscoplastic model is used for both the solid-like and fluid-like SPH particles. The proposed numerical solution scheme is verified by single-phase dam break tests and multiphase simple shear tests. SPH combinations of solid-like and fluid-like particles can replicate the clay–water mixture as long as the liquidity index of the solid-like particles is larger than unity. The proposed numerical scheme is shown to capture key features of an underwater landslide such as hydroplaning, water entrainment and wave generation and thus shows promise as a tool to simulate the whole process of subaquatic geohazards involving solid–fluid transition during mass transport.  相似文献   

我国深海钻探重入钻孔技术优选及设计思路          下载免费PDF全文

熊亮  谢文卫  卢秋平  朱芝同  刘晓林 《探矿工程》2020,47(7):1-7

深海钻探通常采用无隔水管开路钻进，当更换钻头或钻具，测井、处理孔内事故等情况时，需要起下钻后重新进入原钻孔，此过程称为重入钻孔。由于钻探船与海底孔口有数千米的水体相隔，受海浪和洋流作用，钻探船动荡不稳，钻杆柱摇摆不定，要想重新进入原钻孔并非易事。本文通过广泛调研，对海底基盘、声呐重入系统、水下电视重入系统及无人遥控潜水器（ROV）等目前几种常见的重入钻孔技术进行了详细介绍，对各种技术的优缺点进行了综合对比，优选了水下电视重入系统作为我国深海钻探重入钻孔技术方案，初步提出了技术设计思路，为样机研发和工艺制定奠定了基础。  相似文献   

基于分布式控制力矩陀螺的水下航行器轨迹跟踪控制   总被引：2，自引：0，他引：2  

黄道敏  徐瑞昆  唐国元  冯雷  刘智  徐国华 《海洋工程》2018,36(6):69-76

基于控制力矩陀螺群(CMGs)的水下航行器具有低速或零速机动的能力。采用基于分布式CMGs的水下航行器方案,并研究其水平面的轨迹跟踪控制问题。通过全局微分同胚变换将非完全对称的动力学模型解耦成标准欠驱动控制模型,并根据简化的模型构建其轨迹跟踪的误差动力学模型,将轨迹跟踪控制问题转化为误差模型镇定问题。基于一种分流神经元模型和反步法设计了系统的轨迹跟踪控制律,该控制器不需要对任何虚拟控制输入进行求导计算,且能确保跟踪误差的最终一致有界性。仿真结果表明该控制器能够实现在不依赖动力学参数先验知识的情况下对光滑轨迹的有效跟踪。  相似文献   

三维实景地图生产与应用          下载免费PDF全文

曹培国  姚磊  李奎英  赵倩 《山东国土资源》2018,34(9)

实景地图近年来发展迅速,在日常生活中应用广泛,如旅游景点、宾馆、银行、政府服务中心等的空间位置查询、服务内容介绍等。实景地图的生产方法、生产流程有多种多样,产品质量参差不齐。目前,利用轻型无人机航空摄影系统实现三维全景地图生产,生产方式方便、高效且质量较好。该文介绍了生产三维实景地图的无人机系统及三维实景地图生产方法与过程,通过采用无人机系统实景地图的生产实例,讲述了实景地图应用现状、发展前景及存在的问题。  相似文献   

Exploration of remotely sensed forest structure and ultrasonic range sensor metrics to improve empirical snow models          下载免费PDF全文

Andrés Varhola  Nicholas C. Coops  Younes Alila  Markus Weiler 《水文研究》2014,28(15):4433-4448

Current methods to estimate snow accumulation and ablation at the plot and watershed levels can be improved as new technologies offer alternative approaches to more accurately monitor snow dynamics and their drivers. Here we conduct a meta‐analysis of snow and vegetation data collected in British Columbia to explore the relationships between a wide range of forest structure variables – obtained from Light Detection and Ranging (LiDAR), hemispherical photography (HP) and Landsat Thematic Mapper – and several indicators of snow accumulation and ablation estimated from manual snow surveys and ultrasonic range sensors. By merging and standardizing all the ground plot information available in the study area, we demonstrate how LiDAR‐derived forest cover above 0.5 m was the variable explaining the highest percentage of absolute peak snow water equivalent (SWE) (33%), while HP‐derived leaf area index and gap fraction (45° angle of view) were the best potential predictors of snow ablation rate (explaining 57% of variance). This study reveals how continuous SWE data from ultrasonic sensors are fundamental to obtain statistically significant relationships between snow indicators and structural metrics by increasing mean r² by 20% when compared to manual surveys. The relationships between vegetation and spectral indices from Landsat and snow indicators, not explored before, were almost as high as those shown by LiDAR or HP and thus point towards a new line of research with important practical implications. While the use of different data sources from two snow seasons prevented us from developing models with predictive capacity, a large sample size helped to identify outliers that weakened the relationships and suggest improvements for future research. A concise overview of the limitations of this and previous studies is provided along with propositions to consistently improve experimental designs to take advantage of remote sensing technologies, and better represent spatial and temporal variations of snow. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

低空无人飞艇航测相机稳定平台控制方法     

杨应  刘凤珠  翟曦 《测绘通报》2019,(11):64-68,108

针对低空无人飞艇航空遥感系统平台姿态稳定问题，以及现有稳定平台用于无人飞艇航测系统存在的困难，提出了基于轻小型低精度GNSS/IMU系统和PID算法的三轴稳定平台控制方法。该系统结合双GPS轻小型组合GNSS/IMU系统，采用分离相机和GNSS/IMU系统控制方式，采用PID控制方法，利用STM32控制芯片电路实现稳定平台的控制，解决无人飞艇航测系统相机姿态稳定问题。最后通过飞行试验验证了该系统的稳定性。试验结果表明，该方法能够满足相机系统的俯仰和翻滚角度及航偏角度控制的要求，能够有效隔离无人飞艇姿态的不稳定对成像系统的影响，对于提高无人飞艇航测系统成图精度有重要意义。  相似文献