A literature synthesis of LiDAR applications in transportation: feature extraction and geometric assessments of highways     

Suliman A. Gargoum  Karim El Basyouny 《地理信息系统科学与遥感》2019,56(6):864-893

Interest in using Light Detection and Ranging (LiDAR) technology in Transportation Engineering has grown over the past decade. The high accuracy of LiDAR datasets and the efficiency by which they can be collected has led many transportation agencies to consider mobile LiDAR as an alternative to conventional tools when surveying roadway infrastructure. Nonetheless, extracting semantic information from LiDAR datasets can be extremely challenging. Although extracting roadway features from LiDAR has been considered in previous research, the extraction of some features has received more attention than others. In fact, for some roadway design elements, attempts to extract those elements from LiDAR have been extremely scarce. To document the research that has been done in this area, this paper conducts a thorough review of existing studies while also highlighting areas where more research is required. Unlike previous research, this paper includes a thorough review of the previous attempts at data extraction from LiDAR while summarizing the detailed steps of the extraction procedure proposed in each study. Moreover, the paper also identifies common tools and techniques used to extract information from LiDAR for transportation applications. The paper also highlights common limitations in existing algorithms that could be improved in future research. This paper represents a valuable resource for researchers and practitioners interested in knowing the current state of research on the applications of LiDAR in the field of Transportation Engineering while also understanding the opportunities and challenges that lie ahead.  相似文献   

同步改正法平均海面传递应用于海南岛礁测绘的探讨     

张亮  车志伟  张景凯 《海洋技术学报》2019,38(5)

同步改正法因其特点和优势被广泛应用于平均海面传递,文中从平均海面的理论定义和实际计算两方面出发,对同步改正平均海面传递法原理进行了论述。利用海南岛周边的长期验潮站数据,按单站传递和多站组网传递分别分析了同步改正平均海面传递的规律。结果表明,单站传递同步观测10 d能满足岛礁测绘对垂直基准面精度的要求,采用多站组网传递能较明显地减少同步时长较短时的极限误差。当采用多站组网平均海面传递同步观测5 d,其极限误差可达10 cm以内,建议在同步观测时间有限时采用该方法。结合海南岛验潮站和岛礁分布情况,同步改正平均海面传递法应用于海南岛礁测绘是可行的。  相似文献   

贵州省松桃县木耳溪锰矿地质特征及找矿方向     

陈旭  许乔 《云南地质》2020,(1):31-36

贵州松桃县木耳溪锰矿为典型的层控型锰矿床,矿体呈层状赋存于南华系下统大塘坡组第一段(Pt2b3d 1)底部的炭质页岩中,产出层位稳定,矿体产状与围岩产状一致。通过统计对比,锰矿层的矿化程度与含锰岩系的厚度呈正比,即当南华系大塘坡组地层厚度大于15m时,有可能成为锰矿的主要找矿方向。  相似文献   

Understanding the hydrological system dynamics of a glaciated alpine catchment in the Himalayan region using the J2000 hydrological model          下载免费PDF全文

S. Nepal  P. Krause  W.‐A. Flügel  M. Fink  C. Fischer 《水文研究》2014,28(3):1329-1344

This paper provides the results of hydrological modelling in a mesoscale glaciated alpine catchment of the Himalayan region. In the context of global climate change, the hydrological regime of an alpine mountain is likely to be affected, which might produce serious implications for downstream water availability. The main objective of this study was to understand the hydrological system dynamics of a glaciated catchment, the Dudh Kosi River basin, in Nepal, using the J2000 hydrological model and thereby understand how the rise in air temperature will affect the hydrological processes. The model is able to reproduce the overall hydrological dynamics quite well with an efficiency result of Nash–Sutcliffe (0.85), logarithm Nash–Sutcliffe (0.93) and coefficient of determination (0.85) for the study period. The average contribution from glacier areas to total streamflow is estimated to be 17%, and snowmelt (other than from glacier areas) accounts for another 17%. This indicates the significance of the snow and glacier runoff in the Himalayan region. The hypothetical rise in temperature scenarios at a rate of +2 and +4 °C indicated that the snowmelt process might be largely affected. An increase in snowmelt volume is noted during the premonsoon period, whereas the contribution during the monsoon season is significantly decreased. This occurs mainly because the rise in temperature will shift the snowline up to areas of higher altitude and thereby reduce the snow storage capacity of the basin. This indicates that the region is particularly vulnerable to global climate change and the associated risk of decreasing water availability to downstream areas. Under the assumed warming scenarios, it is likely that in the future, the river might shift from a ‘melt‐dominated river’ to a ‘rain‐dominated river’. The J2000 model should be considered a promising tool to better understand the hydrological dynamics in alpine mountain catchments of the Himalayan region. This understanding will be quite useful for further analysis of ‘what‐if scenarios’ in the context of global climate and land‐use changes and ultimately for sustainable Integrated Water Resources Management in the Himalayan region. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Modeling deepwater seabed steady-state thermal fields around buried pipeline including trenching and backfill effects     

《Computers and Geotechnics》2014

Deepwater pipelines are designed to transport mixtures of oil and gas, and their associated impurities at wellhead temperatures that can be in excess of 149 °C (∼300 °F or 422 K) while the external temperature maybe in the range of 5 °C (∼41 °F or 278 K). Depending on the circumstances these pipelines may be buried for physical protection or for additional thermal insulation using robotic trenching equipment. This results in a complex cut and backfill geometry in the seafloor in addition to altering the thermal properties of the backfill. A two-dimensional boundary element model was developed specifically to address to investigate the local steady-state thermal field in the near field of the pipeline. The model allows one to account for the complex geometries in the near field associated with this burial technique, site-specific multi-layered soil conditions and the seawater adjacent to the seafloor. A parametric study was preformed to evaluate effects of the thermal power loss, burial depth, pipe diameter and soil thermal conductivity on the thermal field in the near field of a buried pipeline. The numerical examples illustrate the influence of the backfill thermal property on the temperature at the pipe wall, that the pipe diameter controls the required output thermal power needed to maintain the desired pipe wall temperature, and the importance of pipeline burial depth on seabed temperature distribution above the pipeline.  相似文献   

大型射电望远镜主反射面调整方法研究          下载免费PDF全文

孙正雄  王锦清  虞林峰  张志斌  王广利 《天文学报》2024,65(2):15

随着毫米波天文学和空间通信的重要性日益提高, 对天线性能提出了越来越高的要求, 而天线性能往往受到其反射器表面精度的限制. 微波全息技术是一种快速有效的检测反射面天线表面轮廓的测量技术. 通过微波全息测量得到天线口径场, 计算天马65m射电望远镜反射面与理想抛物面的偏差. 天马65m射电望远镜的主反射面板是放射状的, 有14圈. 面板的每个角都固定在面板下方促动器的螺栓上进行上下移动, 且相邻面板交点处的拐角共用一个促动器. 采用平面拟合的方法可以计算各块面板拐角处的调整值, 但是同一个促动器会得到4个不同的调整量. 通过平面拟合, 同时以天线照明函数为权重的平差计算方法得到相邻面板拐角的一个平差值, 即天马65m射电望远镜1104个促动器的最佳调整值. 通过多次调整和新算法的应用, 天马65m射电望远镜反射面的面形精度逐渐提高到了0.24mm.  相似文献   

小体积液液萃取气相色谱-质谱法测定地下水中的克百威与3-羟基克百威     

周添  刘菲 《岩矿测试》2021,(3):358-364

克百威和3-羟基克百威是一对典型的农药母体及其代谢产物,由于其水溶性高、毒性大,可通过地表水或地下水进行长距离迁移,对人类健康和环境安全造成危害。以往通常采用液相萃取或固相萃取的方式提取样品中的克百威和3-羟基克百威,但这些方法操作繁琐、耗时较长,不利于室内模拟实验中多组样品的检测。为实现克百威与3-羟基克百威在地下水中的快速定量,本文建立了一种小体积液液萃取的前处理方法进行提取,并采用气相色谱-质谱(GC-MS)进行检测,对影响克百威和3-羟基克百威萃取效率的因素进行了研究。通过实验对比不同萃取剂、不同pH、不同离子强度条件下克百威与3-羟基克百威的回收率,优化了前处理条件。结果表明,选择二氯甲烷作为萃取剂且用量为1mL,调节水样pH=5,氯化钠用量为40g/L时克百威和3-羟基克百威的回收率最高,分别为75.1%～98.6%、55.0%～66.3%。性能评价结果显示,方法精密度和方法准确度满足测试要求(相对标准偏差10%,n=5),克百威和3-羟基克百威的方法检出限分别为15.3μg/L、10.2μg/L。该方法操作简便、快速、消耗溶剂少,与传统的液液萃取法相比,本方法耗时约为前者的1/8,消耗溶剂量约比前者小2个数量级,能够满足室内模拟实验需求。  相似文献   

甘肃省重要古植物化石产地区划及保护利用     

王军  李小强  张海峰  郭兵  任文秀  彭措  冯备战  王玉玺  胡振波 《地质论评》2021,67(3):578-592

古植物化石是地质历史时期各类植物实体或遗迹的残留。对古植物化石产地进行系统的调查和区划研究是开展古生物化石保护和利用工作的基础。在资料研究和实地调查的基础上,对甘肃省24处重要古植物化石产地进行了评价和区划研究。甘肃省古植物化石产地可划分为北山地区、祁连山——河西走廊地区、鄂尔多斯和秦岭地区4个古生物化石大区以及6个古植物化石产地集中区。根据古植物化石产地的科学价值和美学价值,具体从科学性、稀有性、完整性、保存程度、可保护性5个单因素分别对24处重要古植物化石产地进行了评价。在单因素评价基础上进行了综合鉴评,共鉴评出世界级化石产地1处,国家级化石产地7处,省级化石产地16处。根据产地自然区划、行政区划等要素划分了古植物化石产地集中保护区6个。根据保护区内古植物化石产地级别及重要程度,划分出特级保护区2个,重点保护区2个和一般保护区2个。提出对重要古植物化石产地实行化石标本保护加原产地保护的建议。  相似文献   

鄂尔多斯盆地延安地区山西组山2段储层可动流体赋存影响因素分析     

刘江斌 《地质与勘探》2021,57(1):231-240

山2段是鄂尔多斯盆地延安地区致密砂岩气生产的重要层段,目前对其流体赋存规律认识明显不足。因此在铸体薄片、扫描电镜、X射线衍射、高压压汞、恒速压汞、核磁共振测试的基础上,分析该储层可动流体的赋存特征及其影响因素。结果表明:山2储层主要为岩屑石英砂岩和岩屑砂岩,溶蚀孔和晶间孔为主要储集空间,粒间溶孔显著发育。山2储层可动流体饱和度为34.74%～91.83%,平均为69.94%,T2谱多为双峰态,呈左低右高型。储层孔隙度、渗透率、孔隙类型、孔喉特征及胶结物影响可动流体饱和度。孔隙为可动流体提供主要空间,平均孔隙半径越大,平均喉道半径越大,孔喉比越小,可动流体饱和度越高。硅质含量越高,粒间孔保存越好,可动流体饱和度越高。铁方解石含量越高,孔隙破坏越明显,可动流体饱和越低。高岭石含量较高,长石溶孔及晶间孔发育较好,有利于流体流动,可动流体饱和度也较高。  相似文献   

基于恒速压汞技术研究页岩气储层孔隙结构:以湘西北地区五峰组页岩为例     

王静 《地质与勘探》2021,57(2):450-456

页岩气储层孔隙结构是页岩气富集成藏、储层评价和优选有利区的关键参数,区分孔隙和喉道是表征页岩气储层孔隙结构的关键。本文选择4块具有不同渗透率的湘西北地区奥陶系五峰组页岩为研究对象,基于恒速压汞实验讨论孔隙和喉道的大小、分布特征及其相互关系以及与渗透率的联系。结果表明:具有不同渗透率的页岩样品表现为较为相近的孔径分布特征但差异较大的喉道分布特征。页岩样品渗透率的大小与孔隙半径没有明显相关关系;喉道大小及其分布特征是控制低渗储层孔隙结构的关键要素之一。渗透率较低页岩样品的喉道以喉道半径小且集中分布为特征,而渗透率较大页岩样品的喉道以喉道半径大呈分散分布但主要以大喉道为特征。喉道特征是研究页岩气储层储集空间和吸附能力的重要部分,在以后对页岩气的勘探开发中应特别注意及重视。  相似文献