无人海洋测绘技术体系构建   总被引：3，自引：1，他引：2  

周立  张阳  张一  付丹丹  陈晨  魏征  冯俊俊  刘泽峰 《测绘通报》2019,(4):130-133

随着无人技术的快速发展，无人测绘的时代即将到来。本文分析了无人时代技术特征与海洋测绘发展机遇；讨论了无人海洋测绘新理念，构建了无人海洋测绘技术体系，论述了无人海洋测绘技术关键技术；展望了无人海洋测绘技术发展趋势，及其在海洋经济、海洋可持续发展中的应用前景。  相似文献   

基于2D地图的城市户外ARGIS视觉辅助地理配准技术     

邓晨  游雄  张威巍  智梅霞 《测绘学报》2019,48(10):1305-1319

针对当前便携式位姿传感器获取的户外6DOF绝对位姿精度通常不足，致使基于位姿传感器的户外AR地理配准精度不高，提出了一种以2D地图作为参考数据进行户外视觉辅助定位进而提高ARGIS系统地理配准精度的方法和技术框架。在位姿传感器获取初始位姿的基础上，详细阐述了基于2D地图进行图像位姿优化和辅助校正的基本原理；并通过试验验证了该方法可以对位姿传感器获取的初始位姿进行优化，进而提高户外AR地理配准精度的有效性。  相似文献   

水资源约束下的河西走廊城市经济脆弱性时空演变及其影响因素     

张戬  陈佳  黄馨  王子侨 《中国沙漠》2019,39(1):203-211

城市经济脆弱性作为当前脆弱性研究中的重要领域，为人-地系统耦合研究提供了新的视角，并为城市可持续健康发展提供有益的决策支持和管理方法。依据城市经济脆弱性内涵，基于暴露度、敏感性、适应能力构建了城市经济脆弱性评价指标体系，运用熵权TOPSIS法评价河西走廊地区及区域内五市的城市经济脆弱性，并采用障碍度模型识别影响区域城市经济脆弱性变化的因素。结果显示：（1）2006—2015年，河西走廊地区城市经济脆弱性呈现出先曲折下降（2006—2011年）再波动上升趋势（2012—2015年）；（2）河西走廊地区的城市经济脆弱性具有明显的空间特征，经历了东西高、中部低到整体较高的演变过程；（3）阻碍河西走廊地区城市经济脆弱性降低的障碍因子由适应能力逐步转变为暴露度。针对河西走廊地区各市主要障碍因子，提出针对性优化措施。  相似文献   

布达拉宫旅游商业化的社区治理研究     

梁坤  罗爽 《世界地理研究》2019,28(5):191-199

以社区为出发点，综合旅游商业化、社区治理等相关理论，在布达拉宫及周边社区旅游商业化表征分类的基础上，梳理其社区旅游商业化的治理成效及治理困境。再运用静态博弈模型与决策树，分析布达拉宫及周边社区旅游商业化的治理中各利益主体博弈的过程，并探析治理困境的原因。研究发现，旅游商业化的社区治理受到各利益主体间权力大小和利益选择的影响。政府及相关部门处于强势地位，主导并采取措施治理旅游商业化。布达拉宫的各空间圈层在商业化治理过程和难度上都存在明显差异。引起治理困境的原因主要是“权”与“利”的纠葛、商业化控制的阈限不清晰、利益主体之间的沟通不畅。在主要利益相关者的博弈中，各治理主体共同重构一个相对均衡的“利益－权力”关系结构，以保证社区旅游商业化得以有效治理。  相似文献   

长白山景区旅游安全风险动态评价研究   总被引：1，自引：0，他引：1  

孙滢悦  杨青山  陈鹏 《地理科学》2019,39(5):770-778

以长白山景区旅游安全为研究对象,以鱼骨图、动态贝叶斯、GIS技术等为基本研究方法,从研究区自然环境、社会环境及责任人为3个方面出发,筛选景区致险因子,构建景区旅游安全风险危险性评价指标体系,利用动态贝叶斯方法综合构建景区旅游安全风险动态评价模型;并以实测数据及景区统计数据为依据,划分景区旅游安全风险评价的4个动态时段,综合实现景区旅游安全风险动态风险评价。研究结果表明：① 中等以上风险区域呈条带状分布;② 高风险区域与主要景点重合;③ 长白山景区安全风险发生高概率的时段发生在第三个时段（12:00~14:00）;较高概率发生分别在第二个时段（10:00~12:00）与第四个时段（14:00~16:00）;中等概率发生较高的时段在第四个时段（14:00~16:00）;较低概率发生在第一个时段（8:00~10:00）。  相似文献   

Cyclical one-way continental rupture-drift in the Tethyan evolution: Subduction-driven plate tectonics     

Wan  Bo  Wu  Fuyuan  Chen  Ling  Zhao  Liang  Liang  Xiaofeng  Xiao  Wenjiao  Zhu  Rixiang 《中国科学:地球科学(英文版)》2019,62(12):2005-2016

Numerous continents have rifted and drifted away from Gondwana to repeatedly open ocean basins over the past-500 millionyears.These Gondwana-derived continents drifted towards and collided with components of the Eurasian continent to successively close the preexisting oceans between the two.Plate tectonics satisfactorily describes the continental drift from Gondwana to Eurasia but does not define the geodynamic mechanism of continuously rifting to collisions of continents in the Tethy an Realm.After reappraisal of geological records of the rift,collision and subduction initiation from the surface and various geophysical observations from depth,we propose that Eurasia-directed subducting oceanic slabs would have driven Tethyan system in the Phanerozoic.The Eurasia-directed subduction would have dragged the passive Gondwana margin to rift and drift northwards,giving birth to new oceans since the Paleozoic.The closure of preexisting oceans between the Gondwana-derived continents and Eurasia led to continental collisions,which would have induced the initiation of oceanic subduction in the Tethyan Realm.Multiple episodic switches between collision-subduction-rift repeatedly led to the separation of continental fragments from Gondwana and dragged them to drift towards Eurasia.The final disappearance of Neo-Tethy s would have induced collision of the Gondwana-derived continents with the Eurasian continent,giving rise to the Cenozoic Alpine-Zagros-Himalayan collisional system.Therefore,the Eurasia-directed oceanic subduction would have acted as a 'one-way train' that successively transferred the ruptured Gondwana continental fragments in the south,into the terminal in the north.In this regard,the engine of this "Tethyan one-way train" is the negative buoyancy of subducting oceanic slabs.  相似文献   

Quantifying flow resistance in mountain streams using computational fluid dynamics modeling over structure-from-motion photogrammetry-derived microtopography     

Yunxiang Chen  Roman A. DiBiase  Nicholas McCarroll  Xiaofeng Liu 《地球表面变化过程与地形》2019,44(10):1973-1987

Flow resistance in mountain streams is important for assessing flooding hazard and quantifying sediment transport and bedrock incision in upland landscapes. In such settings, flow resistance is sensitive to grain-scale roughness, which has traditionally been characterized by particle size distributions derived from laborious point counts of streambed sediment. Developing a general framework for rapid quantification of resistance in mountain streams is still a challenge. Here we present a semi-automated workflow that combines millimeter- to centimeter-scale structure-from-motion (SfM) photogrammetry surveys of bed topography and computational fluid dynamics (CFD) simulations to better evaluate surface roughness and rapidly quantify flow resistance in mountain streams. The workflow was applied to three field sites of gravel, cobble, and boulder-bedded channels with a wide range of grain size, sorting, and shape. Large-eddy simulations with body-fitted meshes generated from SfM photogrammetry-derived surfaces were performed to quantify flow resistance. The analysis of bed microtopography using a second-order structure function identified three scaling regimes that corresponded to important roughness length scales and surface complexity contributing to flow resistance. The standard deviation σ_z of detrended streambed elevation normalized by water depth, as a proxy for the vertical roughness length scale, emerges as the primary control on flow resistance and is furthermore tied to the characteristic length scale of rough surface-generated vortices. Horizontal length scales and surface complexity are secondary controls on flow resistance. A new resistance predictor linking water depth and vertical roughness scale, i.e.  H/σ_z, is proposed based on the comparison between σ_z and the characteristic length scale of vortex shedding. In addition, representing streambeds using digital elevation models (DEM) is appropriate for well-sorted streambeds, but not for poorly sorted ones under shallow and medium flow depth conditions due to the missing local overhanging features captured by fully 3D meshes which modulate local pressure gradient and thus bulk flow separation and pressure distribution. An appraisal of the mesh resolution effect on flow resistance shows that the SfM photogrammetry data resolution and the optimal CFD mesh size should be about 1/7 to 1/14 of the standard deviation of bed elevation. © 2019 John Wiley & Sons, Ltd.  相似文献   

How forest gaps shaped plant diversity along an elevational gradient in Wolong National Nature Reserve?     

Chen  Li  Han  Wangya  Liu  Dan  Liu  Guohua 《地理学报(英文版)》2019,29(7):1081-1097

Journal of Geographical Sciences - Understanding the underlying ecological processes that control plant diversity within (α-diversity) and among (β-diversity) forest gaps is important for...  相似文献   

Characteristics of the modern pollen assemblages from different vegetation zones in Northeast China: Implications for pollen-based climate reconstruction     

Qiaoyu CUI  Yan ZHAO  Feng QIN  Chen LIANG  Quan LI  Rongwei GENG 《中国科学:地球科学(英文版)》2019,(10)

Northeast China is an essential area for studying the strength of East Asian Summer Monsoon(EASM), due to its northernmost location in EASM domain. However, the lack of sufficient modern pollen data in this region hinders an effective interpretation of fossil pollen records and quantitative vegetation/climate reconstructions. Here, 44 surface pollen samples from forest, steppe, and meadow were used to explore pollen-vegetation-climate relationships. Cluster analysis, species indicator analysis, and principal components analysis, were used to identify the discontinuous and continuous trends in pollen dataset. In addition, correlation analysis and boosted regression trees were used to investigate primary explanatory variables, while coinertia analysis and redundancy analysis to examine pollen-vegetation and pollen-climate correlations respectively. Our results show that:(1) vegetation can be well represented by surface pollen assemblages, i.e. forest is characterized by a high proportion of tree pollen(70%) dominated by Betula(40%) along with Alnus, Larix, and Pinus, whereas Steppe by herb pollen(80%),dominated by Artemisia, Chenopodiaceae;(2) significant correlations exist between pollen assemblages and mean annual temperature and then mean annual precipitation;(3) pollen ratios of Artemisia/Chenopodiaceae and arboreal/non-arboreal can respectively be used as good indicators of humidity and temperature in Northeast China.  相似文献   

空间波数混合域磁异常场积分解三维数值模拟          下载免费PDF全文

李昆  戴世坤  陈轻蕊  张钱江  赵东东  王顺国  凌嘉宣 《地球物理学报》2019,62(11):4437-4450

本文提出一种空间波数混合域磁异常场三维数值模拟方法.该方法利用磁位三维空间域积分为卷积的特点，沿水平方向进行二维傅里叶变换，把空间域磁位满足的三维积分问题转化为不同波数之间相互独立的垂向一维积分问题.保留垂向为空间域，优势之一在于便于浅层单元剖分可适当加密，随着深度增加，单元剖分适当稀疏，可以准确模拟任意复杂地形和磁性体的磁异常，兼顾了计算精度与计算效率；优势之二在于一维积分垂向可离散为多个单元积分之和，每个单元采用二次形函数表征磁化强度，可得出单元积分的解析表达式，计算精度高、效率高.该方法充分利用一维形函数积分的高效和高精度、快速傅里叶变换的高效性及算法高度并行性，实现了磁异常场高效、高精度的数值模拟.设计棱柱体模型，将模型解析解与空间波数混合域法的数值解对比，结果表明该方法计算精度高、效率高.设计了组合棱柱体复杂模型，对比分析了标准FFT扩边法与Gauss-FFT法的计算精度与计算效率，总结了标准FFT的扩边系数选取策略.针对任意复杂地形条件下的磁异常模拟问题，本文提出一种适用于起伏地形条件下的磁异常场快速计算方法，并对其有效性进行了验证.  相似文献