The use of cartographic control points in the harmonization and revision of MRDBs

The main purpose of the research is to achieve fully automated approach for supplying multi-resolution databases with linear objects in each scale. Moreover, the proposed solutions maintain the repeatability and accuracy of output data wherever possible according to the input scale. These properties are achieved by keeping the minimal object dimensions as well as the appropriate data pre-processing, based on the classification of source points. The classification distinguishes three classes of points: constant (unchangeable), temporary, and inherited. These classes build a structure of cartographic control points. Based on these solutions, the authors proposed an algorithm for linear object simplification based on minimal object dimensions and cartographic control points. It was also confirmed that the simplification between constant points does not cause geometry discrepancies in relation to the global simplification of the whole line.     

基于面片裁切技术的点云轮廓线生成算法

随着点云在各个领域的广泛应用,对点云处理相关技术的研究更为活跃。目前,研究的热点主要集中在点云去噪、配准、分割、增强、特征提取和重建等方面。其中,特征提取起着承前启后的作用,具有十分重要的研究价值。基于面片裁切技术的点云轮廓线生成算法。首先,对点云数据进行面片提取,通过面片生长、融合生成特征面片,并根据提出的面片双向索引法快速构造特征线,最终实现点云平面轮廓线的生成。实验证明,本算法可快速、准确、有效地实现点云轮廓线的生成。     

盛夏苏北地区一次飑线过程的数值模拟研究

对一次盛夏苏北飑线过程采用区域三重嵌套WRF模式进行了数值模拟和结果分析,给出了飑线径向剖面的概念模型图。结果表明:模拟的飑线与实际飑线非常接近,两者具有相同的性质和特点,利用模拟的线状强降水带及其降水强度来确定模拟飑线的位置和强度是可行的。飑线成熟期,飑线处存在强辐合区、强垂直上升运动区以及假相当位温的高值区,三者均呈柱状向上伸展;飑线前方(飑线移动的方向),低层有位温高值的入流,为飑线带入大量水汽和能量,后方低层有浅薄入流;飑线过境时地面风向发生急剧变化;飑线中层位温值大致不变呈中性层结,这与对流凝结潜热释放有关。该飑线过程可大体看成是假绝热过程,并具有重力波的非平衡性质,其生成演变中存在多尺度的相互作用。     

涌浪对风浪能量影响的实验研究

在实验室风浪水槽中进行纯风浪和混合浪波面位移观测,研究波长较长的规则波对风浪能量的影响.本文用混合浪和纯风浪中的风浪显著波的零阶谱矩之比代表混合浪中的风浪与纯风浪能量之比,并以此表征涌浪对风浪能量的影响.研究了该能量比随涌浪波陡S、风区x、波龄倒数u/C、涌浪频率与纯风浪谱峰频率之比fs/fwp的变化规律.结果表明,涌浪对风浪能量的抑制作用随涌浪波陡的增加、波龄倒数的增大及涌浪频率与纯风浪谱峰频率之比的增大而增强.发现该能量比依赖于无因次量R=(1+80(πS)2)1.9(fs/fwp)0.9(u/C)0.27,并拟合得到2者的经验关系.此外,本文实验还发现,在某些情况下,涌浪的存在使风浪能量增加.     

改进的Hough变换在机场跑道检测中的应用

提出了一种改进的Hough变换方法用于机场跑道的检测。传统Hough变换存在计算量大等缺陷,本文利用直线边缘的梯度相位信息把Hough变换中θ的取值限定在一个较小的范围内,同时减少用于计算的像素点数,大大降低了计算量。通过实验证明了本文方法切实可行。     

基于线段的基本线/线拓扑关系计算

空间拓扑关系是空间数据建模、空间查询、分析、推理、制图综合、数据质量控制、数据更新等的基础。目前空间拓扑关系研究的主要成果仍然集中在拓扑关系的描述方面,在计算方面的阐述都非常薄弱,不足以指导系统开发人员编程实现。本文研究了IR2中两个简单线目标间拓扑关系的计算方法,重点分析了线/线拓扑关系计算的特点,提出了一种基于线段的线/线拓扑关系计算方法,并用VC＋＋采用底层开发模式实现了基本线/线拓扑关系的计算。     

海洋磁力测量中测线方向的选择方法

采用测线间磁异常插值精度分析了测线方向对磁测的影响;探讨了测线方向的选择方法,结合我国不同海区磁异常分布特征给出了不同海区测量时测线方向的选择详细方案。结论表明:海洋磁力测量中,测线方向对磁异常插值精度的影响不大,但是为了获得更高的磁异常插值精度,测线方向应尽量沿磁异常梯度方向布设。给出的测线方向的选择方法和我国不同海区测线方向选择详细方案可供作业人员参考。     

The oxygen isotope composition of water masses within the North Sea

Based on measurements of the ¹⁸O isotope composition of 247 samples collected over a 3-year period we have assessed the oxygen isotope composition of water masses in the North Sea. This is the first δ¹⁸O data set that covers the entire North Sea basin. The waters lie on a mixing line: δ¹⁸O (‰_VSMOW) = −9.300 + 0.274(S) with North Atlantic sub-polar mode water (SPMW) and surface waters, and Baltic Sea water representing the saline and freshwater end members respectively. Patterns exhibited in surface and bottom water δ¹⁸O distributions are representative of the general circulation of the North Sea. Oxygen-18 enriched waters from the North Atlantic enter the North Sea between Scotland and Norway and to a lesser extent through the English Channel. In contrast, oxygen-18 depleted waters mainly inflow from the Baltic Sea, the rivers Rhine and Elbe, and to a lesser degree, the Norwegian Fjords and other river sources. Locally the δ¹⁸O–salinity relationship will be controlled by the isotopic composition of the freshwater inputs. However, the range of local freshwater compositions around the North Sea basin is too narrow to characterise the relative contributions of individual sources to the overall seawater composition. This dataset provides important information for a number of related disciplines including biogeochemical research and oceanographic studies.     

Distinct activity phases during the recent geologic history of a Gulf of Mexico mud volcano

Laser line scan imaging and chirp sub-bottom profiling were used to detail the morphology of a submarine mud volcano and brine-filled crater at 652 m water depth in the northern Gulf of Mexico. The mud volcano has a relief of 6 m and a basal diameter of about 80 m. The feature comprises a central, brine-filled crater (253 m²) surrounded by a continuous bed of methanotrophic mussels (Bathymodiolus childressi) covering 434 m² and a patchy bed covering an additional 214 m² of the periphery. The brine pool was mostly <2 m deep, but there were two holes of >28 m and 12 m deep, respectively at the northern end of the pool which emitted continual streams of small clear bubbles. Sub-bottom profiles indicated three distinct strata beneath the present surface of the mud volcano. Integration of 17 profiles shows that the mud volcano has been built in at least three successive stages: the lowest stage deposited 35,400 m³, while the middle and upper stages deposited 7700 and 20,400 m³, respectively. Piston cores were taken at the northern edge of the mussel bed and a site ∼100 m southwest of the pool. Mussel and lucinid shells were recovered from the closer core, lucinid shells from the distant core. A mussel shell from 3.4 m sub-bottom had a Δ¹⁴C age of 16.2 ka. Mixture of modern carbon with “carbon dead” reservoir material would produce actual ages ∼2 ka less than the radiocarbon ages.     

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