Characterizing the Spatio-temporal Dynamics and Variability in Climate Extremes over the Tibetan Plateau during 1960-2012

Extreme climate events play an important role in studies of long-term climate change. As the Earth’s Third Pole, the Tibetan Plateau (TP) is sensitive to climate change and variation. In this study on the TP, the spatiotemporal changes in climate extreme indices (CEIs) are analyzed based on daily maximum and minimum surface air temperatures and precipitation at 98 meteorological stations, most with elevations of at least 4000 m above sea level, during 1960-2012. Fifteen temperature extreme indices (TEIs) and eight precipitation extreme indices (PEIs) were calculated. Then, their long-term change patterns, from spatial and temporal perspectives, were determined at regional, eco-regional and station levels. The entire TP region exhibits a significant warming trend, as reflected by the TEIs. The regional cold days and nights show decreasing trends at rates of -8.9 d (10 yr)^-1 (days per decade) and -17.3 d (10 yr)^-1, respectively. The corresponding warm days and nights have increased by 7.6 d (10 yr)^-1 and 12.5 d (10 yr)^-1, respectively. At the station level, the majority of stations indicate statistically significant trends for all TEIs, but they show spatial heterogeneity. The eco-regional TEIs show patterns that are consistent with the entire TP. The growing season has become longer at a rate of 5.3 d (10 yr)^-1. The abrupt change points for CEIs were examined, and they were mainly distributed during the 1980s and 1990s. The PEIs on the TP exhibit clear fluctuations and increasing trends with small magnitudes. The annual total precipitation has increased by 2.8 mm (10 yr)^-1 (not statistically significant). Most of the CEIs will maintain a persistent trend, as indicated by their Hurst exponents. The developing trends of the CEIs do not show a corresponding change with increasing altitude. In general, the warming trends demonstrate an asymmetric pattern reflected by the rapid increase in the warming trends of the cold TEIs, which are of greater magnitudes than those of the warm TEIs. This finding indicates a positive shift in the distribution of the daily minimum temperatures throughout the TP. Most of the PEIs show weak increasing trends, which are not statistically significant. This work aims to delineate a comprehensive picture of the extreme climate conditions over the TP that can enhance our understanding of its changing climate.     

城市街区地物的分类识别

"数字中国"、"数字城市"已经成为现代测绘的重点工作,LiDAR测量与数据处理就是其技术根本之一,为三维建模提供了便捷方式。三维建模的主要目标就是进行城市街区地物分类。根据LiDAR点云的不同几何特征讨论了对不同地物进行分类的各种方法。     

LiDAR点云的建筑物立面空洞修复

针对树木等遮挡造成的车载LiDAR建筑物立面点云空洞,该文提出了一种基于机载和车载LiDAR数据融合的建筑物点云修复方法,即在空-地LiDAR点云融合的基础上,基于提取的机载LiDAR建筑物外轮廓线,通过缓冲区分析实现车载LiDAR建筑物点云分割;借助轮廓线信息实现了邻近建筑物间的相似性判断,基于匹配后的相似建筑物点云和空洞探测方法,实现了建筑物立面点云空洞修复。最后通过实验数据验证了该方法的可行性。     

基于全自动标定技术的环物摄影测量平台精度提升策略研究

针对传统的环物摄影测量设备精度不高的缺陷,本文在环物摄影测量法的基础上,提出了基于全自动标定技术的精度提升策略,并成功应用在自主研制的三维环物影像获取系统中.该策略克服了传统相机标定技术需要人工选点,耗时耗力的缺陷,同时有效的解决了环物摄影测量解算中,相机高精度空间参数定位的问题.因此,本文提出的方法可以在保证实时效率的前提下,提高环物摄影测量设备生产的三维数字化模型的精度,具有广泛的应用前景.     

改进SIFT特征描述符在影像匹配中的应用研究

由于成像条件变化造成的遥感图像之间的几何形变和灰度差异给影像匹配带来了困难,深入研究了SIFT特征描述符的生成方法,针对SIFT特征维数过高的问题进行改进,利用特征点邻域的圆形区域构造新的描述符,增强了描述符自身的抗旋转性,并降低了特征描述符的维数。实验表明,改进的特征描述符是可行有效的,在遥感影像目标匹配中取得满意的实验结果。     

高频GPS动态监测地表形变的试验与研究

设计了位移形变模拟试验场并进行位移形变模拟试验,利用Bernese 5.0软件的单历元单点定位功能,处理并分析了位移模拟形变试验获取的1 Hz GPS数据.并以2008年5月12日汶川地震为例,获取了震中附近3个GPS站(成都、简阳和郫县)震前的短临位移过程及震后短时间的动态时变序列,结果显示各站的形变结果在时间上具有很好的一致性.利用动态时序的地震波到时和震中距离估计地震波地壳平均速度为3.17 km/s.     

广义点摄影测量在建筑物立面轮廓重构中的应用

采用广义点摄影测量理论对建筑物立面框架轮廓进行重构。广义点是对当代线摄影测量以及无穷远点（灭点）理论的升华。实验结果表明,采用线面基元进行立面重构相比于经典的点云重构方法,不仅简洁、高效,还能获得清晰的三维边缘轮廓,且自动化程度较高。     

渤、黄、东海M2和K1分潮潮流场的有限元模拟

使用有限元模式(QUODDY)数值模拟了渤、黄、东海浅水区的M2和K1分潮潮流场。对于M2分潮潮流场,东分量和北分量的潮流调和常数与16个测站观测资料的平均绝对误差分别为8.23 cm/s,23.74°();7.36 cm/s,27.78(°)。对于K1分潮潮流场,则分别为8.39 cm/s,36.48(°);9.40 cm/s,38.04(°)。文中得到的M2分潮流在模拟海区共有9个圆流点(秦皇岛附近1个,莱州湾口1个,山东半岛北部海域2个,黄海北部2个,苏北辐射沙洲的外侧1个,舟山群岛东南海域2个)。K1分潮流在模拟海域也存在9个圆流点(秦皇岛附近1个,莱州湾口1个,北黄海2个,南黄海1个,苏北辐射沙洲的外侧1个,济州岛东南海域3个),其中黄海北部偏北的圆流点(39°25′N,123°05′E)和济州岛东南海域最东南的圆流点(32°50′N,127°50′E)以前未见过报道。     

一种基于SX10点云的单株树木骨架点提取方法

骨架点是单株树木几何模型重建的基础。本文结合水平集、聚类方法和图论3种方法,采用ILMSVP和天宝SX10获取模拟与实测单株树木点云数据,并实现单株树木骨架点提取,其中模拟数据用于方法实现,实测数据用于验证。为解决单株树木点云数据缺失情况,本文重复利用水平集、聚类方法和图论方法得到较完整的单株树木骨架点。结果表明:本文采用的单株树木骨架点提取方法可行。     

利用TLS技术与伪单点监测模式进行滑坡变形测量

针对传统离散点监测模式不适用于TLS变形监测,以及现有基于TLS技术变形监测的一维性与仅适用于特定几何对象分析等不足,本文提出了一种基于TLS技术的伪单点变形监测模式,并基于该监测模式提出了一种以表面匹配技术为核心的变形计算新方法.通过构建广义高斯-马尔可夫模型匹配搜索估计伪单点对象的全三维变形参数,利用TLS多期点云...