利用模板阴影体算法实现矢量数据在三维场景中的绘制

提出了一种基于模板阴影体算法的矢量数据绘制方法,实现了矢量数据在三维场景中的高质量实时叠加显示。由于该方法基于屏幕空间,所以具有像素级的精度,不会出现传统的基于纹理方法所产生的绘制走样现象;而且不受地形几何数据的约束,其执行效率与地形数据的复杂度无关,仅取决于矢量数据本身的复杂度。详细论述了基于模板阴影体算法矢量数据绘制的关键技术,并通过试验验证了该方法的有效性。     

压力影构造类型及其剪切指向分析

改变了压力影构造传统的形态分类方法，提出了按压力影的生长方向与片理之间的关系及其本身形态特征进行分类的新方案。制定了相应的剪切指向判别法则，明确指出只有斜方对称平行压力影不具有剪切指向意义。同时，对压力影中矿物的生长习性和多世代压力影等问题进行了分析。对压力影构造的运动学和动力学进行了系统的讨论。较详细地介绍了应用压力影构造的剪切指向推断地质体运动方向的方法     

基于热红外遥感技术的腾冲地区地热异常区温度反演研究

我国云南腾冲地区地热资源丰富,对地热资源进行定量的预测评价势在必行。而以遥感为手段进行地表温度的反演是地热研究的重要方法。本文利用ETM数据的Band6热红外通道,对工作区进行温度反演并通过消除阴影影响对反演温度进行修正使得温度差异较大的情况得到改善,减少了太阳照射造成的温差影响。结果表明,研究区地表温度分布主要有3个区域;通过温度反演结果与已知地热点叠加分析,选取14~21℃为进行地热预测评价的有利区间。     

Worldview-Ⅱ遥感影像的阴影检测方法研究

针对HIS空间变换阴影检测方法仅利用三原色波段数据进行阴影检测而未考虑影像数据之间的相关性及冗余度这一问题,该文结合最佳指数法提出一种适用于多光谱的Worldview-Ⅱ遥感卫星影像阴影检测方法,并引进归一化水体差异指数剔除掉水体的干扰,构建出适用于阴影检测的波段指数模型。实验结果表明,该方法针对Worldview-Ⅱ影像具有普适性,且相对于利用三原色数据进行阴影检测方法能更有效地避免植被信息的干扰,能够精确、快速地检测阴影区域,对后期的阴影去除等研究具有重要的参考价值。     

Detecting shadows in multi-temporal aerial imagery to support near-real-time change detection

Multi-temporal aerial imagery captured via an approach called repeat station imaging (RSI) facilitates post-hazard assessment of damage to infrastructure. Spectral-radiometric (SR) variations caused by differences in shadowing may inhibit successful change detection based on image differencing. This study evaluates a novel approach to shadow classification based on bi-temporal imagery, which exploits SR change signatures associated with transient shadows. Changes in intensity (brightness from red–green–blue images) and intensity-normalized blue waveband values provide a basis for classifying transient shadows across a range of material types with unique reflectance properties, using thresholds that proved versatile for very different scenes. We derive classification thresholds for persistent shadows based on hue to intensity ratio (H/I) images, by exploiting statistics obtained from transient shadow areas. We assess shadow classification accuracy based on this procedure, and compare it to the more conventional approach of thresholding individual H/I images based on frequency distributions. Our efficient and semi-automated shadow classification procedure shows improved mean accuracy (93.3%) and versatility with different image sets over the conventional approach (84.7%). For proof-of-concept, we demonstrate that overlaying bi-temporal imagery also facilitates normalization of intensity values in transient shadow areas, as part of an integrated procedure to support near-real-time change detection.     

资源三号卫星高分影像的城市建筑物阴影提取

针对城市高分影像中普遍存在的建筑物阴影严重影响了高分影像的处理和应用问题,该文通过对资源三号卫星(ZY-3)各波段的影像特征进行分析,分别采用基于直方图的阈值分割法、基于主成分变换和HIS变换集成法对阴影提取并对比分析,在此基础上提出了一种基于谱间关系的阴影提取模型。实验结果表明,该文提出的方法能够较好地区分ZY-3影像中的阴影和偏蓝色地物及水体,能够准确地提取城市高大地物阴影。     

CISK, EVAPORATION-WIND FEEDBACK MECHANISM AND 30-60 DAY OSCILLATIONS IN THE TROPICAL ATMOSPHERE*

A baroclinic semi-geostrophic model with evaporation-wind feedback mechanism(EWFM) and CISK is established,two non-dimensional parameters a and η are introduced to represent EWFM and CISK,respectively.Analytic solutions of the model system are obtained,dynamics analyses and the model atmosphere calculations further confirm that EWFM and CISK are very important physical processes in leading to the low-frequency oscillations in the tropics.     

MODULATION OF MADDEN-JULIAN OSCILLATION ON TIBETAN PLATEAU VORTEX

This study uses NCEP/NCAR daily reanalysis data, NOAA outgoing long-wave radiation (OLR) data, the real-time multivariate MJO (RMM) index from the Australian Bureau of Meteorology and Tibetan Plateau vortex (TPV) data from the Chengdu Institute of Plateau Meteorology to discuss modulation of the Madden-Julian Oscillation (MJO) on the Tibetan Plateau Vortex (TPV). Wavelet and composite analysis are used. Results show that the MJO plays an important role in the occurrence of the TPV that the number of TPVs generated within an active period of the MJO is three times as much as that during an inactive period. In addition, during the active period, the number of the TPVs generated in phases 1 and 2 is larger than that in phases 3 and 7. After compositing phases 1 and 7 separately, all meteorological elements in phase 1 are apparently conducive to the generation of the TPV, whereas those in phase 7 are somewhat constrained. With its eastward propagation process, the MJO convection centre spreads eastward, and the vertical circulation within the tropical atmosphere changes. Due to the interaction between the mid-latitude and low-latitude atmosphere, changes occur in the baroclinic characteristics of the atmosphere, the available potential energy and eddy available potential energy of the atmosphere, and the circulation structures of the atmosphere over the Tibetan Plateau (TP) and surrounding areas. This results in significantly different water vapour transportation and latent heat distribution. Advantageous and disadvantageous conditions therefore alternate, leading to a significant difference among the numbers of plateau vortex in different phases.     

连续局部阈值分割的阴影检测方法

遥感图像中通常存在大量的阴影,阴影会对图像分割、目标识别造成一定的影响,阴影检测是阴影去除的基础。针对传统Tsai算法准确度上不足,提出了一种改进方法。首先,采用chuang所提出的方法定制了新的比例图,通过对定制比例图进行全局阈值分割将输入图像分为候选阴影点与非阴影点;再对大致阴影图中的每一个候选阴影区进行迭代分割处理来从候选阴影点中挑选出真正的阴影点;剩下的每一个候选阴影点进行fine-shadow判断处理。实验证明,改进算法可以提高阴影检测的准确性。     

HSV变换和多尺度分割相结合的高分辨率遥感影像阴影检测

针对阴影在高分辨率遥感影像的特性,提出了一种色彩空间变换和多尺度分割相结合的阴影检测方法。该方法首先对原始影像进行连续两次HSV变换,并分别提取前后两次变换的亮度分量和色度分量;然后引入面向对象思想,进行多个尺度的影像分割并依次实现每一尺度下的阴影检测;最后将多个尺度的检测结果进行决策级融合获取最终检测结果。利用高分二号和Google Earth影像分别进行实验,实验结果表明,该方法有效结合了粗细尺度优势,阴影检测误检率和漏检率较低,同时对较亮阴影和较暗地物均具备较好的识别效果。