基于直方图的遥感图像相似性检索方法比较

相似性度量是用于研究多源数据之间相似程度的，是对空间数据进行模式识别的基础。通过单波段遥感图像的检索对两组直方图相似性检索方法进行了实验研究，即基于特征向量的相似性度量和基于概率的相似性度量。实验中发现第一组相似度量中有两种以往较少用于遥感图像检索的方法表现出色，它们分别是，统计距离和相似夹角余弦度量。第二组实验中，针对其中包含较明显的目标物体且背景较为单一的遥感图像（其直方图可看作混合高斯分布），在类别可分离判据的基础上，根据K-近邻法则提出了一种计算该类图像之间相似值的方法。实验结果表明基于K-近邻法则的计算方法行之有效。所得出的结论将对多源数据分析中相似性度量的理解与选择有积极意义。     

河西走廊春季强冻害成因及防御对策

应用酒泉、张掖、武威实况资料,从作物的各个生长发育期进行了对比分析,结果表明强冷空气爆发是造成冻害的直接原因,前期气温异常偏高使农作物生育期提前、气温和地温较低加剧了冻害程度。并提出了防御冻害发生的有效措施。     

地球物理灾害链有关物理问题的讨论

对地球物理灾害链的致灾机理,地震引起的放气范围、放气时间过程的计算方法,以及地气耦合致灾模式,进行了讨论和分析。分析结果认为,巨灾大都是多种因素迭加和强化的结果。由于单学科往往提出的致灾因素有限,所以预测效果不甚理想。要多学科从多种因素上去研究,才能改进大灾预测手段和方法,最后达到灾害链全链预测的目的。     

建筑物立面激光点云的定位

车载式近景目标3维测量系统,采用激光扫描仪获取建筑物立面点云。激光点云仅具有扫描仪坐标系下的坐标,不便于其他数据融合进行3维建模。文中根据系统的特点和要求,通过建立相应的坐标系,利用已有或优化的坐标转换模型确定坐标系之间的坐标转换关系。依据基准点与载体平台GPS接收机之间同步观测数据将激光点云在扫描仪坐标系下的坐标经过多次坐标转换,得到基准点所在当地坐标系下的坐标。使系统实现了满足精度要求的建筑物立面激光点云的定位工作。     

GPS动态数据处理中的快速Kalman滤波算法

根据GPS数据处理中的Kalman滤波状态转移矩阵和设计矩阵大量存在零元素的特点,将其构造成特定稀疏矩阵。再利用稀疏矩阵乘法,同时结合矩阵对称性、矩阵求逆降维等方法,可大大减少Kalman滤波的乘法次数。在非差C/A伪距情况下,该算法乘法总次数不到传统算法的1/3;在双差伪距P1,P2 双差载波情况下,该算法乘法总次数甚至不到1/6;其耗时也只有传统算法的1/3左右,因而大大提高了Kalman滤波的计算效率。     

一种面向对象的4层空间数据模型

针对“空间数据是否要建立拓扑关系并在数据库中显式地存储记录”一直是G IS领域争论的问题,给出了解决方案:融合拓扑关系数据模型和面向实体数据模型,进而在分析和总结现有数据模型的基础上提出了一种面向对象的4层空间数据模型。对模型作了4个层次划分:几何对象、基本和复杂要素、分层与分区以及多尺度表达。模型具有3个特点,即多尺度描述地理空间;能描述不同要素层、不同区之间的关系;用户可根据实际情况自定义要素层拓扑关系。最后给出了模型在自主开发的地理数据库管理平台Geoinfo中的应用情况。     

一种多前缘多阈值的波形重构算法

为了改善近海测高精度,本文对近海测高波形的特征进行了研究,并在现有算法的基础上提出基于波前缘识别算法的多前缘多阈值波形重构方法.然后将该方法用于中国近海的卫星测高波形数据的处理,得到精度与分辨率更好的海面高数据.作为验证,将此海面高数据换算为重力异常并与船测重力进行比较,结果显示该方法可以明显提高卫星测高精度.     

Automatic onset phase picking for portable seismic array observation

Automatic phase picking is a critical procedure for seismic data processing, especially for a huge amount of seismic data recorded by a large-scale portable seismic array. In this study is presented a new method used for automatic accurate onset phase picking based on the proporty of dense seismic array observations. In our method, the Akaike＇s information criterion （AIC） for the single channel observation and the least-squares cross-correlation for the multi-channel observation are combined together. The tests by the seismic array observation data after triggering with the short-term average/long-term average （STA/LTA） technique show that the phase picking error is less than 0.3 s for local events by using the single channel AIC algorithm. In terms of multi-channel least-squares cross-correlation technique, the clear teleseismic P onset can be detected reliably. Even for the teleseismic records with high noise level, our algorithm is also able to effectually avoid manual misdetections.     

Grain-size features of a Miocene loess-soil sequence at Qinan: Implications on its origin

In northern China, the Quaternary loess-soil se-quences[1] and the Hipparion Red-Earth Formation in the eastern Loess Plateau[2―6] provide a continental climate record for the past 8 Ma. The recently reported Miocene[7] and Pliocene[8] loess-soil sequences near Qinan constitute an eolian record of the western Loess Plateau from 22 to 3.5 Ma. Earlier studies[9] place the Miocene loess deposits into the so-called Gansu Sys-tem. Our investigations show that the Gansu System contains inde…     

δ18O record and temperature change over the past 100 years in ice cores on the Tibetan Plateau

The 213 m ice core from the Puruogangri Ice Field on the Tibetan Plateau facilitates the study of the regional temperature changes with its δ18O record of the past 100 years. Here we combine information from this core with that from the Dasuopu ice core (from the southern Tibetan Plateau), the Guliya ice core (from the northwestern Plateau) and the Dunde ice core (from the northeastern Plateau) to learn about the regional differences in temperature change across the Tibetan Plateau. The δ18O changes vary with region on the Plateau, the variations being especially large between South and North and between East and West. Moreover, these four ice cores present increasing δ18O trends, indicating warming on the Tibetan Plateau over the past 100 years. A comparative study of Northern Hemisphere (NH) temperature changes, the δ18O-reflected temperature changes on the Plateau, and available meteorological records show consistent trends in overall warming during the past 100 years.