在天气图传真信号数字化中的几个问题

本文讨论在天气图传真信号数字化中,通过适当限制取样点密度和线条粗细以控制图像复制质量,并简单介绍解决上述问题的实验装置。     

Comparison and integration of spatial data using covariance matrices

A differential approach to map comparison and integration is presented utilizing the variance-covariance matrices of polynomial trend surfaces. The approach is based on the statistics presented in the trend-surface computer program, CORSURF. Examples in south-central Kansas and the Maracaibo Basin in Venezuela are presented to show how the technique could be used in basinanalysis studies.     

Second Species Periodic Orbits of the Elliptic 3 Body Problem

We consider the plane restricted elliptic 3 body problem with small mass ratio and small eccentricity and prove the existence of many periodic orbits shadowing chains of collision orbits of the Kepler problem. Such periodic orbits were first studied by Poincaré for the non-restricted 3 body problem. Poincaré called them second species solutions.     

中国天山积雪站区的雪崩制图

中国天山是我国积雪丰富、雪崩频繁、灾害性雪崩又具明显周期性的山地。作者以雪崩制图的非变化因素(地形形态)为主,提出了中国天山积雪站区雪崩路径分布图与雪崩分带(区划)图,并作了概略说明。这为当地的土地合理利用、山区道路与矿山建设、雪崩治理提供了科学依据。     

Automatic change detection in lane-level road networks using GPS trajectories

Lane-level road network updating is crucial for urban traffic applications that use geographic information systems contributing to, for example, intelligent driving, route planning and traffic control. Researchers have developed various algorithms to update road networks using sensor data, such as high-definition images or GPS data; however, approaches that involve change detection for road networks at lane level using GPS data are less common. This paper presents a novel method for automatic change detection of lane-level road networks based on GPS trajectories of vehicles. The proposed method includes two steps: map matching at lane level and lane-level change recognition. To integrate the most up-to-date GPS data with a lane-level road network, this research uses a fuzzy logic road network matching method. The proposed map-matching method starts with a confirmation of candidate lane-level road segments that use error ellipses derived from the GPS data, and then computes the membership degree between GPS data and candidate lane-level segments. The GPS trajectory data is classified into successful or unsuccessful matches using a set of defuzzification rules. Any topological and geometrical changes to road networks are detected by analysing the two kinds of matching results and comparing their relationships with the original road network. Change detection results for road networks in Wuhan, China using collected GPS trajectories show that these methods can be successfully applied to detect lane-level road changes including added lanes, closed lanes and lane-changing and turning rules, while achieving a robust detection precision of above 80%.     

Comparing historical and contemporary maps - a methodological framework for a cartographic map comparison applied to Swiss maps

Topographic maps are powerful tools for the purpose of identifying land use and cover change (LUCC) as they are among the most reliable representations of past landscapes for the time prior to the existence of aerial photography. In light of the increased availability of historical maps, we argue that there is a need for a standardized process to assess map comparability in a systematic way in order to avoid, or at least minimize, the detection of spurious landscape changes due to incompatible map series. A full understanding of map quality, background and error distributions is fundamental to attain reliable LUCC results. The conceptual framework presented in this study considers the context, distortion and cartographic generalization of topographic maps. Furthermore, it includes an approach to homogenize the level of generalization of landscape elements (e.g. forests) from maps with different scales. To demonstrate its application, we assessed the comparability of seven topographic maps from Canton Zurich covering a time span of 336 years (1664–2000). Overall, for the maps of Canton Zurich, a wall-to-wall comparison of forest cover based on the topographic maps presented here can be problematic for the oldest map from 1664. Based on the results, a wall-to-wall comparison with the later maps is not recommended, due to its substantial distortion. Yet, after re-generalization of natural landscape elements, such as forests, a comparison based on landscape indices is possible, even for the oldest map. Furthermore, our results demonstrate that maps from the mid-19^th century onward possess an acceptable level of accuracy. This framework can be applied to a wide range of maps at regional, national, or global levels, providing the opportunity to look at land cover history over multiple centuries.     

一种由粗到精的光学与SAR遥感图像配准算法

由于光学遥感图像和SAR图像具有明显的非线性强度差异,且SAR图像存在斑点噪声,使得其配准存在较大难度。为此,本文结合基于特征和基于区域图像配准方法的优点,并组合为混合模型,提出一种由粗到精的自动配准算法。以光学遥感图像和SAR图像分别为参考图像和待配准图像,先以基于特征点的SAR-SIFT完成粗配准,再以基于区域的ROEWA-HOG完成精配准。① 采用SAR-SIFT算法进行特征点检测和特征匹配来计算图像的仿射变换模型,以消除参考图像和待配准图像之间明显的旋转、尺度和平移差异,至此完成图像粗配准;② 在此基础上利用分块Harris角点检测在参考图像上获得特征点,并根据特征点确定待配准图像上的同名点搜索区域;③ 计算图像的ROEWA梯度,构造以特征点为中心的模板区域内的HOG特征向量,以SSD作为相似性测度搜索待配准图像上的同名点,完成高精度的图像配准;④ 进行图像配准实验,对配准结果进行目视检查和精度评估。经过多组光学与SAR图像配准实验,验证本文算法能够结合基于特征和基于区域的图像配准方法的优点,较好地抵抗光学与SAR图像之间的非线性强度、旋转、尺度、平移差异和SAR图像的噪声影响,并逐步提高配准精度,最终配准精度达到1个像素左右,实现了光学与SAR图像的高精度自动配准,能够满足光学与SAR图像后续综合应用。     

多模型协同下的城郊地区DEM构建方法研究

人类活动对地表的改造使其呈现形态多样化、不连续等特征,此时传统的DEM构建方法难以满足这些区域DEM精度要求。为此,本文提出了一种多模型协同构建DEM的思路,首先按照形态特征和语义信息对地形进行分类,然后对不同类型的地形区域,选择、设计适宜的方法分别进行DEM构建,最后将不同区域构建DEM结果融合拼接形成区域完整的DEM结果。本文选择江苏省南京市城市郊区某区域为实验区,以1:500比例尺地形图为基本数据源进行DEM构建实验。实验结果表明,与传统经典DEM构建方法相比,本文提出的多模型协同的DEM构建方法能够有效表达实验区域不同的地形特征,特别是对于人工改造的地形(如道路、边坡等区域),本文方法构建的DEM其形态精度优势显著;同时,基于验证点法的高程精度分析结果表明,本文方法构建DEM的高程精度亦优于传统DEM构建方法,特别是对于一些形态规则而高程信息相对稀少的区域,以边坡区域为例,经典DEM构建法平均误差均超过5 m,而本文构建结果平均误差为0.26 m,精度优势非常明显。研究表明本文提出的多模型协同的DEM构建方法适用于人类活动改造或显著影响的区域的DEM构建。     

盆地构造图三维可视化系统开发的实例介绍

传统的二维构造图难于直观地描述地质构造的空间形态。综合利用VB、VC和OPENGL环境设计的盆地构造图三维可视化系统将构造图上涉及的要素分成点、线、面、区等不同类型,每个类型数据又都由空间数据和属性数据两部分组成,并用数据库方式管理这些数据。系统除了可将各构造要素以三维方式显示外,还可以利用测井数据和剖面图恢复三维地层;同时允许用户与屏幕图形进行交互,从而实现对图形的切割操作。显示成果可以以栅格图形或AVI录像形式输出。通过几个用该系统输出的三维构造图的实例说明该系统基本能满足盆地构造图三维显示的需要。     

Application of the EnKF and Localization to Automatic History Matching of Facies Distribution and Production Data

The performance of the ensemble Kalman filter (EnKF) for continuous updating of facies location and boundaries in a reservoir model based on production and facies data for a 3D synthetic problem is presented. The occurrence of the different facies types is treated as a random process and the initial distribution was obtained by truncating a bi-Gaussian random field. Because facies data are highly non-Gaussian, re-parameterization was necessary in order to use the EnKF algorithm for data assimilation; two Gaussian random fields are updated in lieu of the static facies parameters. The problem of history matching applied to facies is difficult due to (1) constraints to facies observations at wells are occasionally violated when productions data are assimilated; (2) excessive reduction of variance seems to be a bigger problem with facies than with Gaussian random permeability and porosity fields; and (3) the relationship between facies variables and data is so highly non-linear that the final facies field does not always honor early production data well. Consequently three issues are investigated in this work. Is it possible to iteratively enforce facies constraints when updates due to production data have caused them to be violated? Can localization of adjustments be used for facies to prevent collapse of the variance during the data-assimilation period? Is a forecast from the final state better than a forecast from time zero using the final parameter fields?To investigate these issues, a 3D reservoir simulation model is coupled with the EnKF technique for data assimilation. One approach to enforcing the facies constraint is continuous iteration on all available data, which may lead to inconsistent model states, incorrect weighting of the production data and incorrect adjustment of the state vector. A sequential EnKF where the dynamic and static data are assimilated sequentially is presented and this approach seems to have solved the highlighted problems above. When the ensemble size is small compared to the number of independent data, the localized adjustment of the state vector is a very important technique that may be used to mitigate loss of rank in the ensemble. Implementing a distance-based localization of the facies adjustment appears to mitigate the problem of variance deficiency in the ensembles by ensuring that sufficient variability in the ensemble is maintained throughout the data assimilation period. Finally, when data are assimilated without localization, the prediction results appear to be independent of the starting point. When localization is applied, it is better to predict from the start using the final parameter field rather than continue from the final state.