采用复合整数变换差值扩大法的矢量地图可逆水印算法

现有的二维矢量地图可逆水印算法没有充分考虑原始地图的形状特征,其有效信息嵌入率较低,水印嵌入带来的失真较大,为此提出一种有效的二维矢量地图可逆水印算法.该算法考虑二维矢量地图的结构特点和形状特征,利用矢量地图曲线和曲面坐标序列固有的分段单调性来构造多维向量;对多维向量实施复合差值扩大可逆变换,将水印嵌入引入的误差由多个数据点共同承担,使得每个数据点所承受的误差更均匀,避免了在矢量地图单调转折区因水印嵌入带来较大的失真,使矢量地图能承载更多的有效信息;通过设定矢量地图的误差容限来保证精度,可有效地控制信息的嵌入大小.理论分析和实验结果表明,该算法具有较好的透明性和较高的有效信息载荷,可用于矢量地图认证和隐秘通信等领域.     

Real-time GPS track simplification algorithm for outdoor navigation of visually impaired

Outdoor navigation of visually impaired people most often is based on data from the GPS maps and Geographic Information Systems (GIS). Such systems cannot be used for navigation in the regions where there are not any GPS maps or the maps are not sufficiently precise and detailed. This article describes an algorithm for real-time GPS track simplification. The test results show that the proposed algorithm (RSTS) has efficiency similar to the Douglas–Peucker algorithm, which is regarded as the best for track simplification. The reduction of the number of points in different transportation modes, while keeping the shape of the route, is over 90%. The size of the file describing the track is reduced more than 30 times. The algorithm finds the critical points of the route. This allows for navigation along the track so conversion of track to route is not needed. The algorithm is part of a low cost and widely accessible Java 2 Mobile Edition (J2ME) application for navigation of visually impaired.     

Winter and spring surface velocity fields in the Cape Blanc region as deduced with the maximum cross-correlation technique

The ocean surface velocity field in the Cape Blanc region, off Northwest Africa, is investigated with the maximum cross-correlation (MCC) method applied to channel-4 Advanced Very High Resolution Radiometer satellite images. An initial sensitivity analysis allows us to select the four parameters that provide maximum area coverage and the best velocity resolution, while limiting the standard deviation for each velocity component within reasonable values. These are (m, n, MV, CT)?=?(22, 32, 50, 0.6), where m and n are the number of pixels of the search window (SW) and reference window (RW), respectively, MV is the maximum possible velocity (in cm s^?1), and CT is a correlation threshold for a feature to be tracked. A total of 489 images, for years 2005 and 2006, are analysed, and 106 velocity maps are generated with good coverage of the coastal transition zone (CTZ), most of them for the winter (34) and spring (59) seasons. We remove spurious data using the method's own filters (MV, CT, and a neighbour-vector comparison), requesting the velocity components to have Gaussian distributions and smoothing the resulting velocity fields with a median-vector filter. The instantaneous velocity maps illustrate the response of the alongshore coastal jet north of Cape Blanc (and its extension along the Cape Verde frontal region) to wind forcing, as well as the presence of numerous mesoscalar features (100–300 km wide) superposed on a westward offshore transport south of Cape Blanc. We also produce mean and standard deviation winter and spring velocity maps, which are compared with the corresponding mean sea surface temperature fields. The along-shore and offshore flow is better defined and is more intense in spring than in winter, in concordance with cross-slope sharper temperature gradients during this season, and brings about a cooling of the whole region. We identify five different ubiquitous currents: a southwestward jet north of Cape Blanc, a northwestward jet off Banc d'Argin, an offshore convergent jet, a spring jet-like feature at 18° N, and a southward flow in the southwestern CTZ.     

Assessing pre- and post-deformation in the southern Arava Valley segment of the Dead Sea Transform, Israel by differential interferometry

Differential radar interferometry, using archived ERS data over the region of the Dead Sea Transform, allows to detect ground movement (subsidence or uplift) in playas within the southern Arava Valley segment of the Dead Sea Rift. These measurements are consistent with a mean displacement rate of about 0.4 cm/month, in the direction of the radar beam, during the 8-month period preceding the Nuweiba earthquake of 22 November 1995. In the 3 years following the earthquake, the measured rate was smaller by a factor of 10. These movements are not related to salt diapirs or water pumping activities in the area. The exact location, along faults, suggests a possible correlation with pre-seismic and post-seismic fault deformation.A simple fault model consistent with the observed phenomena associates the observed subsidence/uplift to right and left stepping en-echelon fault patterns related to inter-seismic tensional accumulation along the faults. Further observations are necessary on this site and similar fault areas to corroborate the correlation between seismic activity and the observed phenomena. Monitoring of these sites should continue with differential Global positioning system (GPS) measurements and radar interferometric analysis using Envisat and Radarsat as well as archived data (including J-ERS).     

Application of the SBAS-DInSAR technique to fault creep: A case study of the Hayward fault, California

We present a quantitative assessment of the capability of the differential SAR interferometry (DInSAR) technique referred to as Small BAseline Subset (SBAS) approach to investigate fault creep phenomena. In particular we have computed, via the SBAS-DInSAR algorithm, time series of the surface displacements relevant to the Hayward fault zone, within the San Francisco Bay Area (California), from the European Space Agency's ERS-1/2 satellite radar data for the 1992 to 2000 time period. Starting from the DInSAR time series we measured the relative displacements across the fault with no need for any atmospheric filtering step. These results have been systematically compared to the measurements available from the alignment arrays that are located along the fault. Our analysis shows that the standard deviation of the differences between the DInSAR and the in situ measurements is on the order of 2 mm. Moreover, the estimated mean deformation rates have an accuracy that is better than 1 mm/year.     

基于等高线的三维真实感地形系统设计

基于等高线的三维真实感地形系统,首先把等高线地形图扫描进计算机,然后利用ERSI公司的GIS软件Arc/Info跟踪等高线生成矢量化的等高线数据,并根据得到的数据建立三维规则数据场生成三维地形模型。最后利用VC++6.0编程工具和OpenGL编程接口生成具有真实感的三维地形。实践证明该方法简单、实用。     

SSPX: A program to compute strain from displacement/velocity data

SSPX is a Macintosh, Cocoa/Universal application to compute strain from displacement/velocity data in two and three dimensions. SSPX solves small and large deformation problems, in either the undeformed (Lagrangian) or deformed (Eulerian) configuration. The program offers several options to compute strain: best fit for all or selected data, strain at a point, strain at stations, Delaunay, grid-nearest neighbor, and grid-distance weighted. Except for the strain at stations option in 3D, the program computes the strain on a surface that is either flat (slice) or that follows the topography of the data. In the case of a slice and in 3D, the location and orientation of the slice can be varied to visualize the strain along horizontal or vertical east–west, north–south sections. SSPX plots strain in a 2D view (3D strain is displayed as stereonets). We show the application of the program to GPS data, analogue and DEM mechanical simulations.     

模板阴影体扩展方法

模板阴影体是矢量地图3维绘制的一种主要方法,使用线段、多边形等基本的几何图形在3维地形上叠加显示地图要素,因表示形式过于简单,导致其传递的地图要素信息十分有限。为此,对模板阴影体方法进行扩展,提出矢量地图在3维地形上的符号化叠加方法,以提供更丰富的矢量地图3维显示样式。首先,简述基于模板阴影体绘制矢量数据的基本原理。然后,提出对模板阴影体的扩展,包括保持符号边缘光滑的算法和符号轮廓描边、交叉压盖的处理方法。实验结果表明,该扩展方法能够实现矢量地图在3维地形上的实时叠加显示,符号化绘制显著提高了矢量地图显示效果。     

AFNI: Software for Analysis and Visualization of Functional Magnetic Resonance Neuroimages

A package of computer programs for analysis and visualization of three-dimensional human brain functional magnetic resonance imaging (FMRI) results is described. The software can color overlay neural activation maps onto higher resolution anatomical scans. Slices in each cardinal plane can be viewed simultaneously. Manual placement of markers on anatomical landmarks allows transformation of anatomical and functional scans into stereotaxic (Talairach–Tournoux) coordinates. The techniques for automatically generating transformed functional data sets from manually labeled anatomical data sets are described. Facilities are provided for several types of statistical analyses of multiple 3D functional data sets. The programs are written in ANSI C and Motif 1.2 to run on Unix workstations.     

Probabilistic terrain classification in unstructured environments

Autonomous navigation in unstructured environments is a complex task and an active area of research in mobile robotics. Unlike urban areas with lanes, road signs, and maps, the environment around our robot is unknown and unstructured. Such an environment requires careful examination as it is random, continuous, and the number of perceptions and possible actions are infinite.We describe a terrain classification approach for our autonomous robot based on Markov Random Fields (MRFs ) on fused 3D laser and camera image data. Our primary data structure is a 2D grid whose cells carry information extracted from sensor readings. All cells within the grid are classified and their surface is analyzed in regard to negotiability for wheeled robots.Knowledge of our robot’s egomotion allows fusion of previous classification results with current sensor data in order to fill data gaps and regions outside the visibility of the sensors. We estimate egomotion by integrating information of an IMU, GPS measurements, and wheel odometry in an extended Kalman filter.In our experiments we achieve a recall ratio of about 90% for detecting streets and obstacles. We show that our approach is fast enough to be used on autonomous mobile robots in real time.     

Examining runner's outdoor heat exposure using urban microclimate modeling and GPS trajectory mining

It is important to quantify human heat exposure in order to evaluate and mitigate the negative impacts of heat on human well-being in the context of global warming. This study proposed a human-centric framework to examine human personal heat exposure based on anonymous GPS trajectories data mining and urban microclimate modeling. The mean radiant temperature (T_mrt) that represents human body's energy balance was used to indicate human heat exposure. The meteorological data and high-resolution 3D urban model generated from multispectral remotely sensed images and LiDAR data were used as inputs in urban microclimate modeling to map the spatio-temporal distribution of the T_mrt in the Boston metropolitan area. The anonymous human GPS trajectory data collected from fitness Apps was used to map the spatio-temporal distribution of human outdoor activities. By overlaying the anonymous GPS trajectories on the generated spatio-temporal maps of T_mrt, this study further examined the heat exposure of runners in different age-gender groups in the Boston area. Results show that there is no significant difference in terms of heat exposure for female and male runners. The female runners in the age of 45–54 are exposed to more heat than female runners of 18–24 and 25–34, while there is no significant difference among male runners. This study proposed a novel method to estimate human heat exposure, which would shed new light on mitigating the negative impacts of heat on human health.     

地质断层三维可视化模型的构建方法与实现技术

全面而系统地研究了地质断层三维可视化构模的原理、方法及实施过程.针对地质断层三维构模的特点与要求,设计了一种基于边界表示、面向地质实体并兼顾拓扑关系的三维矢量数据模型,以有效地组织和描述包含断层的复杂地质体几何结构模型.提出了断层与地层的统一构模技术,给出了在其实现过程中所遇到的关键问题(如断层面的推演拟合、地层层面重构、断层与地层的交切处理与局部重构)的解决方案.基于断层的属性、断层数据所反映的断层面的特征和质量,应用3种方法来拟合断层面.在地层层面重构时,考虑到了断层面在地层面网格加密、插值时的约束和屏蔽作用,实现了具有多值面的逆断层网格生成技术.应用三角网切割算法TRICUT来实现断层与地层的交切处理.通过北京奥运公园场区基岩地质模型中的断层构模实例验证了这些技术方法的有效性.     

基于剖面拓扑的三维矢量数据自动生成算法研究

地学三维矢量数据生成长期以来一直是三维GIS研究中的一个难点,该文将传统二维GIS的拓扑关系引入到剖面数据中,提出了一种基于剖面拓扑关系的三维空间实体自动生成的算法,并提出了在该方法下断层问题的解决方案。     

Scalable 3D video of dynamic scenes

In this paper we present a scalable 3D video framework for capturing and rendering dynamic scenes. The acquisition system is based on multiple sparsely placed 3D video bricks, each comprising a projector, two grayscale cameras, and a color camera. Relying on structured light with complementary patterns, texture images and pattern-augmented views of the scene are acquired simultaneously by time-multiplexed projections and synchronized camera exposures. Using space–time stereo on the acquired pattern images, high-quality depth maps are extracted, whose corresponding surface samples are merged into a view-independent, point-based 3D data structure. This representation allows for effective photo-consistency enforcement and outlier removal, leading to a significant decrease of visual artifacts and a high resulting rendering quality using EWA volume splatting. Our framework and its view-independent representation allow for simple and straightforward editing of 3D video. In order to demonstrate its flexibility, we show compositing techniques and spatiotemporal effects.     

Deformation monitoring over large areas with multipass differential SAR interferometry: a new approach based on the use of spatial differences

Multipass differential synthetic aperture radar interferometry is becoming increasingly important as a powerful technique for ground deformation retrieval compared with classical geodetic techniques such as levelling and global positioning system (GPS). It proves superior in terms of costs, coverage, data accessibility and availability of historical archives. Application to different areas of risk management such as monitoring of volcanoes and slope instabilities, tectonic movements, urban areas and infrastructure, has already been successfully demonstrated. In this work we discuss a new multipass differential synthetic aperture radar interferometry processing technique that makes extensive use of spatial differences. The results obtained demonstrate that this technique allows the monitoring of ground deformation over wide areas. The processed data were acquired from ERS–1 and ERS–2 sensors over three partially overlapping tracks related to a region, approximately 240 km N–S and 80 km E–W wide, located in the centre‐south of Italy, along the west coast. Comparison of the mean deformation velocity results over the different tracks and of the deformation evolution with levelling measures, available in some areas, shows good agreement and goes to validate the technique.     

A simple method for visualizing the differences between related receptor sites

Pastor and Cruciani [J. Med. Chem. 38 (1995) 4637] and Kastenholz et al. [J. Med. Chem. 43 (2000) 3033] pioneered methods for comparing related receptors, with the ultimate goal of designing selective ligands. Such methods start with a reasonable superposition of high-resolution three-dimensional (3D) structures of the receptors. Next, molecular field maps are calculated for each receptor. Then the maps are analyzed to determine which map features are correlated with a particular subset of receptors. We present a method FLOGTV, based on the trend vector paradigm [J. Chem. Inf. Comput. Sci. 25 (1985) 64] to perform the analysis. This is mathematically simpler than the GRID/CPCA method of Kastenholz et al. and allows for the simultaneous comparison of many receptor structures. Also, the trend vector paradigm provides a method of selecting isopotential contours that are well above "noise". We demonstrate the method on four examples: HIV proteases versus two-domain acid proteases, thrombin versus trypsin and factor Xa, bacterial dihydrofolate reductases (DHFRs) versus vertebrate DHFRs, and P38 versus ERK protein kinases.     

A simple method for visualizing the differences between related receptor sites

Pastor and Cruciani [J. Med. Chem. 38 (1995) 4637] and Kastenholz et al. [J. Med. Chem. 43 (2000) 3033] pioneered methods for comparing related receptors, with the ultimate goal of designing selective ligands. Such methods start with a reasonable superposition of high-resolution three-dimensional (3D) structures of the receptors. Next, molecular field maps are calculated for each receptor. Then the maps are analyzed to determine which map features are correlated with a particular subset of receptors. We present a method FLOGTV, based on the trend vector paradigm [J. Chem. Inf. Comput. Sci. 25 (1985) 64] to perform the analysis. This is mathematically simpler than the GRID/CPCA method of Kastenholz et al. and allows for the simultaneous comparison of many receptor structures. Also, the trend vector paradigm provides a method of selecting isopotential contours that are well above "noise". We demonstrate the method on four examples: HIV proteases versus two-domain acid proteases, thrombin versus trypsin and factor Xa, bacterial dihydrofolate reductases (DHFRs) versus vertebrate DHFRs, and P38 versus ERK protein kinases.     

Combination of model-based observer and support vector machines for fault detection of wind turbines

Support vector machines and a Kalman-like observer are used for fault detection and isolation in a variable speed horizontalaxis wind turbine composed of three blades and a full converter. The support vector approach is data-based and is therefore robust to process knowledge. It is based on structural risk minimization which enhances generalization even with small training data set and it allows for process nonlinearity by using flexible kernels. In this work, a radial basis function is used as the kernel. Different parts of the process are investigated including actuators and sensors faults. With duplicated sensors, sensor faults in blade pitch positions,generator and rotor speeds can be detected. Faults of type stuck measurements can be detected in 2 sampling periods. The detection time of offset/scaled measurements depends on the severity of the fault and on the process dynamics when the fault occurs. The converter torque actuator fault can be detected within 2 sampling periods. Faults in the actuators of the pitch systems represents a higher difficulty for fault detection which is due to the fact that such faults only affect the transitory state(which is very fast) but not the final stationary state. Therefore, two methods are considered and compared for fault detection and isolation of this fault: support vector machines and a Kalman-like observer. Advantages and disadvantages of each method are discussed. On one hand, support vector machines training of transitory states would require a big amount of data in different situations, but the fault detection and isolation results are robust to variations in the input/operating point. On the other hand, the observer is model-based, and therefore does not require training, and it allows identification of the fault level, which is interesting for fault reconfiguration. But the observability of the system is ensured under specific conditions, related to the dynamics of the inputs and outputs. The whole fault detection and isolation scheme is evaluated using a wind