基于夜间灯光数据和空间回归模型的人口格网化方法研究

为了提高地区常住人口回归结果的精度,表现地区及城市内部乡镇、街道以及更小尺度上人口分布特征,以里下河地区为研究区域,以NPP-VIIRS模拟的2020年DMSP-OLS夜间灯光数据为基础,结合土地利用/覆被数据、乡镇和街道常住人口统计数据,采用空间回归模型对各市县常住人口进行建模,并进行精度校验和结果修正,最终得到一种精度较高的人口格网化方法。结果表明:1)里下河地区夜间灯光强度累计值与人口统计数据间相关性为0.8747(P<0.01),相关系数高;选择相关系数最高的二次项式函数作为最优模型,空间回归模型模拟效果较好;2)基于精度检验后各空间单元残差值大小不同,采用分段函数对人口格网化结果进行校正,所绘人口分布图能更加详细、准确地刻画人口的真实分布情况;3)在人口数量和密度都较小的乡镇和农村,将NPP-VIIRS数据模拟为DMSP-OLS夜间灯光数据比直接采用NPP-VIIRS数据做人口空间回归误差更小。

基于GIS的震后修复建筑物空间分布格网化方法研究

针对传统格网化方法存在计算误差较大、计算效率较低等问题,提出一种新的方法——基于GIS的震后修复建筑物空间分布格网化方法。利用DEM数据、土地数据以及基础地理数据等,提取地形、地貌等各种影响因子。利用建筑面积总和以及土地利用分类数据进行多元线性回归建模,获取50mm格网尺度下的建筑分布,利用POI数据与建筑空间的相关性,引入四叉树获取最高中心点集,在上述基础上构建格网震后修复建筑物空间分布模型,完成震后修复建筑物空间分布。实验结果表明,所提方法可有效降低计算误差,提高计算效率。

基于RS和GIS的建筑物空间分布格网化方法研究

本文在概述目前地震风险评估以及震后快速评估中建筑物空间分布格网化处理方法基础上,提出了基于遥感和GIS的多源数据多因子建筑物空间分布格网化方法。以云南省东川区为例,利用DEM数据、土地利用数据、基础地理数据等,提取地形、地貌、河流、道路、居民地和其他土地利用类型等各种影响因子,以300m格网为单元,研究了建筑物空间分布与各类影响因子之间的相关性,确定了各类子因子的建筑面积密度,实现了建筑物空间分布格网化预测。综合分析表明,考虑多影响因子的建筑物空间非均匀性分布,较传统的均匀性分布方法更接近真实空间分布,因而有助于提高地震风险评估和震后快速损失评估的准确性。

卫星测高的垂线偏差格网化方法研究

针对卫星测高技术反演海洋重力场需要解算格网垂线偏差,不同的格网化方法影响垂线偏差的解算精度与空间分辨率的问题,结合Shepard格网化方法与沿轨最小二乘方法的优势提出了一种新的格网化方法,即基于Shepard权函数的沿轨最小二乘方法。采用CryoSat-2卫星约7年的数据,选取中国黄海和南海及其周边海域作为研究区域,分别利用基于交叉点的Shepard法、距离加权沿轨最小二乘法和基于Shepard权函数的沿轨最小二乘法解算1′×1′格网的垂线偏差。将不同方法得到的结果与EGM2008模型的垂线偏差进行比较,利用本文提出的方法解算的1′×1′格网垂线偏差精度最高。研究表明,在基于Shepard权函数的沿轨最小二乘方法在垂线偏差格网化中是可靠的,且该方法可获得高精度结果。

几种插值法在海洋磁力测量数据格网化中的应用

为获得反映海区磁异常分布的磁异常图,海洋磁力测量数据处理中需要将离散数据通过插值方法进行格网化。给出了几种常用的数据格网化方法,并采用磁异常均匀分布和复杂分布情况对方法有效性进行了评价。结论表明:磁异常分布越复杂,对插值方法的要求越严格,无论是磁异常均匀分布还是复杂分布情况,Kriging法的效果最好,建议在海洋磁力测量数据处理中使用。

大河三角洲历史河网密度格网化重建方法——以上海市青浦区1918-1978年为研究范围

本研究以2004年上海市青浦区为研究范围,基于GIS技术构建格网体系,提取1918年和1978年2份军用地形图中的湖荡面积、河网密度、河流长度等指标,比对两者相关指数的分布状况和变化程度发现1918-1978年本区河网密化最主要的原因在于开挖新渠的同时大量保留地表原有水体。通过本个案研究总结出大河三角洲历史河网面貌的复原方法包括图形资料实测情况判断、实际分辨率分析、误差来源探讨、调校误差、格网体系构建等步骤。

Gridding cropland data reconstruction over the agricultural region of China in 1820

Recent studies have demonstrated the importance of LUCC change with climate and ecosystem simulation, but the result could only be determined precisely if a high-resolution underlying land cover map is used. While the efforts based satellites have provided a good baseline for present land cover, what the next advancement in the research about LUCC change required is the development of reconstruction of historical LUCC change especially spatially-explicit historical dataset. Being different from other similar studies, this study is based on the analysis of historical land use patterns in the traditional cultivated region of China. Taking no account of the less important factors, altitude, slope and population patterns are selected as the major drivers of reclamation in ancient China, and used to design the HCGM （Historical Cropland Gridding Model, at a 60 km×60 km resolution）, which is an empirical model for allocating the historical cropland inventory data spatially to grid cells in each political unit. Then we use this model to reconstruct cropland distribution of the study area in 1820, and verify the result by prefectural cropland data of 1820, which is from the historical documents. The statistical analyzing result shows that the model can simulate the patterns of the cropland distribution in the historical period in the traditional cultivated region efficiently.

Installation position determination of wind speed sensors on steel pole along a high-speed railway

In order to consider the influence of steel pole on the measurement of wind speed sensors and determinate the installation position of wind speed sensors, the flow field around wind speed sensors was investigated. Based on the three-dimensional steady Reynolds-averaged Navier-Stokes equations and k-ε double equations turbulent model, the field flow around the wind speed sensor and the steel pole along a high-speed railway was simulated on an unstructured grid. The grid-independent validation was conducted and the accuracy of the present numerical simulation method was validated by experiments and simulations carried out by previous researchers. Results show that the steel pole has a significant influence on the measurement results of wind speed sensors. As the distance between two wind speed sensors is varied from 0.3 to 1.0 m, the impact angles are less than ±20°, it is proposed that the distance between two wind speed sensors is 0.8 m at least, and the interval between wind speed sensors and the steel pole is more than 1.0 m with the sensors located on the upstream side.

ARAP++:an extension of the local/global approach to mesh parameterization

Mesh parameterization is one of the fundamental operations in computer graphics(CG) and computeraided design(CAD). In this paper, we propose a novel local/global parameterization approach, ARAP++, for singleand multi-boundary triangular meshes. It is an extension of the as-rigid-as-possible(ARAP) approach, which stitches together 1-ring patches instead of individual triangles. To optimize the spring energy, we introduce a linear iterative scheme which employs convex combination weights and a fitting Jacobian matrix corresponding to a prescribed family of transformations. Our algorithm is simple, efficient, and robust. The geometric properties(angle and area)of the original model can also be preserved by appropriately prescribing the singular values of the fitting matrix. To reduce the area and stretch distortions for high-curvature models, a stretch operator is introduced. Numerical results demonstrate that ARAP++ outperforms several state-of-the-art methods in terms of controlling the distortions of angle, area, and stretch. Furthermore, it achieves a better visualization performance for several applications, such as texture mapping and surface remeshing.

Surface remeshing with robust user-guided segmentation

Surface remeshing is widely required in modeling, animation, simulation, and many other computer graphics applications. Improving the elements' quality is a challenging task in surface remeshing. Existing methods often fail to efficiently remove poor-quality elements especially in regions with sharp features. In this paper, we propose and use a robust segmentation method followed by remeshing the segmented mesh. Mesh segmentation is initiated using an existing Live-wire interaction approach and is further refined using local mesh operations. The refined segmented mesh is finally sent to the remeshing pipeline, in which each mesh segment is remeshed independently. An experimental study compares our mesh segmentation method as well as remeshing results with representative existing methods. We demonstrate that the proposed segmentation method is robust and suitable for remeshing.

Simulation of hard–soft material interaction under impact loading employing the material point method

Understanding the mechanisms of hard–soft material interaction under impact loading is important not only in the defense industry but also in daily life.However,traditional mesh-based spatial discretization methods that are time consuming owing to the need for frequent re-meshing,such as the finite element method and finite difference method,can hardly handle large deformation involving failure evolution in a multi-phase interaction environment.The objective of this research is to develop a quasi-meshless particle method based on the material point method for the model-based simulation of the hard–soft material interaction response.To demonstrate the proposed procedure,scenarios of a hard–soft material impact test are considered,where a force is applied to layers of materials and a hard bar with an initial velocity impacts a target with layers of different materials.The stress wave propagation and resulting failure evolution are simulated and compared with available data.Future research tasks are then discussed on the basis of the preliminary results.