Ultra-high degree spherical harmonic analysis and synthesis using extended-range arithmetic

We present software for spherical harmonic analysis (SHA) and spherical harmonic synthesis (SHS), which can be used for essentially arbitrary degrees and all co-latitudes in the interval (0°, 180°). The routines use extended-range floating-point arithmetic, in particular for the computation of the associated Legendre functions. The price to be paid is an increased computation time; for degree 3,000, the extended-range arithmetic SHS program takes 49 times longer than its standard arithmetic counterpart. The extended-range SHS and SHA routines allow us to test existing routines for SHA and SHS. A comparison with the publicly available SHS routine GEOGFG18 by Wenzel and HARMONIC SYNTH by Holmes and Pavlis confirms what is known about the stability of these programs. GEOGFG18 gives errors <1 mm for latitudes [-89°57.5′, 89°57.5′] and maximum degree 1,800. Higher degrees significantly limit the range of acceptable latitudes for a given accuracy. HARMONIC SYNTH gives good results up to degree 2,700 for almost the whole latitude range. The errors increase towards the North pole and exceed 1 mm at latitude 82° for degree 2,700. For a maximum degree 3,000, HARMONIC SYNTH produces errors exceeding 1 mm at latitudes of about 60°, whereas GEOGFG18 is limited to latitudes below 45°. Further extending the latitudinal band towards the poles may produce errors of several metres for both programs. A SHA of a uniform random signal on the sphere shows significant errors beyond degree 1,700 for the SHA program SHA by Heck and Seitz.     

我国风蚀区风速日变率时空变化特征

基于我国风蚀区239个气象站点逐时风速数据,采用谐波分析方法分析我国风蚀区风速日变率特征。结果表明：85.3%的站点有且只有第一个谐波通过F检验,日变率以24 h为周期;14.2%的站点第一和二个谐波通过检验,日变率以24 h为主周期,以12 h为副周期;西藏墨竹工卡站第一和三个谐波通过检验。日平均风速变化范围为0.96~8.36 m·s^-1,均值为2.42 m·s^-1;风速>3 m·s^-1站点集中分布在内蒙古北部高原、青藏高原地形平坦的高原区、甘肃河西走廊及新疆东北部。季节风速表现出春季 > 冬季 > 夏季 > 秋季的特征;第一个谐波振幅变化范围为0.28~3.28 m·s^-1;相位变化范围为-1.55~4.67,集中在3.21~4.67,表明大部分站点在午后风速值达到最大。研究可为逐时风速的随机模拟提供基础,进而为风蚀区风蚀量估算提供更好的数据支撑。     

Unveiling movement uncertainty for robust trajectory similarity analysis

Trajectory data analysis and mining require distance and similarity measures, and the quality of their results is directly related to those measures. Several similarity measures originally proposed for time-series were adapted to work with trajectory data, but these approaches were developed for well-behaved data that usually do not have the uncertainty and heterogeneity introduced by the sampling process to obtain trajectories. More recently, similarity measures were proposed specifically for trajectory data, but they rely on simplistic movement uncertainty representations, such as linear interpolation. In this article, we propose a new distance function, and a new similarity measure that uses an elliptical representation of trajectories, being more robust to the movement uncertainty caused by the sampling rate and the heterogeneity of this kind of data. Experiments using real data show that our proposal is more accurate and robust than related work.     

Effects of pollution control measures on carbon emission reduction in China: evidence from the 11th and 12th Five-Year Plans

SO₂ emissions have been declining in China recently. The emission reduction has mainly been achieved engineering reduction, structural reduction, and administrative reduction. In this paper, three key industries (electricity generation, steel, and cement) are selected to measure the effects of SO₂ emission reductions, the synergy effects of energy saving, and CO₂ emission reduction. The main results show that, during the period of the ‘11th Five-Year Plan’, engineering reduction of coal-fired power plant desulfurization played the most crucial role in the emission reduction; both engineering reduction and structural reduction can achieve low-pollution emission, but the contributions are not the same due to the divergence of relevant industries. Generally speaking, structural reduction can relatively easily achieve the synergy effect of the main pollutants and GHGs; in comparison, however, engineering reduction does not easily achieve the synergy effect. During the ‘13th Five-Year Plan’ period, the following plans are proposed: strengthening the front pollution control, increasing the engineering reduction, narrowing the difference between the pollution reduction engineering ability and the actual pollution reduction effect, and strengthening the supervisory and administrative effect of both the approval of the front end and the running of the middle end.

POLICY RELEVANCE

China is on the way to realize industrialization and urbanization. The climate-friendly environmental protection strategy is particularly important for rapidly developing countries such as China, because it can address air pollution and climate change issues at the same time in a more economically efficient manner. This paper selects three key industries to evaluate current pollutant control policy synergy effect from the ‘11th Five-Year Plan’ to the ‘12th Five-Year Plan’ period in order to give more sense to policy makers during 13th Five-Year Plan. The estimate of this study shows that the control of pollutants can generally have synergic control effects on GHG emissions and give detailed measures for 13th Five-Year Plan.     

内蒙古天山地区土壤地球化学测量方法对比

在内蒙古天山地区选择沙尔包吐矿区为工作区,开展1:1万土壤地球化学面积性测量和1:5千土壤地球化学剖面测量工作,采样介质分别为0.365~0.246mm(40~60目)中细粒级土壤和4.699~0.833mm(-4~+20目)大粒级土壤。对比结果认为,两种方法在该区都能形成有效的矿致异常,而以4.699~0.833mm(-4~+20目)大粒级土壤为采样介质,形成的异常强度高,效果好,更有利于本区地球化学找矿工作。     

基于非正定 OCSVM 的高光谱影像地物异常检测

针对基于高斯径向基核函数的OCSVM等异常检测算法,对地物光谱变异极为敏感,导致算法异常检测性能不稳定的问题,根据光谱角度余弦测度对光谱形状相似性的描述不受地物光谱辐射强度变异影响的特性,将具有非正定核特性的光谱角度余弦核测度引入非正定SVM算法中,提出一种基于非正定OCSVM的高光谱影像地物异常检测算法。利用四组模拟数据进行目标异常检测实验,结果表明,该算法能够有效检测出高光谱影像数据中的目标地物,检测精度提升明显。     

结合调和场与刚性匹配的三维形变模型

针对基于表面的三维模型形变方法可描述细粒度形变但不独立于三维几何表示,而基于空间的方法则刚好相反这一问题,该文提出了一种基于三维曲面调和场构建的三维形变模型。通过计算表面调和场,将模型划分为若干个形变单元;通过在每个形变单元上运用刚性形状匹配保证局部刚性形变,实现了三维模型的细节保持形变;基于调和值将形变单元上的形变插值到整个三维模型,支持三维模型的细粒度形变;为实现几何表示不相关性,该文提出了一种三维点云调和场计算方法。实验结果表明,该形变模型利用调和场将基于表面和基于空间两种方法的优点结合了起来,具有较好的实时性和可用性。     

基于GIS和空间句法的空间形态一致性测度

少有学者测度规划道路系统分析出的空间形态与规划师空间形态规划意图的一致性。为更好地落实规划师的空间形态规划意图,以安厚镇为例,提出"基于GIS和空间句法的空间形态一致性测度"方法。主要思路为:首先,基于规划的城镇道路系统用GIS空间分析技术及集成度、智能度等句法变量分析新一轮城镇空间形态,然后,测度分析出空间形态与空间形态规划意图的一致性。测度结果表明经分析出的城镇空间形态与规划师本意的一致性有待改善,主要表现为城镇发展轴整体智能度较低、可理解性不高,城镇空间拓展主轴较大程度偏离原规划拓展方向,城镇发展次轴对空间结构的引导效用高于主轴。     

磁扰日日变改正的最小二乘谐波建模实现方法

采用最小二乘法代替傅里叶系数计算公式来确定谐波系数,使用若干个磁静日的谐波系数均值作为磁扰日的谐波系数,再取一定截断阶数的傅里叶级数作为太阳静日变化模型。以此进行地磁观测数据中太阳静日变化和磁扰的分离。然后对日变站太阳静日变化进行地方时差校正得到测点处的太阳静日变化,将其与地磁扰动一起用于测点的日变改正。通过台站数据的计算结果分析了模型的截断阶数、日变站与测点间的经度差等因素对日变改正精度的影响,并对比了此方法与扰日法的改正效果。结果说明了此方法的合理性与可行性。     

A combined image matching method for Chinese optical satellite imagery

Image matching is one of the key technologies for digital Earth. This paper presents a combined image matching method for Chinese satellite images. This method includes the following four steps: (1) a modified Wallis-type filter is proposed to determine parameters adaptively while avoiding over-enhancement; (2) a mismatch detection procedure based on a global-local strategy is introduced to remove outliers generated by the Scale-invariant feature transform algorithm, and geometric orientation with bundle block adjustment is employed to compensate for the systematic errors of the position and attitude observations; (3) we design a novel similarity measure (distance, angle and the Normalized Cross-Correlation similarities, DANCC) which considers geometric similarity and textural similarity; and (4) we introduce a hierarchical matching strategy to refine the matching result level by level. Four typical image pairs acquired from Mapping Satellite-1, ZY-1 02C, ZY-3 and GeoEye-1, respectively, are used for experimental analysis. A comparison with the two current main matching algorithms for satellite imagery confirms that the proposed method is capable of producing reliable and accurate matching results on different terrains from not only Chinese satellite images, but also foreign satellite images.