Temporal stability of soil moisture in an oasis of northwestern China

Temporal stability of soil moisture has been widely used in hydrological monitoring since it emerged. However, the spatial analysis of temporal stability at the landscape scale is often limited because of insufficient sampling numbers. This work made an effort to investigate the spatial variations of temporal stability of soil moisture in an oasis landscape. The specific objectives of the study were to explore the spatial patterns of temporal stability and to determine the controlling factors of temporal stability in the desert oasis. A time series of soil moisture measurements were gathered on 23 occasions at 118 locations over 3 years in a rectangular transect of approximately 100 km². The nonparametric Spearman's rank correlation coefficient, standard deviation of relative difference (SDRD), and mean absolute bias error (MABE) were used to quantify the temporal stability of soil moisture. Results showed that the temporal stability of soil moisture was depth dependent and season dependent. The spatial pattern of soil moisture in a deep soil layer and between two same seasons generally had a high temporal stability. SDRD and MABE were spatially autocorrelated and exhibited strong spatial structures in the geographic space. The concept of temporal stability can be extended to describe the time‐stable areas of soil moisture with geostatistics. There were great differences between SDRD and MABE in describing the temporal stability of soil moisture and in identifying the controlling factors of temporal stability. In this case, MABE was a better alternative to estimate the areal mean soil moisture using representative locations than SDRD. Land use type, soil moisture condition, and soil particle composition were the dominant controls of temporal stability in the oasis. These insights could help to better understand the essence of temporal stability of soil moisture in arid regions.     

基于网络分析法的武汉市景观生态网络格局特征分析

从网络分析法的角度对武汉市水系网络、道路网络、绿地网络及其复合网络构成的景观生态网络格局进行分析。根据总体景观生态网络格局特征、分区统计景观生态网络格局特征、分等级统计景观生态网络格局特征分析结果显示,道路网络和绿地网络的α指数、β指数、γ指数都明显好于水系网络,相比较而言,三网复合网络都有比独立网络更好的连接度,分区统计结果显示,主城区复合网络的三项指标均处于最高,网络连通度最好,分等级统计结果显示,等级道路网络的α指数、β指数、γ指数均高于全部道路网络,等级水系和等级绿地网络的α指数、β指数、γ指数均低于全部水系和全部绿地网络。     

广东省土地登记信息交换系统的设计与实现

广东省各级土地登记部门经过多年的信息化建设,已经建成了一批土地登记信息管理系统,为业务的开展提供了有效的支撑,但由于缺乏统一的建设标准,这些系统之间无法进行信息共享。广东省通过建设土地登记信息交换系统,在省、市、县三级节点构建起了一套土地登记信息动态汇交体系,打破了信息孤岛,为全省土地登记信息监管系统的构建和运行提供了重要保障。本文重点介绍了该系统的需求分析、系统设计,以及在实现过程中采用的关键技术等。     

兰州市城市治安时空特征分析

治安问题防治是保障城市社会安全与稳定的重要环节。本文以兰州市主城区2014年警情数据为数据来源,选择发案率高且具有代表性的盗窃、两抢(抢劫类和抢夺类)、扒窃及诈骗4类案件为研究对象,运用空间面模式和空间点模式的GIS分析方法,分析了兰州市公共安全空间结构。结果表明:1)研究时段内,案发率呈季节性变化,夏秋季节案发率比较稳定,而冬春季节案发率变化幅度较大。2)4类案件总体在街道上表现为空间聚集分布。从区际尺度来看,城关区治安形势最为严峻;从街道尺度来看,张掖路、火车站等是案发"热点"区域;从案发点分布来看,西关十字、火车站等地属于犯罪"热点"。针对上述情况,宜加强热点附近的警力部署,加大巡逻力度,保障城市公共安全。     

The impact of boreal autumn SST anomalies over the South Pacific on boreal winter precipitation over East Asia

The possible mechanism behind the variability in the dipole pattern of boreal winter precipitation over East Asia is analyzed in this study. The results show that the SST anomalies(SSTAs) over the South Pacific Ocean(SPO) in boreal autumn are closely related to the variability in the dipole pattern of boreal winter precipitation over East Asia. The physical link between the boreal autumn SPO SSTAs and the boreal winter East Asian precipitation dipole pattern is shown to mainly be the seasonal persistence of the SPO SSTAs themselves. The seasonal persistence of the SPO SSTAs can memorize and transport the signal of the boreal autumn SSTAs to the following winter, and then stimulates a meridional teleconnection pattern from the SH to the NH, resulting in a meridional dipole pattern of atmospheric circulation over East Asia in boreal winter. As a major influencing factor, this dipole pattern of the atmospheric circulation can finally lead to the anomalous precipitation dipole pattern over East Asia in boreal winter. These observed physical processes are further confirmed in this study through numerical simulation. The evidence from this study, showing the impact of the SPO SSTAs in boreal autumn,not only deepens our understanding of the variability in East Asian boreal winter precipitation, but also provides a potentially useful predictor for precipitation in the region.     

空间层次聚类显著性判别的重排检验方法

同时顾及空间邻近与专题属性相似的空间层次聚类是挖掘空间分布模式的一种有效手段。空间层次聚类方法虽然可以获得多层次的聚集结构,但聚类结果显著性的统计判别依然是一个尚未解决的难题。为此,本文提出了一种空间层次聚类结果显著性的统计判别方法,用于确定空间层次聚类的停止准则,减少聚类过程对参数设置的依赖。通过试验分析与比较发现,该方法能够有效判别空间层次聚类结果的显著性和确定层次聚类合并过程的停止条件,同时具有很好的抗噪性,避免随机结构的干扰。     

现代专题地图制图研究进展与趋势分析

针对专题地图制作相关研究不足的问题,该文通过归纳总结专题地图理论与应用、网络共享等方面的研究进展,从功能转变、模式转变和内涵冲击三方面分析专题地图研究趋势,并探讨现有制图理论技术存在的不足之处。文章认为:研究专题地图符号的内在结构及统一构建方式,在符号学和微观语言学的理论框架下建立专题符号句法模式,注重对专题地图符号模型的整体描述,并通过相应制图模型的研究来优化制图过程,发掘和创新制图理论成果,将会促进专题地图理论的完善,深化专题符号的自适应表达。     

“GIS工程设计”的实验教学模式研究

"GIS工程设计"的教学目的是培养学生GIS设计的综合能力,因此,该课程的实践教学很重要。本文提出将"GIS工程设计"的实践教学体系分为基础实验和综合设计两部分,研究实践教学安排,改善实习的考核体系和辅助教学方法,形成一套高效的实践教学模式。     

Grid pattern recognition in road networks using the C4.5 algorithm

Pattern recognition in road networks can be used for different applications, including spatiotemporal data mining, automated map generalization, data matching of different levels of detail, and other important research topics. Grid patterns are a common pattern type. This paper proposes and implements a method for grid pattern recognition based on the idea of mesh classification through a supervised learning process. To train the classifier, training datasets are selected from worldwide city samples with different cultural, historical, and geographical environments. Meshes are subsequently labeled as composing or noncomposing grids by participants in an experiment, and the mesh measures are defined while accounting for the mesh’s individual characteristics and spatial context. The classifier is generated using the C4.5 algorithm. The accuracy of the classifier is evaluated using Kappa statistics and the overall rate of correctness. The average Kappa value is approximately 0.74, which corresponds to a total accuracy of 87.5%. Additionally, the rationality of the classifier is evaluated in an interpretation step. Two other existing grid pattern recognition methods were also tested on the datasets, and comparison results indicate that our approach is effective in identifying grid patterns in road networks.