Geodatabase与公交网络数据建模

随着城市交通的迅猛发展,交通问题已成为各国政府面临的首要问题,建立智能交通系统,将先进的地理信息技术引入城市道路交通管理已是必由之路。论文对公交网络数据模型进行深入分析。论文介绍了一种全新的面向对象的空间数据模型——Geodatabase,并对公交网络数据进行建模。     

Simplifying the interpretation of continuous time models for spatio-temporal networks

Autoregressive and moving average models for temporally dynamic networks treat time as a series of discrete steps which assumes even intervals between data measurements and can introduce bias if this assumption is not met. Using real and simulated data from the London Underground network, this paper illustrates the use of continuous time multilevel models to capture temporal trajectories of edge properties without the need for simultaneous measurements, along with two methods for producing interpretable summaries of model results. These including extracting ‘features’ of temporal patterns (e.g. maxima, time of maxima) which have utility in understanding the network properties of each connection and summarising whole-network properties as a continuous function of time which allows estimation of network properties at any time without temporal aggregation of non-simultaneous measurements. Results for temporal pattern features in the response variable were captured with reasonable accuracy. Variation in the temporal pattern features for the exposure variable was underestimated by the models. The models showed some lack of precision. Both model summaries provided clear ‘real-world’ interpretations and could be applied to data from a range of spatio-temporal network structures (e.g. rivers, social networks). These models should be tested more extensively in a range of scenarios, with potential improvements such as random effects in the exposure variable dimension.

     

GIS城市公交网络评价方法探讨——以湘潭市为例

本文建立了湘潭市公交系统评价模型和评价指标体系,借助GIS技术对现状评价指标进行计算、分析和比较。结论表明:湘潭市现有的地面公交线路网存在线路过长、重复系数过大、非直线系数超标准等问题,这些结论为湘潭市公交线路网的后优化工作提供量化依据。     

构建地理空间信息网格基础底层的若干支撑技术

地理空间信息网格基础底层的支撑技术主要有地理空间信息网格计算结点的构建技术、传统网络协议技术、下一代网络协议技术、接口技术等。作为创新技术,地理空间信息网格必须依托已有技术,加之相关领域及更先进技术的支持,才会有发展和前途。     

改进两步移动搜索法的焦作公共交通可达性

针对大部分城市公交发展滞后、公交站点和公交线路供需不平衡等问题,该文采用统计数据与实调数据相结合的方式,利用两步移动搜索法,从供需的角度研究分析城区公交站点服务的空间可达性。以河南省焦作市为例,以城区街道办为基本研究单元,分别采用固定阈值的简单两步移动搜索法和基于实测数据拟合的增强两步移动搜索法,对焦作市公交设施可达性的空间布局和差异性进行研究。实验结果表明:焦作市城区公交站点服务可达性整体上比较差;城区公共交通资源发展不平衡,空间差异比较明显,公交站点供需相对平衡区域主要集中在城区中心城区,低值区主要集中在城区边缘;增强两步移动搜索法考虑了距离衰减对人们公交出行的影响,更能反映焦作市真实的公交状况。     

基于时空影响因子的未来社区生活圈公共服务设施优化配置北大核心CSCD

公共服务设施作为社区生活圈的核心内容,直接决定了社区生活圈的生活品质。对社区公共服务设施建设情况进行量化评价,并对设施建设的未来规划提供科学决策支持逐渐成为规划者和决策者的一大难题。本文通过ArcGIS工具对POI数据进行处理、统计和可视化,在总结他人社区生活圈量化评价方法的基础上,结合温州本地特色,搭建了一套社区生活圈公共服务设施评价模型。利用该模型可对各类社区进行综合评分和分级,并根据模型评分结果挖掘公共服务设施未来优化方向。此外,还实现了社区生活圈评分的动态计算与展示,为社区服务设施建设选址、路网建设与公共服务设施建设优先级评定等提供决策支持。既可帮助规划者和决策者快速建立对整个区域生活圈建设现状的量化认知,又可助力公共服务设施的优化配置,为社区生活圈公共服务品质评价与提升探寻全新的思路与方法。     

专业性学生社团在大地测量教学中的探索

分析了高校学生社团的主要特点,提出了在大地测量教学中建立专业性学生社团的构想,对项目式教学、创新实验式教学以及综合教学模式进行了分析和探讨,对大地测量专业性社团的指导和管理机制进行了总结,并提出了合理化的建议。     

基于MAPGIS下基础地理信息数据采集的实现

地理信息数据的采集是GIS应用的基础和前提,MAPGIS提供了多种方法的数据输入与采集手段。通过对MAPGIS平台下获取地理信息系统数据方法的研究,进一步对各种数据采集方法进行分析,得出各种采集方法的优缺点和实际工作中方法选择的一般规律,为GIS的数据获取提供指导。     

地理国情监测成果在农业、旅游领域中的应用

开展地理国情监测工作的目的是为了获取自然与人类社会经济活动引起的地表变化信息,具体包括地表自然要素、人文地理要素和社会经济信息的空间分布特征及其相互关系,是基本国情的重要组成部分,为政府管理决策、企业生产运营、人民群众生活提供数据基础和决策依据。本文基于地理国情监测数据,结合多种测绘地理信息数据和技术手段,探讨如何利用地理国情监测成果促进农业与旅游业的发展,以期深入挖掘和提升监测成果价值,全面拓展监测成果应用服务的新思路、新方向。     

空间网络对时序InSAR相位解缠的影响——以Delaunay与Dijkstra网络为例EI北大核心CSCD

在时间序列InSAR相位解缠的过程中,相干目标需事先构建空间网络之后再进行模糊度解算。Delaunay三角网是当前时序相位解缠的主流构网方法,但其网络形态易包含高相位梯度的边缘,导致违背相位连续性假设。考虑到目前很少有关于空间网络对解缠影响的研究及相位解缠对InSAR技术测量精度的主导地位,本文在量化分析Delaunay网络对解缠影响的基础上,提出引入图论中的Dijkstra最短路径算法优化Delaunay网络中所有边的相位梯度,进而改善时序相位解缠的精度。本文采用模拟和真实数据对基于Delaunay网络和基于优化网络的相位解缠进行了对比验证。结果表明,本文提出的构网方法能够更好地满足相位连续性假设,减少约33%由解缠误差所导致的不闭合三角环数。较传统研究聚焦解缠方法和目标函数的改进而言,本文研究揭示了空间网络的改善对时间序列相位解缠的重要性。     

Assessment of second- and third-order ionospheric effects on regional networks: case study in China with longer CMONOC GPS coordinate time series

Higher-order ionospheric (HOI) delays are one of the principal technique-specific error sources in precise global positioning system analysis and have been proposed to become a standard part of precise GPS data processing. In this research, we apply HOI delay corrections to the Crustal Movement Observation Network of China’s (CMONOC) data processing (from January 2000 to December 2013) and furnish quantitative results for the effects of HOI on CMONOC coordinate time series. The results for both a regional reference frame and global reference frame are analyzed and compared to clarify the HOI effects on the CMONOC network. We find that HOI corrections can effectively reduce the semi-annual signals in the northern and vertical components. For sites with lower semi-annual amplitudes, the average decrease in magnitude can reach 30 and 10 % for the northern and vertical components, respectively. The noise amplitudes with HOI corrections and those without HOI corrections are not significantly different. Generally, the HOI effects on CMONOC networks in a global reference frame are less obvious than the results in the regional reference frame, probably because the HOI-induced errors are smaller in comparison to the higher noise levels seen when using a global reference frame. Furthermore, we investigate the combined contributions of environmental loading and HOI effects on the CMONOC stations. The largest loading effects on the vertical displacement are found in the mid- to high-latitude areas. The weighted root mean square differences between the corrected and original weekly GPS height time series of the loading model indicate that the mass loading adequately reduced the scatter on the CMONOC height time series, whereas the results in the global reference frame showed better agreements between the GPS coordinate time series and the environmental loading. When combining the effects of environmental loading and HOI corrections, the results with the HOI corrections reduced the scatter on the observed GPS height coordinates better than the height when estimated without HOI corrections, and the combined solutions in the regional reference frame indicate more preferred improvements. Therefore, regional reference frames are recommended to investigate the HOI effects on regional networks.     

地理信息系统专业实践教学内容改革的研究

地理信息系统（GIS）专业的专业性、理论性和实践性较强,在高校的教学实践中,普遍存在实践教学内容针对性不强等现象,影响实践教学效果。针对目前GIS专业实践教学内容出现的问题,并结合本校的实践教学经验,对实践教学内容的改进方法进行研究,目的是获得更好的实践教学效果,提高学生的社会竞争能力。     

关于地理空间信息网格结构层次的设计与研究

地理空间信息网格结构层次设计是重要的基础性工作。目前较为流行的网格结构层次有五层沙漏结构和开放网格服务结构,都志辉等人从开发的角度又提出了一般的网格层次结构,以此为基础试设计并探讨地理空间信息网格的层次结构。     

地理信息技术辅助中学地理教学模式研究

近40年来地理信息系统(GIS)的理论、技术和教育在世界范围内取得了突飞猛进的发展,而GIS辅助地理教学的研究还刚刚起步。文中设计了GIS辅助地理教学的模式,说明了模式的关键内容,论证了GIS是一种分析解决地理问题的良好工具。以"中国年平均降水空间分布"综合图的制作为例,介绍了GIS辅助中学地理教学的具体方法。     

Optimizing multi-resolution segmentation scale using empirical methods: Exploring the sensitivity of the supervised discrepancy measure Euclidean distance 2 (ED2)

Multiresolution segmentation (MRS) has proven to be one of the most successful image segmentation algorithms in the geographic object-based image analysis (GEOBIA) framework. This algorithm is relatively complex and user-dependent; scale, shape, and compactness are the main parameters available to users for controlling the algorithm. Plurality of segmentation results is common because each parameter may take a range of values within its parameter space or different combinations of values among parameters. Finding optimal parameter values through a trial-and-error process is commonly practiced at the expense of time and labor, thus, several alternative supervised and unsupervised methods for supervised automatic parameter setting have been proposed and tested. In the case of supervised empirical assessments, discrepancy measures are employed for computing measures of dissimilarity between a reference polygon and an image object candidate. Evidently the reliability of the optimal-parameter prediction heavily relies on the sensitivity of the segmentation quality metric. The idea behind pursuing optimal parameter setting is that, for instance, a given scale setting provides image object candidates different from the other scale setting; thus, by design the supervised quality metric should capture this difference. In this exploratory study, we selected the Euclidean distance 2 (ED2) metric, a recently proposed supervised metric, whose main design goal is to optimize the geometrical discrepancy (potential segmentation error (PSE)) and arithmetic discrepancy between image objects and reference polygons (number-of segmentation ratio (NSR)) in two dimensional Euclidean space, as a candidate to investigate the validity and efficacy of empirical discrepancy measures for finding the optimal scale parameter setting of the MRS algorithm. We chose test image scenes from four different space-borne sensors with varying spatial resolutions and scene contents and systematically segmented them using the MRS algorithm at a series of parameter settings. The discriminative capacity of the ED2 metric across different scales groups was tested using non-parametric statistical methods. Our results showed that the ED2 metric significantly discriminates the quality of image object candidates at smaller scale values but it loses the sensitivity at larger scale values. This questions the meaningfulness of the ED2 metric in the MRS algorithm’s parameter optimization. Our contention is that the ED2 metric provides some notion of the optimal scale parameter at the expense of time. In this respect, especially in operational-level image processing, it is worth to re-think the trade-off between execution time of the processor-intensive MRS algorithm at series of parameter settings targeting a less-sensitive quality metric and an expert-lead trial-and-error approach.     

LEO星群探测地球重力场的性能分析

探索如何利用低成本的低轨卫星(low Earth orbit,LEO)星群的精密轨道资料探测地球重力场,并以COSMIC(constellation observing system for meteorology ionosphere & climate)为研究实例初步分析了其覆盖性和方法的可行性。     

地理国情普查质量管理探讨

地理国情主要是指地表自然和人文地理要素的空间分布、特征及其相互关系,是基本国情的重要组成部分.正确理解吉林省地理国情普查技术设计和作业指导书以及国情普查的内容与指标,为了保证数据的真实、可靠,需要有组织和人员来控制国情普查项目成果的质量.     

非线性普通秩亏自由网平差

在文献〔1〕的非线性普通秩亏自由网平差模型强度的曲率度量基础上,利用非线性最小二乘的精确正交性条件方程,提出两种顾及二阶偏导数的非线性普通秩亏自由网平差的计算方法。由于非线性度量曲率立体阵的引入,使得平差计算公式表达简洁,且便于非线性平差本质的分析。最终算例分析说明该方法的有效性及实用性