Spatial obfuscation methods for privacy protection of household-level data

The topic of geoprivacy is increasingly relevant as larger quantities of personal location data are collected and shared. The results of scientific inquiries are often spatially suppressed to protect confidentiality, limiting possible benefits of public distribution. Obfuscation techniques for point data hold the potential to enable the public release of more accurate location data without compromising personal identities. This paper examines the application of four spatial obfuscation methods for household survey data. Household privacy is evaluated by a nearest neighbor analysis, and spatial distribution is measured by a cross-k function and cluster analysis. A new obfuscation technique, Voronoi masking, is demonstrated to be distinctively equipped to balance between protecting both household privacy and spatial distribution.     

A first step towards a framework for presenting the location of confidential point data on maps—results of an empirical perceptual study

A common concern when working with health‐related data is that national standard guidelines are designed to preserve individual statistical information, usually recorded as text or in a spreadsheet format (‘statistical confidentiality’), but lack appropriate rules for visualizing this information on maps (‘spatial confidentiality’). Privacy rules to protect spatial confidentiality become more and more important, as governmental agencies increasingly incorporate Geographic Information Systems (GIS) as a tool for collecting, storing, analysing, and disseminating spatial information. The purpose of this paper is to propose the first step of a general framework for presenting the location of confidential point data on maps using empirical perceptual research. The overall objective is to identify geographic masking methods that preserve both the confidentiality of individual locations, and at the same time the essential visual characteristics of the original point pattern.     

广州市居民出行特征分析及交通发展的对策

居民出行调查是城市交通规划、建设、管理的基础依据 ,通过对比分析广州市 1998年万户居民出行调查和 1984年居民出行调查的有关数据 ,总结归纳出广州市城市居民出行的规律、变化特征及其原因 ,并针对其特点 ,提出广州市未来交通发展的对策和建议     

居民家庭日常出行碳排放的发生机制与调控策略——以北京市为例

根据2007年北京市居民活动日志调查数据,利用Amos7.0软件建立单效标因素的路径分析模型,试图在"社区-家庭"层面上挖掘"空间利用-出行特征-碳排放"的内在发生机理,藉此寻找城市空间组织低碳化的调控路径。研究发现:影响居民家庭日常出行碳排放的主要因素是出行距离和出行方式。社区空间利用特征对家庭出行的距离总量有显著影响,对小汽车出行比率则没有明显作用效果;私家车的购置对居民家庭出行行为的高碳化具有不可逆的作用特点;在现有设施条件、空间环境和车辆使用政策下,公共交通对私人交通出行没有替代性。研究认为,城市空间组织和调控优化应通过土地混合利用、设施供给等物质空间组织与再组织手段,形成空间行为组织和行为规划策略,引导居民降低交通发生量,优化居民交通发生的时空结构,建构低碳的城市空间结构。     

个体时空行为的规律性与可预测性研究——以上海市居民工作日活动为例

理解居民日常行为的规律性和随机性是空间行为研究从行为描述向行为预测推进的基础,对空间政策的制定具有重要意义。论文从上海市10个工作日的手机信令数据中提取个体的时空轨迹,从规律性的视角展开多方面分析。首先,根据活动的周期重现、前后联系等特征界定了无出行(包括仅有短距离出行)、仅有随机出行、有规律工作出行和有其他规律出行4种时空行为模式,发现后2种强规律性模式的人数、出行次数、出行距离的占比分别为49.3%、83.6%、82.0%。然后,测度了个体时空轨迹的熵值,推算出个体时空位置的平均可预测性高达0.84。这些结果均表明居民工作日的时空行为整体上具有非常强的规律性。在此基础上,论文还分析了不同行为模式、个体时空位置可预测性的空间分布,发现了强规律性模式人群在外围郊区密集分布等一系列特征,体现了城市空间环境的差异对行为特征和规律性的影响。     

多中心城市中山市职住空间关系特征

以低密度多中心城市——中山市为例,采取政府主导的居民出行调查数据库中40445 个调查样本,应用ArcGIS 等分析工具,利用居民出行调查数据库中的个体属性与职住地点等信息,对居民职住比、通勤时间、通勤距离和通勤方向进行可视化,分析中山居民的职住空间关系格局。结果表明：职住比、通勤时间、通勤距离在空间上有一定的区域差异,但圈层结构均不明显。全市职住空间分布整体较均匀,主城区职住基本平衡;周边镇区尤其是西北组团、东部组团职住比高,而主城区较低。全市平均通勤时间和通勤距离均显著低于国内大城市和发达国家城市。主城区和外围镇区间的通勤量及其比重小,全市没有产生大规模的外围―中心“钟摆式”通勤,在通勤方向上更多表现为内―内通勤和外―外通勤。居民的职住关系空间分布特征与城市空间结构、人口结构、产业结构与产业布局、土地利用以及交通设施建设具有密切的关系,低密度多中心的城市职住平衡程度高、通勤时间和通勤距离均较短,而主城区与外围镇区通勤联系不紧密。     

基于社会属性的北京市居民居住与就业空间集聚特征

制度转型期,中国城市居民社会空间发生了新的变化,居民居住和就业空间组织也变得更为复杂,并引起了广泛关注。基于2010 年问卷调查数据,采用缓冲区、最近邻层次聚类和Ripley K函数等空间分析方法对北京城市不同社会属性居民的居住和就业空间分布特征进行实证分析。研究发现：① 总体上,北京城市居民居住和就业空间圈层分异明显。在各圈层内部,不同人群的居住和就业空间分布比例亦存在相对差异;职住空间错位程度表明距市中心15 km左右是城市就业功能和居住功能主导地位转化的分界线;职住平衡度整体上呈现出由内圈层到外圈层递减的趋势,但高收入阶层和年轻白领的职住平衡度相对较低。② 不同人群居住与就业空间集聚特征存在明显差异。一般平民居住和就业均呈散点状集聚;年轻打工族居住和就业集聚区域紧邻,主要集聚在四环以内的城市东部区域;高收入阶层居住呈现“小集中、大分散”集聚特征,就业集聚区多集中在四环以内的城市东部和西北部区域;年轻白领居住集聚区呈现城市西部条带状和东部散点状相结合特征,就业集聚区主要在中关村和CBD为中心的两条轴状区域。③ 不同人群居住和就业空间集聚的尺度特征较为相似,呈现随距离增加“先增后减”变化趋势,但距离阈值存在差异。表现为高收入群体居住空间可选范围较小,一般平民就业空间可选范围较小,而年轻白领居住和就业空间可选范围均较大。     

Extracting activity patterns from taxi trajectory data: a two-layer framework using spatio-temporal clustering,Bayesian probability and Monte Carlo simulation

ABSTRACT

Global positioning system (GPS) data generated from taxi trips is a valuable source of information that offers an insight into travel behaviours of urban populations with high spatio-temporal resolution. However, in its raw form, GPS taxi data does not offer information on the purpose (or intended activity) of travel. In this context, to enhance the utility of taxi GPS data sets, we propose a two-layer framework to identify the related activities of each taxi trip automatically and estimate the return trips and successive activities after the trip, by using geographic point-of-interest (POI) data and a combination of spatio-temporal clustering, Bayesian inference and Monte Carlo simulation. Two million taxi trips in New York, the United States of America, and ten million taxi trips in Shenzhen, China, are used as inputs for the two-layer framework. To validate each layer of the framework, we collect 6,003 trip diaries in New York and 712 questionnaire surveys in Shenzhen. The results show that the first layer of the framework performs better than comparable methods published in the literature, while the second layer has high accuracy when inferring return trips.     

Integrating Undergraduate Fieldwork into the Study of Human Mobility

Fieldwork has long been fundamental to human geography; however, increasingly unreceptive institutional environments have led to a decline in fieldwork in undergraduate human geography programs. We argue that mobility research presents an opportunity to reinvigorate the undergraduate field trip in human geography. We report on a second-year field course to Noosa, Australia, that blends new technologies with conventional survey techniques to capture data on a spectrum of human spatial behaviour. Over the course of a single weekend, students collect GPS traces of tourist mobility, survey businesses on the journey to work, collect residential migration histories and trace population dynamics on Noosa beach. Over the three years the course has been running, students have constructed a large repository of data on this Australian mobility hotspot, of which we report highlights. Results from standardised student course evaluations confirm the pedagogical value of these initiatives for human geography undergraduates.     

基于多交通模式的长春市公园绿地空间可达性研究

城市公园绿地资源空间配置的有效性和公平性对城市规划建设和居民生活具有重要意义.基于百度地图路径规划API及腾讯宜出行大数据,采用集成多种交通模式(步行、公交、驾车)的引力模型与双变量空间自相关分析等方法,综合测度长春市中心城区公园绿地的空间可达性及其供需匹配特征.研究发现:①长春市中心城区的公园绿地空间可达性随出行方式...     

基于改进两步移动搜索法的县域医疗卫生服务空间可达性研究

针对县域医疗卫生服务设施的空间布局问题,应用改进两步移动搜索法对德清县医疗卫生服务的空间可达性进行评价。具体改进包括：引入核密度型距离衰减函数对两步移动搜索法进行扩展、考虑医疗设施资源的未充分利用、对不同规模等级医疗机构设置不同服务阈值。计算结果表明：① 浙江省德清县域医疗卫生服务空间可达性呈圈层式空间分布特征,高可达性区域主要集中于县城及邻接区域,边缘地区缺医明显;② 基于改进两步移动搜索法和传统两步移动搜索法的可达性计算结果具有不同的整体特征,但前者可达性计算结果及空间分布更符合实际。     

福州城市文化产业空间分布特征研究

文化产业作为知识经济时代的新兴产业、朝阳产业,在经济增长、满足就业、城市文化建设等方面发挥着越来越重要的作用。聚集现象是经济产业研究的重要发现。本研究通过标准距离与L函数相结合的方法和核密度制图法对基于文化企业位置信息的点模式空间分布格局做定量和定性分析。认为福州文化产业的分布总体呈现聚集态势,具有较为明显的中心—外围的圈层结构,不同产业部门的发育阶段、聚集程度和形态特征有明显差别,资源、市场、政策条件的优势下,福州市文化产业具有良好的发展前景,但产业集聚的优势并未充分发挥,文化产业的空间布局亟待进一步优化。     

Race and (Online) Sites of Consumption

Due to the hybrid nature of material and digital spaces, more decisions are being made online that have a direct effect on offline actions. This is increasingly true for the locations where people are choosing to consume goods and services such as restaurants or retail outlets. The growth of the GeoWeb—personal data uploaded to certain Internet sites such as social media platforms—has established large databases showing the locations where people go during their daily lives for the purposes of consumption. One such repository is the social network, Foursquare, which people use to display their physical location to their friends, digitally. In looking more closely at datasets from Foursquare overlaid with information on racial characteristics in census tracts, a pattern emerges: predominantly African‐American tracts are increasingly left out of this type of online participation. This paper will compare Foursquare data from several U.S. cities to discuss the implications of being left off of social media platforms tied to economic activity. It is likely that these virtually invisible areas will have a direct impact on the economic vitality of their physical counterparts     

基于最优供需分配的公共设施空间可达性分析

空间可达性是衡量公共服务设施公平性的重要指标,在医疗、教育、休闲等公共服务的布局规划中得到广泛应用。然而已有设施服务可达性模型难以充分反映服务供需关系,计算指标也缺乏物理意义。本文提出新的最优供需分配的公共设施空间可达性计算方法（OSD）取代现有方法。该方法基于最优供需分配模型,将设施服务分配给需求者,根据分配结果计算空间可达性指标。给定服务设施与需求的空间分布,以最小化旅行成本为目标,顾及设施服务能力,采用经典的运输问题模型确定最优的服务供需分配方案,进而度量服务的空间可达性。以郑州市金水区社区卫生服务为例,求解25个中心与1333个居住小区的最优服务配置。使用最优配置结果确定每个设施的服务范围、每个居住小区使用服务的旅行时间,以及特定时间阈值的服务覆盖比率。与流行的两步移动搜索法相比,新方法的计算指标具有明确的物理意义。本文提出的可达性评价方法无需参数,计算高效,结果易于解释,在公共服务评价及设施布局规划方面具有应用潜力。     

Using landscape characteristics to define an adjusted distance metric for improving kriging interpolations

Interpolation of point measurements using geostatistical techniques such as kriging can be used to estimate values at non-sampled locations in space. Traditional geostatistics are based on the spatial autocorrelation concept that nearby things are more related than distant things. In this study, additional information was used to modify the traditional Euclidean concept of distance into an adjusted distance metric that incorporates similarity in terms of quantifiable landscape characteristics such as topography or land use. This new approach was tested by interpolating soil moisture content, pH and carbon-to-nitrogen (C:N) ratio measured in both the mineral and the organic soil layers at a field site in central Sweden. Semivariograms were created using both the traditional distance metrics and the proposed adjusted distance metrics to carry out ordinary kriging (OK) interpolations between sampling points. In addition, kriging with external drift (KED) was used to interpolate soil properties to evaluate the ability of the adjusted distance metric to incorporate secondary data into interpolations. The new adjusted distance metric typically lowered the nugget associated with the semivariogram, thereby better representing small-scale variability in the measured data compared to semivariograms based on the traditional distance metric. The pattern of the resulting kriging interpolations using KED and OK based on the adjusted distance metric were similar because they represented secondary data and, thus, enhanced small-scale variability compared to traditional distance OK. This created interpolations that agreed better with what is expected for the real-world spatial variation of the measured properties. Based on cross-validation error, OK interpolations using the adjusted distance metric better fit observed data than either OK interpolations using traditional distance or KED.     

县级资源环境数据库建设的技术方法

航空遥感和航天遥感在数据库建设中分别用于获取状态数据和确定变更靶区 ,而全球定位系统用于靶区的准确定位。该文阐述选择GPS机型的几个条件、GPS基准站设立的两个方法并明确了GPS测量方法。GPS数据在进入数据库之前要基于GPS数据处理软件和传统GIS进行数据转换和编辑。说明基于时空地理实体建立一个本质为TGIS的县级资源环境数据库及其完备的时、空、属性查询特点。同时结合空间信息技术的最新发展探讨县级资源环境数据库建设技术路线的发展趋势。     

基于大数据的城市服务业空间关联分析

信息技术与电商平台的发展,产生了各种各样的大数据。在城市服务业中,商家在电商平台上注册自己带有坐标的信息,构成了空间服务业的空间大数据源。首先建立限定距离阈值的空间关联规则数据模型,介绍该模型产生频繁项集和关联规则的方法与步骤。最后利用Python爬取糯米网南宁站的商家信息,用Apriori算法做出了10~1 000 m 6种距离阈值的空间关联规则和服务业空间频繁项集。     

农民工回流创业区位研究——以河南省14个村为例

农民工回流创业正在成为乡村振兴的重要力量,而创业区位选择反映了创业者的空间决策能力,并对创业绩效产生影响。基于河南省14个村田野入户调查数据,采用统计分析和多值logistic分析方法,对农民工回流创业区位特征和影响因素进行了研究。研究发现：① 回流农民工创业区位具有以村庄为中心的近距离分布特征,绝大多数创业者分布于以村庄为中心50 km范围内,约一半的回流者在家门口创业,在时间距离上,主要集中于0.5 h工作圈和1 h工作圈内。② 创业区位主要选择于本村和县城,其次为镇及附近的中心城市。③ 创业企业除了少数较大规模外,大多为小微企业和个体经营,创业企业产值与距离正相关。除村庄区位农业项目较多外,其余各类创业区位之间行业差别并不明显。④ 创业区位选择是以取得经济利润为前提,综合考虑个人因素、务工因素、社区因素和创业因素的结果。其中,学历、村回流比、第二产业创业项目类型对于选择非村落区位具有正向影响,而工龄、务工地数、无务工技能、村庄为平原和丘陵、第一产业创业项目类型则具有负向影响。