Exploration of spatiotemporal and semantic clusters of Twitter data using unsupervised neural networks

ABSTRACT

The investigation of human activity patterns from location-based social networks like Twitter is an established approach of how to infer relationships and latent information that characterize urban structures. Researchers from various disciplines have performed geospatial analysis on social media data despite the data’s high dimensionality, complexity and heterogeneity. However, user-generated datasets are of multi-scale nature, which results in limited applicability of commonly known geospatial analysis methods. Therefore in this paper, we propose a geographic, hierarchical self-organizing map (Geo-H-SOM) to analyze geospatial, temporal and semantic characteristics of georeferenced tweets. The results of our method, which we validate in a case study, demonstrate the ability to explore, abstract and cluster high-dimensional geospatial and semantic information from crowdsourced data.     

GIS and remote sensing integration for environmental applications

Abstract

The combined use of remotely-sensed images and vector GIS data has received considerable interest in recent years. This review article discusses the historical move towards closer integration of remote sensing and GIS technologies and the requirements of integrated software systems to enable remotely-sensed data to be combined with vector datasets for maximum effect. The benefits of integration to users of both GIS and remote sensing for environmental applications are reviewed and some thoughts are given on terminology and future directions in this field.     

The use of digital map data in the segmentation and classification of remotely-sensed images

Abstract

Remotely-sensed data constitute a major potential source of input to geographical information systems (GIS)However, these data often have a relatively poor classification accuracy compared with that of the cartographic data from maps with which they may be combined in the course of GIS analysis. The possibility exists of using data sets (in the form of digital maps) resident within a GIS in order to improve this accuracy, before the classified image is incorporated into the GIS. Results are discussed from a British Alvey Information Technology project to develop a system for the knowledge-based segmentation and classification of remotely-sensed terrain images, in which the knowledge contained in digital map     

Remotely-sensed data as an information source for geographical information systems in natural resource management a review

Abstract

Remotely-sensed image data have long served as a primary source of information for. geographical information systems (GIS), with the transformation of data to information provided by visual image interpretation. Digital image data, in combination with recent advances in computer technology, currently allow visual image interpretation to be realised in a completely digital processing environment. However, it remains desirable to capitalize even further on the potential of digital image data for GIS, through the use of schemes involving automated data processing. The opportunities for, and impediments to, such schemes are considered here with particular reference to the provision of information for natural resource management. It is concluded that further—although foreseeable—developments in both research and technology will be required before fully operational procedures for the automated acquisition of GIS information from image data can be established.     

Database design for a multi-scale spatial information system

Abstract

Growth in the available quantities of digital geographical data has led to major problems in maintaining and integrating data from multiple sources, required by users at differing levels of generalization. Existing GIS and associated database management systems provide few facilities specifically intended for handling spatial data at multiple scales and require time consuming manual intervention to control update and retain consistency between representations. In this paper the GEODYSSEY conceptual design for a multi-scale, multiple representation spatial database is presented and the results of experimental implementation of several aspects of the design are described. Object-oriented, deductive and procedural programming techniques have been applied in several contexts: automated update software, using probabilistic reasoning; deductive query processing using explicit stored semantic and spatial relations combined with geometric data; multiresolution spatial data access methods combining poini, line, area and surface geometry; and triangulation-based generalization software that detects and resolves topological inconsistency.     

Integrated Teaching of Geographic Information Science and Physical Geography Through Digital Terrain Analysis

Abstract

We present an outline of a course in digital terrain analysis that provides students with integrated instruction in geographic information science (GISci) and topics in physical geography and earth science. Integrated teaching of GISci and other sub-fields of geography has value because it presents GISci technologies in the context of their application. Nevertheless, the design of college and university geography courses is often fragmented rather than integrated. Our course provides one potential model for such integration. Assessment of student reaction, using focus groups of both enrolled and non-enrolled students, revealed a generally positive attitude toward the course and pointed out the barriers that prevent some students from taking it.     

Comment on ‘Concerning “The economic evaluation of implementing a GIS‘”

Abstract

A fragmentation index has been implemented as a region based GIS operator to describe the spatial distribution of thematic classes in one data layer within map regions defined in another data layer. It has been applied to integrated analysis of digital maps and classified remote sensing data, for estimation of landscape complexity within watersheds and for detection of logged forest stands. The properties of the fragmentation index, when applied in this manner, are discussed. The fragmentation index is suggested as a valuable means of describing image characteristics of spectrally heterogeneous map regions.     

Coordinating hazardous waste management activities using geographical information systems

Abstract

This paper describes a framework for the role of geographical information systems (GIS) in the monitoring and management of hazardous waste sites. Compilation of required information, incorporation of existing strategies for waste monitoring, analysis of these data in a GIS environment and the integration of computerized models for transport processes are discussed. Examples for the analysis of spatial data using techniques of cartographic overlay and the implementation of geo-statistical methods on monitoring data are provided from work in progress by the authors. These examples are set in the context of developing a fully integrated monitoring and management system utilizing GIS technology.     

James M. Goodman 1929—2004: Professor Emeritus of Geography University of Oklahoma

Abstract

Effective use of time has become even more critical in today's classrooms. Creating geographically literate students by the year 2000 presents some dilemmas for teachers who are faced with expanding curricula. Developing an efficient, meaningful means of teaching geographical features to help curb geographical illiteracy is a possibility. A group of college instructors and more than 75 preservice elementary teachers experimented with an idea that effectively integrated geography, vocabulary development, writing across the curriculum, and the visual arts. Their successful and time-saving idea can be incorporated into any upper elementary to high school classroom committed to teaching children about geographical features.     

The Importance of Geography in Education II

Abstract

The concept of scale is fundamental to geography, yet the definitions for “scale” and related spatial terms can be confusing to those working in other spatial science disciplines. This is particularly true in the emerging multidisciplinary world of integrated remote sensing and geographic information systems, or IGIS's, where data of different types and at various spatial and temporal scales are combined to support complex space-time data analyses. Without a basic lexicon of accepted scale terms, working within an IGIS can breed confusion in the interpretation of data and the models that result from an IGIS construct. This paper provides some terminologies of scale that can be used as a framework for a multidisciplinary lexicon of accepted scaling terms and describes their relationships to an IGIS. It also illustrates how scaling terms can be potentially misunder stood when applied to geographic techniques that are used in disciplines related to geography.     

Monitoring grasshopper and locust habitats in Sahelian Africa using GIS and remote sensing technology†

Abstract

Development programmes in Sahelian Africa are beginning to use geographic information system (GIS) technology. One of the GIS and remote sensing programmes introduced to the region in the late 1980s was the use of seasonal vegetation maps made from satellite data to support grasshopper and locust control. Following serious outbreaks of these pests in 1987, the programme addressed a critical need, by national and international crop protection organizations, to monitor site-specific dynamic vegetation conditions associated with grasshopper and locust breeding. The primary products used in assessing vegetation conditions were vegetation index (greenness) image maps derived from National Oceanic and Atmospheric Administration satellite imagery. Vegetation index data were integrated in a GIS with digital cartographic data of individual Sahelian countries. These near-real-time image maps were used regularly in 10 countries for locating potential grasshopper and locust habitats. The programme to monitor vegetation conditions is currently being institutionalized in the Sahel.     

MARC: a robust method for multiple-aspect trajectory classification via space,time, and semantic embeddings

ABSTRACT

The increasing popularity of Location-Based Social Networks (LBSNs) and the semantic enrichment of mobility data in several contexts in the last years has led to the generation of large volumes of trajectory data. In contrast to GPS-based trajectories, LBSN and context-aware trajectories are more complex data, having several semantic textual dimensions besides space and time, which may reveal interesting mobility patterns. For instance, people may visit different places or perform different activities depending on the weather conditions. These new semantically rich data, known as multiple-aspect trajectories, pose new challenges in trajectory classification, which is the problem that we address in this paper. Existing methods for trajectory classification cannot deal with the complexity of heterogeneous data dimensions or the sequential aspect that characterizes movement. In this paper we propose MARC, an approach based on attribute embedding and Recurrent Neural Networks (RNNs) for classifying multiple-aspect trajectories, that tackles all trajectory properties: space, time, semantics, and sequence. We highlight that MARC exhibits good performance especially when trajectories are described by several textual/categorical attributes. Experiments performed over four publicly available datasets considering the Trajectory-User Linking (TUL) problem show that MARC outperformed all competitors, with respect to accuracy, precision, recall, and F1-score.     

倾向性评分匹配法评估手术联合术中放疗在肝癌治疗中的安全性及有效性

目的 倾向性评分匹配法（Propensity Score Matching,PSM）评估手术联合术中放疗治疗原发性肝癌的安全性及疗效。方法 收集2009~2012年于笔者医院肝胆外科行手术联合术中放疗（intraoperative electron radiotherapy,IOERT）的18例原发性肝癌（primary liver cancer,PLC）患者的临床资料,其中16例经术后病理证实为肝细胞癌（hepatocellular carcinoma,HCC）,2例为肝内胆管细胞癌（intrahepatic cholangiocarcinomas,ICC）;采用倾向性评分匹配方法,按照1∶2比例从同期行单纯手术的原发性肝癌患者中筛选出36例做为对照组（32例HCC,4例ICC）,比较两组患者术中及术后并发症发生情况及HCC患者术后早期（2年内）复发率。结果 所有患者均获随访,随访率100%。两组患者术中出血量、术后3个月内肝功能、凝血功能、血常规及术后住院天数的比较,差异均无统计学意义（P>0.05）,仅在手术时长方面,联合IOERT组长于单纯手术组（P=0.000）。此外,联合IOERT组术后出现1例急性肾功能衰竭和1例胸腔积液,单纯手术组术后出现1例肝创面出血。在疗效方面,以两组48例HCC患者为研究对象,联合IOERT组的HCC患者为16例,其中6例在2年内复发,早期复发率为37.5%;单纯手术组的HCC患者为32例,20例在2年内复发,早期复发率为62.5%,两组早期复发率的比较,差异无统计学意义（P=0.101）。结论 手术联合术中放疗治疗原发性肝癌安全可行,尽管联合放疗组早期复发率低于单纯手术组,但差异并无统计学意义。     

Modelling topographic potential for erosion and deposition using GIS

Abstract

Modelling of erosion and deposition in complex terrain within a geographical information system (GIS) requires a high resolution digital elevation model (DEM), reliable estimation of topographic parameters, and formulation of erosion models adequate for digital representation of spatially distributed parameters. Regularized spline with tension was integrated within a GIS for computation of DEMs and topographic parameters from digitized contours or other point elevation data. For construction of flow lines and computation of upslope contributing areas an algorithm based on vector-grid approach was developed. The spatial distribution of areas with topographic potential for erosion or deposition was then modelled using the approach based on the unit stream power and directional derivatives of surface representing the sediment transport capacity. The methods presented are illustrated on study areas in central Illinois and the Yakima Ridge, Washington.     

Association affairs

Segregation and diversity measures are meant to reflect extent of integration. Based on population counts gathered for enumeration units, these areal-based measures are sensitive to the spatial scale at which the data are tabulated. They are also not effective in capturing various types of assimilation affected by spatial distance among ethnic groups. This paper proposes to use the multiethnic household as a measure of ethnic integration and social assimilation. Using 1990 Public Use Microdata Samples (PUMS), the percentage of multiethnic households is derived for each state and Public Use Microdata Area (PUMA) to indicate integration. Based upon the results, Hawaii and Alaska have extremely high levels of integration. The west and southwest are more integrated than the rest of the U.S., with the exceptions of Oklahoma and several states along the east coast. The least integrated region includes several Appalachian states. The PUMA-level analysis reveals a great deal of variation in ethnic integration within states.     

Strategies for real-time spatial analysis using massively parallel SIMD computers: an application to urban traffic flow analysis

Abstract

The current research focuses upon the development of a methodology for undertaking real-time spatial analysis in a supercomputing environment, specifically using massively parallel SIMD computers. Several approaches that can be used to explore the parallelization characteristics of spatial problems are introduced. Within the focus of a methodology directed toward spatial data parallelism, strategies based on both location-based data decomposition and object-based data decomposition are proposed and a programming logic for spatial operations at local, neighborhood and global levels is also recommended. An empirical study of real-time traffic flow analysis shows the utility of the suggested approach for a complex, spatial analysis situation. The empirical example demonstrates that the proposed methodology, especially when combined with appropriate programming strategies, is preferable in situations where critical, real-time, spatial analysis computations are required. The implementation of this example in a parallel environment also points out some interesting theoretical questions with respect to the theoretical basis underlying the analysis of large networks.     

Integrating multi-criteria evaluation with geographical information systems

Abstract

Geographical information systems (GIS) provide the decision-maker with a powerful set of tools for the manipulation and analysis of spatial information. The functionality of GIS is, however, limited to certain deterministic analyses in key application areas such as spatial search. The integration of multi-criteria evaluation (MCE) techniques with GIS is forwarded as providing the user with the means to evaluate various alternatives on the basis of multiple and conflicting criteria and objectives. An example application based on the search for suitable sites for the disposal of radioactive waste in the UK using the Arc/Info GIS is included. The potential use of a combined GIS-MCE approach in the development of spatial decision support systems is considered.     

What does Gunshot Detection Technology tell us about gun violence?

PurposeEvaluate the sensitivity of Gunshot Detection Technology (GDT) relative to Calls for Service. Existing crime data sources have biases that do not present a complete picture of gun-related crime. GDT may offer a new metric for firearm crimes. However, few studies have assessed the accuracy of GDT and its relationship to other measures of violence.MethodsGDT and gun crime-related Calls for Service in Washington, DC during 2010 were studied. Using temporal comparisons for month, day of year, weekday, and hour of the day, spatial comparisons on a quarter-mile square grid, and a Poisson-Lognormal-CAR spatial regression model on a combined grid by time period dataset, we examined the sensitivity of GDT activations relative to gunshot-related calls for service.ResultsThe results showed that relative GDT sensitivity changed by time and by space. In particular, the relative sensitivity of GDT was much stronger in the evening and at nighttime than in the daytime. In terms of spatial variation, we found that GDT sensitivity decreased with distance from the nearest zone centroid. In addition, there were two small geographic areas in the study area in which the relative GDT sensitivity was lower than expected.ConclusionsGDT systems identify the frequency and locational accuracy of gunshot incidents, particularly at nighttime. This technology has the potential to improve data collection on gun use and violence and produce more accurate representations if the temporal and distance limitations of the technology are understood. GDT may improve gun detection and, thereby, improve police operations and public support for police.     

NEWS FROM DIVISIONS

The following article is first in a contemplated series dcaling with the snbject uf visual commnications for the geographer. The series is an outgrowth of articles and letters to the editor, dealing with the use of visual aids at Association meetings, that have appeared in recrnt issucs of this periodical.