Network Analyst Research Articles

Network-based spatial interpolation of commuting trajectories: application of a university commuting management project in Kyoto, Japan

This study presents an application of network-based spatial interpolation of student commuting trajectories from a series of origin–destination trip datasets. In particular, we incorporated multimodal public transportation networks, including bus networks, to estimate the student commuting routes. The student samples for this study were collected from an online travel diary survey conducted by Ritsumeikan University in Kyoto, Japan. The ArcGIS Network Analyst was used to construct spatial network datasets and reconstruct trajectories from the origin–destination trip dataset. In addition, line densities of estimated trajectories were calculated and displayed on maps for geovisualization. These maps helped us understand the precise locations of congestion and spatial patterns of student commuting, unlike linear representations of people’s movements that connect origins and destinations. Our study also showed that estimated trajectories can simulate quantitative impacts on travel time by promoting walking or the use of public transportation.

Distance to screening site and non-participation in screening for breast cancer: a population-based study

In population-based breast cancer screening programmes, the geographical distance to the screening site may influence a woman's propensity to participate. The aim of this study was to analyse the effect driving distance to the screening unit had on women's participation in a breast cancer screening programme. All women invited to the first round of breast cancer screening in the Central Denmark Region were eligible for inclusion (n = 149,234). Information on participation was collected from a regional administrative database. The shortest road distance between each woman's residence and her affiliated screening site was assessed using Network Analyst, ArcGIS. The unadjusted association between distance and non-participation formed a J-shape curve. Adjustment for socio-demographic characteristics caused the J-shape to disappear, and the probability of non-attendance rose with longer distance to the screening site but flattened after ~45 km. Women without access to a vehicle had a higher risk of non-participation than women with access to a vehicle. A long road distance to the screening site was associated with an increased risk of non-participation. Women without access to a vehicle were at higher risk of non-participation than women who had access to a vehicle.

Predicting Ambulance Time of Arrival to the Emergency Department Using Global Positioning System and Google Maps

Objective. To derive and validate a model that accurately predicts ambulance arrival time that could be implemented as a Google Maps web application. Methods. This was a retrospective study of all scene transports in Multnomah County, Oregon, from January 1 through December 31, 2008. Scene and destination hospital addresses were converted to coordinates. ArcGIS Network Analyst was used to estimate transport times based on street network speed limits. We then created a linear regression model to improve the accuracy of these street network estimates using weather, patient characteristics, use of lights and sirens, daylight, and rush-hour intervals. The model was derived from a 50% sample and validated on the remainder. Significance of the covariates was determined by p < 0.05 for a t-test of the model coefficients. Accuracy was quantified by the proportion of estimates that were within 5 minutes of the actual transport times recorded by computer-aided dispatch. We then built a Google Maps-based web application to demonstrate application in real-world EMS operations. Results. There were 48,308 included transports. Street network estimates of transport time were accurate within 5 minutes of actual transport time less than 16% of the time. Actual transport times were longer during daylight and rush-hour intervals and shorter with use of lights and sirens. Age under 18 years, gender, wet weather, and trauma system entry were not significant predictors of transport time. Our model predicted arrival time within 5 minutes 73% of the time. For lights and sirens transports, accuracy was within 5 minutes 77% of the time. Accuracy was identical in the validation dataset. Lights and sirens saved an average of 3.1 minutes for transports under 8.8 minutes, and 5.3 minutes for longer transports. Conclusions. An estimate of transport time based only on a street network significantly underestimated transport times. A simple model incorporating few variables can predict ambulance time of arrival to the emergency department with good accuracy. This model could be linked to global positioning system data and an automated Google Maps web application to optimize emergency department resource use. Use of lights and sirens had a significant effect on transport times. Key words: emergency medical services; prehospital emergency care.

Permodelan Tsunami dan Implikasinya Terhadap Mitigasi Bencana di Kota Palu

Kota Palu Sulawesi Tengah adalah salah satu wilayah di Indonesia yang rentan terhadap bencanatsunami dan perlu memiliki suatu rencana tindakan preventif dan mitigasi untuk mengurangi potensiresiko. Studi ini menganalisa zona genangan tsunami dan implikasinya terkait kegiatan mitigasibencana di Kota Palu. Studi ini menggunakan pendekatan kuantitatif menggunakan Sistem InformasiGeografis (SIG) untuk memetakan wilayah yang rawan bencana tsunami. Studi ini menggunakan costdistance untuk memodelkan bencana tsunami, serta menggunakan spatial analyst dan network analystuntuk menganalisa tingkat bahaya, kerentanan, dan resiko bencana tsunami, serta penentuan ruteevakuasi. Analisis mengindikasikan berikut ini: (1) Kota Palu memiliki potensi yang besar terhadaprendaman tsunami, (2) kawasan bahaya tsunami mencakup 9,63% dari total luas kota, (3) kawasanrentan tsunami 9,83% total luas kota, (4) kawasan resiko tsunami 3,83% total luas kota, dan (5)terdapat 50 shelter sebagai lokasi evakuasi dan 108 rute evakuasi di seluruh kota. Kawasan terbangundi wilayah pesisir Teluk Palu teridentifikasi memiliki tingkat resiko bencana tsunami yang tinggi. Jalurevakuasi yang ada tersebar melalui kawasan terbangun dengan jumlah rute yang berbanding lurusdengan kepadatan pendudukKata kunci: permodelan tsunami, resiko, shelter, rute evakuasi, Kota Palu

Stability Visualizations as a Low-complexity Descriptor of Network Host Behaviour

Detecting anomalous or malicious behaviour from NetFlow data alone is a difficult task due mainly to the limited information available in a NetFlow record. In this paper we propose a “stability” metric based on only four elements of the NetFlow record (source address, destination address, port, time), which may be efficiently visualized. We show that despite not having access to packet payloads, visualizations of this stability metric display clear patterns in the case of certain anomalous network events. (scanning behaviour, peer-to-peer behaviour, etc.) We propose that these visualizations may be useful to the network analyst in detecting malicious behaviour or other deviations from typical network behaviour.

Improving territorial accessibility of mental health services: The case of Spain

Background and Objectives: Citizens choose their health care services not only depending on their needs, but also on where they are located. The location of the services is especially important in the case of mental health due to the specific features of mental disorders. This article provides an analysis of temporal access by road to outpatient mental health centres in Andalusia (Spain) with a view to improving accessibility for the greatest volume of population possible. Methods: Firstly, accessibility by road to the outpatient mental health centres was calculated in terms of time by establishing journey times using the ArcGIS Geographical Information System�s (GIS) Network Analyst module. These journey times by road enabled travel times to be established for these sections, temporal accessibility areas to be plotted from each of the outpatient mental health centres and the number of people included in each accessibility area to be calculated. Results: The accessibility analysis enabled the sitting of the centres to be evaluated for 2006, a comparison to be made with 2011 (with six new facilities having been set up since 2006) and new locations for the siting of these six new facilities to be proposed. Conclusions: This study has enabled the optimum territorial locations to be proposed for the six mental health centres created between 2006 and 2011 that would allow travel times to be reduced for the greatest numbers of people possible. It can be stated on the basis of this study that, if territorial criteria had been taken into account, 97,720 inhabitants would have seen their travel times to their nearest mental health centres reduced using the same resources.

A validation of ground ambulance pre-hospital times modeled using geographic information systems

BackgroundEvaluating geographic access to health services often requires determining the patient travel time to a specified service. For urgent care, many research studies have modeled patient pre-hospital time by ground emergency medical services (EMS) using geographic information systems (GIS). The purpose of this study was to determine if the modeling assumptions proposed through prior United States (US) studies are valid in a non-US context, and to use the resulting information to provide revised recommendations for modeling travel time using GIS in the absence of actual EMS trip data.MethodsThe study sample contained all emergency adult patient trips within the Calgary area for 2006. Each record included four components of pre-hospital time (activation, response, on-scene and transport interval). The actual activation and on-scene intervals were compared with those used in published models. The transport interval was calculated within GIS using the Network Analyst extension of Esri ArcGIS 10.0 and the response interval was derived using previously established methods. These GIS derived transport and response intervals were compared with the actual times using descriptive methods. We used the information acquired through the analysis of the EMS trip data to create an updated model that could be used to estimate travel time in the absence of actual EMS trip records.ResultsThere were 29,765 complete EMS records for scene locations inside the city and 529 outside. The actual median on-scene intervals were longer than the average previously reported by 7–8 minutes. Actual EMS pre-hospital times across our study area were significantly higher than the estimated times modeled using GIS and the original travel time assumptions. Our updated model, although still underestimating the total pre-hospital time, more accurately represents the true pre-hospital time in our study area.ConclusionsThe widespread use of generalized EMS pre-hospital time assumptions based on US data may not be appropriate in a non-US context. The preference for researchers should be to use actual EMS trip records from the proposed research study area. In the absence of EMS trip data researchers should determine which modeling assumptions more accurately reflect the EMS protocols across their study area.

EMF1 A GIS Evaluation of a Statewide EMS Stroke Routing Protocol on Community Hospital Bypass for Acute Stroke Patients

Background: On January 1st, 2010, the North Carolina (NC) Office of Emergency Medical Services (EMS) implemented an out-of-Stroke Triage and Destination Plan (STDP) for patients with suspected acute stroke. The STDP requires that EMS providers categorize destination hospitals as being a community hospital (CH), a Stroke Capable Hospital (SCH) or a Joint Commission Certified Primary Stroke Centers (JCCPSC). The STDP specifies that, within certain constraints, hospitals unable to routinely provide IV tissue plasminogen activator (CH) should be bypassed for patient transport to hospitals with that capability (SCH or JCCPSC). Study Objective: To determine if the STDP increased the frequency of CH bypass by EMS when transporting patients with an out-of-hosptial impression of acute stroke with the following time constraints: ability to be transported to a SCH or a JCCPSC within 2 hours from symptom onset, and with a transport time not exceeding 50 minutes. Methods: Utilizing a before-after design, geographical information system (GIS) analytical methods, and a statewide Prehospital Medical Information System database, we identified patients with a suspected acute stroke who accessed EMS within 120 minutes of symptom onset. We compared two time periods: the 12 months immediately before implementation of the STDP and the 12-month period beginning 3 months after STDP implementation. We geocoded incident and hospital addresses using Esri ArcGIS software and other available source data, including address points and/or NC Department of Transportation (DOT) Integrated Statewide Road Network (ISRN). We used Esri Network Analyst software and NC DOT ISRN data to determine the closest acute care hospital to stroke incident locations. We then identified cases in which EMS bypass of a community hospital within the specified time constraints was an option and determined if bypass occurred. Chi square analysis was used to compare the pre- and post-STDP periods. Results: We identified 2,624 patients with a symptom onset 120 minutes from EMS arrival, an out-of-hospital impression of acute stroke, and a geocodable scene address with a community hospital as the closest acute care hospital. Of those patients, 43% (n=1141) were in the pre-STDP period, while 57% (n=1483) were in the post STDP period. Preliminary results indicate that a community hospital was bypassed 52% of the time in the pre-STDP period and 50% of the time in the post-STDP period. At the time of abstract submission, it was not yet known how many of these cases met the specified time constraints of the STDP. Sensitivity analyses are ongoing to determine the comparability of patients in each of the study periods. Conclusion: Our preliminary results suggest that the STDP had no impact on the rate of EMS bypass of community hospitals for patients with suspected acute stroke. Final results will be presented at the 2012 ACEP Research Forum.

A novel GIS-based decision-making framework for the school bus routing problem

The school bus routing problem (SBRP) is a central issue in transportation planning and optimization systems. SBRP seeks to plan an efficient schedule for a fleet of school buses where each bus picks up students from various bus stops and delivers them to their designated schools while satisfying various constraints such as the maximum capacity of a bus, and the time window of a school. Due to its inherent complexity, many heuristics have been proposed to solve this combinatorial problem in an effective way. In this paper, a novel geographic information systems (GIS)-based decision-making framework that combines GIS, clustering techniques, network cutting techniques, and a hybrid ant colony optimization metaheuristic with the iterated Lin–Kernighan local improvement heuristic is proposed for solving the SBRP as a split delivery vehicle routing problem (SDVRP). Experiments were conducted for evaluating the proposed framework by comparing the results for solving 11 routing problems using both the proposed decision-making framework and ArcGIS 9.2 Network Analyst which uses the greedy Dijkstra’s algorithm. The reported results of the proposed framework generally outperform that of the ArcGIS Network Analyst. In addition, the proposed decision-making framework was applied to solve a real life SBRP to demonstrate its application.

Analysing spatial accessibility to health care: a case study of access by different immigrant groups to primary care physicians in Toronto

This article analyses the spatial accessibility of a number of immigrant groups to linguistically diverse primary care (family) physicians in the Toronto Census Metropolitan Area (CMA). The two-step floating catchment area (2SFCA) method, a special type of gravity model, is employed to measure spatial accessibility using Network Analyst in ArcGIS 9.3. The context of this study is the predominantly publicly funded Canadian health-care system and a multicultural urban setting where both the population and the physicians are culturally and linguistically diverse. This article focuses on a total of eight ethnicities: six groups of recent immigrants – from Hong Kong, Iran, Mainland China, Pakistan, Russia and Sri Lanka; and two groups of long-standing immigrants – from Italy and Portugal. It examines the spatial (mis)match between the residential distribution of immigrant populations and the distribution of linguistically appropriate family physicians. The quantitative data analysed in this article include the physician data set from the College of Physicians and Surgeons of Ontario and geo-referenced 2006 Canadian Census data. This article highlights areas of poor accessibility and provides a comparison of the different ethnic groups. It demonstrates the use of the geographical information system (GIS) in public health research and yields important policy implications for public health planning.

Estimating O–D travel time matrix by Google Maps API: implementation, advantages, and implications

Many spatial analysis tasks call for the use of travel time between multiple origins and destinations, that is, O–D travel time matrix. Commercial geographical information systems (GIS) software requires the input of a well-defined road network dataset and significant efforts in implementing the task. However, road network data are often outdated, miss critical road condition details, or are expensive to acquire; and skillful usage of related software is a major obstacle for researchers without advanced training in GIS. This research develops a desktop tool for implementing the task by calling the Google Maps Application Programming Interface (API). By doing so, we are able to tap into the dynamically updated transportation network data and the routing rules maintained by Google and obtain a reliable estimate of O–D travel time matrix. The results are compared with those computed by the ArcGIS Network Analyst module to demonstrate its advantages. A case study in accessibility analysis is presented to illustrate the implications.

Derivation of Crop Residue Feedstock Supply Curves Using Geographic Information Systems

This paper reports on the availability, collection and transportation costs of agricultural crop residue for cellulosic ethanol processing in the state of Washington using Geographic Information Systems. The GIS Network Analyst extension toolset is employed to map and spatially analyze the crop residue available within given distances/haul zones for 12 eastern counties. Using census feature classification codes, driving speed limits were assigned to all road segments to calculate haul times to a specific biorefinery location. The feedstock farm gate cost, transportation costs, resource availability and geographic distribution were incorporated to derive feedstock supply curves. To better understand how variation in transportation costs affects the feedstock delivered costs, a sensitivity analysis is conducted incorporating a range of diesel prices.

The Analysis on Performance of Microalgae-based Biofuel Production System Considering Regional Climate Condition and Transportation

Recently, the microalgae that can produce fats and hydrocarbons attracts a lot of attention as means to solve the issue of global warming. The purposes of this study are to design microalgae-based biodiesel fuel (BDF) production system using exhaust gas from thermal power plants and considering regional characteristics, and to analysis potential of the microalgae from the viewpoint of energy balance, CO2 balance and fuel production cost. The system consists of five components: Culture, harvesting, extraction, transportation, conversion. In addition, the methodology of this study has three processes: Allocating microalgae culture plants and BDF production plants, optimizing transportation using Geographic Information System (GIS) with Network Analyst, and evaluating energy balance and CO2 reduction of the system. Besides, to minimize BDF production cost, we change the number of BDF production plants and consider trade-off between transportation cost and BDF production plants costs. The result shows that microalgae-based BDF production system has high potential for CO2 reduction and the possibility to competitive with the fossil fuel cost.

Optimal modelling of a transportation network at the level of Cluj County by using ArcGIS Network Analyst.

This paperwork presents a model of transportation network which uses a package of programs allowing the creation, processing, integration, analysis and posting of geographical data at various levels. ArcGIS was used, extension ArcGIS Network Analyst, with which the area of influence of an economic objective on any location from the map may be identified, representing the network, as well as the data base obtained following the Digital Romania National Project. In the model created by the road network 16 points of interests were added on the map of Cluj County, divided into two themes: Agricultural holdings: Aghires, Baciu, Belis, Berind, Floresti, Huedin, Steluţa; Livestock holdings: Apahida, Cojocna, Copaceni, Dej, Iclod, Floresti, Rascruci, Someseni, Tureni. The modelling of transportation network from this paperwork contains three phases: a) The travel of path through all points of interest having as starting and return point the city of Cluj-Napoca without barriers and without the optimization option; b) The introduction of several restrictions on the previous path; c) The optimization of path with barriers, as well as without them.

How are caseload and service utilisation of psychiatric services influenced by distance? A geographical approach to the study of community-based mental health services

The aim of this study was to assess how the caseload and the utilisation of community-based mental health services is influenced by distance and to socioeconomic characteristics. Spatial and statistical analyses were conducted with a sample of 12,347 patients, with ICD-10 psychiatric diagnosis, who had at least one contact with psychiatric services in Verona, Italy, between 2000 and 2006. Three types of mental health facility were considered: acute inpatient wards, outpatient clinics, and community mental health centres (CMHC). To measure distance and accessibility, the locations of static mental health facilities and patients' homes were geocoded. Data were organised in a spatial database, which included census blocks, catchment areas locations, road network graphs, patients' and facilities' locations. In order to calculate travel distances, patients' and facilities' locations were connected to the road network. Accessibility was modelled by using the Network Analyst Service Area Function and 13 Service Areas were created around all facility locations, by measuring distances along the street network. For the epidemiological analyses, patients and census block centroids were linked to the service areas by using spatial join techniques. Epidemiological and utilisation analyses were performed for each type of setting. The facilities were not equally located in the catchment areas. Of particular significance, rural areas appear to be poorly served by mental health services. The distance decay effect exists, with different trends for the three types of facility. The caseload (number of patients using services) decreased with increasing distance; at a distance of 10km, there was a decrease of 80, 60 and 85%, respectively, for CMHCs, inpatients wards and outpatients clinics. From the Poisson regression models, distance was significantly correlated (p value<0.0001) with service use. Also univariate analyses showed a statistically significant association between distance and caseload for each type of setting (p value<0.05), with a decrease in service use for each service area increase in distance (1.5% for acute inpatient wards, 2.0% for CMHC, and 2.1% outpatient clinics). By adding other predictors in the Poisson regression models, these percentages increased. Further studies are needed to evaluate the influence of other factors, such as environmental variables, that may influence the use of mental health services.

Pipeline Alignment Optimization: Automated GIS-Based Approach

The shortest route from home to work may not be the best alternative, and a longer route may be fastest or safest. Hence, the best route reflective of one factor may not be the ultimate best alternative. This paper discusses a geographic information system (GIS)–based application to analyze and rank a number of potential pipeline routes based on accumulated weights of individual segments composing the route. The goal of this application was to automate the process of defining more than one potential route. Designers and stakeholders determine project-specific criteria and assign weighting factors to each. Additionally, individual scores are assigned to each segment in the so-called decision matrix which is a project-specific spreadsheet. The weights and costs are extracted from the decision matrix and imported as attributes for each segment in the GIS pipe network layer based on the unique segment ID. A network analyst routine was programmatically used to identify a number of potential pipeline routes that were then stored in an output feature class and eventually exported to Microsoft Excel, where a summary chart was generated to summarize the findings. The application was used on a test case in the western United States. The application was developed using Visual Basic for Application and ArcObjects and was intended for use in ESRI’s ArcGIS Desktop 9.3.

Concept Representation and Database Structures in Fuzzy Social Relational Networks

We discuss the idea of fuzzy relationships and their role in modeling weighted social relational networks. The paradigm of computing with words is introduced, and the role that fuzzy sets play in representing linguistic concepts is described. We discuss how these technologies can provide a bridge between a network analyst's linguistic description of social network concepts and the formal model of the network. We then turn to some examples of taking an analyst's network concepts and formally representing them in terms of network properties. We first do this for the concept of clique and then for the idea of node importance. Finally, we introduce the idea of vector-valued nodes and begin developing a technology of social network database theory.

Evaluating the Vulnerability of Network Traffic Using Joint Security and Routing Analysis

Joint analysis of security and routing protocols in wireless networks reveals vulnerabilities of secure network traffic that remain undetected when security and routing protocols are analyzed independently. We formulate a class of continuous metrics to evaluate the vulnerability of network traffic as a function of security and routing protocols used in wireless networks. We develop two complementary vulnerability definitions using set theoretic and circuit theoretic interpretations of the security of network traffic, allowing a network analyst or an adversary to determine weaknesses in the secure network. We formalize node capture attacks using the vulnerability metric as a nonlinear integer programming minimization problem and propose the GNAVE algorithm, a Greedy Node capture Approximation using Vulnerability Evaluation. We discuss the availability of security parameters to the adversary and show that unknown parameters can be estimated using probabilistic analysis. We demonstrate vulnerability evaluation using the proposed metrics and node capture attacks using the GNAVE algorithm through detailed examples and simulation.

Schematic visualisation of ski resort trails

Please click here to download the map associated with this article. Trail maps for winter sports often take the form of highly illustrative landscape paintings, or panorama, overprinted with trails and lifts to allow skiers and snowboarders a mechanism for on-mountain navigation. The character of mountain environments lends itself particularly well to the traditional form of representation which creates aesthetically pleasing maps. These have become the de facto standard for trail mapping in ski resorts. Navigating on mountain is not always easy since conditions, map perspective, orientation and the illustrative form often make reading the map awkward. The map developed here presents an alternative to the traditional trail map by reducing a mountain and its trails to topological primitives. By taking on the style of Harry Beck's famous London Underground schematic map, the network of trails and lifts becomes visible and immediate, thus enhancing a users ability to navigate the mountain. The map illustrates the 176 trails in Breckenridge, Colorado derived from GPS tracklogs and incorporates a range of other contextual datasets. The paper outlines the rationale and design of the map which has been produced entirely using ESRI ArcGIS v9.2 alongside the Network Analyst, Schematics, Spatial Analyst, 3D Analyst, Maplex and ArcScene extensions. It also incorporates a 3D digital panorama of the ski resort rendered across a curved perspective DEM to provide a visual context for the main map.

Routing optimization heuristics algorithms for urban solid waste transportation management

During the last decade, metaheuristics have become increasingly popular for effectively confronting difficult combinatorial optimization problems. In the present paper, two individual meatheuristic algorithmic solutions, the ArcGIS Network Analyst and the Ant Colony System (ACS) algorithm, are introduced, implemented and discussed for the identification of optimal routes in the case of Municipal Solid Waste (MSW) collection. Both proposed applications are based on a geo-referenced spatial database supported by a Geographic Information System (GIS). GIS are increasingly becoming a central element for coordinating, planning and managing transportation systems, and so in collaboration with combinatorial optimization techniques they can be used to improve aspects of transit planning in urban regions. Here, the GIS takes into account all the required parameters for the MSW collection (i.e. positions of waste bins, road network and the related traffic, truck capacities, etc) and its desktop users are able to model realistic network conditions and scenarios. In this case, the simulation consists of scenarios of visiting varied waste collection spots in the Municipality of Athens (MoA). The user, in both applications, is able to define or modify all the required dynamic factors for the creation of an initial scenario, and by modifying these particular parameters, alternative scenarios can be generated. Finally, the optimal solution is estimated by each routing optimization algorithm, followed by a comparison between these two algorithmic approaches on the newly designed collection routes. Furthermore, the proposed interactive design of both approaches has potential application in many other environmental planning and management problems.