Chulmin Jun

A Model for the Association of the Call Volume and the Unavailable-for-Response Interval on the Delayed Ambulance Response for Out-of-Hospital Cardiac Arrest Using a Geographic Information System

Abstract Background. An optimal ambulance response interval is desirable for emergency medical services (EMS) operations. Arriving on scene within a treatment time window is often delayed for many reasons, including overwhelming call volume. Objective. To determine whether an association exists between the ambulance call volume (ACV), the unavailable-for-response (UFR) interval, and the delayed ambulance response for out-of-hospital cardiac arrest (OHCA) patients. Methods. This was a retrospective observational study conducted in Seoul, Republic of Korea. The EMS ambulance logs from the metropolitan citys 22 EMS agencies, from January 1, 2006, to June 30, 2007, were obtained from the National Emergency Management Agency. These data included patient demographics and call location addresses. The addresses of the call locations and ambulance stations were geocoded and configured with a polygon expressing the optimal coverage areas in which an ambulance could travel within 4 minutes from their base station. The median ACV and mean UFR interval of each EMS agency were calculated. An actual response time interval greater than 4 minutes compared with the optimal coverage area was defined as a suboptimal response. Potential influencing factors on suboptimal response were analyzed using a multivariate logistic regression model to calculated the odds ratio (OR) and 95% confidence interval (95% CI). Results. Geocoding was successful for 255,961 calls, and 3,644 cardiac arrests occurred within the configured optimal response coverage areas. The response rate intervals for cardiac arrest patients, however, were optimal in only 22.6% of calls. Influencing factors for suboptimal response (occurring in 77.4% of the cases) were the median ACV and the mean UFR interval of each EMS agency. When the median ACV was seven or more, the OR of suboptimal response was 1.407 (1.142–1.734). If the mean UFR interval was 55 minutes or more, the OR for suboptimal response was 1.770 (1.345–2.329). Conclusion. The ambulance response time intervals in this study setting were associated with EMS agencies with higher ACVs and longer UFR intervals.

An empirical study on sustainable walkability indices for transit-oriented development by using the analytic network process approach

The moving spaces for pedestrians are facilities that have very important functions for urbanities’ comfortable traffic and resting areas. Although research on transit-oriented development (TOD) has recently emerged as an issue, most domestic studies have not addressed comprehensive analysis or concrete inducement techniques when it comes to the effects of TOD. Therefore, a decision support system is needed which assists in policy making systems by analysing quantitative effects concerning major planning factors of TOD, such as transit mode, level of service (LOS), density, diversity of land use and pedestrian-friendly urban design. In this respect, this study is intended to seek ways to consider developing Walkability Indicators that simplify pedestrian environment elements around areas adjacent to subway stations, depending on the types of walking space, with a quantitative index, and evaluating and visualizing the overall degree (in terms of pleasantness and aesthetics) of pedestrian friendliness of the environment, as well as pedestrians’ convenience and accessibility. Accordingly, we measured distribution of the traffic facilities and amenities as well as connectivity of the pedestrian networks quantitatively in order to perform a comprehensive evaluation of the pedestrian environments. To develop a pedestrian environment index, quantifiable parameters such as mobility, safety, convenience, pleasantness and environment-friendliness were organized. As a result, parameters were selected and they are viewed to have the potential to be used as indexes for the development of Geographic Information System (GIS). Twenty-one route segment parameters related to pleasantness and safety, and nine intersection-related parameters were classified into five areas. For setting the weight values of the evaluation criteria obtained from the survey, we employed an analytic network process (ANP). The computed scores using these criteria are classified and normalized according to the levels of pedestrian dependency and, finally, displayed on a map. The proposed system is expected to be applicable in the visualization of pedestrian movements and the evaluation of convenience levels of the pedestrian environments.

A SDBMS-Based 2D-3D Hybrid Model for Indoor Routing

Currently used 3D models, which are mostly focused on visualization of 3D objects and lack topological structure, have limitation in being used for 3D spatial analyses and applications. However, implementing a full topology for the indoor spatial objects is less practical due to the increase of complexity and computation time. In this study, an alternative method to build a 3D indoor model with less complexity using a spatial DBMS is suggested. It is a 2D-3D hybrid data model, which combines the 2D topology constructed from CAD floor plans and the 3D visualization functionality. We show the process to build the proposed model in a spatial DBMS and use spatial functions and queries to visualize in 2D and 3D. And, then, as an example application, we illustrated the process to build an indoor way-finding simulator.

Data simulation of an airborne lidar system

An airborne LIDAR (LIght Detection And Ranging) system can rapidly generate 3D points by densely sampling the terrain surfaces using laser pulses. The LIDAR points can be efficiently utilized for automatic reconstruction of 3D models of the objects on the terrain and the terrain itself. The data simulation of such a LIDAR system is significantly useful not only to design an optimal sensor for a specific application but also to assess data processing algorithms with various kinds of test data. In this study, we thus attempted to develop data simulation software of an airborne LIDAR system generally consisting of a GPS, an IMU and a laser scanner. We focused particularly on the geometric modeling of the sensors and the object modeling of the targets and background. Hence the data simulation software has been developed using these models. For the geometric modeling, we derived the sensor equation by modeling not only the geometric relationships between the three modules, such as a GPS, an IMU and a laser scanner but also the systematic errors associated with them. Moreover, for rapid and effective simulation, we designed the data model for both targets and background. We constructed the model data by converting the VRML formatted data into the designed model and stored these data in a 3D spatial database that can offer more effective 3D spatial indexing and query processing. Finally, we developed a program that generates simulated data along with the system parameters of a sensor, a terrain model and its trajectories over the model given.

An alternative measure of public transport accessibility based on space syntax

The local governments of major cities in Korea are giving focus on public transportation to reduce congestion and improve accessibility in city areas. In this regards, the proper measurement of accessibility is now a key policy requirement for reorganizing the public transport network. However, Public transport routing problems are considered to be highly complicated since a multi-mode travel generates different combinations of accessibility. While most of the previous research efforts on measuring transport accessibility are found at zone-levels, an alternative approach at a finer scale such as bus links and stops is presented in this study. We propose a method to compute the optimal route choice of origin-destination pairs and measure the accessibility of the chosen mode combination based on topological configuration. The genetic algorithm is used for the computation of the journey paths, whereas the space syntax theory is used for the accessibility. The resulting accessibilities of bus stops are calibrated by O-D survey data and the proposed process is tested on a CBD of Seoul using the city GIS network data.

Design of a dynamic land-use change probability model using spatio-temporal transition matrix

This study aims to analyze land use patterns using time-series satellite images of Seoul Metropolitan Area for the past 30 years, and present a macroscopic model for predicting future land use patterns using Markov Chain based probability model, and finally examine its applicability to Korea. Several Landsat MSS and TM images were used to acquire land-use change patterns and dynamic land-use change patterns were categorized from the classified images. Finally, spatio-temporal transition matrices were constructed from the classified images and applied them into a Markov Chain based model to predict land-use changes for the study area.

An application of the UrbanSim land price model in Yongsan-gu, Seoul, Korea

The land price model in Yongsan-gu aims to assist the development of an integrated land-use and transport model for Seoul city. The simulation software and modelling approach used is UrbanSim, which is comprised of a number of models. One of these models is the land price model. Factors that affect land prices in urban areas are analyzed, categorized and used to explain spatial differences at 150 m × 150 m grid cells in Yongsan-gu by employing a hedonic regression model. The current model is part of the data development of an UrbanSim model for Seoul city. The data preparation, estimation and modelling results are described in this working paper. This paper hopes to contribute to developing an agent-based large scale land-use and transport model in Korea and surrounding countries.

A microscale simulation of land prices, household and employment growth using UrbanSim in Yongsan-Gu, Seoul

Since cities continue to suffer from traffic congestion, high growth population, increased pressure of upgrading infrastructure and deterioration in environmental quality; many metropolitan organizations have switched their focus on growth modeling at micro level in order to estimate patterns, evolution and behavior of major elements involved in urban processes. The aim of this study is to employ the UrbanSim microsimulation land use model for Seoul city. This study attempts to simulate a set of UrbanSim land use models based on developed a dataset from Yongsan-Gu. The employed method includes microscale simulation of land prices, household and employment growth in Yongsan-Gu. In addition, by using the statistical model, various factors regarding location, neighborhood, built environment, economics, and demographics are analyzed in order to assess spatial variation of residential and non-residential location patterns. The input data preparation, model estimation, and strategy that were employed within the microsimulation model on different land use characteristics are described in this working paper.

An Indoor Crowd Simulation Using a 2D-3D Hybrid Data Model

Recent LBS-related technologies tend to extend to indoor spaces using localization sensors such as RFID. In order to implement real time evacuation applications, at least two problems must be resolved in advance; first, proper indoor data models and implementation methods that can accommodate evacuees positioning and routing computations should be available, second, evacuation simulations also need to be performed using the same indoor databases for consistent integration. However, none of these have been suggested explicitly as of now. Although some 3D modeling studies have dealt with topological structures, they are mainly focused on outer building volumes and it is difficult to incorporate such theoretical topology into indoor spaces due to complexity and computational limitations. In this study, we suggest an alternative method to build a 3D indoor model with less cost. It is a 2D-3D hybrid data model that combines the 2D topology constructed from CAD floor plans and the 3D visualization functionality. We show the process to build the proposed model in a spatial DBMS and visualize in 2D and 3D. Also, we illustrate a test CA(cellular automata)-based 3D crowd simulation using our model.

A study on transformation of urban layout patterns through analysis of spatial relationships with urban street configurations

Spatial structures of large cities are typically complex and dynamic as a result of constant changes to their physical and socioeconomic characteristics. Studying both spatial and temporal forms is important for understanding their structures, as well as forecasting possible future changes in city growth patterns. In this study, we analyze structural changes of Seoul, the capital city of Korea, using physical and socioeconomic factors such as street structure, land use and population. We used 25 administrative sub-regions that have composed Seoul City for 30 years from the 1960s to the 1990s, with the analysis broken down into 10-year increments. We used the space syntax theory for the analysis of the changing structure of Seouls street pattern in smaller resolution than existing methods that have focused on issues of accessibility based on zone levels. First, we analyze the attribute values of space syntax, population density and land uses changed in each administrative area of Seoul in each time period. Next, we examine the relationship between street networks and spatial patterns and evaluate whether development patterns are positive or not. Finally, we present the differences of spatial structures between planned areas and naturally grown areas.