Delivering light-weight online geographic information analysis using ArcIMS

As of July 9, 2002, more than 300 websites, which provide automated mapping and facilities management over the internet, are registered in the ESRI Internet Map Server (IMS) user registry [1]. But it won’t be an exaggeration to assume that this is only a tiny fraction of the actual number of IMS sold and used over the world. In fact, realising the potential scope and issues of this new form of geographic information delivery, the International Cartographic Association has formed a Commission dedicated to Maps and the Internet [2]. The IMS software has also kept pace with the growing demand and progress in technology. IMS has evolved from the simple HTML image maps to sophisticated servelet-driven mapping services. During this period, a very significant event happened with the arrival of ArcIMS. With the ArcIMS the use of IMS changed from merely an interactive visualisation and query of the spatial databases to a platform for sharing remote spatial databases. In other words, the ArcIMS made the scale of operation of IMS global. While the accessibility and usability of the IMS have certainly increased in the past 5- 6 years, the functionalities provided by IMS however remained fairly static. A widely felt but unreported criticism of IMS has been that the lack of a broader range of spatial analysis functions (except the usual buffering) in the off-the-shelf IMS installation. Therefore a couple of eyebrows always tend to rise if the word “Internet GIS” is used for IMS. Oddly enough, the ArcIMS 3.x and the older versions carry this limitation as well. Essentially, IMS suffer from the limitation for not being able to allow simultaneous update and dynamic manipulation of the thematic content of the online maps. For example, in the case of ArcIMS while there are provisions for complex scale-dependent rendering, it is not easily possible to manipulate (for example add layers or delete layers) the crucial axl file of a mapping service on the fly. The recent launch of ArcIMS 4 promises to bridge this gap by allowing an enhanced integration with the ArcGIS. The aim of this article is to propose a generic framework, which makes the link between an IMS and a standard GIS, to provide geographic analysis in online maps. We will take the example of such a framework developed for ArcIMS

From buildings to cities: techniques for the multi-scale analysis of urban form and function

The built environment is a significant factor in many urban processes, yet direct measures of built form are seldom used in geographical studies. Representation and analysis of urban form and function could provide new insights and improve the evidence base for research. So far progress has been slow due to limited data availability, computational demands, and a lack of methods to integrate built environment data with aggregate geographical analysis. Spatial data and computational improvements are overcoming some of these problems, but there remains a need for techniques to process and aggregate urban form data. Here we develop a Built Environment Model of urban function and dwelling type classifications for Greater London, based on detailed topographic and address-based data (sourced from Ordnance Survey MasterMap). The multi-scale approach allows the Built Environment Model to be viewed at fine-scales for local planning contexts, and at city-wide scales for aggregate geographical analysis, allowing an improved understanding of urban processes. This flexibility is illustrated in the two examples, that of urban function and residential type analysis, where both local-scale urban clustering and city-wide trends in density and agglomeration are shown. While we demonstrate the multi-scale Built Environment Model to be a viable approach, a number of accuracy issues are identified, including the limitations of 2D data, inaccuracies in commercial function data and problems with temporal attribution. These limitations currently restrict the more advanced applications of the Built Environment Model

An overview of virtual city modelling : emerging organisational issues

This paper presents a recent overview of the increasing use of Virtual Reality (VR) technologies for the simulation of urban environments. It builds on previous research conducted on the identification of three-dimensional (3D) city models and offers an analysis of the development, utilization and construction of VR city models. Issues pertaining to advantages, barriers and ownership are identified. The paper describes a case study of the development of a VR model for the city of Newcastle upon Tyne in the UK and outlines the role that academic institutions can play in both the creation and utilization of urban models. The study offers a new approach for the creation, management and update of urban models and reflects on issues which are emerging. Areas for future research are discussed

Domestic energy use in England and Wales: a 3D density grid approach

Household energy use is of relevance for studies of sustainability and fuel poverty. Detailed mapping and spatial analysis is possible in the UK due to the release of fine-scale household energy-use data. The cartographical approach used here focuseson urban energy use and the relative performance of urban areas in England and Wales. The energy-use data were transformed to a 1 km 2 grid of cells allowing con-sistent comparisons to be made between urban areas at the same zonal scale. Addi- tionally cells were extruded according to population density, highlighting basic relationships between density and energy use. The urban perspective on energy use is important due to the strong influence of the built environment in determining energy efficiency, and furthermore due to the clustering of affluent and deprived social groups in cities. The results of the mapping highlight how the lowest and the highest energy-use districts are located within the same city-regions, and how further variations in energy use relate to housing density and energy-efficiency behaviours

Defining and delineating the central areas of towns for statistical monitoring using continuous surface representations

The increasing availability of very high spatial resolution data using the unit postcode as its geo-reference is making possible new kinds of urban analysis andmodelling. However, at this resolution the granularity of the data used to representurban functions makes it difficult to apply traditional analytical and modellingmethods. An alternative suggested here is to use kernel density estimation totransform these data from point or area 'objects' into continuous surfaces of spatialdensities. The use of this transformation is illustrated by a study in which we attemptto develop a robust, generally applicable methodology for identifying the centralareas of UK towns for the purpose of statistical reporting and comparison.Continuous density transformations from unit post code data relating to a series ofindicators of town centredness created using ArcView are normalised and thensummed to give a composite ?Index of Town Centredness?. Selection of key contourson these index surfaces enables town centres to be delineated. The work results froma study on behalf of DETR

Exploring Cities Using Agent-Based Models and GIS

Cities are faced with many problems such as urban sprawl, congestion, and segregation. They are also constantly changing. Computer modelling is becoming an increasingly important tool when examining how cities operate. Agent based models (ABM) allow for the testing of different hypotheses and theories for urban change, thus leading to a greater understanding of how cities work. This paper presents how ABMs can be developed by their integration with Geographical Information System (GIS). To highlight this, a generic ABM is presented. This is then applied to two model applications: a segregation model and a location model. Both models highlight how different theories can be incorporated into the generic model and demonstrate the importance of space in the modelling process. Cities are faced with many problems such as urban sprawl, congestion, and segregation. They are also constantly changing. Computer modelling is becoming an increasingly important tool when examining how cities operate. Agent based models (ABM) allow for the testing of different hypotheses and theories for urban change, thus leading to a greater understanding of how cities work. This paper presents how ABMs can be developed by their integration with Geographical Information System (GIS). To highlight this, a generic ABM is presented. This is then applied to two model applications: a segregation model and a location model. Both models highlight how different theories can be incorporated into the generic model and demonstrate the importance of space in the modelling process

Key challenges in agent-based modelling for geo-spatial simulation

Agent-based modelling (ABM) is fast becoming the dominant paradigm in social simulation due primarily to a worldview that suggests that complex systems emerge from the bottom-up, are highly decentralised, and are composed of a multitude of heterogeneous objects called agents. These agents act with some purpose and their interaction, usually through time and space, generates emergent order, often at higher levels than those at which such agents operate. ABM however raises as many challenges as it seeks to resolve. It is the purpose of this paper to catalogue these challenges and to illustrate them using three somewhat different agent-based models applied to city systems. The seven challenges we pose involve: the purpose for which the model is built, the extent to which the model is rooted in independent theory, the extent to which the model can be replicated, the ways the model might be verified, calibrated and validated, the way model dynamics are represented in terms of agent interactions, the extent to which the model is operational, and the way the model can be communicated and shared with others. Once catalogued, we then illustrate these challenges with a pedestrian model for emergency evacuation in central London, a hypothetical model of residential segregation tuned to London data which elaborates the standard Schelling (1971) model, and an agent-based residential location built according to spatial interactions principles, calibrated to trip data for Greater London. The ambiguities posed by this new style of modelling are drawn out as conclusions

On the problem of boundaries and scaling for urban street networks

Urban morphology has presented significant intellectual challenges to mathematicians and physicists ever since the eighteenth century, when Euler first explored the famous Konigsberg bridges problem. Many important regularities and scaling laws have been observed in urban studies, including Zipf's law and Gibrat's law, rendering cities attractive systems for analysis within statistical physics. Nevertheless, a broad consensus on how cities and their boundaries are defined is still lacking. Applying an elementary clustering technique to the street intersection space, we show that growth curves for the maximum cluster size of the largest cities in the UK and in California collapse to a single curve, namely the logistic. Subsequently, by introducing the concept of the condensation threshold, we show that natural boundaries of cities can be well defined in a universal way. This allows us to study and discuss systematically some of the regularities that are present in cities. We show that some scaling laws present consistent behaviour in space and time, thus suggesting the presence of common principles at the basis of the evolution of urban systems

UrbanDiary - a tracking project

This working paper investigates aspects of time in an urban environment, specifically the cycles and routines of everyday life in the city. As part of the UrbanDiary project (urbantick.blogspot.com), we explore a preliminary study to trace citizen’s spatial habits in individual movement utilising GPS devices with the aim of capturing the beat and rhythm of the city. The data collected includes time and location, to visualise individual activity, along with a series of personal statements on how individuals “use” and experience the city. In this paper, the intent is to explore the context of the UrbanDiary project as well as examine the methodology and technical aspects of tracking with a focus on the comparison of different visualisation techniques. We conclude with a visualisation of the collected data, specifically where the aspect of time is developed and explored so that we might outline a new approach to visualising the city in the sense of a collective, constantly renewed space