Monday, December 22, 2008

ABS2: Agent Based Spatial Simulation

A few weeks ago I attended a S4 workshop entitled “ABS2 Agent Based Spatial Simulation” organised by the SIMBAD (SIMulation Based on Agents to Aid Decision ) working group. The meeting was very interesting bringing agent-based modellers from a range of European countries to discuss recent work. The full program and presentations can be found here.

Modellers used a variety of software toolkits ranging from NetLogo, JADE, MATSims, AnyLogic and bespoke programs to explore a variety spatial simulations ranging from traffic simulations to land use change.

For example, road charging in Moscow (using AnyLogic), using MATSim to model travel and locational choices in Lyon, urban daily mobilities using MADKIT, how agents impact on traffic speed (using NetLogo), slowing down urban networks (e.g. to many cars leads to congestion), exploring how traffic lights affect the speed of movement and the distance between cars at different speeds). Demand responsive transport services of shared taxis over non fixed networks (e.g. the Modulobus project).



Moving away from traffic simulations, others explored the use of agent-based models to examine risks from toxic clouds, urban growth and forest fires (using JADE and GRASS), plague epidemics (NetLogo), landscape evolution due to a shifting cultivation system driven by social dynamics, the interrelationships between the built structure of a city and its social organization (Circle City is available here).



Talks also included the need to make agent-based modelling easier. For example, Philippe Mathieu discussed the need to be able to move agents behaviours between different models without the need to copy chunks of code. To this extent he showed us the IODA project. IODA basically allows one to create an interaction matrix of agent-behaviours (an ontology of agent interactions). Volker Grimm discussed individual-based models, and emphasised that representing agents is only one part of the modelling process. The other is the interaction between the agents. It was also noted that there is a need for better model descriptions with the ODD Protocol potentially being the solution.

Tuesday, December 02, 2008

Territorial Self-organization Model

MATer is an agent-based model that aims at reproducing the historical patterns of population settlement in a territory written using Repast. It is the result a interdisciplinary project at the University of Coimbra that combined agent-based modelling, geographic information systems and historical and archaeological evidence in order to understand how self-organizational processes shape human settlements throughout a territory.

Within the model there is simple population dynamics (birth, growing, reproducing and dying). Individuals require land to survive and seek locations to settle down (low land close to the rivers), migrating when overpopulation makes land scarce. Through these behaviours the model simulates the foundation, growth and decline of settlements, taking into account the actual geography of a territory. What I find particularly appealing is that the simulation generates roads between settlements when there is population movements and once created the roads, affect the ease with which agents move around the area.


Video Simulation of MATer




Click here to see the Project website and to find out more about the model.

Wednesday, November 26, 2008

2 day workshop at CASA

CASA is hosting a two day workshop on the 8th and 9th January 2009 in London: the first day of the event is designed to showcase CASA's use of new technologies for mapping and visualizing information about cities; the second day entails technical workshops, designed primarily for members of the S4 European Spatial Analysis network, but all are welcome.

Click here to see the full program and details about registration .


Thursday, November 20, 2008

CATMOGS from the QMRG

The Quantitative Methods Research Group (QMRG), a Speciality Research Groups of the Royal Geographical Society (with The Institute of British Geographers) has just finished a project of digitizing the Concepts and Techniques in Modern Geography (CATMOG) series.

This series of books were created to fill a teaching need in the field of quantitative methods in undergraduate geography courses. Each book is written by an author currently working with the technique or concept described. Topics range from Markov Chain Analysis, Classification in Geography, Area Cartograms and many more.

To view CATMOGS click here.

Thursday, October 30, 2008

Work Update

Readers of the blog might have been wondering why I been interested in Second Life (click here to see blog posts on Second Life), and why I been exploring fine scale modelling of the London housing market and what this has to do with GIS and ABM. As part of the CASA seminar series, I was asked to give a talk about some of my work from the last year. The talk was entitled "Modelling Cities: An Approach using Agent-Based Models and GIS' which pulled together these topics. The abstract or the talk is below:

The Agent-based modelling (ABM) paradigm is becoming an increasingly used technique to study cities. It allows us to grow social structures in artificial worlds specifically how a set of micro-specifications are sufficient to generate the macro-phenomena of interest. Until recently many applications of agent-based models exploring urban phenomena have used a regular partition of space (cells) to represent space. While these models have provided valuable insights into urban phenomena especially as they can capture geographic detail, they miss geometric detail. This area is critical to good applications but is barely touched upon in the literature. Geometry (points, lines and polygons), forms the skeleton of cities from streets and buildings, through to parks, rivers, etc. The ability to represent the urban environment as a series of points, lines, and polygons allows for different size features such as houses and roads to be directly incorporated into the modelling process onto which other physical and social attributes can be added. Additionally the inclusion of geometry allows us to make agent-based models more realistic compared to representing the urban environment as a series of discrete regular cells. This presentation introduces ABM, explore how agent-based models coupled loosely with geographic information systems (GIS) can be created through illustrated examples focusing on residential location. These applications directly consider geometry when building these artificial worlds and running the simulations. Furthermore, these models highlight how the inclusion of geometry impacts on simulation results. Problems and challenges with this approach and ABM in general will be identified. To conclude we will argue the need for fine scale and extensive datasets of the built and socio-economic environments to ground such models, along with the need to communicate and visualise agent-based models. To this extent we introduce our detailed housing and built environment database for London, which will be used as a building block for agent-based models associated with London. We then explore how such models might be communicated and shared with others using advances in technology, specifically Web 2.0 and Second Life.

Some people have asked for the slides of the talk, so I have made them available, they can be downloaded from here (28MB). Accompanying these I have also made a movie of the talk which give a sense of dynamics from such models.



Any thoughts or comments most welcome.

Monday, October 27, 2008

New Paper: Key challenges in agent-based modelling for geo-spatial simulation

Just found out we (Christian Castle, Mike Batty and myself) have a new article inpress within Computers, Environment and Urban Systems, entitled "Key challenges in agent-based modelling for geo-spatial simulation" Below is the abstract.

Agent-based modelling (ABM) is 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 model tuned to London data, and an agent-based residential location model, for Greater London. The ambiguities posed by this new style of modelling are drawn out as conclusions, and the relative arbitrariness of such modelling highlighted.

Anyone wishing to give us feedback on the article is most welcome.

Tuesday, October 07, 2008

Agent-based models in Second Life

Just a quick update on our work with agent-based modelling (ABM) in Second Life. Below are a series of models that we have created in Second Life as proofs of concept and a test for how well Second Life copes with different types of agent-based models. We have created three models which we demonstrate below.

Our first model is chosen Conway’s Game of Life. The movie below details its inner workings:


Game of Life from Andrew Crooks.


The sound track is 'A Lonely Place without You' by New Inception.

Our second model is Schelling’s (1978) Segregation model. Where through mild tastes and preferences to locate with like groups segregation arises. The above models were chosen as they highlight how classical automata styles of models which have inspired a generation of modellers can be created and explored in Second Life.


Schelling's Segregation Model from Andrew Crooks.


Our third model is a prototype pedestrian evacuation model which is more complex than the previous two and highlights at the variety of models that can be potentially created in Second Life. We first started off with agents randomly walking around a room avoiding each other and walls as the movie below demonstrates.


Random Walking from Andrew Crooks.


Then we took the model further were agents exit the building once an alarm is sounded. Within this model we have designed three different room configurations, from a simple square room, a more complex room with internal walls and tables as obstacles, and a multi-floor building were the agents have to walk down the stairs towards the exit (all of which are shown below). From these three scenarios one can explore how room configurations, obstacles and density of surrounding pedestrians impact on pedestrian egress.

Pedestrian Evacuation Model: simple layout from Andrew Crooks .

To further help understand we record the paths the pedestrians walk when exiting the building. The movie below shows the paths travelled of pedestrians exiting the simple room from the movie above.



Pedestrian Evacuation Model: simple layout-trace movie from Andrew Crooks on Vimeo.



Pedestrian Evacuation Model: complex layout from Andrew Crooks.



Pedestrian Evacuation Model: Multi-floor layout from Andrew Crooks.


All the models where written using the Linden Scripting Language (see Rymaszewski et al., 2007) rather than following a loose coupling approach. Further details (including code and model descriptions) and movies of simulations from the models can be found here. If you use Second Life, you can visit our agent street (The SLURL to go there directly is here). In agent street you can experiment with the models and there are also vending machines which allow you to download the model.



Any thoughts or comments or most welcome.

Monday, September 22, 2008

Concepts, Tools and Applications: The Rise of Neogeography


Just a quick note that Andrew Hudson-Smith from Digital Urban and myself are organizing a session at the 2009 AAG. entitled "Concepts, Tools and Applications: The Rise of Neogeography" Below is an extended abstract for the session:

The world of Geographic Information (GI) Science has changed. It has experienced expeditious growth over the last few years leading to fundamental changes to the field. Web 2.0, specifically The Cloud, GeoWeb and Crowd Sourcing are revolutionising the way in which we gather, present, share and analyse geographic data. This renaissance in the importance of geography in the Web 2.0 world is becoming known as 'Neogeography'.

Neogeography is geography for the general public using Web 2.0 techniques to create and overlay their own locational and related information on and into systems that mirror the real world. Location and space now represents a key part of the Web 2.0 revolution. Tagging not only the type of information but where such information is produced, who uses it and at what time, is fast becoming the killer application that roots information about interactivity generated across the web to systems that users can easily access and use in their own communication with others.

The aim of this session is twofold; first to bring together practitioners to discuss concepts and challenges that the field of Neogeography faces. Secondly, to provide an opportunity for researchers and developers to present recent tools and applications for collecting, sharing and communicating spatial data for the Neogeographer. We are actively seeking topics ranging across the entire spectrum of Neogeography, from Crowdsourcing, Digital Earths, Neogeography, Web Mashups, Volunteered Geographic Information, Virtual Worlds (e.g. Second Life) and associated Web 2.0 technologies.

Anyone who wishes to presents a paper must first register for the annual meeting, submit an abstract (no more than 250 words that describes the presentation's purpose, methods, and conclusions) by the October 16, 2008. Once this has been done, you need to send us your program identification number (PIN), which we will use to add you to the session.

Further details on the paper requirements and cost of registration for the AAG meeting can be found at http://www.aag.org/annualmeetings/2009/index.htm

We look forward to hearing from you

Andrew and Andy

Tuesday, September 16, 2008

Update: Agents in Second Life

At CASA we use Second Life as a online urban laboratory -which could be termed collaboratories, to explore issues pertaining to urban planning and public debate in a visually 3D collaborative environment (click here to see some of CASA's previous work from Digital Urban)


One of the aspects I am working on with others at CASA is exploring Second Life's potential for 3D agent-based modelling for social scientists. To this end we have created three agent-based models using the Linden Scripting Language (see Rymaszewski et al., 2007). It is the purpose of these models to act as pedagogic demonstrators and as a “proof-of-concept”, thus we have chosen Conway’s Game of Life, Schelling’s (1971, 1978) Segregation model. These models were chosen as they highlight how classical automata styles of models which have inspired a generation of modellers can be created and explored in Second Life. The third model we present is a prototype pedestrian evacuation model which is more complex than the previous two and highlights at the variety of models that can be potentially created in Second Life. This model relates to the genus of such models of which the social forces model developed and popularised by Helbing and Molnár (1995) is typical.

While being work in progress we thought its worth showing a short movie of our work to date.



Agent-Based Modelling in Second Life

The sound track for the movie is 'Just a Memory' from ANDYF.

Potentially this environment demonstrates how experts, model builders and the non specialist can view, interact and discuss agent-based models in a 3D collaborative environment. Any thoughts or comments are most welcome.

References:

Helbing, D. and Molnár, P. (1995), 'Social Force Model for Pedestrian Dynamics', Physical Review E, 51(5): 4282-4286.

Rymaszewski, M., Au, W.J., Wallace, M., Winters, C., Ondrejka, C. and Batstone-Cunningham, B. (2007), Second Life: The Official Guide, John Wiley & Sons, Inc, Hoboken, NJ.

Schelling, T.C. (1971), 'Dynamic Models of Segregation', Journal of Mathematical Sociology, 1(1): 143-186.

Schelling, T.C. (1978), Micromotives and Macrobehavior, WW Norton and Company, New York, NY.

Monday, September 01, 2008

Neogeography: disseminating geographic content with Web 2.0 technologies


I gave a talk the other day on behalf of the GeoVue project at CASA at the RGS-IBG Annual International Conference in London, and giving a paper entitled "Neogeography: disseminating geographic content with Web 2.0 technologies" in the The e-Social Science agenda: challenges and opportunities for geographers session. The session showcased new e-Social Science developments, explaining and illustrating the opportunities and challenges it poses for geographers, by disseminating the activities of geographers who are engaged in e Social Science. These include applications of e-Social Science in Evidence-based Policy Assessment (EBPA) and other fields of geographies that matter.

The abstract of the talk was:

"In CASA, we are working on Web 2.0 technologies that take geographic content and disseminate to a range of interested users from professionals to non-experts in a way that enables them to interact with the content and to add value to the visualisations that they are able to produce. This is essentially what Web 2.0 is all about – user driven content involving location and place as well as the networks that connect users together. It is the basis of what is currently being referred to as NeoGeography. In this talk, we will illustrate these technologies starting with our developments of virtual cities through our Virtual London model which is within Google Earth move to show how we can user other Google software to enables users to create their own maps using our GMap Creator software and then illustrate how we are building the equivalent of a YouTube for Geographers that we call MapTube. Much of the content that we are working with can also be ported into virtual worlds which represent the next stage of web based development and we will illustrate how we are porting such content from virtual cities and web -based maps into Second Life where we are piggy-backing this content into Nature’s Second Nature space."

Below is a movie of the talk (including all the movies and nice sound provided by Andrew Hudson-Smith's of Digital Urban, you might want to fast forward bits) and a pdf of the talk can be downloaded from here (15MD).



Neogeography: disseminating geographic content with Web 2.0 technologies.


What was interesting is that while the research is of interest to a large online community as supported by interest from the BBC, potentially neogeography is still a niche topic in UK geography. Maybe it suggests that the 'traditional' geographer (what ever this is) is unaware of the latest digital technologies in reaching out for the masses.

On a side note we have a new working paper entitled "Mapping for the Masses: Accessing Web 2.0 through Crowdsourcing" which might be of interest.

Full reference:
Hudson-Smith, A., Batty, M., Crooks, A. T., and Milton, R. (2008), Mapping for the Masses: Accessing Web 2.0 through Crowdsourcing, Centre for Advanced Spatial Analysis (University College London): Working Paper 143, London, England. (pdf)

More information about the GeoVue project, Web 2.0, Second Life etc can be found and Andrew Hudson-Smith's Blog: Digital Urban http://digitalurban.blogspot.com/

Tuesday, August 26, 2008

The Building Blocks of the City: Points, Lines and Polygons


This week I will be attending the RGS-IBG Annual International Conference in London, and giving a paper entitled "The Building Blocks of the City: Points, Lines and Polygons" in a duel session called "Enhancing Complex Social Simulations with Automata Systems" on Thursday, organised by Geographical Information Science Research Group and Quantitative Methods Research Group of the RGS. The abstract for the talk is below, if you are around the conference come and say hello.

Talk outline:

"The Agent-based modelling (ABM) paradigm is becoming an increasingly used technique to study cities. It allows us to grow social structures ‘in silico’ specifically how a set of micro-specifications are sufficient to generate the macro-phenomena of interest. Until recently many applications of agent-based models exploring urban phenomena have used a regular partition of space (cells) to represent space. While these models have provided valuable insights into urban phenomena especially as they can capture geographic detail, they miss geometric detail. This area is critical to good applications but is barely touched upon in the literature.

Geometry (points, lines and polygons), forms the skeleton of cities from streets and buildings, through to parks, rivers, etc. The ability to represent the urban environment as a series of points, lines, and polygons allows for different size features such as houses and roads to be directly incorporated into the modelling process onto which other physical and social attributes can be added. Additionally the inclusion of geometry allows us to make agent-based models more realistic compared to representing the urban environment as a series of discrete regular cells.

This paper will explore how agent-based models coupled loosely with geographic information systems (GIS) can be created through illustrated examples focusing on residential location. These applications directly consider geometry when building these artificial worlds and running the simulation and highlight how the inclusion of geometry impacts on simulation results. Furthermore problems and challenges with this approach and ABM in general will be identified along with further work."

The talk can be downloaded from here (5.8MB). A previous post and a paper related to this talk can be found here.

Thursday, August 14, 2008

Agent-based model that mimics drunken crowds

While agent-based models are used for many applications, I just came across an article in New Scientist and found quite interesting. A team of researchers from the University of Cardiff have used agents to mimic the movements of drunken crowds. Specifically how the staggering gait and loss of balance associated with being drunk would affect the behaviour of crowds be it a mix of sober, drunk or somewhere in-between.

The model was based on primary data as the team made 24 visits to Cardiff city centre between 11pm and 3am on Friday and Saturday nights, breathalysing people and monitoring their gait and then factoring this information into their simulation.


Find out more:

  • The New Scientist Article
  • Moore, S. C., Flajšlik, M., Rosin, P. L. & Marshall, D. (in press). A particle model of crowd behavior: Exploring the relationship between alcohol, crowd dynamics and violence. Aggression and Violent Behavior.

Tuesday, August 12, 2008

Toolkits update

The pace of development of agent-based toolkits sometimes amazes me. No sooner have I written something and it’s out of date (so ignore some of my earlier posts or at least check the ABM sites).

Just a quick note that Repast Simphony 1.1 was released recently and one of its many updates is its option to link with NASA World Wind. So not only can one have a 3D display but can visualize agents with satellite imagery, elevated terrain, and scientific data sets (as shown in the image below). This is quite important for geo-spatial agent-based models in the form of testing its validity, as Mandelbrot (1983) argues that good models which generate spatial or physical predictions that can be mapped or visualised must ‘look right’. Such visualisation of agent-based models also helps us share (disseminate), communicate and potentially influence people about the model as the model’s spatial outcomes can be mapped to real world places which people can potentially relate to.


For a brief tutorial on using RepastS GIS functionally, Nick Malleson from the Agent-Based Crime Simulation blog has recently written an excellent tutorial (and code) showing a small town with a few agents, some houses and some roads. In the model agents choose a random house and then travel there (Click here for a link to his post).

In other news, NetLogo (4.0.3) has also been released and has the GIS extension for handling geographic data is now included (formerly it was separate download).

Thursday, August 07, 2008

News: New Working Paper and ABM in Second Life

Posts have been a bit sparse the last few months, while I have been exploring the worlds of Neogeography, Web 2.0 and Second Life with colleagues from CASA. Andy Hudson-Smith (who writes an excellent Blog called Digital Urban) and myself have just finished a working paper covering some aspects of the above entitled “The Renaissance of Geographic Information: Neogeography, Gaming and Second Life: Working Paper 142

The abstract is as follows:

Web 2.0, specifically The Cloud, GeoWeb and Wikitecture are revolutionising the way in which we present, share and analyse geographic data. In this paper we outline and provide working examples a suite of tools which are detailed below, aimed at developing new applications of GIS and related technologies. GeoVUE is one of seven nodes in the National Centre for e-Social Science whose mission it is to develop web-based technologies for the social and geographical sciences. The Node, based at the Centre for Advanced Spatial Analysis, University College London has developed a suite of free software allowing quick and easy visualisation of geographic data in systems such as Google Maps, Google Earth, Crysis and Second Life

These tools address two issues, firstly that spatial data is still inherently difficult to share and visualise for the non-GIS trained academic or professional and secondly that a geographic data social network has the potential to dramatically open up data sources for both the public and professional geographer. With our applications of GMap Creator, and MapTube to name but two, we detail ways to intelligently visualise and share spatial data. This paper concludes with detailing usage and outreach as well as an insight into how such tools are already providing a significant impact to the outreach of geographic information.”

Full Reference:

Hudson-Smith, A. and Crooks, A. T. (2008), The Renaissance of Geographic Information: Neogeography, Gaming and Second Life, Centre for Advanced Spatial Analysis (University College London): Working Paper 142, London, England. (pdf)

On another note, Andy, myself and another researcher Joel Dearden are also working on some agent-based models in Second Life. While still rough prototypes, they are looking interesting. We can create, share, and communicate models in a highly visual (3D) and interactive way. The models are simple “proofs of concept” ranging from the Game of Life, Schelling’s segregation model to a pedestrian evacuation model of a building. They are just to demonstrate how virtual worlds could be used by agent-based modellers for outreach purposes. Below are a few screen shots of the models to date. We are currently working on a paper and once written we will give away the code of all the models if anyone is interested in doing such research.
Screen Shot of our Game of Life Model in Second Life:

Screen Shot of Schelling's Segregation Model and GUI in Second Life:

Pedestrian Evacuation Model in Second Life:


While ABM in Second Life is proving interesting we do have an occasional problem of our agents escaping from the pedestrian model and we find them wondering around Second Life:

For more information about Second Life and Andy's work in particular in Second Life see the Digital Urban Blog.

Britain From Above


While nothing to do with ABM, some of us at CASA have been doing some voluntary work for a new BBC TV series called Britain from above. Basically we assisted in organising and refining vast hordes of geographic information such as the 2001 Census, the intricate network of railways and then producing fine scale maps which appear on the show after some amazing CGI and graphics work by a professional company. The program looks great:




I particularly like this clip:




More information about the show:

http://www.bbc.co.uk/britainfromabove/

http://news.bbc.co.uk/1/hi/technology/7539529.stm

http://www.bbc.co.uk/britainfromabove/about/experts.shtml

Tuesday, August 05, 2008

Fractal Cities: available for download

Fractal Cities: A Geometry of Form and Function” by Professors Mike Batty and Paul Longley is a well written, a must read and often cited book for anyone interested in or writing about fractals, urban modelling and complexity sciences.

In the introduction the authors state that...

“The book presents an initial attempt to apply fractal geometry to cities. In fact, we go beyond this and argue that cities are fractal in form, and that much of our pre-existing urban theory is a theory of the fractal city. As befits a beginning, this book is very much an introductory statement and, as we argue throughout, these ideas are simply crude snapshots of a much bigger picture which we hope others will steer their research towards.

In terms of theory, we show here that the architect's physical determinism concerning the city can be captured and elaborated in terms of fractals while the geographer's concern for the economic theory of location is entirely consistent with the use of fractal ideas. We live in an era when physical determinism is still disreputable as architects and city planners seek to minimize the impact of designs which manifestly interfere with the social and economic fabric of cities in countless unanticipated and undesirable ways. But physical form does determine the quality of life in cities.

We see fractal geometry as providing a new hope for understanding the power of determinism, as well as new methods for enabling the synthesis of urban density with central place theory, new ways of visualizing the impact of human decision-making on cities, and perhaps most of all, new goals for achieving the good society through manipulating and planning city form.”

Professors Mike Batty and Paul Longley have now made their book “Fractal Cities: A Geometry of Form and Function” freely downloadable from http://www.fractalcities.org/

Monday, July 21, 2008

Modelling4All

While still in its early stages, the modelling4All site is worth a look. The aim of modelling4All is to reduce the difficulty and effort needed to make agent-based models therefore enabling non-programmers to collaboratively build and analyse computer models. The project was inspired by sites such as easy to use and user generated sites such Scratch, Flickr and Bamzooki.

modelling4All allows one to create agent-based models over the web, models are constructed by composing and parametizing model fragments (bits of code). The model fragment library can be searched and model fragments can be added and combined to a model to create an agent-based model in a very short period of time by just clicking on the fragment (such as a behaviour) which is required for the task at hand.


This approach allows non-expert modellers to get a feel for the modelling process and allows for a collaborative approach to the creation of agent-based models.

Project Websites:

http://modelling4all.wikidot.com/ (Wiki)

http://modelling4all.nsms.ox.ac.uk/(Code)

http://modelling4all.wordpress.com/about/(Blog)

Tuesday, June 17, 2008

Agent-Based Modelling for Housing

Today I attended and gave a talk at a workshop on ABM at the 4th International Conference on e-Social Science in Manchester. The title of the talk was “Agent-Based Modelling for Housing” and relates my previous work from my PhD and what I am currently working on. The abstract for my talk is as follows:

Cities play a critical role in our lives, providing habitats for more than half the world’s population in 2008 and this proportion is predicted to increase to over 75 percent by the year 2100. With this growth comes pressure on housing both in terms of supply and location. However, understanding such systems is extremely complex as they are composed of many parts, with many dynamically changing parameters and large numbers of discrete actors interacting within space. The heterogeneous nature of cities makes it difficult to generalise localised problems from that of city-wide problems. To understand urban problems such as sprawl, congestion and segregation, has recently lead researchers to focus on a bottom-up approach to urban systems, specifically researching the reasoning on which individual decisions are made. One such approach is agent-based modelling (ABM) which allows one to simulate the individual actions of diverse agents, measuring the resulting system behaviour and outcomes over time. Furthermore, such models allow us to test different ideas and theories of urban change in the safe environment of the computer, thus allowing scientists to understand urban phenomena through analysis and experimentation, a traditional goal of science.


With the rise of ABM, there has been a growing interest in developing integrated geographical information systems (GIS) and ABM applications. The linkage between the two allows agent-based modellers to have agents related to actual geographic locations and for GIS users, it provides the ability to model the emergence of phenomena through the individual interaction of features in a GIS over space and time.


This paper will explore how agent-based models coupled loosely with GIS can be created to explore housing issues such as segregation, and how residential and employee groups interact to form urban spatial structures characteristic of large cities through a series of illustrated examples dimensioned upon London. Furthermore the paper will discuss the potential of combing ABM with fine resolution data (e.g. Ordnance Survey MasterMap TOIDS to represent individual buildings; MasterMap’s Address layer to populate these building with a number of units, assigning individual agents to each of these units and sales data from the Land Registry to give the units a price) to create models exploring the small scale dynamics of the London housing market from the individual perspective. ABM is inherently suited to such a study as it allows the representation of an heterogeneous population with individual agents having different behaviours and characteristics. For example, the agent’s decisions/behaviour of where to locate is affected by numerous factors. Location is a trade-off between such things as price of dwelling, type of residence and its location, both in terms of neighbourhood and in relation to place of work, all of which vary depending on age, sex, marital status and income. To conclude the paper will present a series of problems and challenges with this approach and ABM in general.

The talk including useful references can be downloaded from here.

Thursday, May 22, 2008

Agent-Based Models of Crowd Behaviuor

Agent-based modelling allows us to model individuals and how these individuals interact to form emergent phenomena. A great example of this is crowds. Recently we (people at CASA) have been exploring ways to carryout pedestrian agent-based models in 3D and I just came across this short presentation by Paul Torrens entitled “Modelling Crowd Behaviour” from the O'Reilly Where 2.0 Conference. It is worth watching the talk (15min) as it shows how GIS and ABM can be coupled together and why studying crowd movement is important.

The talk can be watched here.

If you interested in pedestrian modelling and software the papers by Christian Castle might be of interest:

Castle, C.J.E. (2007), Guidelines for Assessing Pedestrian Evacuation Software Applications, Centre for Advanced Spatial Analysis (University College London): Working Paper 115, London.

Castle, C.J.E. and Longley, P.A. (2008), 'Emergency Pedestrian Evacuation Analysis: A Review and Interpretation of Software Applications', in Sui, D.Z. and Cutter, S.L. (eds.), Geospatial Technologies and Homeland Security: Research Frontiers and Challenges, Springer, Berlin.


Monday, April 28, 2008

Agent-Based Crime Simulation

I just come across a blog called “Agent-Based Crime Simulation” by Nick Malleson who is building an agent-based model to predict rates of residential burglary. Within the model potential burglars are represented as agents, drawing from studies in criminology and artificial intelligence. The virtual environment is made as realistic as possible by incorporating GIS data (in the form of OS Mastermap) for the area of study.

While the model is still only a prototype, it is one of the first examples I seen using GIS in Repast Simphony, he has also posted a short video showing simple burglar agents moving around their environment.

For more information about the model and Nick's blog see “http://crimesim.blogspot.com/”.


video

GIS Extension for NetLogo

I am a big fan of NetLogo, I have seen many examples and have been wondering how I could easily create agent-based models using GIS within it. Whilst browsing the OpenABM website I came across a post by Eric Russell about a beta version GIS Extension for NetLogo and could not resist trying it out. The extension provides primitives for importing vector GIS data (in the form of ESRI shapefiles) and raster GIS data (in the form of ESRI ascii grid files) into NetLogo.

The extension and instillation instructions can be downloaded from:
http://ccl.northwestern.edu/netlogo/4.0/extensions/gis/
There are two example models, one which loads a raster file of surface elevation for a small area near Cincinnati, Ohio (above). To quote from the documentation:
 “It uses a combination of the gis:convolve primitive and simple NetLogo code to compute the slope (vertical angle) and aspect (horizontal angle) of the earth surface using the surface elevation data. Then it simulates raindrops flowing downhill over that surface by having turtles constantly reorient themselves in the direction of the aspect while moving forward at a constant rate”.
The second example model (below) loads four different GIS datasets: a point file of world cities, a polyline file of world rivers, a polygon file of countries, and a raster file of surface elevation. It provides a collection of different ways to display and query the data, to demonstrate the capabilities of the GIS extension.

Thursday, April 17, 2008

Geographically Explicit Agents

A quick post for anyone interested following on from a presentation that I gave Association of American Geographers (AAG) Annual Meeting in Boston entitled “Using geographically explicit agents to explain and explore urban phenomena” given in the Agent Based Modeling II session

The Abstract of the talk was as follows:

"Agent-based modelling is at the forefront of computer modelling research focusing on the individual or groups of individuals, and how these individuals interact to form emergent structures. In particular, the ABM paradigm is becoming an increasingly used technique to study cities and regions. However, this new paradigm poses many challenges with regard to modelling. These include but are not limited to: 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 way 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. 

This paper will explore how we are addressing these issues with illustrated examples (applications) specifically focusing on residential segregation dimensioned upon London, which the author has developed and is currently developing. Furthermore, the models address other major problems with respect to agent-based modelling specifically integrating GIS within such models via a loose coupling approach. This integration of spatial data adds extra levels of complexity when studying urban phenomena, specifically that of segregation within agent-based models which is hardly touched upon in the literature. Furthermore, this integration allows the models to be grounded in actual places where geometrical features restrict agent interactions and how such places change over time. The paper will conclude with highlighting future avenues of research."
 
The presentation can be downloaded from here and a new working paper entitled “Constructing and Implementing an Agent-Based Model of Residential Segregation through Vector GIS” which slightly mirrors the talk can be found here. The full reference for this paper is:

Crooks, A. T. (2008), Constructing and Implementing an Agent-Based Model of Residential Segregation through Vector GIS, Centre for Advanced Spatial Analysis (University College London), Working Paper 133, London.

While the presentation focuses mainly on the second half of the abstract due to time constraints, further information about the challenges agent-based modelling poses with regard to modelling can be found in the following working paper:

Crooks, A. T., Castle, C. J .E. and Batty, M. (2007), Key Challenges in Agent-Based Modelling for Geo-Spatial Simulation, Centre for Advanced Spatial Analysis (University College London), Working Paper 121, London.

As always any thoughts or comments about the work or presentation are more than welcome.

Wednesday, April 16, 2008

New Working Paper: ABM of Residential Segregation

We just finished a new working paper entitled “Constructing and Implementing an Agent-Based Model of Residential Segregation through Vector GIS

The abstract is as follows:
In this paper, we present a geographically explicit agent-based model, loosely coupled with vector GIS, which explicitly captures and uses geometrical data and socio economic attributes in the simulation process. The ability to represent the urban environment as a series of points, line and polygons not only allows one to represent a range of different sized features such as houses or larger areas portrayed as the urban environment but is a move away from many agent-based models utilising GIS which are rooted in grid-based structures. We apply this model to the study of residential segregation, specifically creating a Schelling (1971, 1978) type of model within a hypothetical cityscape, thus demonstrating how this approach can be used for linking vector-based GIS and agent-based modelling. A selection of simulation experiments are presented, highlighting the inner workings of the model and how aggregate patterns of segregation can emerge from the mild tastes and preferences of individual agents interacting locally over time. Furthermore, the paper suggests how this model could be extended and demonstrates the importance of explicit geographical space in the modelling process.

Keywords: Agent-Based Modelling, GIS, Residential Segregation, Repast

The full reference is:
Crooks, A. T. (2008), Constructing and Implementing an Agent-Based Model of Residential Segregation through Vector GIS, Centre for Advanced Spatial Analysis (University College London): Working Paper 133, London, England. (pdf)

The paper can be downloaded from here. As always, any thoughts or comments about the paper are more than welcome.

Monday, April 14, 2008

OpenABM

The Open Agent Based Modeling (OpenABM) Consortium aims at “to foster and improve the development, communication, and dissemination of agent based models for research, practice, and education” which we think is a great idea.

Further information about the establishment of the OpenABM Consortium can be found in the Journal of Artificial Societies and Social Simulation. (JASSS) paper entitled “Towards a Community Framework for Agent-Based Modelling” by Marco Janssen, Lilian Na'ia Alessa, Michael Barton, Sean Bergin and Allen Lee.

The site (http://www.openabm.org/) is well worth exploring we have found the Overview, Design Concepts, Details (ODD protocol) topic very interesting.

Thursday, April 10, 2008

Pacman: is it an agent-based model?

Discussions around the office about agent-based modelling are becoming interesting. One question arising from the discussion is whether Pacman an agent-based model? While packman himself is controlled by the user, the ghosts are programmed as individuals with the task to find and destroy him.

Richard from Casa and also creator of Google Map Creator has remade Pacman in his spare time.

To play a game click here. As always any thoughts and comments about Pacman being an agent-based model or any other posts are more than welcome.

Wednesday, April 09, 2008

3D Agent Based Modelling in Cities

There are a number of agent-based modelling toolkits available for the creation of 3D agent-based models (e.g. NetLogo, Repast). However there is difficulty in incorporating geographical information into such models. On solution is potentially importing such geographical information into a 3D modelling package and creating agents directly within such a system.

This is exactly what Andy Hudson Smith, a colleague from CASA and writer of the Digital Urban blog has been experimenting with creating agent-based models in 3D Studio Max.

The first movie below displays Andy’s first tentative steps using the system to create an 'Ant Like' behaviour on a surface:




Click here to see the original blog post

While the first movie highlights the first steps in developing 'Ant Like' behaviours on a surface, their second movie displays a degree of intelligence in their agents. The agents are now aware of the environment around them and each other, as such they avoid collisions while wandering around the surface:



Click here to see the original blog post

While this is work in progress, Andy is developing this work further hoping to develop a 3D city model with agents such as cars and pedestrians interacting with their environment and with each other.

For more information on the creation of 3D models and updates of the work its well worth checking out the Digital Urban blog. Andy is planning on writing a tutorial on the system as soon as it is more advanced.

On a side note one can also loosely couple an agent-based model with 3D Studio Max, for example T. Narahara of Harvard University, Cambridge, MA it explores the integration of NetLogo with 3D Studio Max. Under a paper entitled Enactment Software: Spatial Designs using Agents-Based Models.’

The Agent-based Environment in NetLogo (left), and the 3-D Visualization (right)

Tuesday, April 01, 2008

Fine Scale Modelling of the London Housing Market

Over the last few weeks Duncan Smith and I have been working on paper entitled “Fine Scale Modelling of the London Housing Market” for the GISRUK 2008 conference.

The motivation behind this research comes from the lack of fine scale property data within England. Unlike other countries, England has no national cadastre on housing attributes (such as size, type and age) which restricts application of GIS in planning. While new datasets are becoming available, we have become interested in exploring if combining recent datasets, such as OS address data and Land Registry transaction data can begin to fill this data gap? And if this is the case, could a fine scale housing database developed from these datasets be used to improve house price modelling?



Isle of Dogs Housing Density 3D Map.

While at present this is work in progress, the presentation outlines our current work and initial findings while the paper suggests future work, such as the creation of an agent-based model exploring residential choice.




Full Reference:

Crooks, A. T., Smith, D. A., and Theseira, M. (2008), The Fine Scale Spatial Dynamics of the Greater London Housing Market, in Lambrick, D. (ed.), Proceedings of the 16th Geographical Information Systems Research UK Conference, UNIGIS, Manchester Metropolitan University, England, pp. 117-124. (pdf)