Wednesday, July 09, 2014

New Paper: Assessing the impact of demographic characteristics on spatial error in VGI features

LISA analysis of positional accuracy for the OSM  data set
Building upon our interest in volunteered geographic information (VGI) and extending our previous paper  "Assessing Completeness and Spatial Error of Features in Volunteered Geographic Information" we have just published the paper with the rather long title "Assessing the impact of demographic characteristics on spatial error in volunteered geographic information features" where we explore how demographics impact on the quality of VGI data

Below is the abstract of the paper: 
The proliferation of volunteered geographic information (VGI), such as OpenStreetMap (OSM) enabled by technological advancements, has led to large volumes of user-generated geographical content. While this data is becoming widely used, the understanding of the quality characteristics of such data is still largely unexplored. An open research question is the relationship between demographic indicators and VGI quality. While earlier studies have suggested a potential relationship between VGI quality and population density or socio-economic characteristics of an area, such relationships have not been rigorously explored, and mainly remained qualitative in nature. This paper addresses this gap by quantifying the relationship between demographic properties of a given area and the quality of VGI contributions. We study specifically the demographic characteristics of the mapped area and its relation to two dimensions of spatial data quality, namely positional accuracy and completeness of the corresponding VGI contributions with respect to OSM using the Denver (Colorado, US) area as a case study. We use non-spatial and spatial analysis techniques to identify potential associations among demographics data and the distribution of positional and completeness errors found within VGI data. Generally, the results of our study show a lack of statistically significant support for the assumption that demographic properties affect the positional accuracy or completeness of VGI. While this research is focused on a specific area, our results showcase the complex nature of the relationship between VGI quality and demographics, and highlights the need for a better understanding of it. By doing so, we add to the debate of how demographics impact on the quality of VGI data and lays the foundation to further work.

The analysis workflow
Full Reference:
Mullen W., Jackson, S. P., Croitoru, A., Crooks, A. T., Stefanidis, A. and Agouris, P., (2014), Assessing the Impact of Demographic Characteristics on Spatial Error in Volunteered Geographic Information Features, GeoJournal. DOI: 10.1007/s10708-014-9564-8

Thursday, June 05, 2014

The Evolving GeoWeb

We recently contributed a chapter to Geocomputation (2nd edition) entitled "The Evolving GeoWeb". What is interesting is the marked difference between the first edition (which was published in 2000) and the second. For example, in the latest edition, there is a chapter on agent-based modeling (ABM), while in the first, only cellular automata (CA) models were covered and ABMs only briefly discussed. We also see in the second edition new chapters including ours on the GeoWeb which shows how the field of geocomputation has changed with advances in Web 2.0 technology, greater computational power, new devices (such as GPS enabled smart phones) and the rise in new sources of data (volunteered and ambient geographical information, VGI and AGI). The abstract of our chapter is copied below, while examples of early and current web mapping is provided in the figures below.

"The Internet and its World Wide Web (WWW) have revolutionised many aspects of our daily lives from how we access and retrieve information to how we communicate with friends and peers. Over the past two decades, the Web has evolved from a system aimed primarily towards data access to a medium that fosters information contribution and interaction within large, globally distributed communities. Just as the Web evolved, so too did Web-based GeoComputation (GC), which we refer to here as the Geographic World Wide Web or the GeoWeb for short. Whereas the generation and viewing of geographical information was initially limited to the purview of specialists and dedicated workstations, it has now become of interest to the general public and is accessed using a variety of devices such as GPS-enabled smartphones and tablets. Accordingly, in order to meet the needs of this expanded constituency, the GeoWeb has evolved from displaying static maps to a dynamic environment where diverse datasets can be accessed, exchanged and mashed together. Within this chapter, we trace this evolution and corresponding paradigm shifts within the GeoWeb with a particular focus on Web 2.0 technologies. Furthermore, we explore the role of the crowd in consuming and producing geographical information and how this is influencing GeoWeb developments. Specifically, we are interested in how location provides a means to index and access information over the Internet. Next, we discuss the role of Digital Earth and virtual world paradigms for storing, manipulating and displaying geographical information in an immersive environment. We then discuss how GIS software is changing towards GIS services and the rise in location-based services (LBS) and lightweight software applications (so-called apps). Finally, we conclude with a summary of this chapter and discuss how the GeoWeb might evolve with the rise in massive amounts of locational data being generated."

PARC Map Viewer (Source: Putz, 1994)

Google Earth as a base layer for possible trajectories of the radioactive plume from the Fukushima Daiichi nuclear disaster. The different color lines represent different possible paths of the plume (Source:

A proof of our chapter can be downloaded from here. We hope you enjoy it!

Full reference:
Crooks, A.T., Hudson-Smith, A., Croitoru, A. and Stefanidis, A. (2014), The Evolving GeoWeb, in Abrahart R. J. and See, L. M. (eds.), Geocomputation (Second Edition), CRC Press, Boca Raton, FL, pp. 69-96. (pdf)

Tuesday, May 27, 2014

A semester with Spatial Agent-based Models

This last semester, I taught a class entitled "Spatial Agent-based Models of Human-Environment Interactions" which introduces graduate students to the use of agent-based techniques as a means of modelling human-environmental interactions. Within the class we cover a variety of applications in areas such as agriculture, forestry, biodiversity, habitat degradation, interactions between human populations and nonhuman species and urban models. As with many of the courses I teach it combines literature reviews with hands-on modelling. One of the requirements of the class is for students to complete a class project where they develop their own agent-based model in their area of interest. As always there were a range of models and I wanted to share some here.

The first is an agent-based model of gentrification in part of Washington DC. Within the model, developers create new houses, residents can move in and out and as a result the demographics of the area changes over time. The movie below gives a sense of the model dynamics.

In another model, a student developed a simple agent-based model which asks the question if random police patrols vs. a concentrated police effort can reduce the number of burglaries in an area. The burglars have a simple routine and commit crimes when their energy reserves fall below a certain threshold. If the police agents see a crime being committed they arrest the burglar. Over time, crime hotspots emerge (detected using DBSCAN) which lead to an increased police presence in an area. The movie below gives a sense of the model dynamics.

In another model,  a student explored how commuting behaviors of agents might lead to traffic jams and how different transportation options might reduce congestion. The movie below gives a sense of the model dynamics.

Overall it was a fun class with many interesting models programed in a variety of languages and toolkits (Python, Java, MASON, NetLogo).

Friday, April 25, 2014

Special Sessions on GeoComputation @ NARSC


Second Call for participation

Special Sessions on GeoComputation

61st Annual North American Meetings of the Regional Science Association International NARSC - RSAI
November 12-15, 2014, Washington, DC, USA

The special sessions on various aspects of GeoComputation are planned for the North American Meetings of the Regional Science Association International (NARSC) to be held in Washington DC, USA, November 12-15, 2014. Suitable topics for the session presentations are theoretical, methodological and applied issues related to GeoComputation – spatial analysis and modeling, and in the context of regional science.

Please let us know if you are interested to contribute to the special session(s) by sending an email at <> with the title, abstract, name of author(s), affiliations, contact details and the unique ID number at your earliest but not later than June 25th, 2014. The abstract should be 2,000 to 5,500 characters and spaces.

Please note that in order to have your presentation included to the special session we do need the unique identification number (ID). The ID, or PIN, is a number included at the bottom of the confirmation email received following the submission of an abstract.

Detailed information about the NARSC conference can be found at . Information about the submission process can be found at . Conference abstract submission deadline is July 1st, 2014.

Looking forward to seeing you in Washington, DC.

The organizers:

Prof. Suzana Dragićević
Department of Geography
Simon Fraser University, Canada

Prof. Andrew Crooks
Department of Computational Social Science
George Mason University, USA

Prof. Jean-Claude Thill
Department of Geography and Earth Sciences
University of North Carolina at Charlotte, USA

Saturday, April 12, 2014

AAG and Twitter

After spending a rather enjoyable few days at the Association of American Geographers (AAG) annual meeting in Tampa where there were some great talks on agent-based modeling, GIS and many other topics which I find interesting, along with catching up with some old friends and meeting new ones, its now time to head back up North. 

However, before jumping on the plane, I thought it would be intersing to look at the twitter traffic of the event (especially how there so many talks on using social media for geographical research). That being said, before showing the Twitter networks associated with the conference, one issue that was common among the conversion outside of the sessions was the lack of wifi access at the conference which accounts for small numbers of tweets durring the events but also one could argue people were more interested in the talks than that of tweeting. With that being said, within this analysis we show below we collected data using the #aag2014 and the @theAAG to explore the Twitter conversation.

The image below shows the # hashtag network from the conference with the biggest cluster being #aag2014 and associated words (click here to see a high solution image)

In the next image we removed the #aag2014 to only show the details of the network within this cluster. After removing the #aag2014 we re-ran the clustering on this network. The graph below shows the biggest clusters (with 3 or more nodes) within the #aag2014 group. Nicely outlined are the discussion topics (e.g. gender, sexuality, intimacy, climate, geoweb). Click here to see a higher resolution image.

Moving away from the hashtags and looking at the retweet network we were surprised to see that the AAG's account wasn't more active (click here to see a higher resolution image).

Also we are currently working on a spatial-temporal slider to look at the conversion over time. Below is a sneak peak from one moment in time. This will be soon coming to the Geosocial Gauge website.