Population 24/7: population mapping gets out of bed! · 2015-09-08 · Population 24/7: population mapping gets out of bed! David Martin, University of Southampton CASA seminar, 14
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Population 24/7: population mapping gets out of bed!David Martin, University of Southampton
CASA seminar, 14 October 2009
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Acknowledgements
• Samantha Cockings and Samuel Leung
• Economic and Social Research Council award number RES-062-23-1811
• Advantages of gridded population models: esp. stability over time and reconstruction of settlement geography
• Deficiencies of current “night-time approaches”
• Enormous growth of new population-related data sources
7Photos: David Martin, Sam Cockings
Observations…
• This entire sub-branch of geographical and cartographic enquiry is essentially concerned with mapping the population in bed
• We have seen enormous advances in geovisualization techniques, computing power and dynamic modelling sophistication
• We have not adequately tackled the entire area of time-specific population modelling
(Schmitt, 1956, p. 83).
• “One of the most important and difficult problems now facing city planners is the development of accurate, usable techniques for estimating the current daytime population of census tracts in urban areas”
• Why? Reasons included modelling the location and size of bomb shelters and the potential casualties resulting from a nuclear attack
• Schmitt, R. C. (1956) Estimating Daytime Populations. Journal of the American Planning Association 22 (2), 83-85
Space-time population modelling
• ~99% of work based on night-time; ~0.5% daytime?
• Numerous motivations for time-specific models: emergency planning, transportation, business location, etc.
• General approach is to start with night-time population map and transfer population subgroups to specific daytime locations, e.g. schools, workplaces
• Longstanding difficulty of obtaining data with sufficient space/time resolution
• In reality, many different timescales to be modelled
Examples
• Emergency response in US cities – Sleeter and Wood (2006)
• US hazard exposure and response – McPherson et al. (2006)
• Landscan USA - Bhadhuri et al. (2007)
• Helsinki - Ahola et al. (2007)
• UK Health and Safety Executive – Smith and Fairburn (2008)
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Photo: David Martin
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Data sources - residential
• Census- or register-based, using “usual place of residence”
• Residence definition – equivalent to night-time population locations, students counted at term-time residence
• Decennial update interval – long-term population change
• UK census at output area level (OA, pop ~300) and official mid-year estimates (MYEs) at Lower Super OA level (LSOA, pop ~1500)
• Some workplace data from census, but not all people have workplaces and not all workplaces are daytime locations
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Data sources – non-residential
• New administrative sources esp. from government, Neighbourhood Statistics Service (NeSS)
• Huge growth in availability and frequency since 2001 census
• Annual Business Inquiry dataset (employers, employees)