Exploiting census workplace data to build a daytime grid map of England and Wales. David Martin,...

Exploiting census workplace data to build a daytime grid map of England and Wales.

David Martin, Samantha Cockings, Alan SmithEuropean Forum for Geostatistics, 10 November 2015

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Overview• Usual residence

• New census workplace zones and data for 2011

• Space-time population modelling

• 2011 England and Wales time-specific grids

• Conclusion

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Usual residence• Conventional census and register population base is usual residence

• By extension, census geography is itself a geography of usual residence

• England and Wales census output areas 2001, 2011 designed to maximise data utility in context of residential address locations (threshold size, target size, geographical shape) – mean population 309

• Most census counts are therefore representations of the characteristics of the night-time population

• Workplace questions asked but limited output data in 2001 census

• Working population has an entirely different spatial distribution to residences

4Photos: David Martin

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New census workplace zones and data for 2011• New workplace zones (mean 493 workers) for publication of census

statistics relating to the working population at place of work

– Some output areas have large workplace populations and can be subdivided into smaller workplace zones

– Some output areas can also be workplace zones– Some output areas have small (or zero) workplace populations and

need to be combined with others to create a larger workplace zone

• Implemented using automated zone design procedures very similar to those used for output areas

• Control over size allows much more workplace data to be published: 25 tables at workplace zone level

6Contains National Statistics and Ordnance Survey Data © Crown

copyright and database right 2014

Output areas

Workplace zones

Unit postcodes

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Why worry about non-residential population?• It’s a a major component of overall population distribution, especially

during day-time

• Variation over seasons, term times, day of week, time of day and other cycles

• Understanding time-specific population patterns is of particular relevance where population “exposure” is concerned: e.g. delivery of daytime services, transport planning or emergency planning

• Widespread interest in day-time, ambient, real-time populations for relevant applications

• Day-time population distribution also reflects education, health, leisure, transportation and many other activities

Night-time model: residential only, conventional grid

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Residential origin locations e.g. addresses, postcodes, OAs

Daytime destination locations e.g. workplaces, schools, hospitals

Day-time model: mixed activities – but which ones?

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Wednesday morning, school holiday… many grids?

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Space-time population modelling• Population 24/7 project, implemented time-based version of

SurfaceBuilder software – original work limited by lack of Open Data and census workplace data

• Time-specific grids built from library of population centroids, with time profiles

– Origins, defining all locations of residential population (output areas)

– Destinations, which may contain non-residential populations at specified times (workplaces, schools, etc.)

• Background layer (road network, water bodies) defines weighting mask

• Each centroid examined in relation to target time; population redistributed into grid cells according to relevant point in centroid time profile

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Sources of centroids and time profiles• Census population totals by (residential) output areas and workplace

zones

• Non-census destinations populations from Open Data sources on schools, colleges, universities, hospitals and visitor attractions

• Ordnance Survey OpenData for road network, background mapping

• Department for Transport Open Data on average annual daily road traffic flows

• Quarterly Labour Force Survey for working patterns by industry class

• Administrative and survey data sources on school opening hours, hospital appointment times – many possible extensions

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Acronyms: UoS = University of Southampton, HES = Hospital Episode Statistics, DfT = Department for Transport, NTM = National Transport Model, OS = Ordnance Survey

Total population

+/- external visitors

Private dwellings

Non-residential

Communal ests.

Transport

EmploymentEducation

Residential

Temp accomm.

Generalised local

Family/socialRetailLeisureTourism

Healthcare

RailMetro/subwayAirWater

Road

Locations Data Sources

- 2011 census area statistics- 2011 census area statistics

- 2011 census area statistics (workplace pop)- EduBase (school census), UoS travel survey-

--- Visit England- Visit England

- Health and Social Care Information Centre, HES

----

- DfT NTMStatistics, OS Meridian OpenData

-

00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 240

500

1000

1500

2000

2500

University of Southampton Travel Survey: Respondents on-campus, by 15 minute intervals

Persons

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2011 England and Wales time-specific grids• Demonstrating the feasibility of integrating Open datasets to

generate time-specific population models over a large area at 2011 census reference date

• Census output area centroids as population origin locations, define total population to be modelled

• Workplace zone centroids for workplace populations, by industry classification

• School, college, university, hospital, and visitor attractions as destination locations by postcode – treated as additional destination centroids

• Every destination centroid associated with a standard time profile

• England and Wales, weekday 02:00 and 14:00 target times, 200 x200m grid

2011 term-time weekday 02:00Contains National Statistics and Ordnance Survey data © Crown

copyright and database right 2015; Copyright © 2015, Re-used with the permission of the Health and Social Care Information Centre. All rights reserved. Contains public sector information licensed under

the Open Government Licence v3; © OpenStreetMap contributors

2011 term-time weekday 14+02:00/2Contains National Statistics and Ordnance Survey data © Crown

copyright and database right 2015; Copyright © 2015, Re-used with the permission of the Health and Social Care Information Centre. All rights reserved. Contains public sector information licensed under the Open

Government Licence v3; © OpenStreetMap contributors

2011 term-time weekday 02:00 5-17Contains National Statistics and Ordnance Survey data © Crown

copyright and database right 2015; Copyright © 2015, Re-used with the permission of the Health and Social Care Information Centre. All

rights reserved. Contains public sector information licensed under the Open Government Licence v3; © OpenStreetMap contributors

2011 term-time weekday 14:00 5-17Contains National Statistics and Ordnance Survey data © Crown

copyright and database right 2015; Copyright © 2015, Re-used with the permission of the Health and Social Care Information Centre. All

rights reserved. Contains public sector information licensed under the Open Government Licence v3; © OpenStreetMap contributors

Conclusion• 2011 England and Wales workplace zone dataset provides a major

component necessary for day-time population grid modelling

• Other Open Data sources providing increasingly useful evidence for other day-time activities and also for time profiles

• Different demographic sub-groups display different time-specific geographical distributions

• We should be developing and using time-specific population grids that are most appropriate to the intended application

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Exploiting census workplace data to build a daytime grid map of England and Wales. David Martin,...

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