high resolution and local scale: national population surface models from the uk censuses

Gridded Population Workshop: New York: May 2000

High resolution and local scale: national population surface models from the UK Censuses

David Martin

Department of Geography

University of Southampton


High resolution and local scale: overview UK data context 1971-2001 Need for non-zonal representations Redistribution model Implementation Applications Future directions Key references


UK data context 1971-2001

Basic spatial unit for census output: enumeration district (ED) mean c. 400 population

100m population-weighted centroid 1991- improved spatial resolution and

(imperfect) link to postal centroids no cadastral mapping, no large-scale

digital land use mapping


Need for non-zonal representations Wide variations in ED size and shape Space-filling, hence including extensive

unpopulated areas Large-scale redefinition of EDs (68%

1981-91)


Redistribution model (1: basics)

Population-weighted centroid(s) as summary points of local distribution

Locally adaptive kernel estimation based on inter-centroid distances

Redistribution of centroid counts into grid: spatially discontinuous model

Various derivatives, including constraint to zone boundaries (1991- only)


Redistribution model (2: function)

22

22

ij

ijij

dk

dkw

Weighting

Distance

wij

dij k


Redistribution model (3: example)Centroids and boundaries Gridded population model


Implementation (1: data)

10/100m ED centroids and counts 200m grid 250m initial search radius simple distance decay model no ED boundaries national models (c 155,000 centroids) FORTRAN now, Visual Basic to follow...


Implementation (2: example)

300 x 300 km extract from national population model of UK based on 1991 Census


Implementation (3: extensions)

Reallocate ED data onto 100m postcode locations in proportion to household counts, (c. 15 postcodes per ED)

Constraint to zone boundaries where available - preserves zonal populations (at grid resolution)


Applications (1: examples)

Ancillary layer in urban satellite image interpretation (eg. Mesev et al, 1995)

Population base for distance-sensitive applications (eg. Lovett et al, 1997)

Basis for intercensal comparison (eg. Bracken and Martin, 1995)

Non-UK data with no boundaries


Applications (2: visualization)

Visualization of population ‘landscapes’

(eg. Wood et al, 1999)


Applications (3: distance models)

East Anglia population model for modelling predicted visitor rate function

(eg. Brainard et al, 1997)


Future directions

2001: Census design using GIS 2001: new, smaller output areas,

stronger link to postal geography Potential for error estimation and model

calibration from sub-threshold census data

International applications? (eg. Australia)


Key references

Martin, D. (1989) Transactions IBG Bracken, I. and Martin, D. (1995) E&P a Martin, D. (1996) IJGIS http://census.ac.uk/cdu/surpop

high resolution and local scale: national population surface models from the uk censuses

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