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

Gridded Population Workshop: New York: May 2000 High resolution and local scale: overview n UK data context n Need for non-zonal representations n Redistribution model n Implementation n Applications n Future directions n Key references

Gridded Population Workshop: New York: May 2000 UK data context n Basic spatial unit for census output: enumeration district (ED) mean c. 400 population n 100m population-weighted centroid n improved spatial resolution and (imperfect) link to postal centroids n no cadastral mapping, no large-scale digital land use mapping

Gridded Population Workshop: New York: May 2000 Need for non-zonal representations n Wide variations in ED size and shape n Space-filling, hence including extensive unpopulated areas n Large-scale redefinition of EDs (68% )

Gridded Population Workshop: New York: May 2000 Redistribution model (1: basics) n Population-weighted centroid(s) as summary points of local distribution n Locally adaptive kernel estimation based on inter-centroid distances n Redistribution of centroid counts into grid: spatially discontinuous model n Various derivatives, including constraint to zone boundaries (1991- only)

Gridded Population Workshop: New York: May 2000 Redistribution model (2: function) Weighting Distance w ij d ij k 

Gridded Population Workshop: New York: May 2000 Redistribution model (3: example) Centroids and boundariesGridded population model

Gridded Population Workshop: New York: May 2000 Implementation (1: data) n 10/100m ED centroids and counts n 200m grid n 250m initial search radius n simple distance decay model n no ED boundaries n national models (c 155,000 centroids) n FORTRAN now, Visual Basic to follow...

Gridded Population Workshop: New York: May 2000 Implementation (2: example) n 300 x 300 km extract from national population model of UK based on 1991 Census

Gridded Population Workshop: New York: May 2000 Implementation (3: extensions) n Reallocate ED data onto 100m postcode locations in proportion to household counts, (c. 15 postcodes per ED) n Constraint to zone boundaries where available - preserves zonal populations (at grid resolution)

Gridded Population Workshop: New York: May 2000 Applications (1: examples) n Ancillary layer in urban satellite image interpretation (eg. Mesev et al, 1995) n Population base for distance-sensitive applications (eg. Lovett et al, 1997) n Basis for intercensal comparison (eg. Bracken and Martin, 1995) n Non-UK data with no boundaries

Gridded Population Workshop: New York: May 2000 Applications (2: visualization) n Visualization of population ‘landscapes’ n (eg. Wood et al, 1999)

Gridded Population Workshop: New York: May 2000 Applications (3: distance models) n East Anglia population model for modelling predicted visitor rate function n (eg. Brainard et al, 1997)

Gridded Population Workshop: New York: May 2000 Future directions n 2001: Census design using GIS n 2001: new, smaller output areas, stronger link to postal geography n Potential for error estimation and model calibration from sub-threshold census data n International applications? (eg. Australia)

Gridded Population Workshop: New York: May 2000 Key references n Martin, D. (1989) Transactions IBG n Bracken, I. and Martin, D. (1995) E&P a n Martin, D. (1996) IJGIS n