1 / 28

Leeds workshop: May 2001

2001 output areas: specification, demonstration and maintenance. David Martin, Mark Tranmer, Abigail Nolan. Leeds workshop: May 2001. Overview. 2001 Output areas Specification Demonstration Maintenance Current developments. Leeds workshop: May 2001. 2001 Output areas.

medea
Download Presentation

Leeds workshop: May 2001

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 2001 output areas: specification, demonstration and maintenance David Martin, Mark Tranmer, Abigail Nolan Leeds workshop: May 2001

  2. Overview • 2001 Output areas • Specification • Demonstration • Maintenance • Current developments Leeds workshop: May 2001

  3. 2001 Output areas • 1991: EDs designed for data collection, but used for both data collection and output • 2001: separation of collection and output geographies - purpose-specific geographies • New output areas built from synthetic unit postcode polygons • Application of automated zone design (after Openshaw, 1977) Leeds workshop: May 2001

  4. Specification Initial Random Aggregation of Building Blocks Iterative Recombination Design Constraints (Contiguity, Thresholds, Shape, Size, Homogeneity) 2001 Output Areas Leeds workshop: May 2001

  5. OA design (1) Initial random aggregation of postcodes into potential output areas RSS meeting: Nov 2000

  6. OA design (2) Choose one postcode at random as candidate for swapping into a different output area RSS meeting: Nov 2000

  7. OA design (3) Make the swap and evaluate the impact on the overall solution RSS meeting: Nov 2000

  8. OA design (4) If swap does not result in improvement, go back to the previous configuration RSS meeting: Nov 2000

  9. OA design (5) Choose another postcode at random as candidate for swapping into another output area RSS meeting: Nov 2000

  10. OA design (6) If the swap results in an overall improvement, keep it as part of the solution, and examine a new potential swap... RSS meeting: Nov 2000

  11. Basic constraints • Contiguity: output areas from adjacent postcodes (NB problem of stacks) • Thresholds: output areas above population thresholds (NB problem of sub-threshold parishes) Leeds workshop: May 2001

  12. Shape and size • Shape: output areas should be as compact as possible • - minimize perimeter2/area • Size: output areas should be as uniformly sized as possible - avoiding very large and very small populations • - minimize S(OApop-target)2 Leeds workshop: May 2001

  13. Measuring homogeneity • Homogeneity: output areas should be as socially uniform as possible • - maximize proportions in dominant category • - maximize intra-area correlations Leeds workshop: May 2001

  14. Intra-area correlation • Measures similarity of values within any area of interest (Holt et al., 1996). Higher correlation = greater homogeneity (theoretical maximum of d = 1.0) • Can be computed for a single category (eg. owner occupied) or for multi-category variables • Tenure and dwelling type evaluated Leeds workshop: May 2001

  15. Zone design experiments • ONS postcode polygons for test areas • Populated with plausible synthetic populations by iterative sampling of SAR individuals (PCs structured by dwel. type) • Test OAs constructed using alternative combinations of design constraints, including both homogeneity measures Leeds workshop: May 2001

  16. Sample urban and rural results Leeds workshop: May 2001

  17. EDs Leeds workshop: May 2001

  18. Unit postcodes Leeds workshop: May 2001

  19. Shape and tenure Leeds workshop: May 2001

  20. IAC Leeds workshop: May 2001

  21. Demonstration: website http://www.geog.soton.ac.uk/research/oa2001/ Leeds workshop: May 2001

  22. OA Demonstrator • Experimental results for Kerrier (rural-villages), Cardiff (urban-suburban) and Manchester (metropolitan) • ONS prototype postcode polygon set • Threshold population 100, targets of 150, 250 • Combinations of population, shape and intra-area correlation controls • PDF, CSV and Shape file samples online Leeds workshop: May 2001

  23. Demonstrator data Leeds workshop: May 2001

  24. Maintenance • Continual postcode change • Recoded and analysed postcode change in Manchester test area • Most changes: relabelling or splitting • Developments during course of project: • ONS to maintain postcode to OA directory • OS to create postcode boundary set Leeds workshop: May 2001

  25. External developments • ONS create own synthetic postcode polygons for input to OA design • NISRA digitize postcode polygons, then input to ONS OA design • Homogeneity – for consultation and final decision. NB different considerations in NI • GROS already have postcode polygons, but different OA design procedure (smaller OAs) Leeds workshop: May 2001

  26. Project developments • Examining application of OA design algorithm to matching of two incompatible areal geographies, eg. 1991 EDs and 2001 OAs • Visual Basic implementation of code imminent • Contribution to small area microdata (SAM) design project Leeds workshop: May 2001

  27. Hampshire: threshold 5000 n = 176 mean = 8230 min = 5035 max = 15684 Leeds workshop: May 2001

  28. For further information • Project website: http://www.geog.soton.ac.uk/research/oa2001/ • For demonstrator datasets, follow: • OA demonstrator Leeds workshop: May 2001

More Related