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Empirical study on location indeterminacy of localities

Empirical study on location indeterminacy of localities. Julie Sungsoon Hwang & Jean-Claude Thill Department of Geography State University of New York at Buffalo U.S.A. August 24, 2004 11th Int’l Symposium of Spatial Data Handling. Research question.

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Empirical study on location indeterminacy of localities

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  1. Empirical study on location indeterminacy of localities Julie Sungsoon Hwang & Jean-Claude Thill Department of Geography State University of New York at Buffalo U.S.A. August 24, 2004 11th Int’l Symposium of Spatial Data Handling

  2. Research question • How can we represent vague concepts of spatial object in a (discrete) computing environment (e.g. GIS)? • Nearness in localities • Mental maps of localities • Indeterminate boundaries of localities

  3. Research scope • Mental maps • Generals: f (distance, relation, scale) • Specifics : f (preferences, experience, …) • Localities • Official recognition: eg. administrative unit • Unofficial recognition: eg. vernacular region

  4. Research objective [1] • Building the model of locality boundary using fuzzy regions (egg-yolk model) and some rules regarding nearness B 1 A 0 A B 2-Dimensional Geographic Space x: 1-Dimensional Geographic Space Y: Degree of Membership

  5. Buffalo Wilson Urban Rural Research objective [2] • Examining any difference in location indeterminacy between urban and rural settings

  6. Example: identifying localities… Which city? Accident location?

  7. Task 1: theoretical Building the model of locality boundary using fuzzy region and rules of nearness

  8. Fuzzy regions Core Exterior Boundary

  9. Nearness Near “Syracuse”? = Fuzzy set membership of belonging to “Syracuse” What determines the fuzzy set membership function value? • Euclidean distance • Spatial qualitative relation • Scale-dependent

  10. Exterior Boundary Core Locality as a fuzzy region 1stOrderGr 2ndOrderGr

  11. 1. Delineate boundaries 2. Assign membership values 3. Create TINs 4. Interpolate values on TINs Computing fuzzy set membership value in GIS: work steps

  12. Computing fuzzy set membership value in GIS: results

  13. 1 1 0.5 0.5 Distance Buffer Fuzzy proximity core 0.5-cut boundary exterior core 0.5-cut boundary exterior core 0.5-cut boundary Comparison to other proximity measures

  14. Task 2: empirical Examining any difference in location indeterminacy between urban and rural settings

  15. Georeferencing traffic accident data We considered 5460 out of 8631 cases from NYS ‘96-’01 Of these, 246 urban, and 298 rural localities are compared

  16. Computing location indeterminacy index of localities i= 1 - (Σi)/n 78% sure 95% sure 58% sure

  17. Comparing location indeterminacy index of urban versus rural localities • Average number of fatal crashes in rural areas is 2 whereas those in urban areas is 16 • To work around small number problem, we compute Bayesian estimates of both groups adjusted for within-group distributions People are 94% (or somewhere between 93% and 95%) sure in identifying urban localities while they are 88% (or somewhere between 86% and 90%) sure in identifying rural localities

  18. ANOVA Analysis of variance conducted on Bayesian estimates of location indeterminacy confirms the difference between urban versus rural locality is significant in terms of location indeterminacy Neighborhood types may affect the degree of certainty to which the boundary of locality is perceived

  19. Interpretation of results • Mental maps of urban settings may be less error-prone than those of rural settings • Spatial knowledge acquisition: city provides more landmark or route upon which judgment on indeterminate boundaries of localities can be based • Scale factor: dense urban settings provide a reasonable scale in which humans can conceptualize localities without much difficulty

  20. Conclusions • Fuzzy set theory provides a reasonable mechanics to represent vague concept of geospatial objects • Neighborhood types affect the way humans acquire spatial knowledge and forge mental representations of it

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