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4B_2_A step towards the improvement of spatial quality of web 2.0 geo-applications

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4B_2_A step towards the improvement of spatial quality of web 2.0 geo-applications

  1. 1. A step towards the improvement of spatial data quality of Web 2.0 geo-applications The case of OpenStreetMap Vyron Antoniou, Muki Haklay, Jeremy Morley Department of Civil, Environmental and Geomatic Engineering
  2. 2. A fundamental GIS problem Information System Real World http://www.bing.com/maps Google Earth
  3. 4. OSM Map Features
  4. 5. Wiki Democracy +
  5. 6. OSM Data Geometry Attributes (Tags) +
  6. 7. OSM’s Geometry Haklay et al. Antoniou et al. Completeness Positional Accuracy
  7. 8. Tags?
  8. 10. Unique Tags vs Total Tags for each OSM Feature Category (GB) Sum: 2.25M tags
  9. 11. How many tags do we have for each entity?
  10. 12. Residential (2826) Primary (623) How often there is a new Tag introduced?
  11. 13. How often there is a new Tag introduced?
  12. 14. Unique Tags vs Popular Tags (95% of population)
  13. 15. From OSM wiki-pages to XML Schema XML Schema = OSM Specification
  14. 16. From OSM wiki-pages to XML Schema
  15. 17. <ul><li>Data Quality changes whenever there is a change in: </li></ul><ul><li>The data (e.g. due to a transformation) </li></ul><ul><li>The ground truth </li></ul><ul><li>The specifications of the product </li></ul>
  16. 18. <ul><li>Data Quality changes whenever there is a change in: </li></ul><ul><li>The data (e.g. due to a transformation) </li></ul><ul><li>The ground truth </li></ul><ul><li>The specifications of the product </li></ul>
  17. 19. Merkaartor Potlatch JOSM Freedom, Formalization and Quality Standards?
  18. 20. Freedom, Formalization and Quality Standards?
  19. 23. Final Points <ul><li>Tags can greatly affect the quality of a VGI Map. </li></ul><ul><li>The loose structure of Feature extraction and attribution introduces errors. </li></ul><ul><li>Errors are proportional to the tags’ population. </li></ul><ul><li>The uncontrolled voting system deteriorates the overall quality of the OSM data. </li></ul><ul><li>Errors or discrepancies in Features’ Tags can spread around. </li></ul><ul><li>Formalization can be achieved under the hood. </li></ul>
  20. 24. Thank you
  21. 25. Thank you!
  22. 26. User Discrepancies Start and Stop Digitizing?
  23. 27. Name: X Road One-way: Yes Name: Y Road One-way: No User Discrepancies
  24. 28. OSM Quality Assurance Openstreetbugs Keep Right
  25. 29. The purpose of this specification (566 pages!) is to: • provide a list of the RWOs present in OS MasterMap data; • define the RWOs present in OS MasterMap data; • list the features and attributes of each of the RWOs in OS MasterMap data; • clarify the representation of the RWOs in OS MasterMap data when needed; a nd • provide a document that will accommodate change as OS MasterMap data is enhanced.
  26. 30. OSM Growth Source: http://www.openstreetmap.org
  27. 33. OSM Data Quality Tests
  28. 36. Video
  29. 37. Tags: 2.25M tags in 18 OSM Feature Categories (UK)
  30. 38. Unique Tags per OSM Feature Category
  31. 39. Unique Tags vs Total Tags for each OSM Feature Category
  32. 40. What is really new with OSM? Free Raster maps…..Google Maps, Bing Maps, Yahoo! Maps? Licence terms User generated Content Geometry….. Vector data Attributes….. Tags

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