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Ramya Raghupathy, Mapbox, Basemap Completeness in Asian Cities | SotM Asia 2017

  1. How Complete is the Map? State of the Map Asia
  2. Completeness assessment • Tries to answer how much of the real world details reflect on the map • Feature level focus
  3. Completeness is a relative idea. A map is never complete!
  4. Why is completeness research important? • Identify areas to focus editing • Understand health of mapping community
  5. Prior work
  6. 80 cities for assessment
  7. From cities to tiles
  8. Compute basemap details for 1 billion z15 tiles worldwide
  9. Gold Standard • Benchmark / Baseline for a reliable reference • Helps measure quality in other datasets • Human Stamp of Approval • Use case: To determine model for feature level completeness that can be applied to estimate completeness elsewhere
  10. Gold Standard for Completeness Assessment • Identify Gold Standard tiles • Could be different for each feature • Start with a simple feature: building
  11. Identification of gold standard tiles for buildings I. Identify candidate tiles • Manual selection of candidate tiles likely to be excellent quality • Based on location (known edit patterns), feature counts/properties, “popularity”
  12. “Popular” = attracts lots of eyeballs
  13. Identification of gold standard tiles for buildings II. Three mappers rate each candidate tile on: • Coverage • Quality • Height • Building Type • Address Data
  14. Coverage:
  15. Coverage:
  16. Coverage:
  17. Coverage:
  18. Early learnings What predicts completeness?
  19. Densest tiles often have higher completeness
  20. Dense buildings in gold standard tile Kathmandu
  21. Dense buildings in gold standard tile Jakarta
  22. Dense buildings in gold standard tile New York City
  23. Dense buildings in gold standard tile Los Angeles
  24. Dense building tiles in gold standard tile San Francisco
  25. Dense building tiles in gold standard tile Washington DC
  26. But some less dense tiles are also very good
  27. Commercial areas have larger buildings, so less dense
  28. Built area as a better metric?
  29. Built area must account for parks, waterbodies, etc.
  30. But outside urban core, built area still not a predictor
  31. Suburb: low built area; quality map
  32. Road <-> building correlation?
  33. Residential roads in residential areas
  34. Commercial areas are surrounded by Major Highways
  35. Conclusion: It’s complex!
  36. Next steps: Building model integrating multiple factors based on gold standard ratings
  37. Dashboard
  38. ?