Geocoding is more difficult than mapping and routing due to challenges with parsing unstructured address inputs and inconsistencies in reference data. Parsing addresses requires probabilistic approaches like hidden Markov models to understand varied address formats. Reference databases are complicated by issues like multiple valid address names and changing street names. While mapping and routing rely on established algorithms and standardized data, geocoding requires continuously trying to improve parsing techniques and enriching reference data with historical records to better match unpredictable real world addresses.

1. The Black Art of GeocodingFinding that elusive lat/lon John Fagan, Microsoft

2. The Black Art of GeocodingFinding that elusive lat/lon John Fagan Program Manager Microsoft Corporation @johnbfagan

3. We been making maps for 1000’s of years

4. Well known and established standards/principles

5. Lots of experience in building software to create bitmaps from vector and raster data

6. Data availability & Simple data model

7. Mapping easy to scale

8. ...and so is routing 1000’s years experience in wayfinding Over 50 years experience in routing algorithms Dijkstra's shortest path algorithm (1959)

9. Data availability & Simple data model

10. Routing, easy to scale

11. Geocoding not so easy 20 years experience 10 years of global Geocoding 5 years exposing geocoding to the mass consumer No standard algorithms Very few databases purpose built (maybe GNAF) Very hard to scale

12. Geocoding is fundamental Cant get a map without a geocode Cant get a route without a geocode Cant view your data without a geocode 80% of all information contains a geographic element.

13. It used to be easier

14. Now its hard

15. User expectations change with unstructured input 67 hill veiw road, s61 2bn in the 1850's 1.5 hours from Nice exact directions from Bangkok Patana School to Suvanapumi Airport in Bangkok. 10 mile radius from se20 7ua how long would it take me to walk around cancun how to get to m13 gb from g83 9le by car do bearded dragons bite?

16. But ......Geocoding NOT about Search

17. 52.19157,-1.70415

18. The reason it's called 'I'm Feeling Lucky,' is of course that's a pretty damn ambitious goal. I mean to get the exact right one thing without even giving you a list of choices, and so you have to feel a little bit lucky if you're going to try that with one go," tried to explain Sergey Brin.

19. Why is it hard (2 reasons)

20. Parsing: Hard to understand unstructured input

21. Finding Stratford-upon-Avon stratford stratford upon avon Stratford upon haven StratfordUponAvon Stratford-Upon-Avon stratford on avon stratford-on-avon stratford 0n avon stratford - upon-avon stratford on avaon stratfordaponavon stratford upon aavon stratfordupponavon

22. Finding Stratford-upon-Avon

23. Parsing In computer science and linguistics, parsing, or, more formally, syntactic analysis, is the process of analyzing a text, made of a sequence of tokens (for example, words), to determine its grammatical structure with respect to a given (more or less) formal grammar. http://en.wikipedia.org/wiki/Parsing

24. Old way of Parsing – Rules based A rules based approach (mainly done with regular expressions)

25. Probabilistic approach Machine learned Requires you to “train” the engine Requires truth sets of training data http://en.wikipedia.org/wiki/Hidden_Markov_model

26. Probabilistic approach: Hidden Markov Model input --> 165 fleet street london EC4A 2DY output --> address { street number : 165 street : fleet street city : london postcode : EC4A 2DY }

27. Multimap stats

28. Parsing has its limitations Parsing failures Multimap/Bing Maps (standrewsscotland) Google (uk near Boston, MA, USA) All fail - House number plus postcode (165, EC4A 2DY)

29. Parsing using a Spatial Engine http://research.microsoft.com/en-us/people/josephj/acm_gis_2007_robust_location_search.pdf

30. Why is it hard (Data)

31. Hard to match input with reference database

32. [OSM-talk] Baghdad maps I am informed that any road may have up to 4 names (which may be the same or different): The pre-Saddam name The Saddam-era name. The "public" name - What the people who live there call it. The "Official" name - What the new Government calls it. This situation is further complicated by language and social issues: Language The roads are names in Arabic. There is no fixed translation between the Arabic and Latin alphabets. Social Issues: 1) Sunnis tend to use the Saddam-era names Shia tend to rename streets and won't acknowledge Saddam-era names. Ethnic cleansing is changing the neighbourhoods and hence the names. Names (such as 14th July Bridge) will change later. My translator's opinion is that street names are going to take at least 2-3 years to settle down. http://lists.openstreetmap.org/pipermail/talk/2007-February/011273.html

33. Don't throw away your data Multimap have always kept old postcodes 10% of Multimap’s postcode database is of “dead” postcodes This might not work for routing and mapping, but very valuable for Geocoding

34. EC4A 1HE – Postcode of vintage 2002

35. Lash data and enrich Stratford-upon-Avon

37. Future = Real time Geocoding?

38. Summary Mapping and Routing – FIXED Geocoding – Must Try Harder Parsing Data

39. thanksjohn faganubergeo.com@johnbfagan