OpenStreetMap is a collaborative project to create a free editable map of the world. It uses a wiki model where volunteers can collect and edit map data using various software tools. Data is represented as nodes, ways and relations with tags to describe attributes. The project aims to build an accurate and detailed map that can be used for navigation and shared by anyone for any purpose.

1. OpenStreetMap
Carsten Keßler
Center for Advanced Research of Spatial Information and Department of Geography,
Hunter College, City University of New York
Presented by : Mohamed Nageh
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2. Roadmap
• Introduction
• Map Services in the Market
• Why can’t we use google maps ?
• Why OpenStreetMap Was Created ?
• The Wikipedia of Maps
• Contribution Statistics Summary
• Data Model
• Core OpenStreetMap Elements
• Node
• Way
• Relation
• Tags
• Technology Stack
• OpenStreetMap Data Editors
• Servers
• Data Paths
• Database Schema
• Data Quality
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3. Roadmap
• Introduction
• Map Services in the Market
• Why can’t we use google maps ?
• Why OpenStreetMap Was Created ?
• The Wikipedia of Maps
• Contribution Statistics Summary
• Data Model
• Core OpenStreetMap Elements
• Node
• Way
• Relation
• Tags
• Technology Stack
• OpenStreetMap Data Editors
• Servers
• Data Paths
• Database Schema
• Data Quality
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4. Map Services
• Google Maps
• Apple Maps
• Here
• Bing Maps
• TomTom
• Waze
• OpenStreetMap
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5. Why can’t we use google maps ?
• Wonderful hi-res aerial imagery
• License their data from teleatlas who license data from Navteq /
Teleatlas
• Google terms & conditions
• Doesn't allow deriving data from their maps
• Doesn't allow copying & re-distributing with a different license
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6. Why OpenStreetMap Was Created ?
• Geographical data and maps are generally not free.
• The OpenStreetMap project was born in UK in 2004 to create User-
Generated Street Maps as free geospatial data for anybody to use and
share.
• OpenStreetMap is free and editable map of the world built by
volunteers.
• People and commercial companies can use the map data.
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7. The Wikipedia of Maps
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OpenStreetMap is The Wikipedia of Maps

8. Contribution Statistics Summary
• 7.5 Million registered
users
• 7 Billion nodes, way,
and relation creation
• 7.5 Million user gpx
uploads
• 4 Million map
update/day
• 1.6 Million different
user contributors
Source 8

9. Contributions
• There are 3 main ways to contribute to OSM:
• Outdoor/Field Mapping
• Requires to have knowledge of the area to be mapped, data are captured using specific
hardware, e.g. GPS receivers
• Armchair /Remote Mapping
• Consists of digitizing elements (roads, buildings, etc.) in areas for which users have no
previous knowledge, data are usually obtained from aerial/satellite imagery
• Community/Bulk Import
• Consists of the direct import of data which is available with an open (and compatible)
license; this mapping method is not for beginners and can introduce problems if not
correctly performed.
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10. Roadmap
• Introduction
• Map Services in the Market
• Why can’t we use google maps ?
• Why OpenStreetMap Was Created ?
• The Wikipedia of Maps
• Contribution Statistics Summary
• Data Model
• Core OpenStreetMap Elements
• Node
• Way
• Relation
• Tags
• Technology Stack
• OpenStreetMap Data Editors
• Servers
• Data Paths
• Database Schema
• Data Quality
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11. Data Model
A geographic feature (object) is represented by geometry and tags that
describe the attributes of the feature
for example a path with a tag for classification (e.g. highway=footway).
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12. Core OpenStreetMap Elements
• In OSM there are 3 core elements that define geometries:
• 1. NODE
• defining points in space (e.g. tree, gate, trash bin, etc.)
• Has latitude and longitude
• Can stand alone, or form part of a way
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13. Core OpenStreetMap Elements
• In OSM there are 3 core elements that define geometries:
• 2. WAY
• defining linear features (e.g. road, river, etc.) and area boundaries (e.g. building, park,
etc.)
• Joins together several nodes
• Direction sometimes matters
• Can form a 'closed way' (area)
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14. Core OpenStreetMap Elements
• In OSM there are 3 core elements that define geometries:
• 3. RELATION
• providing explanation on how other elements work together (e.g. building with
courtyard, etc.)
• For complex things such as routes
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15. Tags
• Each element is characterized by at least one tag corresponding to a
specific attribute
• Tags are composed of two parts: a key and a value
• Conventions are agreed on the meaning and use of tags, which are
captured in Wiki (in the next slide)
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16. Tags
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Source

17. Multiple Tags for Elements
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• A road (polyline) along which people live, for which the maximum
legal speed is 50 km/h and whose name is ‘Via Roma’ will have tags:
Key Value
Highway = residential
Maxspeed = 50
Name = Via Roma

18. Examples : Node
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19. Examples : Node
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<node id="25496583" lat="51.5173639" lon="-0.140043"
version="1" changeset="203496" user="80n" uid="1238“
visible="true" timestamp="2007-01-28T11:40:26Z">
<tag k="highway" v="traffic_signals"/></node>

20. Examples : Way (Polyline)
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21. Examples : Way (Polyline)
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<way id="5090250" visible="true“
timestamp="2009-01-19T19:07:25Z“
version="8" changeset="816806“
user="Blumpsy" uid="64226">
<nd ref="822403"/>
<nd ref="21533912"/>
<nd ref="821601"/>
<nd ref="21533910"/>
<nd ref="135791608"/>
<nd ref="333725784"/>
<nd ref="333725781"/>
<nd ref="333725774"/>
<nd ref="333725776"/>
<nd ref="823771"/>
<tag k="highway" v="residential"/>
<tag k="name" v="Clipstone Street"/>
<tag k="oneway" v="yes"/>
</way>

22. Examples : Way (Polygon)
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23. Examples : Relation (Multi-polygon)
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Relations of type multipolygon are used, for example, to represent complex areas.

24. Roadmap
• Introduction
• Map Services in the Market
• Why can’t we use google maps ?
• Why OpenStreetMap Was Created ?
• The Wikipedia of Maps
• Contribution Statistics Summary
• Data Model
• Core OpenStreetMap Elements
• Node
• Way
• Relation
• Tags
• Technology Stack
• OpenStreetMap Data Editors
• Servers
• Data Paths
• Database Schema
• Data Quality
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25. Technology Stack
• OpenStreetMap runs entirely on an open-source software stack,
consisting of components that handle the editing, storage,
processing, rendering, and delivery of the map
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26. OpenStreetMap Data Editors
• ID Editor : web-based editor, suitable for beginners. ~Link
• JOSM (Java OpenStreetMap Editor) : is a feature-rich desktop editor,
suitable for advanced users. ~Link
• Vespucci : A full editor for OpenStreetMap that works both on small
(phones) and large (tablet) screen Android devices. ~Link
• And many other tools available that enable Creating, editing and
deleting nodes, ways, relationships and tags.
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27. Servers
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Around 15 servers hosted at UCL(University College of London) Source

28. Database Server
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Source
• Motherboard
• Supermicro X7DWN
• Motherboard with Intel 5400 (Seaburg) Chipset
• CPU
• 2x Intel Xeon Processor E5420 Quad Core 2.5Ghz
• Memory
• 32GB DDR2 667 ECC
• Disk
• 2x 73GB (3.5) SAS 15K
• 10x 450GB (3.5) SAS 15K
• Since 2009

29. Data Paths
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Source

30. Database - MySQL
• Generally fast and scalable enough
• Quadtile indexing extension
• Several annoying flaws:
• schema changes cause table copies
• different features on different db engines
• silently accepts invalid utf8
• some non-standard SQL syntax
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31. Database - Postgres
• Addresses a lot of MySQL flaws:
• Faster schema changes
• Better support for transactions, utf8, etc
• Personal preference of OSM system admins
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32. Database Schema
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33. Database Schema
• Users
• users / user_tokens / user_preferences / user_roles / user_blocks
• Geodata
• changesets / changeset_tags / changeset_comments / ...
• current_nodes / current_node_tags / nodes / node_tags
• current_ways / current_way_tags / current_way_nodes / …
• current_relations / current_relation_tags / current_relation_members / …
• GPS Data
• gpx_files / gpx_file_tags / gps_points
• Notes
• notes / note_comments
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34. Database Schema
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35. Database Schema
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36. Database Schema
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37. Database Schema
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38. Roadmap
• Introduction
• Map Services in the Market
• Why can’t we use google maps ?
• Why OpenStreetMap Was Created ?
• The Wikipedia of Maps
• Contribution Statistics Summary
• Data Model
• Core OpenStreetMap Elements
• Node
• Way
• Relation
• Tags
• Technology Stack
• OpenStreetMap Data Editors
• Servers
• Data Paths
• Database Schema
• Data Quality
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39. Data Quality
• Built by a large online community
• Many hands make light work
• Openly editable (and easy)
• Poor quality contributions?
• Gradual refinement
• Assume good faith
• Monitoring and correction
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40. Sources
• OpenStreetMap: User-Generated Street Maps | IEEE Journals &
Magazine | IEEE Xplore ~ 2008
• OpenStreetMap Carsten Keßler Center for Advanced Research of
Spatial Information and Department of Geography, Hunter College,
City University of New York, New York, NY, USA
• OpenStreetMap Wiki
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41. Questions
• How is a polygon represented?
• Multiple (sequence) nodes create Way.
• A way is either an open polyline or closed polyline(closed if the start and end
nodes are identical).
• A polygon is a closed polyline with tag area = yes
• It can be both with extra tags (area with exterior line)
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42. Questions
42
How is a polygon represented?

43. Questions
• How is a multi-polygon represented?
• Multi-Polygon is represented as a relation between more than one
polygon(way)
• Every polygon is a member of the relation and has its own properties(tags).
• The tag (role) defines the + or – of a polygon
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44. Questions
• How is a multi-polygon represented?
• Multi-Polygon is represented as a relation between more than one
polygon(way)
• Every polygon is a member of the relation and has its own properties(tags).
• The tag (role) defines the + or – of a polygon
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45. Questions
• How is a multi-polygon represented?
• Multi-Polygon is represented as a relation between more than one
polygon(way)
• Every polygon is a member of the relation and has its own properties(tags).
• The tag (role) defines the + or – of a polygon
45

46. Questions
• How is a multi-polygon represented?
• Multi-Polygon is represented as a relation between more than one
polygon(way)
• Every polygon is a member of the relation and has its own properties(tags).
• The tag (role) defines the + or – of a polygon
46

47. Questions
• How is a multi-polygon represented?
• Multi-Polygon is represented as a relation between more than one
polygon(way)
• Every polygon is a member of the relation and has its own properties(tags).
• The tag (role) defines the + or – of a polygon
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48. Questions
• What if a way has many sub-ways with different characteristics ?
• A relation between multi-way ( maintainable)
• every way is a member of the relation with its own tags.
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49. Questions
• What about altitude ?
• The OSM Data Model stores the 2D position (latitude and longitude) of
points, and elevation is just an "afterthought" stored in the tag system under
the ele=* and its subkeys.
• The following keys are recommended:
• ele=* – Used to store the elevation relative to a EGM96 geoid
• ele:wgs84=* – Used to store the ellipsoidal height in WGS84
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50. Questions
• Database columns in tables ?
• Sequence_id
• Member_role
• Member_type
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