OpenStreetMap

OpenStreetMap of Cambridge

OpenStreetMap (OSM) is a collaborative project to create free editable maps. The maps are created using data from portable GPS devices and other free sources.

The map data and rendered maps are licensed under Creative Commons Attribution-ShareAlike 2.0 license

Wiki map

The makers of OpenStreetMap are aiming for a wiki-like approach to map editing. Inspired by sites such as Wikipedia, the map display features a prominent 'Edit' tab, taking the user to a simple editing interface.

Also in keeping with wiki concepts, the back-end data structures include storing a full revision history, although visible history & revert features are still under development.

History

OpenStreetMap was founded in July 2004 by Steve Coast. In April 2006 OSM began a process of transforming itself into a foundation.

"The OpenStreetMap Foundation is an international non-profit organisation dedicated to encouraging the growth, development and distribution of free geospatial data and to providing geospatial data for anybody to use and share."

Raw GPS data (tracklogs) for Hedge End

Mapping Process

The map data in the system so far has mostly been built from scratch, through a collaborative mapping process. This normally begins with users uploading data onto OSM from their handheld GPS units. This is followed by a manual editing process, creating the "nodes", "segments" and "ways", and tagging these with key-value pairs to represent information about the different types of street, names of the streets etc.

Yahoo! Aerial Imagery Agreement

A special agreement has been made with Yahoo! to allow OpenStreetMap to make use of their vertical aerial imagery. The online editing tools are permitted to display the imagery as an overlay, and OpenStreetMap contributors may create their vector based maps as a derived work, released with an open license.

This greatly simplifies the mapping approach for areas where this is available, but the aerial imagery coverage is limited to a few major cities.

Data format

OpenStreetMap uses a topological data structure

• Nodes are points with a geographic position
• Segments connect two nodes with a line
• Ways are groups of segments, representing a polyline or polygon
• Tags can be applied to nodes, segments, or ways, and consist of name=value pairs

The Ontology of map features (the meaning of tags) is maintained on a wiki

OpenStreetMap of Soho, central London

Tools

• GPS
  • GPSBabel - convert tracklogs
• Editing
  • 'Potlatch' - online Flash editor
  • JOSM - Desktop Java editor
• Viewing
  • Online Ajax-style Slippy maps.
    • Mapnik renderer
    • Osmarender using XSLT to generate SVG
    • Tiles@home distributed map-rendering project.
  • Phone and GPS displays
• Routing
  • Gosmore (software)

Data sources

• GPS tracklogs recorded by people out walking, cycling, and driving, combined with their notes and photos from the journey
• Local knowledge
• Public domain sources:
  • Landsat 7 satellite imagery
  • Prototype Global Shorelines (PGS)
  • TIGER data of the United States
  • Out-of-copyright Ordnance Survey maps
• Satellite and aerial images
  • Ability to derive maps from Yahoo! Maps imagery
• Contributed datasets
  • AND Automotive Navigation Data data for Netherlands, China, India

See also

• Category:OpenStreetMap maps

External links

• www.openstreetmap.org - Project page
• Project Wiki
• Featured map images