AT4 - Spatial Database Group

Citizens as Sensors: The World of
Volunteered Geography
Michael F. Goodchild
GeoJournal (2007) 69:211–221
DOI 10.1007/s10708-007-9111-y
Presented by:
Group 1:
Sampada kogje
Pavithra Panneerselvam
Evolving World of VGI
• What is VGI?
– Volunteered Geographic Information – special case of
user-generated content.
• Who do it?
– Citizens that willing to contribute information about
any geographic location
• What information is shared?
Information about a place, landmark, building, etc.
Pictures taken at a place
Routes that connect different parts of a city
A lot more!
Emerging Technologies
• Web 2.0: Allows users to post information in the form
of content, pictures, videos and VGI.
• Geo-referencing: Captures users’ geographic
information (such as Lat/Long, points on map).
• Geo-tags: Code that can be inserted into information to
note appropriate geographic location.
• GPS: Stand-alone and in-dash GPS devices compares
current location of vehicles with the digital street maps
and provide faster routes.
• Graphics: High-quality 2-D and 3-D graphics support
most of the applications.
Problem Statement
What drives people to do provide VGI?
How accurate are the results?
Will they threaten individual privacy?
How can they augment more conventional
Motivation for VGI
• World mapping is declining - Governments not willing
to pay for increasing costs of mapping and consider
map users as sources of income.
• Remote sensing replaced mapping – satellites not able
to sense many phenomena with remote sensing.
• Patchwork coverage: Collection of individuals that act
independently and respond to needs of local
communities create a patchwork coverage. With
appropriate tools and internet, the patchworks are
integrated removing inconsistencies and distributed
over the web.
Humans as Sensors
• Three types of sensor networks:
– Most fit in this first category that includes sensors
used for specific measurements, traffic movement etc.
– Less commonly used category include physical sensors
carried by humans, vehicles or animals.
– Most interesting category: Humans
Five senses
Intelligence to compile and interpret what they sense
Free to move around anywhere
Available in abundant (over 6 million)
• Citizen Science: Communities or networks of
citizens who act as observers
Types of Contributions
• Wikimapia – Users share information about all places around the globe.
• Companies that produced digital maps relied on networks of local
observers and paid them.
• Military personnel are potential sources of information about battlefield
• Human population in areas affected by natural disasters such as tsunami,
hurricanes, etc report conditions through mobile phone using voice, text
or pictures. VGI may not be used in many of these cases but reports
obtained from humans are useful in providing VGIs.
• Motivating Factors:
– Self-promotion
– Share information to only a close group of people – which later is
available to all
– Personal satisfaction
• Traditional mapping agencies had standards
which over the years changed.
• Google had no reputation in geography domain.
(Google Earth’s imagery over the University of
California campus was mis-registered by 20 miles)
• VGI is often called asserted geographic
information as the content is asserted by its
creator without any references, citations, or
Accuracy is still an issue!
Major Contributions of the Paper
• Coins the term Citizen Sensors that describe
individuals who "sense" geographic
information and who use this information to
construct "elaborate mental understanding of
the areas where [they] live and work.
• Outlines how development of mobile devices,
increased broadband access, and the
emergence of Web 2.0 technologies further
allow for VGI to be shared widely.
Concepts to be Refined
• Accuracy of VGI data
• Individual privacy in VGI
Further Reading
• Goodchild, M. 2007a. Citizens as voluntary
sensors: spatial data infrastructure in the
world of Web 2.0. International Journal of
Spatial Data Infrastructure Research 2:24-32.
• Wiersma, YF. 2010. Birding 2.0: Citizen Science
and Effective Monitoring in the Web 2.0
World. Avian Conservation and Ecology 5 (2):
Thank You!

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