gisruk2010 - a step towards the improvement of spatial data quality of web 2.0 geo-applications.the...
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A step towards the improvement of spatial A step towards the improvement of spatial data quality of Web 2.0 geo-applicationsdata quality of Web 2.0 geo-applications
The case of OpenStreetMapThe case of OpenStreetMap
Vyron Antoniou, Muki Haklay, Jeremy MorleyVyron Antoniou, Muki Haklay, Jeremy MorleyDepartment of Civil, Environmental and Geomatic Engineering
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A fundamental GIS problemA fundamental GIS problem
Information SystemInformation SystemReal WorldReal World
http://www.bing.com/maps Google Earth
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OSM Map FeaturesOSM Map Features
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WikiWiki DemocracyDemocracy++
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OSM DataOSM Data
Geometry
Attributes (Tags)
+
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OSM’s GeometryOSM’s Geometry
Haklay et al.Haklay et al. Antoniou et al.Antoniou et al.
CompletenessCompleteness Positional AccuracyPositional Accuracy
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Tags?Tags?
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Unique Tags vs Total Tags for each OSM Feature Unique Tags vs Total Tags for each OSM Feature Category (GB)Category (GB)
Sum: 2.25M tags
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How many tags do we have for each entity?How many tags do we have for each entity?
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Residential (2826)
Primary (623)
How often there is a new Tag introduced?How often there is a new Tag introduced?
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How often there is a new Tag introduced?How often there is a new Tag introduced?
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Unique Tags vs Popular Tags (95% of population)Unique Tags vs Popular Tags (95% of population)
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From OSM wiki-pages to XML SchemaFrom OSM wiki-pages to XML Schema
XML SchemaXML Schema
==
OSM OSM SpecificationSpecification
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From OSM wiki-pages to XML SchemaFrom OSM wiki-pages to XML Schema
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Data Quality changes whenever there is a change in:Data Quality changes whenever there is a change in:
• The data (e.g. due to a transformation)
• The ground truth
• The specifications of the product
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Data Quality changes whenever there is a change in:Data Quality changes whenever there is a change in:
• The data (e.g. due to a transformation)
• The ground truth
• The specifications of the product
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MerkaartorMerkaartor
PotlatchPotlatch
JOSMJOSM
Freedom, Formalization and Quality Standards?Freedom, Formalization and Quality Standards?
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Freedom, Formalization and Quality Standards?Freedom, Formalization and Quality Standards?
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Final PointsFinal Points
•Tags can greatly affect the quality of a VGI Map. •The loose structure of Feature extraction and attribution introduces errors.
• Errors are proportional to the tags’ population.
• The uncontrolled voting system deteriorates the overall quality of the OSM data.
• Errors or discrepancies in Features’ Tags can spread around.
• Formalization can be achieved under the hood.
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ThankThank youyou