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

A fundamental GIS problemA fundamental GIS problem

Information SystemInformation SystemReal WorldReal World

http://www.bing.com/maps Google Earth

OSM Map FeaturesOSM Map Features

WikiWiki DemocracyDemocracy++

OSM DataOSM Data

Geometry

Attributes (Tags)

+

OSM’s GeometryOSM’s Geometry

Haklay et al.Haklay et al. Antoniou et al.Antoniou et al.

CompletenessCompleteness Positional AccuracyPositional Accuracy

Tags?Tags?

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

How many tags do we have for each entity?How many tags do we have for each entity?

Residential (2826)

Primary (623)

How often there is a new Tag introduced?How often there is a new Tag introduced?

How often there is a new Tag introduced?How often there is a new Tag introduced?

Unique Tags vs Popular Tags (95% of population)Unique Tags vs Popular Tags (95% of population)

From OSM wiki-pages to XML SchemaFrom OSM wiki-pages to XML Schema

XML SchemaXML Schema

==

OSM OSM SpecificationSpecification

From OSM wiki-pages to XML SchemaFrom OSM wiki-pages to XML Schema

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

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

MerkaartorMerkaartor

PotlatchPotlatch

JOSMJOSM

Freedom, Formalization and Quality Standards?Freedom, Formalization and Quality Standards?

Freedom, Formalization and Quality Standards?Freedom, Formalization and Quality Standards?

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.

ThankThank youyou