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Improving volunteered geographic data quality Improving volunteered geographic data quality using semantic similarity measurementsusing semantic similarity measurements
Arnaud Vandecasteele - Arnaud Vandecasteele - Rodolphe DevillersRodolphe Devillers Memorial University of Newfoundland, CanadaMemorial University of Newfoundland, Canada
8th International Symposium on Spatial Data Quality, 30 May - 1 June 2013
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Outline
Introduction
Conclusion
Semantic SimilarityP-Rank algorithmTobler's Law
OSM Semantic PluginDescriptionExamples
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IntroductionNational Mapping Agencies
What make National Mapping Agencies Authoritative ?
Positional Accuracy
Completeness
Attribute Accuracy
ISO 19113ISO 19115
...ISO 19157
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IntroductionGeographic Information Quality view asa Project Management Triangle
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IntroductionGeographic Information Quality view asa Project Management Triangle
Really?
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Introduction
Could Another Map be authoritative* ?
* and cheap, and fast, accurate and in the better of worlds free
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IntroductionVolunteered Geographic Information (VGI)
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IntroductionVolunteered Geographic Information (VGI)
the widespread engagement of large numbers of private citizens, often with little in the way of formal qualifications, in the creation of geographic information
“
Goodchild - 2007
”
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Source: http://wiki.openstreetmap.org/wiki/Stats
OpenStreetMap (OSM) is a collaborative project to create a free editable map of the
world
+ 1 million
+ 1.8 billion nodes+ 180 million ways+ 1.9 million relations
Started in 2004
IntroductionThe OpenStreetMap project
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IntroductionData Quality & Volunteered Geographic Information
What aboutData Quality ?
Good geometric accuracyHaklay – 2010, Girres and Touya – 2010, Ludwig et al., - 2011
ButGeographic coverage patchwork
Goodchild - 2007
Semantics can be inconsistentBallatore et al., - 2012, Mooney and Corcoran - 2012
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Introduction
VGI changed the way we produce, publish and share Geographic Information
BUT
Semantic Quality is still an important issue
How to improve semantic quality using a VGI approach ?
Research Problem
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Semantic SimilarityWhat is Semantic Similarity ?
Landuse =
Forest
How to describe a forest in OpenStreetMap
Natural =
Wood
One concept, different representation !Q ? -> When should we use landuse=forest rather than natural=wood?* https://help.openstreetmap.org/questions/324/when-should-we-use-landuseforest-rather-than-naturalwood
11 different answers and no real general agreement
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Semantic SimilarityHow to measure the semantic similarity ?
● Geometric Model● Feature Model● Alignment Model● Network models● Transformation Model
Different models exist:
Semantic similarity applied to VGI:
Mooney and Corcoran - 2012
Ballatore et al., - 2012
Natural =
Wood
Landuse =
Forest
Natural =
Wood
Landuse =
Forest
Natural =
Wood
Landuse =
Forest
Measure?
Semantic Network created from the OpenStreetMap Wiki
Point Pattern analysis and semantic pattern
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Semantic SimilaritySemantic Network from the OSM Wiki, who it works ?
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Source: OSM WIKI
Semantic SimilaritySemantic Network from the OSM Wiki
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Measuring Semantic similarity
Two entities are similar if :
1 They are referenced by similar entities
2 They reference similar entities
A B
C
=
A B
C
=
Semantic Similarity
P-Rank Algorithm
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Semantic similarity
all things are related, but nearbynearby things
are more relatedrelated than distant things“
”Tobler - 1970
Semantic similarity and Geography
Tobler's first law of geography
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New Object in a cityNew Object in a cityA
P-Rank score
P-R
an
k s
core
P-Rank sc
ore
P-R
ank s
core
P-Rank score
P-R
ank
score
Semantic similarityApplied Tobler's first law to semantic similarity
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Java OpenStreetMap Editor
OpenStreetMap Semantic Plugin
OSM Editor usage stats (source OSM Wiki)
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Description
OpenStreetMap Semantic Plugin
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A BP-Rank Score
0.18
A CP-Rank Score
0.35
A DP-Rank Score
0.05
How similar are they ?
P-Rank scores
OpenStreetMap Semantic Plugin (aka OSMantic)Description
A
AC
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Creation of a new objectExamples - Creation of a new object
New object
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OpenStreetMap Semantic PluginExamples - Edition of an existing object
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OpenStreetMap Semantic PluginExamples – Semantic Similarity Evaluation
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Conclusion
The next big question ?
When will VGI be the next authoritative dataset ?
Semantic Similarity can be used to enhance the quality of VGI dataset
OSM Semantic plugin uses a collaborative approach to reduce the potential semantic similarity
How to improve the results:● Using the Tag Info database to know the most used tags ● By mixing the Geographic and the semantic approach (Ballatore + Mooney)
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Questions ?
Rodolphe DevillersMarine Geomatics Labhttp://www.marinegis.com/ Memorial University of Newfoundland
Acknowledgements
Natural Science and Engineering Research Council of Canada (NSERC)Andrea Ballatore for sharing his results