surveying geonames gazetteer data for the nordic countries

Surveying GeoNames

Gazetteer Data for the Nordic Countries

Dirk Ahlers

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Motivation Location information is vital for many

applications Gazetteers provide basic geospatial

knowledge Quality is often only implicitly assumed Quality indicators are needed

NIK 2015

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Gazetteers Geographical Thesaurus

Coordinates, name, type, hierarchy, population, … Main data source for geoparsing and subsequent

geocoding, ‘what is around’ location finding etc. Data sources

GeoNames.org Large worldwide coverage, freely available

TGN – The Getty Thesaurus of Geographic Names Used in museums, license needed. New: LOD

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Nordic Countries Denmark (DK)

Faroe Islands (FO) and Greenland (GL)

Finland (FI) Åland Islands (AX)

Iceland (IS) Sweden (SE) Norway (NO)

Svalbard and Jan Mayen (SJ) [plus Antarctic territories]

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Comparison GeoNames-TGN

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Mapping all places

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Populated places

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Anomalies Geospatial irregularities

Both large-scale and small-scale Also in metadata

Simplified locations Grid-aligned positions Coverage with “holes” Repeated positions Inaccurate feature classes Places outside their assigned country Near-identical places

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Example: ‘Simplified’ Locations

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Grid positions: Lofoten

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Example: Nordfjord

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Magnitude of error

Dependent on latitude

Distortion or error may influence calculations

Manually edited points may have better positional accuracy

Solution: error annotation?

NIK 2015[Assessment of the Accuracy of GeoNames Gazetteer

Data, GIR2013]

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Separating on/off grid

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Intrinsic Quality Indicators

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POIs

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Population numbers

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Conclusion Set of intrinsic indicators

Highlighting of problematic areas Selection according to

requirements Impact depends on granularity

requirements of application Varying quality levels Dependencies differ from

mainland Future work

Provenance data not available, comparison with Web sources

World scale

NIK 2015

Let’s talk!

Contact

search://Dirk Ahlersgeo: 63°25‘10“N 10°24‘9“E @dirkahlersdirk.ahlers@idi.ntnu.no