Presented at the Linking Geospatial Data workshop
More details can be found in the position paper
Aims at providing reference geography, contribute to the usability of INSPIRE data
Most data in ELF is from mapping and cadastral agencies
Talk is largely driven by work that interactive instruments is doing in ELF
Services and data shown are work in progress and have known issues; most data access currently requires a licence
⇒ In many cases we can only download complete datasets
Linking data is fundamental in INSPIRE, to geo-reference "business data" and improve data integrity and reliability
ELF provides access to data in more than one platform, including ArcGIS Online
Helsinki administrative unit feature in ArcGIS Online - in HTML or JSON
Query to all Finnish administrative unit features on level 4 in ArcGIS Online - in HTML or JSON
Helsinki gazetteer entry in ELF GeoLocator WFS
⇒ Enables links to reference data from my "business data" and access it when needed, e.g. to determine its location
Pre-condition for linking
Recognized in INSPIRE, although persistent identifiers are often optional
ELF aims at providing reference geography: persistent identifiers are foreseen for all features
On the web, persistent identifiers should be http URIs
Sample ArcGIS Online URI: https://services1.arcgis.com/YIzHghteMOSU5dIR/arcgis/rest/services/elf_ebm_fs/FeatureServer/10/7999
Sample WFS URI: https://54.247.101.37/elf/GeolocatorService?SERVICE=WFS&REQUEST=GetFeature&typename=SI_LocationInstance& VERSION=1.1.0&OUTPUTFORMAT=text/xml;%20subtype=gml/3.1.1&FILTER=%3Cogc:Filter%20xmlns:ogc=%22http://www.opengis.net/ogc%22%3E %3Cogc:PropertyIsEqualTo%3E%3Cogc:PropertyName%20xmlns:iso19112=%22http://www.isotc211.org/19112%22 %3Eiso19112:geographicIdentifier%3C/ogc:PropertyName%3E%3Cogc:Literal%3EFI.NLS.GNR.10342733%3C/ogc:Literal%3E %3C/ogc:PropertyIsEqualTo%3E%3C/ogc:Filter%3E
Open issue: In ELF features are accessible via http URIs, but these are document URIs using OGC Web Feature Service queries or GeoServices REST API URIs
Copies of the same feature will be available via different services - and different document URIs
Open issue: which URIs should be used in links?
If ELF would manage persistent URIs for its features, it would have to support redirecting to appropriate document URIs for the requested media type, but this is significant overhead and difficult to maintain
In practice, links will often be implicit. Example: NUTS codes as attribute values
Statistical data from EUROSTAT
Infant mortality data with NUTS codes
How to establish the join?
How to show features in maps that get their geo-reference from referenced features?
Not addressed in INSPIRE yet
Geo-processing is typically used to geo-reference or otherwise enrich data, e.g. using ⇒ FME (interacting with ArcGIS Online directly)
Other options: OGC Table Join Service, OGC WFS join queries, Google Fusion Tables, Esri Maps for Office, etc.
Depends on availability of tools, APIs, good documentation
And familiarity of the user/developer with the tools/APIs
⇒ ELF supports additional platforms beyond the OGC web service technologies typically used in spatial data infrastructures
Use ELF/INSPIRE data in ArcGIS Online (compile and publish an application in 2 minutes)
Open issue: Mechanisms how to keep the copies of the data synchronized