Spatial Data on the Web: Experiences and outlook

Frans Knibbe - Geodan

Spatial Data on the Web Working Group

http://www.w3.org/2015/spatial/wiki

SDWWG Timeline

● March 2014: Linking Geospatial Data workshop

● January 2015: First teleconference● March 2015: First face to face meeting● January 2017: All deliverables should be

finished.

SDWWG Mission From the Charter:1. To determine how spatial data can best be integrated with other data on

the Web;2. to determine how machines and people can discover that different facts in

different datasets relate to the same place, especially when 'place' is expressed in different ways and at different levels of granularity;

3. to identify and assess existing methods and tools and then create a set of best practices for their use;

4. where desirable, to complete the standardization of informal technologies already in widespread use.

SDDWG scope● Also concerned with OWL Time, so actually it is about

spatiotemporal data;● Not limited to Linked Data / Five Star Data;● Mindful of the needs of front end Web developers but

rendering technologies will not be developed;● Not only for experts.● Spatial data, not only geographical data;

Spatial data

Small kitchen - perspective - textures" by Elektron - Own work. Licensed under CC BY 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Small_kitchen_-_perspective_-_textures.PNG#/media/File:Small_kitchen_-_perspective_-_textures.PNG

Spatial data

Spatial data

Spatial data

● Eschenbachgasse 9, 1010 Wien● Αθήνα● That nice restaurant near the Como lake● The top drawer of my night table● pirate.dealings.suppers● 8FWR6C84+83● Atlantis?

SDWWG Deliverables

1. Use Cases & Requirements (Note)2. Spatial Data on the Web Best Practices

(Note)3. OWL Time Ontology (Recommendation)4. Semantic Sensor Network Ontology

(Recommendation)5. Coverage in Linked Data (Recommendation)

Deliverable: Spatial Data on the Web Best PracticesIt should include:1. An agreed spatial ontology conformant to the ISO 19107 abstract model

and based on existing available ontologies such as GeoSPARQL, NeoGeo and the ISA Core Location vocabulary;

2. advice on use of URIs as identifiers in GIS;3. advice on providing different levels of metadata for different usage

scenarios (from broad sweep metadata to metadata about individual coordinates in a polygon);

4. develop advice on, or possibly define, RESTful APIs to return data in a variety of formats including those defined elsewhere, such as GeoJSON, GeoJSON-LD and TopoJSON.

Deliverable: OWL TimeThe WG will work with the authors of the existing Time Ontology in OWL to complete the development of this widely used ontology through to Recommendation status. Further requirements already identified in the geospatial community will be taken into account.

Space and time

image source:NASA

Why time?1. The OGC is involved in time (e.g. time series);2. Serious data sets have serious requirements for time

and space;3. Time and space have similarities:

○ compare Allen’s Algebra for time (precedes, meets, overlaps, contains, starts, equals, ...) with the DE-9IM for 2D geometry (equals, overlaps, covers, crosses, touches ...)

○ different Reference Systems○ similar requirements for expressing vagueness and uncertainty

4. Spatial Coordinate Reference Systems can be time dependent

ISO 8601

2015-09-14T17:51:31+00:00

Deliverable: Semantic Sensor Network Ontology

The WG will work with the members of the former Semantic Sensor Network Incubator Group to develop its ontology into a formal Recommendation, noting the work to split the ontology into smaller sections to offer simplified access.

Deliverable: Coverage in Linked Data

Develop a Recommendation for coverage data, based on existing work (e.g. ISO 19123, Data Cube Vocabulary).

Coverage: a feature whose properties vary with space and/or time; for example, the variation of air temperature within a given geographic region, or the variation of flow rate with time at a hydrological monitoring station.

First deliverable: Use Cases and Requirements

● 50 use cases● 57 requirements● Still some issues to resolve

Coordinate Reference Systems

http://www.opengis.net/def/crs/EPSG/0/4326http://www.opengis.net/def/crs/OGC/1.3/CRS84http://data.ign.fr/id/ignf/crs/NTFLAMB2E

● Should only geographic CRS be standardized?● Should there be a default CRS?

CRS (1)

CRS (2)

image from U.S. Geological Survey

Other issues

● Vagueness● Versioning

Requirements for best practices

● Metadata (bounding box, centroid, CRS, spatial resolution);

● Linkable, crawlable;● Usable by machines;● 3D;● Tiling (raster & vector), compression;● Spatial relationships and spatial operators.