Finding & Querying Big Linked Geodata

Wouter Beek wouter@triply.cc, John Walker john.walker@semaku.com
Kadaster Data Platform: https://data.pdok.nl

Big Linked Geodata

Linked Open Data

Use (Geo)SPARQL endpoints i.o. copying data locally.

Big Linked Geodata @ Kadaster

  • Over 5,000,000,000 graph edges
  • Over 500,000,000 geo shapes
  • High precision
  • Performance
PrecisionMeaning
+/-east/west or north/south
1.0e2must be longitude
1.0e11111 kilometer, continent
1.0e0111 kilometer, country
1.0e-111 kilometer, city
1.0e-21.1 kilometer, village
1.0e-3111 meter, large field
1.0e-411 meter, parcel of land
1.0e-51.1 meter, tree
1.0e-611 centimeter, engineering
1.0e-711 milimeter
1.0e-81.1 milimeter, tectonic plate motion
1.0e-9110 micron, microscopy

Geo + Linked Data is still very new

GeoSPARQL standard

  1. Core
  2. Topology Vocabulary: relations between geometries
    • Simple Features
    • Egenhofer
    • RCC8
  3. Geometry
    • GML
    • WKT
  4. Geometry Topology: properties of geometries & geometry functions
  5. RDFS Entailment: shape hierarchy
  6. Query Rewrite: rules for shapes (RIF)

GeoSPARQL implementations

GeoSPARQL implementations

  1. Not that many implementations to choose from.
  2. FOSS implementations do not perform.
  3. Challenging to deliver Open endpoints.

Querying Big Linked Geodata

(Programmers & Data Analists)

Support for Programmers & Data Analists

DBpedia

Things a programmer needs

Autocompletion

Linked Open Vocabularies

Result set formats

  • Raw triples (N-Quads, N-Triples, RDF/XML, TriG, Turtle) (example)
  • Raw solutions (CSV/TSV, JSON, XML) (example)
  • Table (example)
  • Pivot table
  • Google Chart (example)
  • Map (example)

Finding Big Linked Geodata

Browsing paradigms

Hierarchical browsing

Tabular browsing: concepts

Tabular browsing: instances

Graph navigation

LodLive

Faceted browsing

Map navigation

Purpose Technique
Concept browsing Hierarchical browsing
Display one concept/instance Tabular browsing
Explorative browsing; instance in context Graph navigation
Instance browsing Faceted browsing
Domain-specific overview Map navigation

Getting started with a new schema

Use case: BAG

Thank you!

Kadaster Data Platform: data.pdok.nl

John Walker john.walker@semaku.com
Wouter Beek wouter@triply.cc