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An effective good practice to boost interoperable provision of (raster) INSPIRE Coverage data and services: Revision

What is a coverage?

A coverage is a unifyed paradigm for modelling and encoding raster data of all kind, from 1D sensor timeseries, over 2D raster images, up to spatio-temporal datacubes. 
It describes spatio-temporal regular and irregular grids (i.e., multi-dimensional datacubes), point clouds, and general meshes.

In plain words coverage are modelled like a function, composed by the following elements:

  • Domain set, answering “at what coordinates can I find values?” (the domain of the function). 
  • Range set, determining “what are the values?” (the image set of the function). 
  • Range type, informing "which are the basic characteristics of the values?". It is utilised to capture the full semantics of the values in the coverage. 
  • Optional metadata bucket, carrying any additional information that may be also relevant for users.

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The range type of a coverage is also an standardized description based on the SWE (Sensor Web Enablement) Common (http://www.opengeospatial.org/standards/swe) concepts.  

This allows sensor data to be transformed into coverages without information loss, thereby enabling seamless service chains from upstream data acquisition (e.g., through OGC SOS) to downstream analysis-ready user services (such as OGC WMS, WCS, and WCPS). 

Such coverages can be represented in a variety of shapes – including tilings, coordinate/value pair lists – and formats - such as GML, JSON, RDF, a variety of binary encodings, as well as “containers” with mixed encodings. Hence, tools can request coverages in their favourite format from a server.

Coverage standards

Coverages are fully standardized by the OGC (Open Geospatial Consortium):

  • At abstract, conceptual level, in OGC Abstract Topic 6 which is identical to ISO 19123
  • At concrete, interoperable level in the OGC Coverage Implementation Schema (CIS), which is adopted by ISO as 19123–2.

Several versions of the OGC Coverage Implementation Schema (CIS):

CIS 1.0, formerly known as “GML 3.2.1 Application Schema – Coverages” (GMLCOV).

CIS 1.1, which provides a comprehensive, more consistent schema for grid coverages.

Find here more details on coverage standardisation.

Use of coverages in INSPIRE

Coverages are widely used in different thematic domains in the scope of the INSPIRE Directive:

  • Annex II: Elevation (EL), Land cover (LC), Orthoimagery (OI), Geology (GE);
  • Annex III: Soil (SO), Land use (LU), Natural risk zones (NZ), Environmental Monitoring Facilities (EF), Atmospheric conditions (AC), Meteorological geographical features (MF), Oceanographic geographical features (OF), Energy resources (ER), Species Distribution (SD);

However, two different approaches are used by INSPIRE themes to serve coverage data to the user:

1. WCS view: Coverages are considered as features (i.e. INSPIRE FeatureTypes in these themes are based on Coverage Classes).

Regular or irregular grids are used by the WCS view INSPIRE themes.

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2. SOS view: Coverages are considered as observation results.

Regular or irregular grids are used by the SOS view INSPIRE themes.

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Which is the main issue about INSPIRE coverages?

 

Good Practice: Proposal for an interoperable solution

 

INSPIRE Coverages Demystified:

http://inspire.rasdaman.org/

 

Find more details

 

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