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Experience from IGN-Spain I (Coverage data: generation of GMLCOV files)

Experience from IGN-Spain - September 2015


Implementation experience in Spain for the the Elevation and Orthoimagery themes for a small pilot area - Including:

  • Selection of data sets to be transformed.
  • Technical choices for INSPIRE data:
    • Provision of EL & OI gridded data using Multipart representation:
      • OI: reference to an external TIFF file.
      • EL: rangeSet values obtained from WCS request.
    • Using EPSG:25830 (UTM Projection Zone 30N) projected coordinates (to be transformed to the ETRS89-TM30N projection used in INSPIRE in the future) and EVRS (conversion from national height system not implemented yet).
  • Transformation procedure:
    • Source data
      • EL: PNOA DTM with 25m grid cell size.
      • OI: PNOA Orthophotos Resolution 0.25m.
    • Overview of the process for generating the GMLCOV files in FME, using GML reader and GML writer (available since FME 2014) and appropriate transformers to: 
      • Generate or rename the necessary INSPIRE coverage attributes (e.g. Attribute renamer, TimeStamper, AttributeGenerator, GeometryPropertySetter).
      • Parameters needed to categorize voidable attributes and attributes with cardinality 0..*.
      • Reference external codelists (e.g. using xLink:href).
      • Build XML-fragment structures + variable parameters (using XML-Templater) - 'domainSet', 'rangeSet', 'rangeType', 'coverageFunction' components.
      • Proposals or constructs for modeling of mosaic elements, coverages and coverage aggregations within the GMLCOV files.
      • Edition of the specific format (GeoTIFF / JPEG2000) image tags.

Data themes covered

Elevation and Orthoimagery.

Software used

FME - For generating the GMLCOV files and automate the process, avoiding as possible manual editions.


On-going / Quite complete (CRS transformations not available yet).

Issues / Questions

  • Observed quality degradation from the original files to the resulting files providing the gridded data by a WCS - To be taken into account together with the LoD.
  • Size of the original files is high (1 Gb GeoTIFF/BigTIFF)  - Need to resample original files to get a practical solution for the pilot area.
  • Some conceptual redundances identified between INSPIRE coverages components and GMLCOV  components.

New Proposals for INSPIRE

  • Apart from TIFF and JPEG2000 formats, allow provision of data using internal-tiled GeoTIFF with JPEG compression.
  • Provide EL and OI data using a Square Nested Pan-European Grid (e.g. Mercator projection).
  • Proposal to access original data for both, visualization (with WMTS) and download (WFS for the GMLs / WCS for the GeoTIFF files), without internediate re-sampling, compression or tiling.


Workshop Coverages and WCS - Experience data transformation - IGN-Spain


Elevation, Ortho & Grids

Elevation, Ortho & Grids

INSPIRE Thematic Cluster Elevation, Orthoimagery, Reference systems, Geographical grids - Join this group to share your knowkledge, learn and collaborate in solving issues related to the Elevation, Orthoimagery, Reference systems and Geographical grids themes