European Commission logo
INSPIRE Community Forum

How to encode coverages (GMLCOV example files) and improvement of TG related explanatory sections

Some discussion threads have been opened in the cluster asking to provide more guidelines as regards the implementation / encoding of coverages.

- General thread to inform about existing experiences on data transformation and coverage encoding:

https://themes.jrc.ec.europa.eu/discussion/view/2843/experiences-on-encoding-of-elevation-and-orthoimagery-coverages

- Asking more guidelines in the case of the Elevation theme:

https://themes.jrc.ec.europa.eu/discussion/view/42326/need-more-guidance-for-elevation-encoding-and-correct-example-for-elevationgridcoverage-on-the-basis-of-gmlcov-schema

- Asking more guidelines in the case of the Orthoimagery theme:

https://themes.jrc.ec.europa.eu/discussion/view/23508/example-data-in-accordance-with-oi-application-schema-for-copernicus-guidelines

They show the need to add encoding examples (GMLCOV files) in the INSPIRE Technical Guidelines (TGs) - for Elevation and Orthoimagery coverages in the case of Cluster #3 - but also to improve the related explanatory sections in these documents.

The INSPIRE-KEN & TC #3 Workshop on Transformation of Coverage-based Data Themes and WCS celebrated in Barcelona at the end of September, gave the attendees an update of the state-of-the-art regarding coverages, their encoding and the use and capabilities of the WCS services (including very useful experiences). 

In particular, it helped to draft a list of aspects that need to be discussed and solved - to be taken into account when preparing the GMLCOV examples and the updates of the TGs:

1. Propose a clearer structure for sections “Default encoding(s)” and “Alternative encoding(s)” in the TGs, aligned with the different options foreseen to deliver coverages (Multipart representation / External file encoding / Inline encoding).

Discuss it here: https://themes.jrc.ec.europa.eu/discussion/view/49915/clarify-the-structure-of-coverage-encoding-related-sections-in-the-tgs-default-encodings-and-alternative-encodings

2. How and where within the GMLCOV to inform about the Vertical CRS utilized to express the elevation values provided in the 'rangeSet' - This information should be provided in the 'rangeType' component, in an harmonized, common way.

Pointed and discussed here (Elevation subgroup): https://themes.jrc.ec.europa.eu/discussion/view/42326/need-more-guidance-for-elevation-encoding-and-correct-example-for-elevationgridcoverage-on-the-basis-of-gmlcov-schema

3. Harmonize the CRS used in the “srsName” parameter for different GMLCOV file components.

Discuss it here: https://themes.jrc.ec.europa.eu/discussion/view/50299/harmonize-the-crs-used-in-the-%E2%80%9Csrsname%E2%80%9D-parameter-for-different-gmlcov-file-components

4. How to implement tiling / model mosaic elements, coverages and coverage aggregations within the GMLCOV files.

Discuss it here: https://themes.jrc.ec.europa.eu/discussion/view/50412/how-to-implement-tiling-model-mosaic-elements-coverages-and-coverage-aggregations-in-gmlcov-files

5. How to proceed with some partial conceptual redundances identified between INSPIRE coverages attributes and GMLCOV components.

An example of this redundances is identified and discussed here - 'domainExtent' vs. 'gml:boundedBy' discussion: https://themes.jrc.ec.europa.eu/discussion/view/12901/domainextent-vs-gmlboundedby-el-oi-coverages-encoding

6. Any other items you may consider necessary to make TGs more understandable as regards GMLCOV encoding and improve them.

In order improve the following GMLCOV examples (from IGN-Spain) presented in the above-mentioned Workshop:

EL GMLCOV example

Elevation grid coverage - GMLCOV Example implementation (IGN-Spain)

OI GMLCOV example

Orthoimage grid coverage - GMLCOV Example implementation (IGN-Spain)

Please, provide your input:

  • On each item of the list - Using the discussion threads enumerated above this lines.
  • Proposals of new tems to be discussed and/or comments on the GMLCOV examples - Using the present discussion thread.

My aim is to propose these examples (once improved and corrected) as an addition / update of the TGs, as possible before 20th October.

All based on your valuable discussion!!

Jordi

  • Jordi ESCRIU

    Dear collegues,

    This is an update on the status of the above-mentioned discussion topic aspects:

    1. Propose a clearer structure for sections “Default encoding(s)” and “Alternative encoding(s)” in the TGs, aligned with the different options foreseen to deliver coverages (Multipart representation / External file encoding / Inline encoding).

    Discussion topic closed and final proposal (already forwarded to MIG-T for endorsement) described in the following page:

    Clarify structure of coverage encoding-related sections in TGs

    2. How and where within the GMLCOV to inform about the Vertical CRS utilized to express the elevation values provided in the 'rangeSet' - This information should be provided in the 'rangeType' component, in an harmonized, common way.

    This item has been treated in this Discussion topic of the Elevation subgroup, which has been already closed. The proposed solution (use of the ‘referenceFrame’ property from the ‘swe:Quantity’ element - defined in OGC 08-094r1 SWE Common Data Model, as part of the 'rangeType' component of the coverage) has been described in the following page:

    Provide an ElevationGridCoverage encoding example and guidelines for identifying the Vertical CRS

    3. Harmonize the CRS used in the “srsName” parameter for different GMLCOV file components.

    As highlighted during the Follow-up webinar on coverage data and services (18th January 2016), it does not make sense to harmonize the CRS used / informed under different GMLCOV file components, because OGC coverages offer this simple, powerful (n-Dimensional) way of handling space/time coordinates

    The related Discussion topic is now closed.

    4. How to implement tiling / model mosaic elements, coverages and coverage aggregations within the GMLCOV files.

    Discussion remains open and waiting for your opinion / input in this Discussion topic.

    It might help in elaborating a more complete GMLCOV example for both, Elevation and Orthoimagery coverages, at least for agreeing on a standardized way to implement tiling (describing logical structures like e.g. mapsheets, administrative units like regions or districts, etc.), for modelling mosaic elements (OI-related, only) and for modelling coverage aggregations.

    5. How to proceed with some partial conceptual redundances identified between INSPIRE coverages attributes and GMLCOV components / INSPIRE coverage model extensions.

    This is based on the 'domainExtent' vs. 'gml:boundedBy' long discussion, which is only an example of these redundances.

    At the moment, it was agreed in the mentioned thread that the use of INSPIRE coverage model extensions shall be minimized as possible. In other words, all the attributes / properties proposed by INSPIRE models as an extension of the pure coverage structure described by the encoding standards (OGC GML / OGC GMLCOV / Future CIS v1.1) implies certain duplication of information (not always). Additionally, WCS2.0 technology does not take account such extensions and this pose dangers and issues.

    Therefore, the discussion should continue - probably in a new thread (still to be opened).

    Jordi

  • Jordi ESCRIU

    During the past INSPIRE Conference 2016 in Barcelona, Thematic Cluster #3 organized the Workshop "Implementation and potential of INSPIRE coverage data and WCS" (celebrated on 30th September 2016).

    The activity counted with the crucial support of Peter Baummann and Alex Dumitru (from the Jacobs University - Bremen & Rasdaman GmbH) as well as the EuroGeographics INSPIRE-KEN, with its chair Dominique Laurent.

    Objectives and Preceding events

    This event is the continuation of the cluster discussion activities about the main issues and questions from implementers of coverage data and related services in the Member States, which were already summarized and explained during the 29th INSPIRE MIG-T in Ispra (19-20 April 2016).

    The preliminar collection of information for this new activity (issues and first reactions related) were originally gathered during the INSPIRE KEN / Thematic Clusters Workshop on Transformation of Coverage-Based Data Themes and WCS and the subsequent Follow-up Webinar on Coverage Data and Services.

    Overview & Results

    The minutes and results of the Workshop in Barcelona are now available here:

    https://themes.jrc.ec.europa.eu/pages/view/115418/results-from-the-ws-on-implementation-and-potential-of-inspire-coverage-data-and-wcs

    Update on the status of open issues

    In the workshop there was fruitful discussion about the aspects highlighted in this thread which remain open:

    4. How to implement tiling / model mosaic elements, coverages and coverage aggregations within the GMLCOV files.

    For clarity and allowing a clear and smooth run of the discussions in the workshop in Barcelona, this aspect was splitted in separate / different topics. As a result, new separate discussion threads has been open in the platform, while the original discussion post has been closed.

    The results and the new threads are detailed below:

    • How to deal with huge volume of coverage data (Issue 1 in the Workshop in Barcelona / INSPIRE Conference 2016)
    • Case 1. Delivery through Predefined datasets - Discussion item closed (open for comments):  Consolidated results and recommendations agreed by the cluster are stated in this Dedicated page.
    • Case 2. Delivery through WCS - Discussion item closed (open for comments): Consolidated results and recommendations agreed by the cluster are stated in this Dedicated page.
    • How to implement the concept of coverage aggregation (Issue 2 in the Workshop in Barcelona / INSPIRE Conference 2016).

    The discussion is more advanced but open yet in the following thread: How to implement the concept of coverage aggregation.

    • How to implement the concept of mosaicking (Issue 3 in the Workshop in Barcelona / INSPIRE Conference 2016).

    The discussion is more advanced but open yet in the following thread: How to implement the concept of mosaicking.

    Both coverage aggregation and mosaicking constitutes INSPIRE Extensions to a standard WCS implementation, as explained below.

    5. How to proceed with some partial conceptual redundances identified between INSPIRE coverages attributes and GMLCOV components / INSPIRE coverage model extensions.

    This aspect was treated under the title "INSPIRE Coverage extensions vs. OGC standard coverages" (Issue 4 in the workshop).

    Summary

    The INSPIRE coverage model extends the OGC coverage model in ways not anticipated by OGC. As a result, WCS implementations (being based on the OGC definitions) often ignore the extra information defined by INSPIRE. In the workshop, there was no time to discuss and examine case by case the need for each INSPIRE extension item.

    However, there was agreement to remove these extensions from the raster INSPIRE data models and make specific proposals to provide this information – if really needed – using some other procedure.

    The most appropriate way would be to include the information as metadata, to be linked to the coverage by means of the metadata hook. This is compliant with the OGC coverage definition and with WCS, since WCS by definition of the standard must deliver the metadata compartment of a coverage.

    Action

    Discuss about the removal of the INSPIRE extensions to standard coverages from the raster INSPIRE data models shall take place. Concretely, specific proposals shall be made to provide this information using other procedures, examining case by case each extension, when each information item proves to be really necessary.

    The discussion may take place in the INSPIRE Thematic Cluster #3 platform, complemented by specific virtual meetings – To be organized and scheduled soon through the cluster.

     

  • Jordi ESCRIU

    Dear members of the cluster,

    Find below a recent presentation in the INSPIRE Conference 2017 in Strasbourg - "Pushing implementation of European coverage data and services forward", summarizing the main challenges and issues related to INSPIRE coverage data implementation identified in the context of our cluster:

    https://themes.jrc.ec.europa.eu/file/view/153918/pushing-implementation-of-european-coverage-data-and-services-forward

    It also explains proposals (in draft status) to solve such issues and align implementation of INSPIRE Coverage data to the one foreseen in OGC (OGC-standard coverage data).

    The proposals would be properly updated, explained and discussed in an Online Webinar of the cluster scheduled by early November - Webinar "Implementation of INSPIRE Coverages":

    https://themes.jrc.ec.europa.eu/pages/view/159283/webinar-implementation-of-inspire-coverages

    Happy to count with your collaboration to get consensus in a final solution.

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