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EL GridCoverage Model - CV_Grid:extent or CV_Grid:limits

Hi everybody,

I am rather new to the Coverages subject and am right now working on transforming Elevation data into the INSPIRE Elevation GridCoverage model.

I have a question concerning the domainSet-attribute of the ElevationGridCoverage-FeatureType: The Data Specification (section 5.5.1.2.2.) mentions the attribute CV_RectifiedGrid:extent (which it inherits from CV_Grid according to the UML diagram of OI https://inspire.ec.europa.eu/data-model/approved/r4618-ir/html/index.htm?goto=2:2:4:1:1:7835 - this association is not diaplayed in the UML diagram of EL, which is why I am reffering to OI here). In contrast to that, "extent" cannot be found in the corresponding xsd (http://schemas.opengis.net/gml/3.2.1/grids.xsd#0:0). It seems that it has been replaced by CV_Grid:limit?.

I could not find any part in the Data Specification or any thread in this Cluster, that explains, why that is the case. Could someone help me out and explain to me, why the xsd differs from the model representation?

 

Thank you in advance and all the best

Johanna

  • Enrico Iredi

    Hello Johanna,

    the rectified grid attribute looks like this. There is no extent?

    Sample coverage: https://themes.jrc.ec.europa.eu/file/view/214982/gml-example-renewableandwastepotentialcoverage-er-c

    Best regards

    Enrico

  • Johanna Ott

    Hello Enrico,

    Thank you for the reply. Exactly, as I mentioned, in the XSD, there is no extent attribute. But looking at this UML diagram, I would expect one in CV_RectifiedGrid:

    (the diagram extract is taken from the OI specification - figure 8 as the EL specification is less detailed there).

    Also, section 5.5.1.2.2. of the EL Data Specification mentions an extent attribute: "By inheritance from RectifiedGridCoverage, the value type is restricted to CV_RectifiedGrid. This ISO 19123 element allows defining the characteristics of the internal grid structure: the grid dimension, which is constrained to two (CV_RectifiedGrid::dimension), the extent which reports the extreme internal grid coordinates of the DEM (CV_RectifiedGrid::extent) and the names the grid axes (CV_RectifiedGrid::axisNames)."

    That is why I am confused there is no extent in the XSD.

  • Jordi ESCRIU

    Dear Johanna,

    Thank you very much for your question.

    Please have a look at the material from the Webinar "Implementation of INSPIRE Coverages": 

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

    In this activity we explained that the INSPIRE UML models (included in the data specifications) are defined at conceptual level, and extends the standard content expected in an standard OGC coverage implemented according to CIS 1.0.

    The following article describes the issues in more detail:

    INSPIRE Coverages: An Analysis and Some Suggestions., Open Geospatial Data, Software and Standards, (2019) 4:1, DOI: https://doi.org/10.1186/s40965-019-0059-x

    Therefore, there is a need to clarify the mapping between the conceptual elements foreseen in an INSPIRE coverage according to the data specifications and the elements expected according to an OGC standard implementation.

    As a result, the INSPIRE coverages schemas shall be corrected and translated to the "implementation" level while being conformant to the OGC standard CIS 1.0.

    I have recently agreed with JRC to help in updating the INSPIRE coverage schemas to solve this situation. 

    I will be informing the Thematic Cluster about the progress.

    Excuse me for the delay in responding.

    Jordi

  • Johanna Ott

    Dear Jordi,

    Thank you very much for your detailed and helpful reply! The information given and linked there clarify a lot of the questions I had in mind concerning the coverage subject.

    The links to the webinar recording for the linked "Implementation of INSPIRE Coverages" webinar do not work. Is there a way to make the recordings available again? I think that would be very helpful to everybody who is rather new in this subject.

     

    All the best

    Johanna

  • Katharina SCHLEIDT

    By Katharina SCHLEIDT

    Hi Johanna,

    related question - via which download service are you planning on making the EL data available? At present, the following options are foreseen:

    * WFS: Advantage: implementable, Disadvantage: user can only access the entire coverage, often massive

    * WCS: Advantage: allows for subsetting and server-side calculations, allowing the user to access exactly what they require, Disadvantage: currently not implementable due to how the INSPIRE Coverage Schemas have been generated (lack OGC compliance)

    Reason I'm asking: Jordi and I are working on creating INSPIRE Coverage Schemas aligned with the IR requirements AND complaint with the underlying OGC Coverage requirements. As part of this process, we'd also need data providers to deploy these new schemas on WCS as part of an INSPIRE Good Practice.

    Thus note to all - if you're interested in deploying your coverage data via WCS, please get in touch with Jordi and myself!

    :)

    Kathi

  • Jordi ESCRIU

    Thank you Kathi,

    This makes a lot of sense.

    So Johanna, feel free to contact us if you are interested!

    Jordi

  • Peter BAUMANN

    By Peter BAUMANN

    Hi Johanna,

    indeed, you have spotted a divergence in INSPIRE: INSPIRE WCS is based on OGC coverages (GMLCOV = CIS), but INSPIRE has its own, deviating coverage schema. Kathi + Jordi + myself are working on how to gently lead INSPIRE coverages into compatibility with OGC and ISO. I am the editor of the OGC and ISO specifications, so if you have further questions just contact me/us. In the Fall INSPIRE conference (if I may call it so) in Helsinki we plan to present results.

    Right now, rasdaman is our vehicle for experimentation - does not implement all INSPIREtions yet, but its flexibility helps us to find out ways. You are more than welcome to join us by providing use cases = sample coverages with ideas about INSPIRE metadata.

    @Enrico: just to point out, your example models gml:FeatureCollection which is not a coverage as per schema - sorry to say! A standard-conformant WCS requires something validating against CIS 1.0 or 1.1.

    best,

    Peter

     

  • Johanna Ott

    Hi Kathi, hi Jordi, hi Peter,

    Thanks a lot for your replies and input. We are currently planning with WFS for this case as we want to have something up as soon as possible.

    We don't have a WFS up yet (as we are running into issued using RectifiedGrid in deegree). But for now I could provide you with the GML file we are planning to publish via the WFS - you can download it using this link: https://wetransform.box.com/shared/static/aa6s1c6uw48guqye13k2omog32s5b7q5.gml

    Is that the kind of data you would expect in a WFS containing elevation data?

     

    All the best

    Johanna

  • Katharina SCHLEIDT

    By Katharina SCHLEIDT

    Hi Johanna,

    I'm currently on mission, so a bit limited in my infrastructure. Based on a quick look at the GML file, I understand your encoding as follows:

    * you create seperate coverage elements for small areas, serve these individually instead of subsetting functionality as would be available via WCS?

    * for the rangeSet (the actual data you're serving), you're then refering to a WCS?

    Formally, it looks like a valid approach. I'd be interested if any client applications can cope!

    :)

    Kathi

  • Peter BAUMANN

    By Peter BAUMANN

    Hi Johanna,

    on another aspect: I wonder why you pick WFS and not WCS. WFS only allows to download the complete coverage, and without any modification (such as CRS transformation, band extraction, scaling, etc.). Plus it poses additional difficulties as you obviously experience already.

    my 2 cents,

    Peter

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