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ETRS89-TMzn and raster data for OI and EL

I have some doubts regarding  use of valid INSPIRE coordinate reference system (CRS) especially for providing raster data for orthoimagery (OI) and elevation (EL) themes.

According to Regulation No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services Annex II chapter 1.3.2. we should be using following CRSs

  • Two-dimensional geodetic coordinates (latitude and longitude) based on a datum specified in 1.2 and using the parameters of the GRS80 ellipsoid.
  • Plane coordinates using the ETRS89 Lambert Azimuthal Equal Area coordinate reference system.
  • Plane coordinates using the ETRS89 Lambert Conformal Conic coordinate reference system.
  • Plane coordinates using the ETRS89 Transverse Mercator coordinate reference system.

In my opinion for large scale OI and EL data with resolution (GSD) 1 m or better the only last CRS form above list can be used.

When we take a look into a document D2.8.I.1 Data Specification on Coordinate Reference Systems – Technical Guidelines we will see that this CRS has been more precisely defined as Transverse Mercator (ETRS89-TMzn) (chapter 5.4.2.1). Moreover in the table 1 of the document we will find EPSG codes of the ETRS89-TMzn CRSs for different zones. For example EPSG codes of ETRS89-TMzn that applies for the territory of Poland are 3045, 3046 and 3047.

However, in Poland we use national CRS PUWG 1992 (EPSG:2180). Like ETRS89-TMzn our national CRS is based on ETRS89. Therefore, it seems to be conformant to mandatory Regulation No 1089/2010, but it is not conformant to Technical guidelines. In particular parameters of PUWG 1992 CRS (longitude of origin, scale factor, etc.) are different than those defined for ETRS89-TMzn zones.

In Poland during data transformation process from our national data models to INSPIRE data models we also transform CRS (in most cases to INSPIRE ETRS89-GRS80 (EPSG:4258)). However, for raster data this approach is not as feasible as in case of vector data. First of all, because WCS service profile for INSPIRE download services is not ready yet, the only possibility to publish download service raster data is ATOM feed. However, this requires a lot of additional storage space to actually store raster data in both: our national and INSPRE ETRS89-TMzn CRS. Secondly, when transforming raster data form one CRS to another we lose quality as a result of resampling. Therefore, taking above into consideration in case of raster data we would like to stay with our national CRS.

 

 

I have a questions.

  • Can you confirm (comment) that we by sticking to our national CRS are conformant to Regulation No 1089/2010?
  • Can you confirm (comment) that we by sticking to our national CRS we are not conformant to  Technical Guidelines? However, as Technical Guidelines are not mandatory we are still conformant to INSPIRE.
  • Is really that important for the INSPIRE  interoperability to provide raster data in ETRS89-TMzn? In my opinion as both INSPIRE ETRS89-TMzn and Polish PUWG 1992 CRSs are based on ETRS89 most GIS applications can make a transformation between CRSs on the fly.
  • Jordi ESCRIU

    Dear Marcin,

    First of all, many thanks for spotting this issue. Other Member States may struggle with the same doubt.

    I see the following issues here:

    1. The requirements from the Implementing Rule on Interoperability of Spatial Data Sets and Services (IR ISDSS) are not specific enough, either intentionally or not - e.g. the requiment establishing the ETRS89 Transverse Mercator projected CRS for INSPIRE data provision is not mapped to the EPSG codes allowed for this purpose.
    2. Technical Guidelines on CRS (D2.8.I.1) does specify this mapping, clarifying in Table 1 of Section 5.5 the applicable EPSG codes for the ETRS89-TMzn projections.  All of them share the same parameters for the projection.

    In my opinion the lack of specificity in the IR ISDSS is not intentional, but I would prefer that this is confirmed by the former TWG RS experts - who participated in the drafting process of this document.

    I hope you are able to wait for an answer to the first two questions you raised.

    As regards the third one: 

    • The use of ETRS89-TMzn projections is not explicitly required for the provision of large scale data to INSPIRE (although it is recommended in D2.8.I.1 TG for conformal pan-European mapping at scales larger than 1:500,000 - this is more related to visualization purposes) - I can see the point in establishing only a set of TM projection parameters in the INSPIRE context, for the sake if interoperability.
    • Hence, you have other options for providing data to INSPIRE: as you mentioned, e.g. using ETRS89-GRS80 geodetic coordinates - However, this requires to make resampling. This approach is somehow recommended for EL and OI data with the proposal to use the 'Zoned Geographic Grid' (defined in Section 2.2.2 of Annex II of the IR ISDSS) - Have a look at the following discussion thread: https://themes.jrc.ec.europa.eu/discussion/view/10935/usability-of-the-zoned-geographic-grid-grid-etrs89-grs80 . WCS is probably a missing piece for raster data downloading services: MIG-T is addressing this issue in MIWG-07b.

    Any other views on the topic introduced by Marcin?

  • Jordi ESCRIU

    Hi Marcin,

    I will try to engage TWG-RS members in this topic, especially to clarify Point 1 of my last reply.

    The implications are really important - There is a need to clarify if national UTM projection-based CRS are valid for INSPIRE data provision.

  • Jordi ESCRIU

    Hereby I provide the link to a new discussion topic on WCS, since it was slightly mentioned here as an INSPIRE missing piece:

    https://themes.jrc.ec.europa.eu/discussion/view/22150/web-coverage-service-wcs-a-missing-piece-in-inspire

    Feel free to participate as well.

     

  • Lars ENGBERG

    Hello Marcin,

    I was member of TWG-RS but since it was closed, I have not been involved in Inspire-work so take my comments on 1.3.2 with that reservation.

    1.3.2.  Two-dimensional Coordinate Reference Systems

    • Two-dimensional geodetic coordinates (latitude and longitude) based on a datum specified in 1.2 and using the parameters of the GRS80 ellipsoid.
    • Plane coordinates using the ETRS89 Lambert Azimuthal Equal Area coordinate reference system.
    • Plane coordinates using the ETRS89 Lambert Conformal Conic coordinate reference system.
    • Plane coordinates using the ETRS89 Transverse Mercator coordinate reference system.

    From my point of view it is totally clear, the meaning of the line in 1.3.2 above is: ETRS89-TMzn, which is equivalent to a UTM-zone, a reference frame that is a realization of ETRS89 and the GRS80 ellipsoid. As I remember, we intentionally omitted reference to EPSG codes because this was not an official registry.

    So, Marcin you have to convert the co-ordinates from PUWG 1992 to ETRS89-TM33, TM34 or TM35 depending on where in Poland you operate.

    In Sweden, we have our own system SWEREF 99 TM that is equivalent to ETRS89-TM33 for almost all Sweden (within UTM-zone 33) but in the eastern part we have to convert to ETRS89-TM34 to fulfill the Inspire rules.

    I don't know why TMzn is omitted in 1.3.2. Much better wording in 1.3.2 had been something like this:

    1.3.2.  Two-dimensional Coordinate Reference Systems

    • Two-dimensional geodetic coordinates (latitude and longitude) based on a datum specified in 1.2 and using the parameters of the GRS80 ellipsoid.
    • Plane coordinates using the ETRS89-LAEA coordinate reference system.
    • Plane coordinates using the ETRS89-LCC coordinate reference system.
    • Plane coordinates using the ETRS89-TMzn coordinate reference system.

    Using the identifiers implies all parameter values for the projections and no uncertainty appears.

     

  • Marcin GRUDZIEŃ

    By Marcin GRUDZIEŃ

    Hello Lars,

    Thank you for your interpretation.

    Do you know whether there are any plans to clarify chapter 1.3.2 of the Regulation according to your suggestion?

  • Lars ENGBERG

    Hello Marcin,

    I am not involved in any Inspire work today so I have no knowledge about future plans.

      

  • Jordi ESCRIU

    Many thanks for your input, Lars.

    Answering Marcin, one of the goals of the thematic cluster activity is to find existing INSPIRE issues, discuss which are the most suitable solutions and propose them to the MIG-T for further discussion and endorsement.

    Therefore, the rewording proposed by Lars may be proposed to the MIG-T to clarify Section 1.3.2 of the IR ISDSS.

    Do you (both) agree on that?

  • Marcin GRUDZIEŃ

    By Marcin GRUDZIEŃ

    Hi Jordi,

    I agree. It definitely should be clarified.

  • Jordi ESCRIU

    As a conclusion, the following rewording for section 1.3.2 of the IR ISDSS will be proposed to the MIG-T:

    1.3.2.  Two-dimensional Coordinate Reference Systems

    • Two-dimensional geodetic coordinates (latitude and longitude) based on a datum specified in 1.2 and using the parameters of the GRS80 ellipsoid.
    • Plane coordinates using the ETRS89-LAEA coordinate reference system.
    • Plane coordinates using the ETRS89-LCC coordinate reference system.
    • Plane coordinates using the ETRS89-TMzn coordinate reference system.

    Additionally, a consistent rewording of the Technical Guidelines document.

    I proceed to close the discussion topic. Feel free to add a new one if further related issues are identified.

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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