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Support to CRSs transformations in Europe / Need for an official CRS registry in Europe?

One of the most important implementation issues concerning the Coordinate reference systems theme is the need to transform existing data in Member States, referenced to national CRSs, to the European CRSs required by INSPIRE, i.e. requirements in the Coordinate reference systems technical guidelines.

The project Coordinate Reference Systems of Europe (CRS-EU) was developed with this objective in mind. As a result, a website - namely "Information and Service System for European Coordinate Reference Systems" - is currently working and is being mainteined, providing implementers with useful information such as:

  • Description of national Coordinate Reference Systems.
  • Description of pan-European Coordinate Reference Systems.
  • Description of the official transformation parameters from national Coordinate Reference Systems to pan-European Coordinate Reference Systems.
  • Links to the organizations responsible for the establishement of such transformations (National Mapping Agencies of the European Countries).

However, the continuation of such website is not guaranteed forever and the stability and updation of the information contents is not assured.

Additionally, in some Member States other CRSs already exist (e.g. at regional level) and there is a need to support data provider organizations and users in the transformation process.

Hence, a formal public CRSs registry is found to be necessary in order to guarantee a correct, unambiguous definition of the parameters defining each CRS in the European scope (regional, national and pan-European), as well as the official transformations to the final pan-European referencing framework. This initiave should be accompanied with a proper supporting team (either at Euroepan level or at the level of Member States) which helps data providers and users to implement the official transformations.

A similar initiative is being developed in Germany, but nor publicly available yet.

Would you find it useful this kind of public/official initiave at European level in order to help to both, implementers and users?

 

  • Markus SEIFERT

    By Markus SEIFERT

    How to implement Data Specification on Coordinate Reference Systems?

    According to the Interoperability Implementing rules (IR) (Annex II, sec. 1.5. in the consolidated version), coordinate reference system (CRS) parameters and identifiers shall be managed in one or several common registers for CRS. Only identifiers contained in a common register shall be used for referring to the CRS listed in the IR (Annex II, sec. 1).

    Requirement 1 of the Technical Guidelines (TG) for CRS stipulates the use of http URIs provided by the Open Geospatial Consortium as coordinate reference system identifiers (http://inspire.jrc.ec.europa.eu/documents/Data_Specifications/INSPIRE_DataSpecification_RS_v3.2.pdf, p 15). These are based on and redirect to the definition in the EPSG Geodetic Parameter Registry.

    In the German Surveying Authorities’ view, CRS parameters and identifiers should be provided and maintained by an authorized, official institution. Additionally, a need to register other (local) CRS which are not included in the EPSG Registry, is seen. Therefore, the German Surveying Authorities decided to set up an own web-based CRS registry as part of the German SDI Registry (GDI-DE Registry). This approach is based on the ISO/TC 211 Registry for geodetic codes and parameters which is currently under development. The German SDI will use this open source software and implement some additional specific requirements.

    The Implementation will be based on

    − ISO 19111 Spatial referencing by coordinates

    − ISO 19127 Geodetic codes and parameter

    − ISO 19135 Procedures for item registration.

    The registry also contains transformation parameters in order to establish transformation services (WPS) and will replace the current implementation of the Coordinate Reference Systems of Europe (CRS-EU). The question is, whether there are any similar approaches in other countries to set up an European federation of CRS registries?

     

    When there are several activities in the field of CRS registers, the need for coordination (e.g. at European level) is seen in order to avoid duplication and interoperability issues. Thoughts should also be given to the usability in GIS-clients, as registry implementations which are independent of the EPSG Registry would lead to new CRS-identifiers.

     

    However, according to its terms of reference, the scope of the work in MIWP-6 Registries and registers (https://ies-svn.jrc.ec.europa.eu/projects/inspire-registry/wiki) is limited to the registers currently included in the INSPIRE Registry (i.e. doesn’t include the CRS topic).

     

  • Jordi ESCRIU

    Many Thanks Markus! - This is a valuable input.

    In my view it would be very interesting to explore the potential links to the ISO/TC 211 Registry for the INSPIRE purposes, beyond reusing its open source software components.

    It is nice to see the progress of the german CRS registry in the context of the national SDI.

    As you mentioned, it would be interesting to know what other countries are doing in this context and analyse the feasibility of the federation of CRS registries.

    Any other approaches and experiences regarding national CRS registries in Member States?

    Jordi

  • Jan ŘEZNÍČEK

    By Jan ŘEZNÍČEK

    Local or national CRSs registers are not used in the Czech Republic, established practice is to use EPSG identificators of CRS.

    Situation in the description of transformations within the current registers (EPSG or CRSeu) is really somewhat ambiguous. Transformation procedures described in these registers are mostly only approximate (there are generally described only parameters of Helmert transformation) with the accuracy of some meters.

    It is little complicated or eventually impossible to describe precise transformations within these registers. For example precise transformation between Czech national CRS (EPSG:2065 S-JTSK (Ferro) / Krovak) and ETRS89, includes not only Helmert transformation and equations of projection, but also transformation grid with the range of 2x2 kilometres. And the question is: How to describe transformation grid within the CRSs registers?

    If the current CRSeu register will be actualized or the new register will be developed (possibly with the functionality of international transformation service), it would be also useful to implement possibility of upload transformation grid within this register (directly or as a weblink). Other posibility is to publish web links to the national transformation services within this register.

  • Jordi ESCRIU

    Dear Jan,

    Thank you for your post. I agree with you that official transformations are complex to determine in a CRS registry, which is often suited for registering just geodetic codes and parameters.

    The case in the Czech Republic is similar to that in Spain, where i.e. the transformation from our national vertical reference system to EVRS has a precise transformation (formally defined with approprate equations) but also an approximate transformation grid (which provides the user with an approximate vertical shift for each grid cell in the whole grid - to be used with caution depending on the LoD / scale).

    In my view, the most important thing here is that both, formal / precise transformations and approximate transformations should be somehow published at Member State level and/or EU level with the aim to make them available for implementers and users, who should be always aware of their existence and official status. This is important to achieve interoperability and should be within the responsibility of the national coordination bodies in Member States.

    A possible solution - While the complete description and formulation of these transformations may be included in a technical data specification (i.e. provided and maintained by the national CRS coordination body), the CRS registries - either at Member State and/or EU level - may contain a register with the name of the transformation and a link to such technical document - e.g. by means of a document identifier.  

    Does this makes sense?

     

     

  • Jan ŘEZNÍČEK

    By Jan ŘEZNÍČEK

    Dear Jordi,

    I am convinced that it makes sense.

    Web link to the official technical document describing national transformation procedure (or possibly also link to the national transformation service) could be valuable not only as a information for users, but it could be also inspiration for the developers of transformation procedures themselves, for the comparison of different ways of transformation solutions within EU.

     

  • Jordi ESCRIU

    A presentation concerning this topic, and specificaly about the need for an official CRS registry in Europe, was presented during the 29th Meeting of the INSPIRE MIG-T, host in Ispra (19-20 April 2016) - See below.

    Need for an Official Registry for Geodetic Codes and Parameters in Europe - Presentation 28th MIG-T Meeting, Ispra - 19-20 April 2016

    The idea to set up a European Registry for geodetic codes and parameters, taking into account the possibility to build it on top of the ISO/TC 211 (Global) Registry, was presented to the INSPIRE MIG-T receiving positive feedback.

    However, the main outcome from the group was that this was not a priority in the current stage of the INSPIRE implementation.

    Therefore, I proceed to close this topic by now, with the possibility to re-open it in the future.

    Jordi

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Elevation, Ortho & Grids

Elevation, Ortho & Grids

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