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Orthoimagery CRS & grids

I am posting here a question reported from Anna Bober (anna.bober@codgik.gov.pl), Poland.


I have some questions connected with coordinate reference system (CRS) especially for providing raster data for orthoimagery (OI) and elevation (EL) themes. CRS of my source OI is EPSG:2180-PUWG 1992 (grid also) . I want to adjust the data to Inspire specification, so I transform data from EPSG:2180 to ETRS89-TM33, TM34 or TM35. For all Poland the size of data is about 3.5TB. Transformation is no problem, but I have problem with adjustment of grid. If I want to adjust grid to INSPIRE I need to merge all data and next I need to intersect to new grid. It is very difficult to do because of size of data (3.5TB).

My question is:

Is it necessary to change grid from EPSG:2180 to ETRS89-TM33 , TM34 or TM35 in INSPIRE framework? Can I only change CRS (to ETRS89-TM33, TM34 or TM35) without change of grid?

I will be grateful for response!

 

Anna Bober

Starszy specjalista

Dział Fotogrametrii i Teledetekcji

Centralny Osrodek Dokumentacji Geodezyjnej i Kartograficznej

ul. Jana Olbrachta 94B

01-102 Warszawa

tel. /+48 22/ 532 25 38  e-mail:anna.bober@codgik.gov.pl

www.codgik.gov.pl

Niniejsza wiadomość jest własnością Centralnego Ośrodka Dokumentacji Geodezyjnej i Kartograficznej i może zawierać informacje poufne i/lub prawnie chronione. Jeśli nie są Państwo właściwym adresatem (lub otrzymali Państwo tę wiadomość na skutek pomyłki), prosimy o tym fakcie niezwłocznie poinformować nadawcę i usunąć otrzymaną wiadomość. Każde nieautoryzowane kopiowanie, ujawnianie lub rozpowszechnianie załączonej informacji jest zabronione.

 


Jordi

  • Jordi ESCRIU

    Dear Anna, 

     

    Looking at Section 2.2 of the Implementing Rule on Interoperability of Spatial Data Sets and Services - and in my personal view... :

     

    • You have to make first a CRS transformation for your orthoimagery dataset, using as a target one of the CRSs that are allowed in the INSPIRE context.
    • If you choose geodetic coordinates based on ETRS89-GRS80, then you shall be using the "Zoned Geographic Grid".
    • If you choose projected coordinates based on ETRS89-LAEA projection, then you shall be using the "Equal Area Grid".
    • But If you opt for providing your data using any of the other CRSs allowed in INSPIRE, e.g. ETRS89-TMzone projection (your case), you are not obliged to use any of the grids stated above.

    Note that:

    • The use of the "Zoned Geographic Grid" (based on ETRS89-GRS80 geodetic coordinate reference system) is only recommended for data provision in the Technical Guidelines for the Orthoimagery and Elevation themes (i.e. no obligation to use it), and;
    • The use of the "Equal Area Grid" is mainly inteded for reporting and statistical purposes where the Lambert Azimuthal Equal Area (LAEA) projection is required.

     

    Hope my answer helps you - If not, do not hesitate to ask again using this thread.

     

    Jordi

  • Anna BOBER

    Dear Jordi,

    Many thanks for Your response.

    For INSPIRE we transform orthoimagery from EPSG:2180 to ETRS89-TMzone projection.

    So do we have to change grid EPSG:2180 to grid for ETRS89-TMzone projection (I mean that grid for EPSG:2180 is another than grid for ETRS89-TMzone projection)? For us change of grid is very difficult because of size of data (3.5TB). Transformation between CRS is no problem but change of grid will take too long time (in this case we need to merge all data and next we need to intersect to new grid).

    Can we provide data in ETRS89-TMzone projection using grid dedicated for EPSG:2180?

     

  • Peter STROBL

    I don't see how you could change the CRS of your Orthoimagery (raster) data without changing their grid. That a (orthogonal) grid in one CRS will resemble a (orthogonal) grid in another CRS is rather unlikely and if at all only exact for a relatively small area. Two CRSs sharing the same grid throughout are only imaginable if based on the same Geoid, datum, and projection i.e. with nothing else than an (integer multiple of the cell size) offset in their origin.

  • Anna BOBER

    I'm sorry. I wrote it wrong (briefly). When I wrote about grid I meant grid sheet.

    We have to change orthoimagery EPSG:2180 to grid for ETRS89-TMzone projection. Grid sheet for EPSG:2180 is another than grid sheet for ETRS89-TMzone projection)? For us change of grid sheet is very difficult because of size of data (3.5TB). Change of grid sheet will take too long time (in this case we need to merge all data and next we need to intersect to new grid sheet).

    Can we provide data in ETRS89-TMzone projection using grid sheet dedicated for EPSG:2180?

  • Julián DELGADO

    By Julián DELGADO

    Dear Anna

    To deal with raster data and cartographic projection is not easy. As you are discovering now, there are some concepts that complicate the issue to generate INSPRIE dataset (i.e. squareness of pixels and greographical grids, scale deformations and cartographic sheet). Our advice from IGN Spain is to dont' try focus your resulting dataset accoring cartographic demands, in other words don't preserve traditional division of sheets. Remain that most of the INSPIRE data will be delivered by webservices.

    I recommend you to read the following post in the GGS cluster. Where a zoned geographical grid have been proposed in mercator projection.

    https://themes.jrc.ec.europa.eu/discussion/view/10935/usability-of-the-zoned-geographic-grid-grid-etrs89-grs80

    My best regards

  • Jordi ESCRIU

    Dear Anna,

    If you transform the CRS of an orthoimage data set series you are 'implicitly' changing the geographic grid - which is what Peter said, if I understood him well. And the map sheet distribution of your series is linked to its geographic grid, since map sheets are conformed by blocks or aggregations of geographic grid cells.

    Note that the basic characteristics conforming the nature of a geographic grid are its reference system and projection (if any).

    Apart from reading the thread proposed by Julián, it could be also interesting for you to look at some ongoing data transformation experiences from other data providers:

    https://themes.jrc.ec.europa.eu/pages/view/48834/implementation-experiences-el-oi

    Hope this helps,

    Jordi

     

  • Jordi ESCRIU

    Dear Anna,

    I assume that your question was already answered. Hence, I proceed to close this discussion topic.

    Please, send me message through the platform in case you need something else related to this topic.

    Jordi

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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