Implementation of the Buildings theme using data managed by ČÚZK in conformity with the INSPIRE data specification

  • Author
    Michal MED
  • Post date: 
    15 Feb 2016
  • Last modified: 
    31 May 2017
  • Country: 
    Czech Republic
  • Themes: 
    • Buildings
  • Content needs review

    The objective is to cover application schemas of the theme Buildings as completely as possible by data managed by Czech Office for Surveying, Mapping and Cadastre (ČÚZK) and to transform these data according to the INSPIRE data specification. Transformation process is set up, tested and executed on two levels and is documented to provide a guideline and best practice for reuse in the transformation of data for the theme Buildings, specifically for the application schemaBuildingsExtended2D.

    Source databases

    The source is represented by two databases managed by the Czech Office for Surveying, Mapping and Cadastre (ČÚZK). Databases are Information System of the Cadastre of Real Estates (ISKN), containing buildings in the cadastral context, and Information System of Territorial Identification (ISÚI), containing buildings as construction objects. Both databases are based on Oracle database system, using Oracle Spatial for storing spatial data. Data from ISÚI are publicly available by law, as well as spatial data from ISKN. Databases do not have any metadata.

     

    Target INSPIRE application schemas used

    Application schemas BuildingExtended2D and BuildingsExtendedBase (XSD schemas were written by ourselves, according to the application schemas and available fromhttp://services.cuzk.cz/xsd/inspire/bu-ext/3.0/BuildingsExtendedBase.xsdand http://services.cuzk.cz/xsd/inspire/bu-ext2d/3.0/BuildingsExtended2D.xsd) were used, extending application schemas BuildingsBase and BuildingsCore2D.

     

    Implementation steps

    The mapping from ČÚZK databases into the INSPIRE BuidlingsExtended2D application schema was based on the analysis of data in source databases.

    In 2010 so called Publication database has been set up for publishing both INSPIRE and national network services. This database is on-line linked to the mentioned source databases ISKN and ISÚI and inside this database is the necessary conversion (using PL/SQL) into the INSPIRE data structure (including the Buildings theme) proceeded.

    In the Publication database were created tables containing relevant data from source databases. Data were further displayed in database views in the structure conform to INSPIRE application schemas.

    Special attention had to be paid to identifiers. Data came from two source databases, using different identification keys of objects.

    Data Structures in source data were mapped on INSPIRE application schema structure. In some cases, one INSPIRE attribute could have be mapped to one of two or more attributes in source data. This was caused by the fact, that some buildings from two source databases overlapped.

    Data in the same structure as in the database views respecting INSPIRE application schema structure were transformed into GML format. Transformation process itself was done using Marushka (3rd party software).

    Transformation was tested on an integrated data sample. After testing, transformation process was executed on the whole data source. Part of the testing is also a validation. While the transformation is done, data are kept up-to date by syncing with the database.

    Data are shared by both view and download service. Through download service, direct access and pre-defined files are shared. Pre-defines files are available via WFS 2.0.0 and ATOM feed.

    The last step of sharing spatial data sets is creating metadata records for series of datasets and for both services. Series of datasets is a collection of all data sets for one INSPIRE theme. Metadata describes the data itself without taking its location into account.

    Resource Link: 
    http://services.cuzk.cz/wfs/inspire-bu-wfs.asp?service=WFS&version=2.0.0&request...

    Steps

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    The analytical part of implementation was done in two steps. In the first step, data specification for Buildings was carefully studied. It contains 6 application schemas divided by geometry and semantic level of detail. The second step analysis was focused on available data in databases.

    The analysis of Data Specifications on Buildings resulted to the following conclusions:

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    Data for the theme Buildings have to be desribed by metadata. For the creation of metadata, the oXygen XML Editor wa used. A metadata document was created according to the ISO 19115 standard with respect to the INSPIRE metadata profile. Metadata were created to be consistent with the ČÚZK Metadata Profile.

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    Using results from the previous step, in this step, mapping of the source data to the INSPIRE structure was set up. According to the fact, that there were two source databases, there were two steps of transformation. Basically, mapping is set up only on one level, but in layers. It is important to set up the source attributes for INSPIRE attributes.

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    The database tables from source databases ISKN and ISUI were replicated into the Publication database that then publishes of data. The publication database contains only up-to-date data and is updated continuously in a period not more than 2 hours.

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    The next step of the implementation involved creating views in the publication database. Views are created in the structure similar to those of INSPIRE's feature catalogue structure. Multiplicities found in the previous steps are now solved. In the view there is only the proper value of the attribute as the relevant attributes have their appropriate codelists value replaced.

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    The next step involved the most visible part of data transformation from database views in the Publication database into the GML format following the INSPIRE application schema BuildingsExtended2D, whose XSD schemas were created for this purpose.

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    The result of the transformation was a file in the GML format following the structure given by the INSPIRE Data Specification, executed by the INSPIRE application schema and XSD schema. The quality of the output GML file was validated against XSD files.

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    Pre-defined files and the structure of data returned by a Web Feature Service (WFS) was set up in the Marushka software, which provides WFS in version 2.0.0. The data provided by this service were transformed in the previous step. The service created by the tool was not certificated by the OGC and the service support was created as needed.