Once geologic map data is automated into a structured digital form, publication of the data for access as an OGC WMS/WFS is a process of Extracting data from the source data set, Transforming it to the GeoSciML-Portrayal schema, and Loading the transformed data into whatever sort of data store is most convenient for the server implementation of the OGC WMS and WFS. This process is commonly called ‘ETL’. There exists a broad spectrum of approaches to the ETL process. We focus in this tutorial on what we deem to be a common situation in which the source data is in a database feature class (possibly in an ESRI geodatabase, shapefile, or PostGIS table) with one record for each geometric feature (line or polygon), and each feature either includes fields specifying the age and lithology of the unit, or has a link to a map unit description table that contains the information. Source information for the map data and unit descriptions is also required.
The most difficult part of the process is typically determining what representative lithology, age, younger age, and older age categories from a standard vocabulary to assign to each unit using URIs. OneGeology conformance prescribes that these vocabularies should be either the CGI SimpleLithology vocabulary for lithology and the CGI2011 time scale (see listing in portrayal template workbook, CGI2011 tab), or their INSPIRE vocabulary equivalents. This time scale includes the International Stratigraphic Commission Geologic Time Scale 2009 for age, and Fennoscandian age additions (Asch, Kristine, Klicker, Marco, and Schubert, Chris, 2009-11, Draft Portrayal Rules for OneGeology Europe, OneGeology-Europe WP3 Data Portrayal, Downloaded from http://onegeology-europe.brgm.fr/how_to201002/OneGeologyWP3-DataSpec_Portrayal_v%201%205KA.doc 2011-11-30). Mapping data structure from the source data tables into a GIS feature class (a table with the GeoSciML-Portrayal data structure with a geometry column for the line or polygon location) is described in the next section.
Once the GeoSciML-Portrayal feature class is ready, set up the configuration for the WMS server. This procedure will be specific to the particular server implementation that is being used. To support the use of SLD for user defined map portrayals, it is important to provide WMS layers with standard layer names as discussed in the section on Styling, below.
The final step is to create metadata for the dataset and its service distribution. This includes checking the WMS GetCapabilities response document that the service will present to describe itself, as well as loading a metadata record into a catalog server to make the serviced discoverable. The OneGeology catalog is populated automatically using the WMS capabilities document, so the catalog registration does not require an extra step on the part of the service provider.
Section last modified: 21 October 2015