OGC Maritime Limits and Boundaries S-121 GML Pilot

Liz Sanderson
Liz Sanderson
  • Updated


The primary goal of the Maritime Limits and Boundaries Pilot was to develop and exercise the S-121 GML standard for maritime boundaries data. This is the first digital standard for maritime boundaries. The conceptual model has been developed by the IHO under a mandate from the UN. The main sponsors of this pilot were UK Hydrographic Office, GeoScience Australia, Canadian Hydrographic Service and National Research Council of Canada.

Central to the MLB Pilot was the development of the S121 GML encoding. The overall architecture involved reading from sponsor datasets and databases, and generating S-121 GML according to this application schema. This standardized GML data then served as the basis for a range of OGC web services and was also transformed to generate official or legal human readable text output. FME served a central role in this project as the main tool for generating S121 GML. FME was also one of the tools tested as a client for GML, and OGC web services such as WFS, WMS and CSW. In addition, FME was used to read back the human readable legal text and generate validation reports. Finally, we ran a series of tests to show that FME could also support GeoJSON encodings of S-121 data. This is important as the new generation of OGC services involve the use of REST, JSON and GeoJSON.

One of the big challenges was that the application schemas for S121 GML evolved through the course of the pilot so we had a moving target in terms of syncing with the schema and data generation / validation. This is likely one reason why FME was the only tool able to generate a complete encoding of the S121 feature definitions during the pilot. While not so complex in terms of geometry, it does involve a complex array of relationships between the various objects - from border points to boundaries to areas and then on to the non-spatial types such as basic administrative units, governance, party and sources. One challenge was reading all these relationships from geodatabase relationship classes and building the nested complex relationship properties and embedding them in the appropriate S121 feature objects. All of these are required to generate the legal text which will ultimately go to the UN as a boundary submission.

The Engineering Report for the Pilot will soon be available and links to it provided here. As well, the FME workspaces, schemas and shareable data sources and outputs will also be provided.

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