To enable habitat maps from different sources to be compared and combined into the large datasets used in EMODnet Seabed Habitats and displayed on the interactive map, the map’s attribute table must be converted into a standardised format. We call this a Data Exchange Format (DEF).
For the purposes of EMODnet Seabed Habitats, data are required to be submitted in an updated version of the MESH DEFs as they provide a tried and tested method of standardising maps for collation and conflation.
There are two possible habitat data exchange formats, dependant on the habitat map itself, described on the Data Exchange Formats page and downloadable (PDF, 268KB)) (EMODnet Seabed Habitats data provider package).
The map should first be converted into the Original Habitat DEF. If the map is detailed enough to be translated into the EUNIS classification system, or is already in EUNIS classification, the attribute table should be extended into the Translated Habitat DEF and the habitats translated. If the map represents habitats from Annex I of the EU's Habitats Directive (for Natura2000 sites), the attribute table should be extended into the Habitats Directive DEF.
The values for the fields in the DEF should be entered as per the Data Exchange Format guidance. Mandatory fields must contain a valid value for each feature/polygon, non-mandatory fields need not contain values but the field itself must still exist in the final submission for the data to be valid.
If the original habitat map does not contain many polygons, it should be viable to enter the DEF field values manually. If the habitat map contains a number of habitats repeated within a large number of polygons, an attribute join can be used to fill the HAB_TYPE and T_RELATE fields with less effort. A possible method of doing this is outlined in "EMODnetSBH Supplying data - GIS tips" (PDF, 283KB) from the data provider package.
Once converted into the required DEF, the final attribute table should contain all of the DEF’s fields, and all extraneous fields should be removed.
If you have ArcMap and are comfortable with python, the change to the DEF schema can be automated by using either of two python scripts available in our GitHub repository. The script to use depends on your habitat map:
"add_MESH_ORIG.py" adds all fields required by the Original Habitat DEF.
"add_MESH_TRANS.py" adds all fields required by the Translated Habitat DEF.
After translation, extraneous fields may either be deleted manually, or by using either of two python scripts supplied in the data provider package. Again, the script to use depends on your habitat map:
"trim_MESH_ORIG.py" removes all fields not required by the Original Habitat DEF.
"trim_MESH_TRANS.py" removes all fields not required by the Translated Habitat DEF.
The scripts provided will act on all shapefiles within a folder or location provided by the user, and so can be used to batch-process addition and removal of fields with multiple maps.
Warning: It should be noted that due to the behaviour described above, maps to be translated must moved into their own folder before running the scripts to avoid affecting any other shapefiles.