Merging and Joining Land Cover and Land Use Areas

Often times, Land Use (lu) and Land Cover (lc) Area features are represented by multiple polygons. This can result in lu and lc official names being displayed multiple times in an application. Merging and Joining of these polygons resolves this problem. The following rules are followed in order to merge or join lu and lc areas correctly.

Joining an LU or LC Area that is entirely in an Order 8 Area

Join all parts of an lc or lu, that are the same lc or lu feature, and that have the same attributes and the same Official Name.
If an Official Name is not present for a polygon, no joining is allowed.

Merging an LU or LC Area that crosses an Order 8 Area to an Adjacent Order 8 Area

Merge only parts of lc or lu areas, when:
- they are adjacent at the Order 8 border; AND
- the same Official Name for the same language code is available; AND
- all other attributes are equal.
Never merge part of Land Cover or Land Use when adjacent at the Order 8 border if the same Official Name for the same language code is not available.
Parts of the same object have to be adjacent at the Order 8 border in order to be subject to merging even if they have the same Official Name:

An Exception to the Merging Rules

Display Features that are face based and adjacent have to be merged within the Order 8 Area. The adjacent faces are merged to one object for one feature type, even if they have no Official Name. Non-adjacent faces result in separate polygons.

Results of Merging and Joining of LU and LC Areas in Shapefile

Larger polygons are created that have the same Official Name;
All other objects without an Official Name are separate polygons;
No dataset crossing polygons.

Figure: Merging and Joining of LU and LC Areas