NZ Coastlines and Islands Polygons (Topo 1:250k)

This provides a polygon coastline and islands layer which is based on the Topo250 products. It is a combination of the following layers:

• NZ Mainland coastlines (Topo, 1:250k)
• NZ Mainland island polygons (Topo, 1:250k)
• NZ Chatham Is island polygons (Topo, 1:250k)

This topographic coastline is the line forming the boundary between the land and sea, defined by mean high water.

Islands from the NZ Island Polygons layer that lie within the NZ Coastline and Chatham Islands areas (i.e. islands in lakes, rivers and estuaries) have been removed.

The GIS workflow to create the layer is:

1. NZ Coastlines were converted from a polyline to a polygon using a polyline to polygon tool.
2. The resulting coastal polygon was then used as an input into an erase tool and run against the NZ Island Polygon layer to remove all islands lying within the NZ Mainland and Stewart Island.
3. This was then merged with the NZ Chatham Is island polygons (Topo, 1:250k) that have had the islands within the main island polygon removed using a merge tool.
4. Lake Onoke from the NZ Mainland lake polygons (Topo, 1:250k) layer and Te Whanga Lagoon from the NZ Chatham Is lagoon polygons (Topo, 1:250k) layer were then erased from the resultant polygon layer to include these two water bodies in the coastline definition.

For more detailed description of each layer refer to the layer urls above.