Topo50 coastline

posted 28 Nov 2011, 17:39 by David Pairman   [ updated 1 Jul 2012, 21:28 by David Pairman ]
Should we replace the LCDB current coastline with the TOPO50 coastline? 

The coastline of LCDB seems unique to LCDB. It differs from Topo50 which most would consider to be New Zealand’s authoritative coastline and (before our smoothing) it contained segments of stepped linework from early raster classification. We are contemplating delimiting the LCDB with a Topo50 coastline (through an as-yet undetermined process). What do you think?

Collaborating agencies: Please leave your views as comments below, along with your name/organisation. 

Example from Whangaroa Harbour (click image to expand)


At the April 2012 Technical Advisory Group meeting it was resolved to adopt the Topo50 coastline for LCDB to make it easier and more consistent to use with other data sets. In general previously mapped areas outside the Topo50 coast were truncated at the coastline. Where the Topo50 coastline fell outside the previously mapped boundary, the old "coastline" boundary was removed. Polygon boundaries (dangles) and other intersection points that previously touched the old "coastline" boundary were then extended to meet the new Topo50 boundary. In general their direction was maintained so long as they intersected within 200 metres, otherwise a direct line was taken to join the Topo50 coastline at its nearest point. 

Three classes; "Estuarine Open Water", "Herbaceous Saline Vegetation", and "Mangrove" to exist outside of the Topo50 coastline. An "onshore" attribute is used to indicate when a polygon is inside or outside the Topo50 coastal boundary. See the Coastal saline vegetation issue for more discussion on the offshore treatment.