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I'm a complete newbie to this GIS stuff, but I've attempted some due diligence as follows -

It being election season I'm after shapefiles for the NZ electorates, however I'm just after a map of the land areas, not one that includes the marine margins (12 mile limit?), as the latter don't really look like the country, and how many fish vote anyway.

Related stuff I've found would include

  1. Various administrative areas, but not general electorates, at http://www.diva-gis.org/gdata
  2. General election shapes including marine areas, for example at http://m.stats.govt.nz/browse_for_stats/Maps_and_geography/Geographic-areas/digital-boundary-files.aspx
  3. That same page (and elsewhere) has NZ coastline maps without electoral areas.

In theory I could clip (2) against (3), but after looking around a bit I couldn't figure out how to do that with the likes of ogr2ogr.

My output target is GeoJSON in d3.

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  • linz.govt.nz/about-linz/our-organisation/linzs-responsibilities/…
    – BradHards
    Commented Aug 9, 2017 at 3:56
  • Thanks all in particular @leasmaps. I didn't find a file directly, so used the ones I mention in the question, but did get there using clipping in QGIS. The main gotcha is that I had to "convert lines to polygons" on the coastline shapefile to allow it to clip. Then used "Simplify geometries" at tolerance 200 to shrink the resulting file.
    – Craig
    Commented Aug 19, 2017 at 2:27

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I think you will have to have a look at a GIS Editing Tool like QGIS to do the clipping/editing for you. QGIS is free as well.

I would however consider using the electoral boundaries as provided as your final data clipped is going to be very large (all those fjords at the top of the south island look pretty complex - lots of points). Have a look at http://www.elections.org.nz/events/electorate-boundary-review/final-electorate-boundaries/interactive-mapping-2014-boundary if you are looking to create a web map which is what I'm guessing you are looking to do.

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