nzgeom 0.0.3

provide geospatial geometry for NZ coastlines and administrative regions

NZ geometries

Provides geospatial geometries describing New Zealand coastlines and regional administrative boundaries.

Installation

pip install nzgeom

Usage Examples

>>> import nzgeom.coastlines
>>> c =  nzgeom.coastlines.get_NZ_coastlines()
>>> c
                               name macronated  ...                     name_ascii                                           geometry
0                              None          N  ...                           None  MULTIPOLYGON (((175.76343 -36.43109, 175.76327...
1                              None          N  ...                           None  MULTIPOLYGON (((175.76337 -36.43096, 175.76312...
2                              None          N  ...                           None  MULTIPOLYGON (((168.14925 -47.11982, 168.14868...
3                              None          N  ...                           None  MULTIPOLYGON (((166.90386 -46.58083, 166.90376...
4                         Lion Rock          N  ...                      Lion Rock  MULTIPOLYGON (((175.75020 -36.77198, 175.74985...
...                             ...        ...  ...                            ...                                                ...
9134  Tāhuahua-Paopao-Karoro Island          Y  ...  Tahuahua-Paopao-Karoro Island  MULTIPOLYGON (((173.28982 -34.90622, 173.29034...
9135              Wakatehāua Island          Y  ...              Wakatehaua Island  MULTIPOLYGON (((172.89280 -34.68681, 172.89304...
9136               Ōhau/West Island          Y  ...               Ohau/West Island  MULTIPOLYGON (((172.03345 -34.18387, 172.03354...
9137     Manawatāwhi / Great Island          Y  ...     Manawatawhi / Great Island  MULTIPOLYGON (((172.14683 -34.14436, 172.14729...
9138  North Island or Te Ika-a-Māui          Y  ...  North Island or Te Ika-a-Maui  MULTIPOLYGON (((175.13516 -41.37745, 175.13507...

If matplotlib is available, it's easy to plot the coastline geodataframe (or add the coastlines to an existing plot):

>>> import matplotlib.pyplot as plt
>>> ax = c.plot
>>> ax.set_xlim([165, 180])
>>> plt.show()

For the council region boundaries:

>>> import nzgeom.regions
>>> r = nzgeom.regions.NZRegions()
>>> r.list_regions()
        Northland Region
         Auckland Region
          Waikato Region
    Bay of Plenty Region
         Gisborne Region
      Hawke's Bay Region
         Taranaki Region
Manawatu-Wanganui Region
       Wellington Region
       West Coast Region
       Canterbury Region
            Otago Region
        Southland Region
           Tasman Region
           Nelson Region
      Marlborough Region
     Area Outside Region
>>> r.get_region_geodataframe("Auckland Region")
  REGC2018_V1_00 REGC2018_V1_00_NAME  LAND_AREA_SQ_KM    AREA_SQ_KM   Shape_Length                                           geometry
1             02     Auckland Region      4941.572557  16156.610062  659677.328124  MULTIPOLYGON (((1788533.265 6047342.800, 17891...

Mask a grid's coordinates to land areas within the Wellington Region:

import numpy as np
import matplotlib.pyplot as plt
import geopandas as gpd
from shapely.geometry import Point
import nzgeom.coastlines
import nzgeom.regions

LATLON = "EPSG:4326"

coast = nzgeom.coastlines.get_NZ_coastlines().to_crs(LATLON)
nzreg = nzgeom.regions.NZRegions()
wellington_region = nzreg.get_region_geodataframe("Wellington Region").to_crs(LATLON)

# make a 0.1 by 0.1 degree grid, put it in a geopandas.GeoDataFrame
grid_lons, grid_lats = np.meshgrid(
    np.arange(174.4, 176.5, 0.1), np.arange(-41.8, -40.4, 0.1)
)
dummy_grid = gpd.GeoDataFrame(
    geometry=[
        Point(lon, lat) for lon, lat in zip(grid_lons.flatten(), grid_lats.flatten())
    ],
    crs=LATLON,
)
# mask out points outside Wellington Region
dummy_grid_wellington_landonly = gpd.clip(dummy_grid, wellington_region)
# mask out water points
dummy_grid_wellington_landonly = gpd.clip(dummy_grid_wellington_landonly, coast)

# draw the coastlines, Wellington Region, the full grid, and the masked grid.
fig, ax = plt.subplots()
coast.plot(ax=ax, color="lightgray", label="New Zealand")
wellington_region.plot(ax=ax, color="None", label="Wellington Region")
dummy_grid.plot(ax=ax, marker="x", color="#1b9e77", alpha=0.7, label="full grid")
dummy_grid_wellington_landonly.plot(
    ax=ax, marker="+", color="#d95f02", alpha=0.7, label="Wellington & land"
)
ax.set_xlim([172, 179])
ax.set_ylim([-43.0, -39.5])
ax.legend()
plt.show()

Credits

The Regional Council boundary data are provided by Stats NZ Tatauranga Aotearoa under the terms of the Creative Commons Attribution 4.0 International.

The NZ coastlines data are provided by Toitū Te Whenua Land Information New Zealand under the terms of the Creative Commons Attribution 4.0 International.