mirror of
https://github.com/wassname/geopandas.git
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Joris Van den Bossche
766b9fcda5
* DOC: add example to add basemap with contextily * add contextily to readthedocs environment
69 lines
2.6 KiB
Python
69 lines
2.6 KiB
Python
"""
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Adding a background map to plots
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--------------------------------
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This example shows how you can add a background basemap to plots created
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with the geopandas ``.plot()`` method. This makes use of the
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`contextily <https://github.com/darribas/contextily>`__ package to retrieve
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web map tiles from several sources (OpenStreetMap, Stamen).
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"""
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# sphinx_gallery_thumbnail_number = 3
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import geopandas
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###############################################################################
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# Let's use the NYC borough boundary data that is available in geopandas
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# datasets. Plotting this gives the following result:
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df = geopandas.read_file(geopandas.datasets.get_path('nybb'))
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ax = df.plot(figsize=(10, 10), alpha=0.5, edgecolor='k')
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###############################################################################
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# Convert the data to Web Mercator
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# ================================
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#
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# Web map tiles are typically provided in
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# `Web Mercator <https://en.wikipedia.org/wiki/Web_Mercator>`__
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# (`EPSG 3857 <https://epsg.io/3857>`__), so we need to make sure to convert
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# our data first to the same CRS to combine our polygons and background tiles
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# in the same map:
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df = df.to_crs(epsg=3857)
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###############################################################################
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# Contextily helper function
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# ==========================
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#
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# We define a small helper function that uses
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# `contextily <https://github.com/darribas/contextily>`__ to add a map
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# as background to an existing plot:
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import contextily as ctx
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def add_basemap(ax, zoom, url='http://tile.stamen.com/terrain/tileZ/tileX/tileY.png'):
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xmin, xmax, ymin, ymax = ax.axis()
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basemap, extent = ctx.bounds2img(xmin, ymin, xmax, ymax, zoom=zoom, url=url)
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ax.imshow(basemap, extent=extent, interpolation='bilinear')
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# restore original x/y limits
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ax.axis((xmin, xmax, ymin, ymax))
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###############################################################################
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# Add background tiles to plot
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# ============================
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#
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# Now we can use the above function to easily add a background map to our
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# plot. The `zoom` keyword is required and let's you specify the detail of the
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# map tiles (be careful to not specify a too high `zoom` level, as this can
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# result in a large download):
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ax = df.plot(figsize=(10, 10), alpha=0.5, edgecolor='k')
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add_basemap(ax, zoom=10)
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###############################################################################
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# By default, contextily uses the Stamen Terrain style. We can specify a
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# different style using ``ctx.sources``:
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ax = df.plot(figsize=(10, 10), alpha=0.5, edgecolor='k')
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add_basemap(ax, zoom=11, url=ctx.sources.ST_TONER_LITE)
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ax.set_axis_off()
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