Map tile acquisition

Demonstrates cartopy’s ability to draw map tiles which are downloaded on demand from the MapQuest tile server. Internally these tiles are then combined into a single image and displayed in the cartopy GeoAxes.

(Source code)

# -*- coding: utf-8 -*-
"""
Map tile acquisition
--------------------

Demonstrates cartopy's ability to draw map tiles which are downloaded on
demand from the MapQuest tile server. Internally these tiles are then combined
into a single image and displayed in the cartopy GeoAxes.

"""
import matplotlib.pyplot as plt
from matplotlib.transforms import offset_copy

import cartopy.crs as ccrs
import cartopy.io.img_tiles as cimgt


def main():
    # Create a MapQuest open aerial instance.
    map_quest_aerial = cimgt.MapQuestOpenAerial()

    # Create a GeoAxes in the tile's projection.
    ax = plt.axes(projection=map_quest_aerial.crs)

    # Limit the extent of the map to a small longitude/latitude range.
    ax.set_extent([-22, -15, 63, 65])

    # Add the MapQuest data at zoom level 8.
    ax.add_image(map_quest_aerial, 8)

    # Add a marker for the Eyjafjallajökull volcano.
    plt.plot(-19.613333, 63.62, marker='o', color='yellow', markersize=12,
             alpha=0.7, transform=ccrs.Geodetic())

    # Use the cartopy interface to create a matplotlib transform object
    # for the Geodetic coordinate system. We will use this along with
    # matplotlib's offset_copy function to define a coordinate system which
    # translates the text by 25 pixels to the left.
    geodetic_transform = ccrs.Geodetic()._as_mpl_transform(ax)
    text_transform = offset_copy(geodetic_transform, units='dots', x=-25)

    # Add text 25 pixels to the left of the volcano.
    plt.text(-19.613333, 63.62, u'Eyjafjallajökull',
             verticalalignment='center', horizontalalignment='right',
             transform=text_transform,
             bbox=dict(facecolor='wheat', alpha=0.5, boxstyle='round'))
    plt.show()


if __name__ == '__main__':
    main()