Cropping a Map

How to crop a map by using submap.

import matplotlib.pyplot as plt

import astropy.units as u
from astropy.coordinates import SkyCoord

import sunpy.data.sample
import sunpy.map

We start with the sample data

swap_map = sunpy.map.Map(sunpy.data.sample.SWAP_LEVEL1_IMAGE)

To crop the data you create a submap, specifying the top right and bottom left as SkyCoord objects.

top_right = SkyCoord(0 * u.arcsec, -200 * u.arcsec, frame=swap_map.coordinate_frame)
bottom_left = SkyCoord(-900 * u.arcsec, -900 * u.arcsec, frame=swap_map.coordinate_frame)
swap_submap = swap_map.submap(bottom_left, top_right=top_right)

Let’s plot the results.

fig = plt.figure()
ax = fig.add_subplot(projection=swap_submap)
image = swap_submap.plot(axes=ax)
swap_submap.draw_limb(axes=ax)
swap_submap.draw_grid(axes=ax)

# Make some room and put the title at the top of the figure
ax.set_position([0.1, 0.1, 0.8, 0.7])
ax.set_title(ax.get_title(), pad=45)

plt.show()

🏷 Tags: Map, SWAP, Coordinates