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)

Out:

INFO: Missing metadata for solar radius: assuming the standard radius of the photosphere. [sunpy.map.mapbase]
INFO: Missing metadata for solar radius: assuming the standard radius of the photosphere. [sunpy.map.mapbase]

Let’s plot the results.

fig = plt.figure()
ax = fig.add_subplot(111, projection=swap_submap)
swap_submap.plot()
swap_submap.draw_limb()
swap_submap.draw_grid()

plt.show()
SWAP $174 \; \mathrm{\mathring{A}}$ 2011-06-07 06:33:29

Out:

INFO: Missing metadata for solar radius: assuming the standard radius of the photosphere. [sunpy.map.mapbase]
INFO: Missing metadata for solar radius: assuming the standard radius of the photosphere. [sunpy.map.mapbase]
INFO: Missing metadata for solar radius: assuming the standard radius of the photosphere. [sunpy.map.mapbase]
INFO: Missing metadata for solar radius: assuming the standard radius of the photosphere. [sunpy.map.mapbase]

Total running time of the script: ( 0 minutes 1.031 seconds)

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