# Drawing a rectangle on a map#

This example will demonstrate how to draw a rectangle on a map using draw_quadrangle().

import matplotlib.pyplot as plt

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

import sunpy.data.sample
import sunpy.map


aia_map = sunpy.map.Map(sunpy.data.sample.AIA_171_IMAGE)


Here are four different ways to draw a rectangle. The first three ways directly calls the SkyCoord class. The fourth way converts pixel coordinates to the equivalent SkyCoord objects using GenericMap.wcs.pixel_to_world.

fig = plt.figure(figsize=(5, 5))
aia_map.plot(axes=ax, clip_interval=(1, 99.99)*u.percent)

<matplotlib.image.AxesImage object at 0x7f2a675ac1c0>


Specify two opposite corners of the rectangle as a single, two-element SkyCoord object.

coords = SkyCoord(
Tx=(100, 500) * u.arcsec,
Ty=(200, 500) * u.arcsec,
frame=aia_map.coordinate_frame,
)
coords,
axes=ax,
edgecolor="blue",
linestyle="-",
linewidth=2,
label='2-element SkyCoord'
)

<astropy.visualization.wcsaxes.patches.Quadrangle object at 0x7f2a675ada20>


Specify two opposite corners of the rectangle as separate SkyCoord objects.

bottom_left = SkyCoord(-500 * u.arcsec, 200 * u.arcsec, frame=aia_map.coordinate_frame)
top_right = SkyCoord(-100 * u.arcsec, 500 * u.arcsec, frame=aia_map.coordinate_frame)
bottom_left,
axes=ax,
top_right=top_right,
edgecolor="green",
linestyle="--",
linewidth=2,
label='two SkyCoords'
)

<astropy.visualization.wcsaxes.patches.Quadrangle object at 0x7f2a675ac1f0>


Specify one corner of the rectangle and the rectangle’s width and height.

bottom_left = SkyCoord(-500 * u.arcsec, -500 * u.arcsec, frame=aia_map.coordinate_frame)
width = 400 * u.arcsec
height = 300 * u.arcsec
bottom_left,
axes=ax,
width=width,
height=height,
edgecolor="yellow",
linestyle="-.",
linewidth=2,
label='width/height'
)

<astropy.visualization.wcsaxes.patches.Quadrangle object at 0x7f2a675ad240>


Draw a desired rectangle in pixel coordinates by first converting to SkyCoord objects.

bottom_left = aia_map.wcs.pixel_to_world(600 * u.pixel, 350 * u.pixel)
top_right = aia_map.wcs.pixel_to_world(800 * u.pixel, 450 * u.pixel)
bottom_left,
axes=ax,
top_right=top_right,
edgecolor="red",
linestyle=":",
linewidth=2,
label='pixel_to_world()'
)
ax.legend()

plt.show()


Total running time of the script: (0 minutes 0.469 seconds)

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