Resampling Maps

How to resample a map using the resample method, which implements interpolation, or using superpixels, which combines pixels.

import matplotlib.pyplot as plt

import astropy.units as u

import sunpy.data.sample
import sunpy.map

We start with the sample data.

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

To reduce the angular resolution of the map, you can use the resample() method, specifying the new dimensions in pixels. By default, this method uses linear interpolation but this can be changed with the method argument (‘nearest’, ‘linear’ or ‘spline’).

new_dimensions = [40, 40] * u.pixel
aia_resampled_map = aia_map.resample(new_dimensions)

Let’s plot the result.

fig = plt.figure()
ax = fig.add_subplot(projection=aia_resampled_map)
aia_resampled_map.plot(axes=ax)
plt.show()

Another way to reduce the angular resolution of the map is by using the superpixel() method, which combines pixels. The superpixel dimensions do not need to be square, and the intensity of each superpixel defaults to the sum of the constituent pixels. For example, you can reduce the AIA map resolution by a factor of 16 by specifying 16x16 superpixels.

superpixel_size = [16, 16] * u.pixel
aia_superpixel_map = aia_map.superpixel(superpixel_size)

Let’s plot the result.

fig = plt.figure()
ax = fig.add_subplot(projection=aia_superpixel_map)
aia_superpixel_map.plot(axes=ax)
plt.show()