Bathymetry — shaded relief¶

Render a GEBCO 2020 subset of the Mid-Atlantic Ridge near the Azores as a hillshaded relief map. Hillshading turns a flat depth grid into an intuitive 3D-looking surface that makes the rift valley and transform faults pop — exactly how a marine geologist would eyeball seafloor structure.

In [ ]:

import tempfile

import matplotlib.pyplot as plt
import numpy as np
from matplotlib.colors import LightSource
from pyramids.dataset import Dataset

from earthlens import EarthLens

import tempfile import matplotlib.pyplot as plt import numpy as np from matplotlib.colors import LightSource from pyramids.dataset import Dataset from earthlens import EarthLens

In [ ]:

out = tempfile.mkdtemp()
paths = EarthLens(
    data_source='gebco',
    dataset='gebco_2020',
    aoi=[-29.5, 36.2, -27.7, 38.0],
    path=out,
).download(progress_bar=False)

arr = np.asarray(Dataset.read_file(str(paths[0])).read_array(), dtype='float32')
arr = arr[0] if arr.ndim == 3 else arr
arr = np.where(arr == 32767, np.nan, arr)
# LightSource needs finite values; fill the (rare) gaps with the deepest value.
filled = np.where(np.isnan(arr), np.nanmin(arr), arr)
print('grid', arr.shape, '| depth range', round(np.nanmin(arr)), '..', round(np.nanmax(arr)), 'm')

out = tempfile.mkdtemp() paths = EarthLens( data_source='gebco', dataset='gebco_2020', aoi=[-29.5, 36.2, -27.7, 38.0], path=out, ).download(progress_bar=False) arr = np.asarray(Dataset.read_file(str(paths[0])).read_array(), dtype='float32') arr = arr[0] if arr.ndim == 3 else arr arr = np.where(arr == 32767, np.nan, arr) # LightSource needs finite values; fill the (rare) gaps with the deepest value. filled = np.where(np.isnan(arr), np.nanmin(arr), arr) print('grid', arr.shape, '| depth range', round(np.nanmin(arr)), '..', round(np.nanmax(arr)), 'm')

Hillshade¶

Light from the NW (azdeg=315) at 45 degrees elevation; dx/dy are the approximate metres-per-pixel of a 15-arcsec grid so the relief is physically scaled rather than wildly exaggerated.

In [ ]:

ls = LightSource(azdeg=315, altdeg=45)
rgb = ls.shade(
    filled, cmap=plt.cm.gist_earth, vert_exag=1.0, dx=460, dy=460, blend_mode='soft'
)
plt.figure(figsize=(6, 6))
plt.imshow(rgb)
plt.title('GEBCO 2020 shaded relief — Mid-Atlantic Ridge (Azores)')
plt.axis('off')
plt.show()

ls = LightSource(azdeg=315, altdeg=45) rgb = ls.shade( filled, cmap=plt.cm.gist_earth, vert_exag=1.0, dx=460, dy=460, blend_mode='soft' ) plt.figure(figsize=(6, 6)) plt.imshow(rgb) plt.title('GEBCO 2020 shaded relief — Mid-Atlantic Ridge (Azores)') plt.axis('off') plt.show()