Bathymetry — coastal depth profile¶

Download a small GEBCO 2020 subset across the Iberian continental margin and draw a west-east depth transect — the classic shelf → slope → abyssal-plain cross-section a user would pull to size a cable route or a survey line.

In [ ]:

import tempfile

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

from earthlens import EarthLens

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

Download the margin¶

An AOI off Lisbon spanning the shelf (east) out to deep water (west).

In [ ]:

out = tempfile.mkdtemp()
paths = EarthLens(
    data_source='gebco',
    dataset='gebco_2020',
    aoi=[-11.0, 38.4, -9.3, 38.8],
    path=out,
).download(progress_bar=False)

ds = Dataset.read_file(str(paths[0]))
arr = np.asarray(ds.read_array(), dtype='float32')
arr = arr[0] if arr.ndim == 3 else arr
arr = np.where(arr == 32767, np.nan, arr)
print('grid', arr.shape, '| epsg', ds.epsg)

out = tempfile.mkdtemp() paths = EarthLens( data_source='gebco', dataset='gebco_2020', aoi=[-11.0, 38.4, -9.3, 38.8], path=out, ).download(progress_bar=False) ds = Dataset.read_file(str(paths[0])) arr = np.asarray(ds.read_array(), dtype='float32') arr = arr[0] if arr.ndim == 3 else arr arr = np.where(arr == 32767, np.nan, arr) print('grid', arr.shape, '| epsg', ds.epsg)

Take the central transect¶

The middle row is a west-east line of elevations; map the column index onto longitude using the AOI bounds.

In [ ]:

transect = arr[arr.shape[0] // 2, :]
lons = np.linspace(-11.0, -9.3, transect.size)
shelf_break = lons[np.nanargmin(np.abs(transect + 200))]  # ~200 m isobath
print('depth range', round(np.nanmin(transect)), '..', round(np.nanmax(transect)), 'm')

transect = arr[arr.shape[0] // 2, :] lons = np.linspace(-11.0, -9.3, transect.size) shelf_break = lons[np.nanargmin(np.abs(transect + 200))] # ~200 m isobath print('depth range', round(np.nanmin(transect)), '..', round(np.nanmax(transect)), 'm')

In [ ]:

plt.figure(figsize=(7, 4))
plt.fill_between(lons, transect, np.nanmin(transect), color='#9ecae1')
plt.plot(lons, transect, color='#08519c')
plt.axhline(0, color='k', lw=0.8)
plt.axvline(shelf_break, color='crimson', ls='--', lw=1, label='~200 m shelf break')
plt.xlabel('longitude (deg)')
plt.ylabel('elevation (m)')
plt.title('GEBCO 2020 west-east depth profile — Iberian margin')
plt.legend()
plt.show()

plt.figure(figsize=(7, 4)) plt.fill_between(lons, transect, np.nanmin(transect), color='#9ecae1') plt.plot(lons, transect, color='#08519c') plt.axhline(0, color='k', lw=0.8) plt.axvline(shelf_break, color='crimson', ls='--', lw=1, label='~200 m shelf break') plt.xlabel('longitude (deg)') plt.ylabel('elevation (m)') plt.title('GEBCO 2020 west-east depth profile — Iberian margin') plt.legend() plt.show()