sandplover.plan.compute_shoreline_length

sandplover.plan.compute_shoreline_length(shore_mask, start=(0, 0), origin=None, return_line=False)

Compute the length of a shoreline from a mask of the shoreline.

Algorithm attempts to determine the sorted coordinates of the shoreline from a ShorelineMask.

Warning

Imperfect algorithm, which may not include all True pixels in the ShorelineMask in the determined shoreline.

Changed in version 0.5: Changed keyword origin to start.

With v0.5 the input keyword argument origin is deprecated, and replaced with keyword argument start.

Parameters:

• shore_mask (ShorelineMask, ndarray) – Shoreline mask. Can be a ShorelineMask object, or a binarized array.

• start (tuple, np.ndarray, optional) – Determines the location from where the starting point of the line sorting is initialized. The starting point of the line is determined as the point nearest to start. For non-standard data configurations, it may be important to set this to an appropriate value. Default is (0, 0).

• return_line (bool) – Whether to return the sorted line as a second argument. If True, a Nx2 array of x-y points is returned. Default is False.

Returns:

• length (float) – Shoreline length, computed as described above.

• line (np.ndarray) – If return_line is True, the shoreline, as an Nx2 array of x-y points, is returned.

Examples

Compare the length of the shoreline early in the model simulation with the length later. Here, we use the elevation_offset parameter (passed to ElevationMask) to better capture the topography of the pyDeltaRCM model results.

>>> from sandplover.mask import ShorelineMask
>>> from sandplover.plan import compute_shoreline_length
>>> from sandplover.sample_data.sample_data import golf

>>> golf = golf()

Early in model run

>>> sm0 = ShorelineMask(
...     golf["eta"][15, :, :], elevation_threshold=0, elevation_offset=-0.5
... )

Late in model run

>>> sm1 = ShorelineMask(
...     golf["eta"][-1, :, :], elevation_threshold=0, elevation_offset=-0.5
... )

Compute lengths

>>> len0 = compute_shoreline_length(sm0)
>>> len1, line1 = compute_shoreline_length(sm1, return_line=True)

Make the plot

>>> import matplotlib.pyplot as plt

>>> fig, ax = plt.subplots(1, 2, figsize=(6, 3))
>>> golf.quick_show("eta", idx=15, ax=ax[0])
>>> _ = ax[0].set_title("length = {:.2f}".format(len0))
>>> golf.quick_show("eta", idx=-1, ax=ax[1])
>>> _ = ax[1].plot(line1[:, 0], line1[:, 1], "r-")
>>> _ = ax[1].set_title("length = {:.2f}".format(len1))

(Source code, png, hires.png)