deltametrics.plan.shaw_opening_angle_method

deltametrics.plan.shaw_opening_angle_method(below_mask, numviews=3)

Extract the opening angle map from an image.

Applies the opening angle method [1] to compute the shoreline mask. Adapted from the Matlab implementation in [2].

This function takes an image and extracts its opening angle map.

[1] (1,2)

Shaw, John B., et al. “An image‐based method for shoreline mapping on complex coasts.” Geophysical Research Letters 35.12 (2008).

[2]

Liang, Man, Corey Van Dyk, and Paola Passalacqua. “Quantifying the patterns and dynamics of river deltas under conditions of steady forcing and relative sea level rise.” Journal of Geophysical Research: Earth Surface 121.2 (2016): 465-496.

Parameters:

• below_mask (ndarray) – Binary image that has been thresholded to split water/land. At minimum, this should be a thresholded elevation matrix, or some classification of land/water based on pixel color or reflectance intensity. This is the startin point (i.e., guess) for the opening angle method.

• numviews (int) – Defines the number of largest angles to consider for the opening angle map for each pixel. Default is 3, based on [1].

Returns:

• shoreangles (ndarray) – Flattened values corresponding to the shoreangle detected for each ‘look’ of the opening angle method

• seaangles (ndarray) – Flattened values corresponding to the ‘sea’ angle detected for each ‘look’ of the opening angle method. The ‘sea’ region is the convex hull which envelops the shoreline as well as the delta interior.