openpiv.validation.local_median_val

openpiv.validation.local_median_val(u, v, u_threshold, v_threshold, size=1)[source]

Eliminate spurious vectors with a local median threshold.

This validation method tests for the spatial consistency of the data. Vectors are classified as outliers and replaced with Nan (Not a Number) if the absolute difference with the local median is greater than a user specified threshold. The median is computed for both velocity components.

The image masked areas (obstacles, reflections) are marked as masked array:
u = np.ma.masked(u, flag = image_mask)

and it should not be replaced by the local median, but remain masked.

Parameters:
  • u (2d np.ndarray) – a two dimensional array containing the u velocity component.
  • v (2d np.ndarray) – a two dimensional array containing the v velocity component.
  • u_threshold (float) – the threshold value for component u
  • v_threshold (float) – the threshold value for component v
Returns:

flag – a boolean array. True elements corresponds to outliers.
Return type:

boolean 2d np.ndarray