Welch Overlapping Sub-Aperture (WOSA) PSD

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The WOSA method can be implemented for PSD to reduce variance in the PSD estimate. The subapertures can also be shifted away from the center an extra amount to enable robust PSD calculation for data with annular support.

Interferogram.mask can be used for inspiration on how to embed a (shifted) circular mask. The data should be cropped before feeding through the PSD function. Each subaperture is guaranteed to have the same sample spacing. Roundoff should be carefully controlled to ensure each sub window has the same shape, ensuring the DFT samples are aligned and they can be easily averaged. An in-place add, then divide by K approach to the average is likely faster (and is much more memory efficient) than allocating an NxMxK matrix and using mean across one of the axes.