Fix spatial temporal filter

GeoscienceAustralia / PyRate

A Python tool for estimating velocity and time-series from Interferometric Synthetic Aperture Radar (InSAR) data.

https://geoscienceaustralia.github.io/PyRate/

Apache License 2.0

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Fix spatial temporal filter #311

Closed mcgarth closed 3 years ago

mcgarth commented 3 years ago

This PR fixes the spatio-temporal filter functionality (that previously produced spurious results) in pyrare.core.aps and puts the functionality under unit test.

change temporal filter cutoff to units of days (rather than years); default 30 days
remove filter types and only retain only the gaussian option for spatial and temporal filter
remove superfluous config options slpfmethod, slpforder, tlpfmethod
convert spatial cutoff distance (default 1 km) to a scaled "sigma" value for use in gaussian kernel
spatial interpolation by nearest neighbour is on by default; needed to reduce edge effects in FFT used by spatial filter
Implement unit tests for temporal and spatial gaussian filter options. Compare bespoke code against scipy.ndimage equivalents (these functions only support regularly sampled data in time and space, whereas the functions implemented in pyrate.core.aps support irregular temporal sampling and different x and y spatial resolutions)

chandra2ga commented 3 years ago

I reviewed this PR and performed different unit tests. Now I can confirm that this PR is working as expected and ready to merge.

Here are some feedback:

1- 4 comments are checked.
5th comment regarding spatial interpolation, it's good to have nearest neighbor method as default option but I would definitely suggest to keep other options open for users to choose, and might suitable for their processing.
I checked and performed unit test for temporal and spatial gaussian filters option. Looks alright to me.

So I approved this PR and ready to merge into develop/ 👍

mcgarth commented 3 years ago

To be clear, nearest is the default option for spatial interpolation in the APS filter, but cubic and linear methods are still selectable via the slpnanfill_method config parameter option.

I have removed slpnanfill_method from the top level input_parameters.conf because I believe nearest to be the best choice. But those users who are in the know, can add that parameter into their config file and choose linear or cubic options instead. ;-)