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GeoscienceAustralia / ga_sar_workflow

InSAR processing workflow used by Geoscience Australia
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Nearest neighbour or bicubic spline for back geocoding????? #30

Open mcgarth opened 5 years ago

mcgarth commented 5 years ago

Interpolation during back-geocoding was changed to nearest neighbour at e68ded4f77a4b4f641860f7383ea971b65e354ff

In the latest commit e8ca42fb828055c61b0cfed29c9f13135c616d3e this has been reversed back to bicubic spline.

We need a good reason to choose one method over another. Please add here your observations and we can come up with a decision.

mcgarth commented 5 years ago

I changed the interpolation to nearest neighbour because I think it makes sense, particularly for phase data, where the geocoded output will be sub-sampled before further analysis (e.g. PyRate) and phase closure loops checked. A smoothing introduced during interpolation with another method could add noise to the phase closure loop check.

mcgarth commented 5 years ago

The plot thickens...

In the reference manual for geocode_back GAMMA recommend the following for MLI images: The interpolation should be performed on the square root of the data. A mid-order (3 to 5) B-spline interpolation is recommended.

In 1d9e03d I changed the code to use option 5 (B-spline on the log of data) with order 5 (default) for MLI products (e.g. sigma0/gamma0)