Description of proposed changes

Allow different options of multilook interpolation while loading data by parsing a method variable

• 'nearest' method (default)
• 'mean' method
• 'median' method

This applies to multilook the unwrapPhase, coherence, wrapPhase. But not the connectedComponent.

Propagate the method variable from the template file named as mintpy.load.stepMethod

##---------multilook (optional):
## multilook while loading data with nearest interpolation, to reduce dataset size
mintpy.load.ystep          = 10    #[int >= 1], auto for 1 - no multilooking
mintpy.load.xstep          = 10    #[int >= 1], auto for 1 - no multilooking
mintpy.load.stepMethod     = mean    #[nearest, mean, median], auto for nearest - lines/rows skipping approach

By setting the multilook while loading data to mean or median, the noise in the loaded datasets is reduced. So this can be used for a smoother visualization of interferograms and the resulting time series, and the velocity.

Use with care. Because using mean or median multilook on the unwrapped phase can smoothen the integer of $2\pi$ phase jumps (due to unwrapping errors). This may result in issues in unwrapping errors identification and correction. Average multilooking will also introduce a lack of phase closure over an interferometric circuit. So we better still use 'nearest' as the default setting.

Reminders

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