Best Practices for Subsetting Interferogram Stack for Snow Free Periods Over Multiple Years

[Omineca Geospatial]

Hello MintPy Community,

I’m working on a time series analysis of ground displacement for a slow-moving landslide using Sentinel-1 data processed with GAMMA and MintPy. The goal is to analyze multiple years but only during the snow-free period (May–October).

I’m unsure about the best way to handle multi-year time series while excluding snow-covered months. Here are the three approaches I’m considering:

Method 1: Multiple Stacks (No Network Modification)

• Run SBAS search for each year, including only snow-free months.
• Download separate stacks for each year and process them individually in MintPy.
• Use the same reference point for all stacks.
• Compare annual velocity changes by loading the time series rasters into QGIS.

Method 2: Single Stack (No Network Modification)

• Run SBAS search for all years, including only snow-free pairs.
• Connect yearly segments by adding custom pairs at the start and end of each snow-free period.
• Process everything in MintPy as one combined stack.

Method 3: Single Stack with Network Modification

• Run SBAS search for all years, including all pairs (snow and snow-free).
• Process in MintPy but apply network modification to ignore snow-covered dates.

Would method 3 improve the coherence for the snow-free interferogram pairs? What is the recommended method I should be using?

The main drawback I see with this approach is that the stack would require significantly more storage, take longer to process, and consume more GAMMA credits.

Apologies if this question has been asked before. This is my first post to the group. I searched both this forum and the GitHub discussions. I found a related post in the past but can no longer locate it.

Thank you for any help.

[Zhang Yunjun]

I would vote for method 2, but be sure to add some redundancy to the inter-year pairs, so that the connection is more robust.

Yunjun