I don’t know of a thread online explaining the column and row overlap, so I will try to explain some here. There is an option in SNAPHU to divide a large interferogram into tiles with some number of rows and columns in the division. With the tile option, it runs the SNAPHU optimization on each tile separately, which uses less memory and time than doing the optimization on the full interferogram. At the end, it takes the unwrapped phase from each tile and uses the overlap with adjacent tiles to estimate an overall offset for each tile relative to the other tiles and prepare a final unwrapped phase for the full interferogram. The amount of overlap is specified in pixels, and usually 100 pixels is enough overlap for SNAPHU to estimate the offset between the tiles. I think SNAPHU works best with tiles that are between 1000 and 3000 pixels across. The interferogram size will depend on the number of looks you are using, so you should choose the number of rows and columns of tiles to get a tile size in that range and set the overlap to 100 pixels.