Majority filter (minimum mapping unit) in ArcGIS with larger window size

Question

I want to run the majority filter in ArcGIS with a window size of 4 or 5 i.e. greater than the default 3. Is it possible? Or some other command (or tool) which might help me achieve that?

thanks!

Answer 1

A Focal Majority function does a very poor job at establishing a MMU. I would recommend using a sieve approach. This will provide an exact defined MMU.

I believe that GDAL has a sieve model and it is also available in our Gradient Metrics ArcGIS Toolbox. It is an easy procedure to implement. The ArcGIS steps for using sieve to establish a minimal mapping unit of 10 cells are, more or less, as follows:

MinCells = 10
tmp1 = RegionGroup(InRaster, "EIGHT", "WITHIN", "ADD_LINK", "") 
  query = "VALUE > " + minCells
tmp2 = ExtractByAttributes(tmp1, query)
outraster = Nibble(InRaster, tmp2)

Answer 2

Try using the Focal Statistics tool with a Majority rule. It allows you to set a variety of window shapes, sizes, etc.