This is a morphological filter to extract ground level points from unfiltered elevation rasters. It can be used to generate a DTM from a minimum elevation raster. It comes with a PythonCaller template for FME that allows plugging directly into an existing FME workspace (given that translation is pointed to a custom python 3.6 with scipy installed).
The algorithm is build on the methodology described in Pingle, Clarke, McBride (2013). The main filtering proceedure is comparison of the input raster to a morphological opening of that input raster with a stepwise increasing window. It discards non-ground points if the difference between original point and opening exceeds a slope threshold.