I have calculated curvature using ArcGIS (curvature) and SAGA (Slope, Aspect, Curvature; based on 9 parameter 2nd order polynom (Zevenbergen & Thorne 1987) method), however, the output rasters are not the same.
I've done some research and now I understand how curvature works in ArcGIS: http://pro.arcgis.com/en/pro-app/tool-reference/spatial-analyst/how-curvature-works.htm
But it's still a mystery to me how SAGA calculates curvature.
Which formula is used?