DTM Creation Steps

Step	Free programs	Notes
Noise removal	PDAL WhiteBox toolbox	Many (most?) point clouds will have this mostly accomplished
Ground classification	Fusion mcc-lidar WhiteBox toolbox (2 methods)	Many (most?) point clouds will have this mostly accomplished Would be nice to have water, vegetation, and buildings as well, but no free software does this.
Surface generation to grid TIN--triangulated irregular network IDW--Inverse distance weighting Drop in the bucket (highest, lowest, average, closest to center of grid cell)	Fusion mcc-lidar MICRODEM PDAL (2 methods) WhiteBox toolbox (2 methods)
Void filling in grid	MICRODEM WhiteBox toolbox	Not needed for TIN and IDW, unless they had a size limit imposed for interpolation. Can lead to artefacts.
Surface smoothing in grid	MICRODEM	Could be accomplished Filter directly Two steps Set larger grid size intially Filter grid, and then subsample/thin
Hydrologic conditioning of grid	TauDEM WhiteBox toolbox

Leaf-off will have fewer vegetation spikes, and more points on the ground
Create with Ceiling/floor grid option.
To lessen the impact of vegetation spikes, you can
- Thin starting DEM first to get a larger grid size (hoping you set at least on true ground return in each pixel), and the Reinterpolate, UTM the resulting grid. This will work well on level ground, but introduce a different kind of anomaly in sloping ground.
- If you have two point clouds (snow/no snow, leaf on/leaf off) to you can compute the DTM with each, and then do a minimum of the two grids (Raster GIS, Multiple grid arithmetic)..
You could filter and use just the "Ground" classification points. This is likely to leave a lot of voids. You can then try the Edit, DEM holes, Interpolate across holes (smooth) and would likely have to adjust the parameters to make it work.

Last revision 7/28/2018