Not only I am hoping that this will help people but I am sure some of you have your own methods and may be able to give advice on how this process can be best performed/refined.
Digital Elevation Modelling using Cloud Compare
1.) Open Point cloud
2.) Remove Outliers Using Statistical Approach (on main interface, SOR)
a. > Number of points to use for mean distance estimation: 10 (Default)
b. > Standard Deviation Multiplier Threshold: 1.00 (Default)
(10 and 0.1 seem to work well for me though I am not entirely sure about the math behind this, more of a guess and check approach)
3.) Manually remove buildings and known infrastructures.
a. > Select the cloud in the DB (Database) tree
b. > Select the ‘segment’ tool on the interface (scissors)
c. > Manually click around the object you want to segment
d. > Right click to close the polygon
e. > Select ‘segment out’ in the segment toolbar
f. > Continue selecting points which you want to segment*
g. > Select ‘Confirm Segmentation’ in the segment toolbar
h. > Viewing only the segment which you just created, tilt it such that the ground can clearly be distinguished from the structure and use segment again to remove it.
4.) Segregate bare earth surfaces (pits, roads, barren areas) from vegetated or noisy areas (forests, water). Use segment tool again
5.) Resample bare earth point cloud to 1.00m (or whatever step size is necessary) using the average point.
a. > Tool
b. > Projection
c. > Rasterize
d. > Step: 1.00
e. > direction: Z
f. > cell height: average height
g. > Fill with: leave empty
h. > Export: click ‘Cloud’
6.) Resample vegetation point cloud to 10.00m (or whatever step size is necessary) using the minimum point.
a. > Tool
b. > Projection
c. > Rasterize
d. > Step: 10.00
e. > direction: Z
f. > cell height: minimum height
g. > Resample Input Load ‘Checked’
h. > Fill with: leave empty
i. > Export: click ‘Cloud’
7.) Manually remove noticeable noise/vegetation that is remaining using the segment tool.
8.) Export Contours
a. > Tool
b. > Projection
c. > Rasterize
d. > Step: 1.00
e. > direction: Z
f. > cell height: minimum height
g. > Fill with: interpolate
h. > Export: click the Contour Tab
i. > Just minimum vertex as needed to avoid producing tiny contours*
j. > Select Generate
k. > Select Export
I generally finish the contours in ArcGIS by removing small ones (<20m in length) as well as smoothing the contours as they can be very rigid/messy from small areas of interpolation as well as area of very dense point coverage.
*EDIT 1(21/01/2016):
Here is a before and after example of this process. Both figures show point clouds overlaid on the associated aerial photography. As you can see in Figure 1, the point cloud is very dense.
Figure 1: Raw point cloud with associated imagery.
As seen in figure 2, this process does a good job of only selecting points which are associated with the gaps between trees. The spacing can be adjusted based on the density of the vegetation cover and how dense you need your resulting point cloud to be.
Figure 2: Raw point cloud with associated imagery.