DESCRIPTION

Figure: Proportional count of points per 3D cell. When 50% of all points in a vertical column fall into a given 3D cell, the value is 0.5. Here, the green color was assigned to 0.5, red to 1 and yellow to 0. The figure shows vertical slices and green color indicates high vegetation while red color indicates bare ground.

NOTES

This module is highly experimental. Don't rely on its functionality or interface. Please report issues on the mailing list or in the bug tracker.
No projection check or reprojection is performed, make sure you are using data in the right projection for your GRASS Location.
Selection of points according to return or class is not yet supported.
All outputs are currently mandatory.
Some temporary maps are created but not cleaned up.
Expects points to have intensity (random result for related outputs when they don't).

EXAMPLES

Set the region according to a 2D raster and adding 3D minimum (bottom), maximum (top) and vertical (top-bottom) resolution.

g.region rast=secref b=80 t=160 tbres=5 -p3

Now, r3.in.lidar will create the 3D raster of the size given by the computation region:

r3.in.lidar input=points.las n=points_n sum=points_sum \
    mean=points_mean proportional_n=points_n_prop \
    proportional_sum=points_sum_prop

Point density vertical structure reduced to the terrain

Create ground raster:

r.in.lidar input=points.las output=ground method=mean class_filter=2

Set vertical extent of computational region to (relative) coordinates above ground:

g.region rast=secref b=0 t=47 -p3

Compute point density:

r3.in.lidar input=points.las n=points_n sum=points_sum \
    mean=points_mean proportional_n=points_n_prop \
    proportional_sum=points_sum_prop \
    base_raster=ground

REFERENCES

V. Petras, A. Petrasova, J. Jeziorska, H. Mitasova (2016): Processing UAV and lidar point clouds in GRASS GIS. XXIII ISPRS Congress 2016 [ISPRS Archives, ResearchGate]
ASPRS LAS format
LAS library
LAS library C API documentation

AUTHOR

Vaclav Petras, NCSU GeoForAll Lab