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NAME

r3.in.lidar - Creates a 3D raster map from LAS LiDAR points using univariate statistics.

KEYWORDS

raster3d, import, LIDAR, statistics, conversion, aggregation, binning

SYNOPSIS

r3.in.lidar
r3.in.lidar --help
r3.in.lidar [-dvopsg] [input=name] [file=name] [n=name] [sum=name] [mean=name] [proportional_n=name] [proportional_sum=name] [return_filter=string] [class_filter=integer[,integer,...]] [base_raster=name] [zscale=float] [intensity_range=min,max] [intensity_scale=float] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-d
Use base raster actual resolution instead of computational region
-v
Use only valid points
Points invalid according to APSRS LAS specification will be filtered out
-o
Override projection check (use current location's projection)
Assume that the dataset has same projection as the current location
-p
Print LAS file info and exit
-s
Scan data file for extent then exit
-g
In scan mode, print using shell script style
--overwrite
Allow output files to overwrite existing files
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog

Parameters:

input=name
LAS input file
LiDAR input file in LAS format (*.las or *.laz)
file=name
File containing names of LAS input files
LiDAR input files in LAS format (*.las or *.laz)
n=name
Count of points per cell
Name for output 3D raster map
sum=name
Sum of values of point intensities per cell
Name for output 3D raster map
mean=name
Mean of point intensities per cell
Name for output 3D raster map
proportional_n=name
3D raster map of proportional point count
Point count per 3D cell divided by point count per vertical column
proportional_sum=name
3D raster map of proportional sum of values
Sum of values per 3D cell divided by sum of values per vertical column
return_filter=string
Only import points of selected return type
If not specified, all points are imported
Options: first, last, mid
class_filter=integer[,integer,...]
Only import points of selected class(es)
Input is comma separated integers. If not specified, all points are imported.
base_raster=name
Subtract raster values from the z coordinates
The scale for z is applied beforehand, the filter afterwards
zscale=float
Scale to apply to Z data
Default: 1.0
intensity_range=min,max
Filter range for intensity values (min,max)
intensity_scale=float
Scale to apply to intensity values
Default: 1.0

Table of contents

DESCRIPTION

The r.in.lidar module is very similar to the r3.in.lidar module and many parts of its documentation apply also for r3.in.lidar.

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

EXAMPLES

Basic import of the data

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

Complete workflow for vertical structure analysis

Compute the point density of points in 2D while setting the output extent to be based on the data (-e) and the resolution set to a relatively high number (here 10 map units, i.e. meters for metric projections).
r.in.lidar input=points.las output=points_n method=n -e resolution=10
This step can be repeated with using different resolutions (and the --overwrite flag) to determine the resolution for the further analysis.

The class_filter option should be also provided if only part of the points is analyzed, for example class_filter=3,4,5 would be used for low, medium, and high vegetation if the LAS file follows the usedstandard ASPRS class numbers.

The resolution should be suitable for computing digital elevation model which will be computed in the next steps. Once you decided on the resolution, you can use the 2D raster to set the computational region extent and resolution:

g.region raster=points_n -p3
class_filter=2 is used to limit
r.in.lidar input=points.las output=ground_mean method=mean class_filter=2
The following steps are not necessary if the point density is high enough to fill the raster continuously.

Convert the raster to vector point resulting in a decimated point cloud:

v.to.rast input=ground_mean type=point output=ground_decimated use=z
Interpolate the ground surface from the decimated ground points:
v.surf.rst input=ground_decimated elevation=ground
Now we need to determine upper vertical limit for the 3D raster (the top value from g.region -p3). This can be potentially done with lower resolution. The -d flag ensures that the ground raster will be used in its actual resolution regardless of the resolution of the output.
r.in.lidar input=points.las method=max output=veg_max class_filter=3,4,5 base_raster=ground -d
With that, we can finally set up the 3D extent and resolution:
g.region rast=secref b=0 t=40 res=1 res3=1 -p3
Note that the 2D and 3D resolutions are separate so that user can perform the 2D calculations on a finer resolution than the 3D calculations. The vertical resolution can be and often is set to a different value as well. Here we use the same value for all resolutions for simplicity.

Finally, we perform the 3D binning where we count number of points per cell (voxel):

r3.in.lidar input=points.las n=n class_filter=3,4,5 base_raster=ground -d

SEE ALSO

r3.in.xyz, r.in.lidar, v.in.lidar, r.to.rast3, r3.to.rast, r3.mapcalc, g.region

REFERENCES

AUTHOR

Vaclav Petras, NCSU GeoForAll Lab

Last changed: $Date: 2017-11-25 14:04:19 -0800 (Sat, 25 Nov 2017) $

SOURCE CODE

Available at: r3.in.lidar source code (history)


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