16.53. point2las

This tool can be used to convert point clouds generated by ASP to the LAS format. It relies on the PDAL library, which is shipped with ASP.

If the input cloud has a datum, or the --datum option is specified, then the output LAS file will be created in respect to this datum. Otherwise ECEF \(x,y,z\) values will be saved.

The point cloud triangulation error can be saved, if desired, in the LAS intensity field.

Example usage:

point2las output-prefix-PC.tif -o output-prefix

This will create the file output-prefix.las. If the --compressed option is used, it will write instead output-prefix.laz

A LAS or LAZ file can be inspected as:

pdal info --all file.las

The point2dem program (Section 16.52) can be used to create a DEM from the LAS file, and pc_align (Section 16.49) can be invoked to align point clouds, including in the LAS format.

16.53.1. Outlier removal

The point2las program filters out outliers in the input point cloud using the ray triangulation error (the fourth band in the cloud), hence points with an error above a certain threshold are not included in the output LAS file.

It first picks a desired number of samples from the cloud, sorts the positive triangulation errors from the sample (the errors equal to 0 correspond to invalid points, so these are ignored), and computes some statistical measures which are printed to the screen. Those include the minimum, mean, standard deviation, maximum, and the error percentiles at 25% (Q1), 50% (median, Q2) and 75% (Q3).

Then, given the desired percentile and factor in --remove-outliers-params, it computes the error for this percentile and multiplies it by the factor. With the default settings, this amounts to 3*Q3. This value is used as the cutoff threshold to remove outliers.

If the option --use-tukey-outlier-removal is set, the outlier cutoff is computed as Q3 + 1.5*(Q3 - Q1) [Tuk77]. This takes precedence over the earlier approach.

Alternatively, the user can specify a custom outlier cutoff via --max-valid-triangulation-error, when it will be used instead of any of the above.

If it is desired to not remove any outliers, the percentage in --remove-outliers-params can be set to 100.

After the LAS file is saved, the number of outliers and their percentage from the total number of points are printed on the screen. Generally, the outlier threshold should not be so restrictive that more than approximately 30% of the points are eliminated.

16.53.2. Command-line options for point2las

--datum <string>

Create a geo-referenced LAS file in respect to this datum. Options:

  • WGS_1984

  • D_MOON (1,737,400 meters)

  • D_MARS (3,396,190 meters)

  • MOLA (3,396,000 meters)

  • NAD83

  • WGS72

  • NAD27

  • Earth (alias for WGS_1984)

  • Mars (alias for D_MARS)

  • Moon (alias for D_MOON)

--reference-spheroid <string>

This is identical to the datum option.

--t_srs <proj string>

Specify the output projection (PROJ.4 string).


Compress using laszip.

-o, --output-prefix <filename>

Specify the output file prefix.

--remove-outliers-params <pct factor (default: 75.0 3.0)>

Outlier removal based on percentage. Points with triangulation error larger than pct-th percentile times factor will be removed as outliers.


Remove outliers above Q3 + 1.5*(Q3 - Q1) ([Tuk77]). This takes precedence over --remove-outliers-params.

--max-valid-triangulation-error <float (default: 0)>

Outlier removal based on threshold. Points with triangulation error larger than this, if positive (measured in meters) will be removed from the cloud. Takes precedence over the above options.

--triangulation-error-factor <float (default: 0)>

If this factor is positive, save the point cloud triangulation error to the 2-byte LAS intensity field by storing min(round(factor*error), 65535). Resulting values that equal 65535 should be treated with caution.

--num-samples-for-outlier-estimation <integer (default: 1000000)>

Approximate number of samples to pick from the input cloud to find the outlier cutoff based on triangulation error.


Save the point cloud in ECEF, rather than with a projection relative to a datum.

--threads <integer (default: 0)>

Select the number of threads to use for each process. If 0, use the value in ~/.vwrc.

--cache-size-mb <integer (default = 1024)>

Set the system cache size, in MB.

--tile-size <integer (default: 256 256)>

Image tile size used for multi-threaded processing.


Tell GDAL to not create BigTIFF files.

--tif-compress <None|LZW|Deflate|Packbits (default: LZW)>

TIFF compression method.

-v, --version

Display the version of software.

-h, --help

Display this help message.