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Getting Started with libLAS


The libLAS ‘command-line utilities’ provide the bulk of user-facing operational software for libLAS, although the underlying libLAS library is what powers them. Below is a listing of common operations that you might want to do on LAS data, and the utilities and approaches to take to complete those tasks. The demo data can be found in /home/user/data/las/srs.las

Reprojecting an LAS file

All LAS data are in some sort of coordinate system, even if that coordinate system is not described in the LAS file. For terrestrial LAS data, these coordinate system descriptions often map to coordinate systems described by the EPSG database. Another source of information about coordinate systems in

lasinfo --no-check srs.las


The –no-check option tells lasinfo to only print the header information for the file and to not scan through all of the points. For a 10 point file, this of course isn’t much of a concern, but with a 50 or 500 million point file, it isn’t worth waiting for a full scan of the data if all you want is header information.

Our ‘lasinfo’ invocation tells us that the srs.las file is in a UTM North Zone 17 coordinate system:

PROJCS["WGS 84 / UTM zone 17N",
    GEOGCS["WGS 84",
            SPHEROID["WGS 84",6378137,298.257223563,

Now that we know our input coordinate system, we can make a decision about what to reproject the data to. In our first example, we’re going to use the venerable plate carrée non-coordinate system, EPSG:4326.

las2las srs.las --t_srs EPSG:4326

Our process succeeds, but after a quick inspection of the data with lasinfo output.las we see a problem:

Scale Factor X Y Z:          0.01 0.01 0.01
Offset X Y Z:                -0.00 -0.00 -0.00
Min X, Y, Z:                -83.43, 39.01, 170.58,
Max X, Y, Z:                -83.43, 39.01, 170.76,

The srs.las file had a scale of 0.01, or two decimal places of precision for its X, Y, and Z coordinates. For UTM data, this is ok, because it implies an implicit precision of 1 cm. For decimal degree data of the unprojected Plate Carrée coordinate system, it causes us to lose a bunch of precision. We need to set our scale values to something that can hold more precision in our case:

las2las --t_srs EPSG:4326 srs.las --scale 0.000001 0.000001 0.01

Another quick inspection with ‘lasinfo’ gives us something we’re more comfortable with:

Scale Factor X Y Z:          0.000001 0.000001 0.01
Offset X Y Z:                -0.000000 -0.000000 -0.00
Min X, Y, Z:                -83.427598, 39.012599, 170.58
Max X, Y, Z:                -83.427548, 39.012618, 170.76

Output LAS file to text

las2txt input.las --parse xyzti