.. _compression:

Compression
================================================================================

.. include:: ../../includes/substitutions.rst

Exercise
--------------------------------------------------------------------------------

This exercise uses PDAL to compress |ASPRSLAS| data into |LASzip|.

.. _`LASzip`: http://laszip.org

1. Issue the following command in your `OSGeo4W Shell`.


    .. literalinclude:: ./compression-command.txt

    LAS is a very fluffy binary format. Because of the way the data are stored,
    there is ample redundant information, and |LASzip| is an open source solution
    for compressing this information


2. Verify that the data are in fact compressed:

    .. literalinclude:: ./compression-command-verify.txt


    .. image:: ../../images/compression-verify.png
        :target: ../../../_images/compression-verify.png

.. seealso::
    :ref:`las_tutorial` contains many pointers about settings for |ASPRSLAS|
    data and how to achieve specific data behaviors with PDAL.

Notes
--------------------------------------------------------------------------------

1. Typical |LASzip| compression is 5:1 to 8:1, depending on the type of
   |LiDAR|. It is a compression format specifically for the |ASPRSLAS|
   model, however, and will not be as efficient for other types of
   point cloud data.

2. You can open and view LAZ data in web browsers using http://plas.io

.. _`CSV`: https://en.wikipedia.org/wiki/Comma-separated_values
.. _`JSON`: https://en.wikipedia.org/wiki/JSON
.. _`XML`: https://en.wikipedia.org/wiki/XML
