.. _writers.pgpointcloud:

writers.pgpointcloud
====================

The **PostgreSQL Pointcloud Writer** allows you to write to PostgreSQL database
that have the `PostgreSQL Pointcloud`_ extension enabled. The Pointcloud
extension stores point cloud data in tables that contain rows of patches. Each
patch in turn contains a large number of spatially nearby points.

While you can theoretically store the contents of a whole file of points in a
single patch, it is more practical to store a table full of smaller patches,
where the patches are under the PostgreSQL page size (8kb). For most LIDAR
data, this practically means a patch size of between 400 and 600 points.

In order to create patches of the right size, the Pointcloud writer should be
preceded in the pipeline file by :ref:`filters.chipper`.

The pgpointcloud format does not support WKT spatial reference specifications.  A subset of spatial references can be stored by using the 'srid' option, which
allows storage of an `EPSG code`_ that covers many common spatial references.
PDAL makes no attempt to reproject data to your specified srid.  Use
:ref:`filters.reprojection` for this purpose.

.. plugin::

Example
-------


.. code-block:: json

  [
      {
          "type":"readers.las",
          "filename":"inputfile.las",
          "spatialreference":"EPSG:26916"
      },
      {
          "type":"filters.chipper",
          "capacity":400
      },
      {
          "type":"writers.pgpointcloud",
          "connection":"host='localhost' dbname='lidar' user='pramsey'",
          "table":"example",
          "compression":"dimensional",
          "srid":"26916"
      }
  ]

Options
-------

connection
  PostgreSQL connection string. In the form *"host=hostname dbname=database user=username password=pw port=5432"* [Required]

table
  Database table to write to. [Required]

schema
  Database schema to write to. [Default: "public"]

column
  Table column to put patches into. [Default: "pa"]

compression
  Patch compression type to use. [Default: ""dimensional""]

  * **none** applies no compression
  * **dimensional** applies dynamic compression to each dimension separately
  * **lazperf** applies a "laz" compression (using the `laz-perf`_ library in PostgreSQL Pointcloud)

overwrite
  To drop the table before writing set to 'true'. To append to the table
  set to 'false'. [Default: false]

srid
  Spatial reference ID (relative to the `spatial_ref_sys` table in PostGIS)
  to store with the point cloud schema. [Default: 4326]

pcid
  An optional existing PCID to use for the point cloud schema. If specified,
  the schema must be present. If not specified, a match will still be
  looked for, or a new schema will be inserted. [Default: 0]

pre_sql
  SQL to execute *before* running the translation. If the value
  references a file, the file is read and any SQL inside is executed.
  Otherwise the value is executed as SQL itself. [Optional]

post_sql
  SQL to execute *after* running the translation. If the value references
  a file, the file is read and any SQL inside is executed. Otherwise the
  value is executed as SQL itself. [Optional]

scale_x, scale_y, scale_z / offset_x, offset_y, offset_z
  If ANY of these options are specified the X, Y and Z dimensions are adjusted
  by subtracting the offset and then dividing the values by the specified
  scaling factor before being written as 32-bit integers (as opposed to double
  precision values).  If any of these options is specified, unspecified
  scale_<x,y,x> options are given the value of 1.0 and unspecified
  offset_<x,y,z> are given the value of 0.0.

output_dims
  If specified, limits the dimensions written for each point.  Dimensions
  are listed by name and separated by commas.

.. _PostgreSQL Pointcloud: http://github.com/pramsey/pointcloud
.. _laz-perf: https://github.com/hobu/laz-perf
.. _EPSG code: http://www.epsg.org
