PolygonClassStatistics - Polygon Class Statistics
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Computes statistics on a training polygon set.

Detailed description
--------------------

The application processes a set of geometries intended for training (they should have a field giving the associated class). The geometries are analysed against a support image to compute statistics : 
  - number of samples per class
  - number of samples per geometry
An optional raster mask can be used to discard samples. Different types of geometry are supported : polygons, lines, points. The behaviour is different for each type of geometry :
  - polygon: select pixels whose center is inside the polygon
  - lines  : select pixels intersecting the line
  - points : select closest pixel to the point

Parameters
----------

This section describes in details the parameters available for this application. Table [#]_ presents a summary of these parameters and the parameters keys to be used in command-line and programming languages. Application key is *PolygonClassStatistics* .

.. [#] Table: Parameters table for Polygon Class Statistics.

+-------------+----------------------------------+--------------------------+
|Parameter Key|Parameter Name                    |Parameter Type            |
+=============+==================================+==========================+
|in           |InputImage                        |Input image               |
+-------------+----------------------------------+--------------------------+
|mask         |InputMask                         |Input image               |
+-------------+----------------------------------+--------------------------+
|vec          |Input vectors                     |Input File name           |
+-------------+----------------------------------+--------------------------+
|out          |Output Statistics                 |Output File name          |
+-------------+----------------------------------+--------------------------+
|field        |Field Name                        |List                      |
+-------------+----------------------------------+--------------------------+
|layer        |Layer Index                       |Int                       |
+-------------+----------------------------------+--------------------------+
|elev         |Elevation management              |Group                     |
+-------------+----------------------------------+--------------------------+
|elev.dem     |DEM directory                     |Directory                 |
+-------------+----------------------------------+--------------------------+
|elev.geoid   |Geoid File                        |Input File name           |
+-------------+----------------------------------+--------------------------+
|elev.default |Default elevation                 |Float                     |
+-------------+----------------------------------+--------------------------+
|ram          |Available RAM (Mb)                |Int                       |
+-------------+----------------------------------+--------------------------+
|inxml        |Load otb application from xml file|XML input parameters file |
+-------------+----------------------------------+--------------------------+
|outxml       |Save otb application to xml file  |XML output parameters file|
+-------------+----------------------------------+--------------------------+

**InputImage**: Support image that will be classified.

**InputMask**: Validity mask (only pixels corresponding to a mask value greater than 0 will be used for statistics).

**Input vectors**: Input geometries to analyse.

**Output Statistics**: Output file to store statistics (XML format).

**Field Name**: Name of the field carrying the class name in the input vectors.

**Layer Index**: Layer index to read in the input vector file.

**[Elevation management]**: This group of parameters allows managing elevation values. Supported formats are SRTM, DTED or any geotiff. DownloadSRTMTiles application could be a useful tool to list/download tiles related to a product.

- **DEM directory**: This parameter allows selecting a directory containing Digital Elevation Model files. Note that this directory should contain only DEM files. Unexpected behaviour might occurs if other images are found in this directory.
- **Geoid File**: Use a geoid grid to get the height above the ellipsoid in case there is no DEM available, no coverage for some points or pixels with no_data in the DEM tiles. A version of the geoid can be found on the OTB website (http://hg.orfeo-toolbox.org/OTB-Data/raw-file/404aa6e4b3e0/Input/DEM/egm96.grd).
- **Default elevation**: This parameter allows setting the default height above ellipsoid when there is no DEM available, no coverage for some points or pixels with no_data in the DEM tiles, and no geoid file has been set. This is also used by some application as an average elevation value.

**Available RAM (Mb)**: Available memory for processing (in MB).

**Load otb application from xml file**: Load otb application from xml file.

**Save otb application to xml file**: Save otb application to xml file.



Example
-------

To run this example in command-line, use the following: 
::

	otbcli_PolygonClassStatistics -in support_image.tif -vec variousVectors.sqlite -field label -out polygonStat.xml

To run this example from Python, use the following code snippet: 

::

	#!/usr/bin/python

	# Import the otb applications package
	import otbApplication

	# The following line creates an instance of the PolygonClassStatistics application 
	PolygonClassStatistics = otbApplication.Registry.CreateApplication("PolygonClassStatistics")

	# The following lines set all the application parameters:
	PolygonClassStatistics.SetParameterString("in", "support_image.tif")

	PolygonClassStatistics.SetParameterString("vec", "variousVectors.sqlite")

	# The following line execute the application
	PolygonClassStatistics.ExecuteAndWriteOutput()

Limitations
~~~~~~~~~~~

None

Authors
~~~~~~~

This application has been written by OTB-Team.