.. _DSMGenerator:

Spatial Data: DSM Generator
~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Developer:
.. list-table::
   :widths: 50 50
   :header-rows: 1

   * - Name
     - Institution

   * - Nils Wallenberg
     - Gothenburg


* Introduction:
    Digital Surface Models (DSMs) is not always available for the area you want to investigate. The **DSM Generator** can be used to create or alter a DSM by using information from a polygon building footprint layer where a building height attribute is available. An option to acquire building footprints, and also in some cases building height from `Open Street Map <http://www.openstreetmap.org>`_ data, is available from this plugin.

* Dialog box
    .. figure:: /images/DSMGenerator.png
        :align: center

        Dialog for the DSM generator plugin

* Dialog sections:
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   :widths: 30 70
   :header-rows: 0

   * - top
     - input DEM data is specified
   * - middle upper
     - input polygon with height data or OSM is specified
   * - middle
     - map extent is specified
   * - middle lower
     - to specify the output DSM and output resolution
   * - bottom
     - to run the calculations

* Digital Elevation Model:
    A raster file containing elevation values needed to create the DSM. Raster elevation data (DEM) can be retrieved from e.g. `OpenDEM <http://www.opendem.info/>`__.

* Polygon Vector File:
    A polygon vector file including height values of buildings needed to create the DSM.

* Necessary attributes:
    Building height values in meters.

* Use Open Street Map:
    Tick this in if you do not have a polygon layer with building heights. Open Street Map (© OpenStreetMap contributors) data will be used instead. If no building height is found **building level height** will be used instead. Set to appropriate value, e.g. a three level building with building level height set to 3 will be 3 \* 3 = 9 meters high.

* Save OSM as shapefile:
    Tick this in if you want to save the Open Street Map data as a polygon layer. This can be used if you want to look at what values has been used and if you want to add values manually.

* Map extent:
    Set either to map canvas extent or extent from layer. Extent have to be smaller or equal to the raster DEM extent specified in the top section.

* Digital Surface Model:
    Set output for the generated DSM. Also set output resolution.

* Run:
    Starts the calculations.

* Close:
    Closes the plugin.

* Output:
    One GeoTIFF is created, a DSM.

* Remarks:
    -  The DEM raster and map canvas should be in a projection with meters as units.
    -  Raster elevation data (DEM) can be retrieved from e.g. `OpenDEM <http://www.opendem.info/>`__.
    -  If you use Open Street Map make sure you read `Open Street Map <http://www.openstreetmap.org/copyright>`__ © OpenStreetMap contributors.