.. _dem_generation_app:

DEM Generation
==============

**Name**: "dem_generation"

**Description**

Generates dem from a DSM. The details in the DSM allow to create upper and lower dems.
The DEMs generated are less resolved than the input DSM.

Up to 4 dems are generated, with different methods:

* median
* min
* max
* initial_elevation_fit (only if ``coregistration`` is set to ``true``)

The DEMs are generated in the application dump directory.
You can find the shift values applied to the initial elevation in ``metadata.json``.


**Configuration**

+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| Name                                | Description                                                                     | Type       | Available value                      | Default value           | Required |
+=====================================+=================================================================================+============+======================================+=========================+==========+
| method                              | Method for dem_generation                                                       | string     | "bulldozer_on_raster"                | "bulldozer_on_raster"   | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| height_margin [#scaled]_            | Height margin [margin min, margin max], in meter                                | int        |                                      | 5 [#scaled]_            | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| min_dem                             | Min value that has to be reached by dem_min                                     | int        | should be < 0                        | -500                    | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| max_dem                             | Max value that has to be reached by dem_max                                     | int        | should be > 0                        | 1000                    | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| coregistration                      | Use the median dem to correct shifts in the initial elevation provided          | boolean    |                                      | true                    | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| coregistration_max_shift            | Maximum shift allowed on X/Y axes for the coregistered initial elevation        | int, float | should be > 0                        | 180                     | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| save_intermediate_data              | Save DEM as TIF                                                                 | boolean    |                                      | false                   | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| margin [#scaled]_                   | Margin to use on the border of dem: [factor_of_dem_size, margin_in_meters]      | list       | should be > 0                        | [0.2, None [#scaled]_ ] | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| fillnodata_max_search_distance      | Max search distance for rasterio fill nodata                                    | int        | should be > 0                        | 50                      | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| morphological_filters_size          | Size (in pixels) of erosion and dilation filters used to generate DEM           | int        | should be > 0                        | 30                      | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| preprocessing_median_filter_size    | Size (in pixels) of first median filter used to smooth median DEM               | int        | should be > 0                        | 5                       | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| dem_median_downscale                | Downsample factor on dsm to generate median DEM                                 | int        | should be > 0                        | 10                      | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| dem_min_max_downscale               | Downsample factor on dsm to generate DEM min and DEM max                        | int        | should be > 0                        | 2                       | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| postprocessing_median_filter_size   | Size (in pixels) of second median filter used to smooth downsampled median DEM  | int        | should be > 0                        | 7                       | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| bulldozer_max_object_size           | Bulldozer parameter "max_object_size"                                           | int        | should be > 0                        | 8                       | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| compute_stats                       | Compute statistics of difference between DEM min/max and original DSM           | boolean    |                                      | true                    | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| disable_bulldozer                   | Disable Bulldozer step to fasten the DEM generation                             | boolean    |                                      | false                   | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+
| resolution                          | The resolution of the dems                                                      | int, float | should be > 0                        | 0.5 [#scaled]_          | No       |
+-------------------------------------+---------------------------------------------------------------------------------+------------+--------------------------------------+-------------------------+----------+

**Example**

.. include-cars-config:: ../../example_configs/configuration/applications_dem_generation

.. rubric:: Footnotes

.. [#scaled] This parameter is computed at runtime depending on the resolution of the input sensor images. You can still override it in the configuration.