.. _demcompare_module:


Demcompare pipeline module
===========================

The main demcompare module in `demcompare_module file <https://github.com/CNES/demcompare/blob/master/demcompare/__init__.py>`_ orchestrates the demcompare
API from an input configuration file, hence, from an execution using the :ref:`demcompare_cli`.

The configuration file specifies digital elevation models inputs to compare and also the pipeline to execute.
This pipeline depends on the optional :ref:`coregistration` and/or :ref:`statistics` steps configuration.

If coregistration and/or statistics steps are to be computed,
then each step orchestration will be handled by demcompare module as follows:

Coregistration step orchestration
---------------------------------

.. figure:: /images/coreg_api.png
    :width: 800px
    :align: center

    Demcompare coregistration step orchestration


To perform the dems coregistration :ref:`coregistration`, demcompare's module performs the following steps:

1. Loads the input dems using the **dem_tools** module's *load_dem* function.
2. Creates a **Coregistration** object and obtains the dem's transformation object using the **coregistration**'s *compute_coregistration* function.
3. Applies the obtained transformation to the secondary dem using the **transformation**'s *apply_transform* function.

For more details on the coregistration modules architecture, please see :ref:`coregistration_modules`.

Statistics step orchestration
-----------------------------

.. figure:: /images/stats_api.png
    :width: 800px
    :align: center

    Demcompare's orchestration for statistics step.

To perform the dems statistics :ref:`statistics`, demcompare's module performs the following steps:

1. Loads the input dems using the **dem_tools** module's *load_dem* function.
2. Reprojects both dems to the same size and resolution using **dem_tools** module's *reproject_dems* function.
3. Process the two DEMs by using the **dem_processing** module (see :ref:`dem_processing`).
4. Creates a **Stats_processing** object and obtains the **stats_dataset** using the **stats_processing**'s *compute_stats* function.

.. note::

    If coregistration has previously been done, the **coregistration**'s objects internal dems called **reproj_coreg_ref** and **reproj_coreg_sec** are used for the altitude difference computation, so that no manual reprojection needs to be done. Please see :ref:`statistics` "With coregistration step" section for more details.

.. note::

    If only one input is provided to demcompare, this input is directly used by the **dem_processing** module (there is no reprojection).

For more details on the statistics modules architecture, please see :ref:`stats_modules`.

Module files description
************************

- **helpers_init** module in `helpers_init.py file <https://github.com/CNES/demcompare/blob/master/demcompare/helpers_init.py>`_

.. _helpers_init:

In this module high level parameters of the input configuration are checked and default options are set when
not already defined. Some helper functions to handle the output paths from the ` are also included here.

- **log_conf** module in `log_conf.pyfile <https://github.com/CNES/demcompare/blob/master/demcompare/log_conf.py>`_

.. _log_conf:

The logconf module in demcompare contains logging configuration functions.