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☷ :doc:`return to Workflows <../../../4_workflows/workflows>`

DEMs from IGN
===============================

🌍 `Access data <https://cartes.gouv.fr/rechercher-une-donnee/dataset/IGNF_BD-ALTI>`_


|IGN| provides several |DEM| datasets at different resolutions (`IGN datastore <https://cartes.gouv.fr/rechercher-une-donnee/search?q=MNT>`_).

BD ALTI 25m
^^^^^^^^^^^^

Description
"""""""""""""

These data are available on `cartes.gouv.fr <https://cartes.gouv.fr/rechercher-une-donnee/dataset/IGNF_BD-ALTI>`_ in the ASCII format, as
square tiles of 25 km × 25 km, under the CRS epsg:2154.

GEOP4TH workflows
""""""""""""""""""""

Once downloaded, these ASCII tiles can be standardized (one single file, embedded CRS, geospatial format such as GeoTIFF...) by using the function :meth:`standardize_bdalti <standardize_fr.standardize_bdalti>`.

Standardized DEM data can then be used in application workflows such as :func:`cwatm_dem <cwatm.cwatm_dem>`, which reprojects and clips data as demanded, and generates maps of flow directions and elevation standard deviation.


  
.. |IGN| raw:: html
  
  <abbr title="Institut géographique national">IGN</abbr>
  
.. |DEM| raw:: html

  <abbr title="Digital Elevation Model">DEM</abbr>



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