.. _l2i-format:

Output Format
=============

.. note::

  It is recommended to output the "improPhed" Level 2 data to the Level 2 directory, i.e. ``DIR_LOWER = DIR_HIGHER``.
  This way, the refined dataset is appended to the original dataset as a separate product.
  Thus, after running this submodule, two surface reflectance versions are available for each date. 
  The new product will have higher spatial resolution (more pixels) than the other products (e.g. ``QAI``).
  :ref:`higher-level` can digest this data structure, and the user can choose to use the original BOA or the refined product (``USE_L2_IMPROPHE``).


Data organization
^^^^^^^^^^^^^^^^^

The data are organized in a gridded data structure, i.e. data cubes.
The tiles manifest as directories in the file system, and the images are stored within.

.. seealso:: 

  Check out this `tutorial <https://davidfrantz.github.io/tutorials/force-datacube/datacube/>`_, which explains what a datacube is, how it is parameterized, how you can find a POI, how to visualize the tiling grid, and how to conveniently display cubed data.


Data Cube definition
^^^^^^^^^^^^^^^^^^^^

The spatial data cube definition is appended to each data cube, i.e. to each directory containing tiled datasets, see :ref:`datacube-def`.


File format
^^^^^^^^^^^

Refer to :ref:`hl-format` for details on the file format and metadata.


Naming convention
^^^^^^^^^^^^^^^^^

Following 29-digit naming convention is applied to all output files:

Example filename: 20160823_LEVEL2_SEN2A_IMP.tif

+--------+-------+--------------------------------------------+
+ Digits + Description                                        +
+========+=======+============================================+
+ 1–8    + Acquisition date as YYYYMMDD                       +
+--------+-------+--------------------------------------------+
+ 10–15  + Product Level                                      +
+--------+-------+--------------------------------------------+
+ 17–21  + Sensor ID                                          +
+        +-------+--------------------------------------------+
+        + LND04 + Landsat 4 Thematic Mapper                  +
+        +-------+--------------------------------------------+
+        + LND05 + Landsat 5 Thematic Mapper                  +
+        +-------+--------------------------------------------+
+        + LND07 + Landsat 7 Enhanced Thematic Mapper         +
+        +-------+--------------------------------------------+
+        + LND08 + Landsat 8 Operational Land Imager          +
+--------+-------+--------------------------------------------+
+ 23–25  + Product Type                                       +
+        +-------+--------------------------------------------+
+        + IMP   + ImproPhed Bottom-of-Atmosphere Reflectance +
+--------+-------+--------------------------------------------+
+ 27–29  + File extension                                     +
+        +-------+--------------------------------------------+
+        + tif   + image data in compressed GeoTiff format    +
+        +-------+--------------------------------------------+
+        + dat   + image data in flat binary ENVI format      +
+        +-------+--------------------------------------------+
+        + hdr   + metadata for ENVI format                   +
+--------+-------+--------------------------------------------+


Product type
^^^^^^^^^^^^

* Reflectance

  There is only one product type, i.e. the ImproPhed Bottom-of-Atmosphere Reflectance (IMP). 
  The IMP product has the same specification as the BOA product (see :ref:`level2-format`), but spatial resolution was enhanced.
  The scale is 10000, and nodata value is -9999.
  IMP data contain multiple bands, which represent wavelengths, see metadata and following tables).
  All bands are provided at the same spatial resolution (see :ref:`l2-param`).