Sentinel-2 Level 3A ################### Description *********** Levels 3A are a monthly syntheses of cloud surface reflectances. A short documentation about the product is available at `CESBIO's multitemp blog `_. Also, the `ESA's document `_ provides explanations about algorithms used to generate L3A products. Download data ************* Data are downloadable from : https://geodes.cnes.fr/ . iota2's cook ************ Configuration file parameter ============================ ``chain.s2_l3a_path`` is the parameter to enable the use of L3A products. .. code-block:: python chain: { ... s2_l3a_path:"/absolute/path/to/Storage_directory" ... } Data storage ============ Data must be stored by tile as the in following tree : .. code-block:: console └── Storage_directory ├── T31TCJ │ ├── SENTINEL2X_20181015-000000-000_L3A_T31TCJ_D_V1-1 │ │ ├── MASKS │ │ │ └── *.tif │ │ └── *.tif │ └── ... ├── T31TDJ │ └── ... └── ... Where tiles are T31TCJ, T31TDJ ... Data usage ========== Time series +++++++++++ All dates are chronologically stacked together in order to provide a temporal series to the learning / classification system. Then, if the configuration file parameter ``sensors_data_interpolation."use_gapfilling`` is set to ``True``, the gapfilling is processed. .. Note:: Every band is resampled to a 10m resolution. Gapfilling ++++++++++ Gapfilling allows iota2 to interpolate cloudy dates and resample every tile's time series on the same temporal grid. The cloud interpolation is based on masks provided by L3A products. Masks usage +++++++++++ A ``BINARY_MASK`` raster is generated for each L3A date and placed next to native data. ``BINARY_MASK`` is the raster provided to the gapfilling algorithm to know which pixels to interpolate by date. iota2 uses ``_FLG_R1.tif`` raster to determine pixels to flag as to be interpolated. Every pixel under ``0`` and ``1`` respectively ``NODATA`` and ``Cloud / Cloud's shadow`` will be interpolated. Features ++++++++ Once the gapfilling is done, if the configuration file parameter ``arg_train.features`` is different from ``[]``, then features are computed from the the gapfilled time series. ``NDVI, NDWI and brightness`` are automatically computed. Also, users could provide a set of features described as a BandMath expression using : ``Sentinel_2_L3A.additional_features`` configuration file parameter. By default, every band is used as a feature and used by the classification process to find pixels label, but with the joint use of ``Sentinel_2_L3A.keep_bands`` and ``iota2_feature_extraction.extract_bands`` only targeted bands will be used. Available bands +++++++++++++++ All bands provided by THEIA L3A products are available. .. code-block:: python Sentinel_2_L3A: { keep_bands:["B2", "B3", "B4", "B5", "B6", "B7", "B8", "B8A", "B11", "B12"] }