…use other loading parameters with load_product?

Warning

The following section is only relevant if you deliberately want to override the default loading parameters and if you know what you are doing. If you are not sure, please skip this section and just be happy with the default values 🙂 or get in contact with me to discuss your use case.

All data products except for the MSWEP product are loaded internally using the odc.stac.load -function. As mentioned above, some loading parameters are set to default values to make this package beginner-friendly and easier to use. To be more precise, the following defaults are used:

• crs='EPSG:4326'

• resolution=0.0002

• resampling='bilinear'

• chunks={'time': -1, 'latitude': 'auto', 'longitude': 'auto'}

The default values for crs and resolution, for example, are the native CRS and resolution of the Sentinel-1 RTC and the Sentinel-2 L2A products (most bands of the latter at least). The resampling-parameter is only relevant if a data product needs to be reprojected (note that this is overriden by default for the SANLC product to use resampling='nearest', which is a better choice for categorical data). The chunks-parameter is important for loading the data lazily using Dask (see Xarray, Dask and lazy loading for more information). The default values have been chosen to work well for time series analysis (alignment of chunks along the time dimension) and to be memory efficient (automatically choose the chunk size along the spatial dimensions based on Dask’s default).

If you want to override these defaults or add additional parameters that influence the loading process, you can do so by providing the override_defaults-parameter to the load_product -function. This parameter should be a dictionary with keys corresponding to parameter names of the odc.stac.load -function and values corresponding to the desired values. It is also possible to partially override the defaults while keeping the rest unchanged. The following is a simple example of how to override only the default resolution-parameter when loading the Sentinel-1 RTC product:

from sdc.load import load_product

override_defaults = {"resolution": 0.0001}
s1_data = load_product(product="s1_rtc", 
                       vec="/path/to/my_area_of_interest.geojson", 
                       time_range=("2020-01-01", "2021-01-01),
                       override_defaults=override_defaults)

Note

The above example might be a bit misleading, especially for beginners, as we can’t magically increase the spatial resolution of Earth Observation data by simply changing a parameter called resolution. What we do here instead is changing the pixel spacing of the loaded data. Both terms are often used interchangeably, but they are not the same. Please keep this in mind! In the example we need to use the term resolution as this is the name of the corresponding parameter of the odc.stac.load-function.