Sentinel-2¶

Overview¶

Sentinel-2 is a wide-swath, high-resolution, multi-spectral imaging mission supporting Copernicus Land Monitoring services. It provides optical imagery at 10m, 20m, and 60m resolution with a revisit time of 5 days at the equator.

In GeeFetch, Sentinel-2 data is accessed via the Google Earth Engine collection COPERNICUS/S2_SR (Surface Reflectance).

Processing¶

Filtering by date range and area of interest
Cloud masking using the COPERNICUS/S2_CLOUD_PROBABILITY product (see configuration options)
a. Remove images where CLOUDY_PIXEL_PERCENTAGE > 100 - cloudless_portion
b. Remove images where HIGH_PROBA_CLOUDS_PERCENTAGE > 50 - cloudless_portion/2
c. Mask pixels which have a probability of being a cloud > cloud_prb_threshold
d. Mask pixels based on the QA60 band
Resampling to target resolution
Mosaicking of multiple images
Scaling to maximize precision within the requested data type. Pixels outside of the range \((0, 3000)\) saturate. For instance, if the requested datatype is uint8, the image is scaled by \(255/3000\).

Available Bands for download¶

Band	Description	Native resolution	Download by default
B1	Coastal aerosol	60m	no
B2	Blue	10m	yes
B3	Green	10m	yes
B4	Red	10m	yes
B5	Red Edge 1	20m	yes
B6	Red Edge 2	20m	yes
B7	Red Edge 3	20m	yes
B8	NIR	10m	yes
B8A	Narrow NIR	20m	yes
B9	Water vapor	60m	no
B11	SWIR 1	20m	yes
B12	SWIR 2	20m	yes
QA60	Cloud mask	60m	no
AOT	Aerosol Optical Thickness	10m	no
WVP	Water Vapor Pressure	10m	no
SCL	Scene Classification	20m	no
TCI_R	True Color Red	10m	no
TCI_G	True Color Green	10m	no
TCI_B	True Color Blue	10m	no
MSK_CLDPRB	Cloud Probability	20m	no

Refer to COPERNICUS/S2_SR for more details.

Configuration Options¶

See common configuration options for non Sentinel-2-specific configuration. Additionnally, you may provide the following options.

Attributes:

Name	Type	Description
`cloudless_portion`	`int`	Threshold for the portion of filled pixels that must be cloud/shadow free (%). Images that do not fullfill the requirement are filtered out before mosaicking. Default is 40.
`cloud_prb_threshold`	`int`	Threshold for cloud probability above which a pixel is filtered out (%). Default is 40.

Example Usage¶

Command Line¶

Write the following config.yaml

data_dir: ~/satellite_data
satellite_default:
  aoi:
    spatial:
      left: 2.2
      bottom: 48.7
      right: 2.5
      top: 49
      epsg: 4326
    temporal:
      start_date: "2023-06-01"
      end_date: "2023-06-30"
  gee:
    ee_project_ids: ["your-gee-id"]
  tile_size: 2000
  resolution: 10
s2: # more scrict cloud filtering than the defaults
  cloudless_portion: 60
  cloud_prb_threshold: 20

then download with

geefetch s2 -c config.yaml

Python API¶

Though this is not geefetch main intended use, you can bypass the configuration and directly download Sentinel-2 data with the geefetch.data.get.download_s2 function. For instance, the CLI command above is roughly equivalent to

import logging
from pathlib import Path

from geobbox import GeoBoundingBox

from geefetch.data.get import download_s2
from geefetch.utils.gee import auth
from geefetch.utils.log import setup

setup(level=logging.INFO)

data_dir = Path("geefetch_data/")
data_dir.mkdir(exist_ok=True)

auth("your-gee-id")

download_s2(
    data_dir,
    bbox=GeoBoundingBox(2.2, 48.7, 2.5, 49),
    start_date="2023-06-01",
    end_date="2023-06-30",
    tile_shape=2000,
    cloudless_portion=60,
    cloud_prb_thresh=20,
)

See the API reference of geefetch.data.get.download_s2 for more details.

Relevant library code¶

S2
geefetch.data.get.download_s2