Sentinel 2 Imagery

This is a European Space Agency (ESA) satellite.  Data is available or Copernicus Open Access Hub (Directions)  .  There are two satellites on opposite sides of the earth, and each revisits the same locations every 10 days, so one will visit every 5 days.  Imagery is acquired at 1030 local time, which minimizes the effect of shadows while also minimizing potential cloud cover.   This is the close to the same time as Landsat and SPOT-5, allowing integration with their archive for time-series studies.

First data in 2015. 

Multiple resolutions complicates intelligent display (unlike Landsat, which provides the TIR bands at the same resolution, with only the Pan band a different size)

Landsat versus Sentinel-2

Bands and resolution

To identify the desired tile(s)

• https://sentinel.esa.int/web/sentinel/missions/sentinel-2/news/-/asset_publisher/Ac0d/content/sentinel-2-level-1c-product-tiling-grid-released has a KML file
• Square tiles, with data right out to the edge in many cases.  The tile only contains data from a single satellite pass, so the coverage edges will lead to incomplete tiles.  The tile name uses MGRS, and has a T for tile,  two digits for UTM zone, a letter for the latitude band, and two letters for the 100K UTM square.
• Because the tile names use MGRS, you can use NGA shapefiles with 100K MGRS names to see tile outlines.
• Satellite passes often do not completely fill a tile, and it will have voids that were not imaged with that pass

Complex data structure, JP2 file format; the imagery is buried 4 levels down in directories with very long names.  You should use folder selection to pick scenes.

• L1C_T32NNF_A009285_20170402T093844\--top level directory, with the key information
  • L1C: Multispectal imagery, level 1C for this image
  • T32NNF--tile number in MGRS
  • 20170402T093844--date acquired Year-Month-Day-Hours-Minutes-Sconds
• S2A_MSIL1C_20170402T093031_N0204_R136_T32NNF_20170402T093844.SAFE\
  • S2A: Sentinel-2, the A satellite (A/B currently flying)
  • MSIL1C: Multispectal imagery, level 1C for this image
  • 20170402T093031: date imagery acquired, date acquired Year-Month-Day-Hours-Minutes-Sconds
  • N0204--baseline processing number
  • R136: Relative orbit number, 1-143; there are all descending orbits in sequential order, so the next one will be displaced quite a distance to the west
  • T32NNF--tile number in MGRS
  • 20170402T093844
  • SAFE\--Sare Archive Format for Europe.  Some software wants you to load this directory;  which may decompress under another directory with some of the same information in a different format
• GRANULE\L1C_T32NNF_A009285_20170402T093844\
• IMG_DATA\
• T32NNF_20170402T093031_B08.jp2

Level

• 1C: top of atmosphere reflectance
• 2A: bottom of atmosphere reflectance, with three folders with the 10, 20, and 60 m data.  This has an addtional folder after IMG_DATA with the resoluution (R10m, R20m, and R60m), and the band files have "_10m" after "_B02".  Only the 10 m folder has Band 8; the others have Band 8A.

Download available from Copernicus Open Access Hub

MICRODEM will use GDAL to convert the JP2 files to Geotiff .  There is an option on the Imagery tab of the options form on whether to keep the JP2 files (needed if you want to use ACOLITE) .

• The L1C tile  JP2 files for a scene take about 800 MB, but require about a minute with GDAL before they can be used by MICRODEM.
• The Geotiffs take about 1.6 GB.

Working with Sentinel-2 in MICRODEM

• Two ways to use in MICRODEM so you can combine bands and do analysis.
  • If the program does not recognize a Sentinel-2 image, put the data in a directory with the word "SENTINEL" somewhere in the path.
  • Insure you have GDAL to convert the JPEG2000 files
  • If you have a lot of scenes, you can do a batch conversion and take a walk while they process.  File, Tools, Sentinel 2 data prep.  Pick a directory, and all images in the first level of subdirectories  will be extracted.
• File, Open submenu, Open Landsat/Sentinel-2 multiband image: particularly good for Sentinel-2 which buries the image files many directories deep.  Will let you pick the high level directory, GDAL convert the bands from JP2 to Geotiff.   This will take some time for the conversion.

Metadata:

References

• https://sentinel.esa.int/web/sentinel/missions/sentinel-2
• https://sentinel.esa.int/web/sentinel/user-guides/sentinel-2-msi/revisit-coverage
• https://sentinel.esa.int/documents/247904/685211/Sentinel-2_User_Handbook  pages 48-49 describe the process for creating Level 2 data (surface reflectance)

Using in QGIS:

• https://medium.com/sentinel-hub/control-sentinel-hub-from-within-qgis-2a83eb7f13db
• We could not (some time ago) get the plugin to work in the version of QGIS from OSGeo4W, but did in the build from QGIS.  It wants to download data from the web.

Last revision 11/25/2022