Landsat satellites have been supplying data with a resolution of 30 metres for 30 years. During this time, data covering the whole planet have been regularly acquired with a revisit frequency of 16 days. While the repetitiveness and resolution of Landsat satellites is now supplanted by Sentinel-2, Landsat images allow multi-temporal analyses to be performed over a very long period of time, since the mission began in 1972. This is why the Theia thematic cluster has decided to provide its users with the Landsat data acquired for the whole of France since 2009.
Landsat products are provided by Theia in surface reflectance (level 2A) with cloud masks, the processing being performed with the MAJA algorithm developed at Cesbio. They are orthorectified and cut on the same tiles as Sentinel-2 products.
Level 2A : data ortho-rectified surface reflectance after atmospheric correction, along with a mask of clouds and their shadows, as well as a mask of water and snow.
Name : Landsat-5, Landsat-7 and Landsat-8
Imaging mode : optical
Spectral bands : 8 Spectral bands from visible to mid-infrared
Resolutions : 30 m (multispectral)
Observation capability :
- Swath : 185 km
- Revisit : 16 days
- Area : Time series for France
- Period : 2009 – 2011 Landsat 5 et 7
2013 – présent for Landsat 8
For more information see landsat.gsfc.nasa.gov
The TAR file distributed by Theia contains 4 files and MASK directory.
The 4 files provide the following information :
- An XML file (as in Level 1C)
- Two .TIF files in GeoTiff format that provide surface reflectances, corrected from atmospheric effects, including adjacency effects (ORTHO_SURF_CORR_ENV, not provided for LANDSAT) and even terrain effects (ORTHO_SURF_CORR_PENTE).
- the AOT TIF file provides the estimates of Aerosol Optical Thicknesses (AOT)
The mask directory provides :
- A saturated pixels mask _SAT.TIF (as in Level 1C)
- A saturated pixel mask _SAT.TIF, with an 8 bit information
- A mask of clouds and cloud shadows _NUA.TIF
- Diverse binary masks : water, snow and no_data mask, plus (V2.0) pixels lying in terrain shadows _DIV.TIF
For more information, see Landsat Product Format.
The Sentinel-2 level 2A data distributed by THEIA are based on USGS/NASA Landsat Program level 1C data.
These 1C data are released with the following license : Licence Landsat
The level 2A products correct the data for atmospheric effects and detect the clouds and their shadows.
This processing is carried out using MACCS processor (https://labo.obs-mip.fr/multitemp/?p=6203), through MUSCATE processing centre at CNES, in the framework of THEIA land data centre For any communication and/or any derivative product using this dataset, please cite :
“Contains USGS/NASA Landsat Program data [year of reception] processed at level 2A by CNES for THEIA Land data centre”.