Level-2A product data
The Level-2A Top-of_Canopy (TOC) reflectance product is a geometrically and atmospherically corrected version of the original data proviced by the European Space Agency (ESA) with additional information on pixel classification, Aerosol Optical Thickness (AOT), water vapour (WVP), and angular configuration: Solar Zenith Angle (SZA), Viewing Zenith Angle (VZA), and Relative Azimuth Angle (RAA). Level-2A TOC products are systematically generated at ESA’s ground segment over Europe from March 2018 onwards and coverage was extended to global in December 2018. The Terrascope workflow was adapted accordingly and starts with the download of these L2A products.
In case Level-2A data are not available, Level-1C Top-Of-Atmosphere data are downloaded and processed using the Sen2Cor v2.8 atmospheric correction Louis et al. (2017). Subsequently, pixels are classified into pre-defined categories: vegetation, bare soil, water, snow, cloud, cloud shadow, dark area, saturation or defect and are provided at 20 m resolution. See Table 1 for the Scene Classification category overview.
Table 1: Scene classification categories.
| Value | Classification |
|---|---|
| 0 | NO_DATA |
| 1 | SATURATED_OR_DEFECTIVE |
| 2 | DARK_AREA_PIXELS |
| 3 | CLOUD_SHADOWS |
| 4 | VEGETATION |
| 5 | BARE_SOIL |
| 6 | WATER |
| 7 | UNCLASSIFIED |
| 8 | CLOUD_MEDIUM_PROBABILITY |
| 9 | CLOUD_HIGH_PROBABILITY |
| 10 | THIN_CIRRUS |
| 11 | SNOW |
The current Terrascope Level-2A data collection is V200 (released in May 2020) and contains data from July 2015 onwards. Table 2 provides an overview of the modifications from the previous collection (V102) to V200.
| Adaptations between V200 and V102 | Clarification |
|---|---|
| Scene selection | |
| No processing for tiles with cloud cover > 95% | For data storage optimization, almost fully cloud-covered scenes with clouds will no longer be processed. |
| Scene classification | |
| Sen2Cor version update (v2.8.0) | The previous version (v2.5.5) was replaced with the latest version. See Müller et al. (2019) for the modifications. |
| Atmospheric correction | |
| Sen2Cor replaces iCOR for atmospheric correction | To be consistent with ESA processing, iCOR was replaced with Sen2Cor. Both are valid atmospheric correction processors and have been included in various inter-comparison exercises (e.g. ACIX-I and ACIX-II). |
| Download of Sentinel-2 L2A Near-Real-Time products | ESA has processed L2A products over Europe since March 2018, extended to global coverage in December 2018. |
| Output data | |
| Additional layers at 60 m _*WV at 60 m_ _*Angular information: RAA, VZA, and VAA_ |
Can be used for quality control or for further processing by users. |
| Removed layers _*Cloud_ _*Cloud shadow_ |
Cloud and cloud shadow information can be found in the Scene Classification layer. |
| INSPIRE metadata update | To be compliant with the ISO-19115-2 standards. |
| Values in dense clouds of processed tiles (cloud cover < 95%) are masked with a conservative buffer. |
Masking of dense clouds allows for an optimised data storage. |
| Data archive | |
| Switch from Product Distribution Portal (PDF) to TerraCatalogue, with accompanying GeoJSON metadata information. |
The new catalogue is easier to use. |
| Change in Mission Exploitation Platform (MEP) folder structure |
Folder structure has been revised, made more concise, and user-friendly. |
Sen2Cor provides TOC reflectances for each spectral band, a scene classification layer, AOT, WVP, SZA, VZA, and RAA output layers. All Level-2A TOC data are provided as single-layer compressed Cloud-Optimized Geotagged Image File Format (COG). Figure 1 shows the file list.
Figure 1: Sentinel-2 Level-2A TOC data file overview.
More details on the Level 2A processing chain and the various algorithms involved are given in the Level2A ATBD. An extensive validation is reported in the Level2A Quality Assessment Report.
Back to top