Sentinel-2 L3 WASP - Monthly Composite
This Sentinel-2 L3 collection provides for each month an almost cloud free composite of atmospherically corrected Sentinel-2 data (Sentinel-2 L2A MAJA) over Germany. The composite is created using the processor WASP and is typically available 5 days after the end of the month.
The data are very convenient to get a good view of a territory, create nice seamless mosaics and posters and - most important for automated processing - Sentinel-2 L3 WASP data require less robustness from the processors as the amount of clouds is low.
Details
Even if Sentinel-2 L2A MAJA products are already high quality, they are not fully easy to use, because most Sentinel-2 images have a significant cloud cover. The processors which use these products must be robust to the presence of spatial or temporal gaps in the coverage.
During Level 3A processing with WASP, the atmospherically corrected data from a predefined time interval are collected, weighted based on distance in time and integrated into a new data set to remove the clouds.
Other methods of time synthesis often use the 'best available pixels' method, where for each pixel the date for which the best recording conditions are available is selected. The best available pixel mosaics are prone to artifacts on the boundaries between the different dates selected for each pixel. The weighted average method of WASP minimizes these artifacts by merging the different data without clouds.
Note
- Due to the WASP synthesis method, the knowledge of the exact date of each product is much less accurate than that provided by a L2A product. If applications require a good accuracy in terms of date, such as estimating phenology (date of flowering or senescence...), then the use of Sentinel-2 L2A is recommended instead.
- The WASP synthesis method assumes that surface reflectance changes very slowly with time. This assumption is wrong over some surfaces such as water or snow.
- It is not always possible to get at least one clear observation for each pixel in a certain time period. As a result, there might still be a certain percentage of cloudy pixels, but these pixels are flagged.
- A few clouds or shadows can escape the detection, especially small clouds or shadows of thin clouds, but the weighted average usually decreases their influence, except during very cloudy periods.
- For atmospheric correction of the first and last data set of a month, data sets from the respective neighboring months are used.
Availability
- Germany: 2015-07 - now
- Europe: -
- Global: -
Updates
- Monthly updates, whereby new data sets are usually available 5 days after the end of the month.
Processing details
WASP (Weighted Average Synthesis Processor) is a C++/Python software from CNES to produce monthly cloud free images from Sentinel-2 Level 2A data obtained with MAJA software. On CODE-DE, the processor WASP 1.0 is used to generate the product Sentinel-2 L3 WASP. For each pixel and each band a weighted average from all Sentinel-2 Level 2A data within the respective calendar month (synthesis day is middle of the month) is calculated and the following steps are performed:
- A directional correction is made to homogenise the surface reflectances as if they had been taken from the vertical, avoiding differences where the Sentinel-2 orbits overlap.
- Weights are computed.
- Pixels close to a detected cloud or shadow have a lower weight.
- Pixels with a lower aerosol optical thickness have a higher weight.
- A greater weight is given to dates close to the synthesis date.
- The weighted average is computed.
Usage requirements
There are certain requirements that must be met for use. Some data or services require an individual application. For more information, please contact CODE-DE Support.
| Required? | Remark | |
| Registration on CODE-DE | No | --- |
| Cloud resources on CODE-DE | No | --- |
| Individual request | No | --- |
Access
Depending on the environment and the intended use, there are several ways to access the data:
- EO Browser: Sentinel-2 --> Sentinel-2 L3A WASP - Monthly Composite
- Data Explorer:
- Data Catalogue: CODE-DE
- Path to repository on a Virtual Machine:
- /codede/Sentinel-1/MSI/L3-WASP
More information
Further information on this product can also be found on the following external pages:
Terms of use
Use of the product is subject to the following terms of use:
