FAQ

  • Posted on: 13 June 2018
  • By: bc_editor

S2GM FAQ

Q: Why can't I download my processed data?
A: Be sure to have the Mosaic Downloader installed. See here.

Q: Why can’t I just order and download the mosaics via my browser?
A:  Downloading bulky and structured data that requires several hours for data processing and download is not efficient with a browser. The Mosaic App was implemented to solve this and other issues relating to data management. The Mosaic App has the same functionality as the browser instance and allows for download of bulky data as well as for proper data handling. It might be even more convenient to work with the app from the beginning to avoid switching between the browser and the Mosaic Downloader.

Q: The images seem to be resampled and a little bit blurred, is the final product showing the original band values?
A: The Sentinel-2 L2A input products do not include all bands in all three spatial target resolutions; a spatial resampling is thus necessary prior to the production of the mosaics. For detailed information, see here.

Q: Why do I have no-data values in the result and how are the pixels selected?
A: Sen2cor includes a scene classification (SCL) algorithm which generates a classification map. If it classifies pixels as no-data, there is no input for the pixels. Also, different flag combinations have an influence on the outputs. See here and for more detailed information the ATBD.

Q: Are there data available outside Europe?
A: Yes. ESA started distributing global data at Dec. 13, 2018. Earlier data is limited to Europe.

Q: My request for a WGS84 region will not be processed. Why?
A:  Currently, WGS84 products are only available for regions smaller than 11000x11000 pixels in the composite. This restriction will be addressed and revoked in a future update of the service.

Q: My lake is split into two parts. Can I get a real mosaic? 
A: There are two possibilities: 
    1. Your region spans over tile borders. Solution: define a smaller region.
    2. Your region spans over UTM zones. Solution: use WGS84 instead

Q: What does the warning ‘Output mosaic is very large …’ mean?
A:  When the order is very large, the system will issue this warning to make you aware that you are about to order a very large dataset. Producing a mosaic for such a large area requires heavy data processing and we just want to verify by email that this order was not created by chance. Note that the provisioning and download of the data will probably take some days. In case you want to test the suitability of S2GM products for your specific application, it may be worthwhile to start with a smaller test area (which would be available faster) before ordering the full area of interest.

Q: I have placed an order for a larger region. However, the service seems to get stuck after providing the data for a few tiles?
A:  For large orders, the processing is not immediately done for the full region but rather continuously provided once you start downloading the data. This is done to handle multiple user requests in parallel and not to block the system by individual large requests.