Spot the 1 000 000 differences

After France monthly synthesis generated from Sentinel-2 data in July 2018, the monthly syntheses have become ... monthly. The new composite products for France from August 2018 are now available from Theia, using the WASP processor.

As a few days ago, we did a visualization of the mosaic at 20m resolution. You just need to click to on the links below to see them

But of course, we are interested in comparing the two. A very nice visualization was set-up by Michel Le Page, who also found the post title (Merci Michel !). Beware, do not go further if you have something urgent to do.

 

See it full screen

By comparing the two, you will see the evolution of the landscape, generally much dryer, with a lot of fields cropped, but this representation will also help you spot the composite artefacts. These are not very numerous, but you will see them :

  • on some web browsers (firefox V58), geometrical differences appear even at a low resolution. Other browsers and versions do not have this defect. It is really not due to Sentinel-2 or Theia products
  • above water and snow (we must work on this defect)
  • where clouds have covered a place during the whole month of July or August. These pixels are flagged as invalid in the products (but not on the mosaic).
  • where clouds or shadows were not properly detected by MAJA
  • at the edges of Sentinel-2 swath (but the effect is really faint)
  • some tile edges in July, due to the fact that Level 3A products were not all generated for the 15th of July, but for dates between the 8th and the 26th. This has been corrected for August.

 

Posted under: CESBIO, Composite (3A), Corrections (geometry, atmosphere, clouds), In English, Sentinel-2, THEIA

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