S3A mosaic problem

Optical Toolbox
#1

Dear All,

I tried to create a mosaic over Sentinel 3A products (OGVI).

S3A
S3A1363×714 247 KB

  • 1th image (on the left) represents the original file with original projection;
  • 2nd image represents the OGVI output obtained from SNAP using SUBSET (over OGVI) and then MOSAIC with specific boundaries to speed up the process;
  • 3th image represents a REPROJECTION using original file with preserve resolution checked from original S3A file;
  • last image shows the correct output reprojection obtained using MOSAIC over the original S3A file;

It seems there is a problem because there are some missing information over France.
Any idea about the correct metodology to do a mosaic?

Thanks in advance for your collaboration,
Monica

#2

Hi Monica,

In the mosaic function you have a label with Variables & Conditions, there you have to select with variables you want to have as bands in your output mosaic and the combination (AND/OR). Have you checked that you are using the right logic?

#3

The only check done was on valid values of OGVI (!=NaN).
Here another example:

image
image.png747×590 89.8 KB

where on reprojected image there are a missing area.

Is there a problem on mosaic procedure?

#4

I have similar problem to mosaic 2 scenes of S3 OLCI. I get the mosaic but i can not see adg443 band mask. I have the raster but only if use adg443 color classification show me same value for all pixels. :S

#5

Can you post some image which show the problem?
Also your configuration of the mosaic might be of interest.

#6

Thanks, attached the picture. I use snap gui interface but i would like build gpt code to next steps.

captura_snap
captura_snap1918×1042 126 KB

#7

The image looks really good and I don’t see any issue.

For starting with gpt you can have a look at this guide:
https://senbox.atlassian.net/wiki/spaces/SNAP/pages/70503590/Creating+a+GPF+Graph

Type for example

gpt mosaic -h

For getting help on the mosaic operator.
However, the mosaic is a bit complex to configure.
You can save the configuration from the GUI of the Mosaic (File/Save Parameters…) or
you use the GraphBuilder, save the graph and andapt later the xml file.

#8

Yes, is really nice the mosaic, but the flags (clouds, land) show the major index (red) of chla.

Thanks for help. I will post the result soon.