What can I expect when CAMS is not valid (probably due to too many clouds or No_data values) ?

[Seam8]

Hello,

I am currently running MAJA with CAMS on a cloudy dataset (one month is specifically cloudy).

I am having the following log in the console:

2019-11-25 13:22:55,116 - Start-Maja - INFO - => processing date 20190712 2019-11-25 13:22:55,213 - Start-Maja - INFO - Using MUSCATE L2 type 2019-11-25 13:22:55,215 - Start-Maja - INFO - previous L2 : /workspace/workdir/L2A//36UVB/GIPP_S2AS2B_xxx/SENTINEL2_TM_CAMS/SENTINEL2A_20190702-090611-775_L2A_T36UVB_C_V1-0 2019-11-25 13:22:57,044 - Start-Maja - INFO - ################################# 2019-11-25 13:22:57,044 - Start-Maja - INFO - ################################# 2019-11-25 13:22:57,044 - Start-Maja - INFO - processing /media/scratch/MAJA/L1C/36UVB/S2A_MSIL1C_20190712T085601_N0208_R007_T36UVB_20190712T110428.zip in nominal mode 2019-11-25 13:22:57,044 - Start-Maja - INFO - MAJA logfile: /workspace/workdir/L2A//36UVB/GIPP_S2AS2B_xxx/SENTINEL2_TM_CAMS//S2A_MSIL1C_20190712T085601_N0208_R007_T36UVB_20190712T110428.zip.log 2019-11-25 13:22:57,045 - Start-Maja - INFO - ################################# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! L2A product /workspace/workdir/L2A//36UVB/GIPP_S2AS2B_xxx/SENTINEL2_TM_CAMS is not valid (probably due to too many clouds or No_data values) !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! My questions are the following:

• What can I expect as result ?
• Would it be better to run MAJA without CAMS ?
• Is it likely to decrease the quality result of the cloud free images from the timeserie dataset, as well ? Which means that I should manually select and remove images which are too cloudy before running MAJA.

[olivierhagolle]

Hi ! In MAJA, we have decided not to deliver the products with more than 90% of clouds. This save computing time, disk space, and usually, the few cloud free pixels can be badly corrected. There are undetected shadows, adjacency effects due to the vicinity of clouds, and it's hard to estimate the AOT when you have no pixel to estimate it.

But it is a parameter, and you may change it if you really need these pixels, but the result might be quite wrong. It is contained in all L2COMM GIPP files. There are four of them (2 per satellite for a bad technical reason that we will correct in version 4.0+).

90

Using CAMS or not should not change much the result regarding cloud detection. It changes just a little bit, as we do a basic atmospheric correction with 0.005 AOT before applying the cloud detection thresholds. The effect of this corrections lightly changes with the aerosol type.

And you don't need to select images manually, discarding the images with too many clouds contributes to a better quality of the time series, but it is done automatically by MAJA.

Olivier

[Seam8]

Ok, it is all good for me. Thank you for the answer.