Bit 7 "Sun Tangent To Slope" in MG2 not activated (?) and Bit 0 and 1 in CLM (All Clouds (except Thinnest Clouds) + All shadow for bit 0) activated at the same time as bit 4 (Thinnest Clouds)
Currently using MAJA v4.5.3 (with a slight adaptation : W_Dark value set to 1 instead of 0.5), but what is reported here has been experienced in the few MAJA v4.7.1 outputs we already generated.
Exploring the MAJA outputs, as we use them in the frame of Copernicus Land project HR-WSI, we found two potential issues :
- bit 7 of mask MG2 (aka "s_un direction tangent to slope (inaccurate terrain correction)")_ seems to never be activated. We studied a solid dozen of scenes on several tiles and never found it activated. Is it a rarely activated bit, or is abnormal (some tiles are mountainous ones, hence with slopes, and good candidates to a sun tangent exposition).
- On mask CLM, we thought bit 0 and bit 1 ("all clouds except the thinnest and all shadows" and "all clouds (except the thinnest)") could not be activated at the same time as bit 4 ("thinnest clouds"). Still we observed it several times over several tiles. Is it an expected behavior (and we misunderstood the meaning of "except the thinnest") or is it an issue ?
- On a side note, we also observed bit 1 and bit 5/6 to be activated simultaneously (and at the same time as bit 4 as well). We thought it would not be the case, as bit 0 looks like it is split between bit 1 on a one hand and bits 5 and 6 and the other. Though it would not be so strange to have pixels both tagged as shadow and clouds. This happens mostly at the border of the cloud clusters.
Thanks for your help. I can provide some L2A on which we observed those behaviors if needed.
Adrien Ceschin, on behalf of Magellium HR-WSI team