When I open an AATSR file and go the mask-manager to look at the individual cloud flags, the option to mask the visible NDVI cloud flag is not there. This is one of the basic cloud flags and there should be an option to see this flag.
Can you point me to the documentation where this flag is described. If it is there we miss it since years and so far no one complained. Actually we are also participating in the AATSR QWG and haven’t heard about missing flags.
Maybe there is something missing, but I couldn’t find it in the AATSR documentation.
This document shows that the visible channel cloud flag is set at bit 13. I also notice that the snow flag is missing too.
I have just opened up Beam and notice this flag is not there either! I know that for the AATSR ESL we tended to use our own software tools for cloud analysis rather than Beam. Now I am looking at SLSTR data I use snap, and now use this for any AATSR products that I need to look at. Therefore I have noticed this flag is missing. It is a bit worrying that this has not been picked up previously by any others users.
Interesting. In the official ESA AATSR Handbook it is stated that bit 13 to 15 are unused.
You can get the values of those bits by using the Band Maths.
Create a band with the expression ‘
bit_set(cloud_flags_nadir, 14)’ and the name
But it seems as there is now data. At least in the two products I have tried.
We contact also the QWG. Let’s see what they are saying.
The visible cloud flag is included in the summary cloud and so it should really be included. Otherwise, if you look at the summary cloud, you cannot account for all of it using the individual cloud flag masks that are available in the masking tool.
Yes, as you say, in the AATSR Product Handbook (issued February 2007) it says that these flag bits are unused. However, changes were later made to the relevant IPF which saw to, amongst other things, the addition of these two cloud flags (e.g. bit 13 –visible channel cloud test shows pixel cloudy, bit 14 – NDSI snow flag) which are documented in the technical note (issued September 2007) that Caroline has included above. It may have been that BC were not notified of this change (sorry) but the issue was discussed at the QWG meeting and they have asked if we could have SNAP incorporate these 2 cloud flags in the mask manager also as they’re needed.
I think we can solve this issue for the next release. We haven’t been informed about this change or we forgot it. Who can tell it after 10 years?
But still now the outdated documentation is online. Maybe ESA should update this too.
I’ve put it into our issue tracker (SNAP-733). Maybe we can include it already in the next module update.
I just wanted to let you know that this issue is fixed and will be available with the next release.