[GRASS-dev] [GRASS-user] Calling all imagery (especially i.maxlik and i.smap) users

[Moritz Lennert]

On 6/05/20 08:33, Maris Nartiss wrote:
> Hello lists (sorry for cross-posting),
> as GRASS 8 starts to look less Duke Nukem Forever (a.k.a. never), it
> is a chance to change some things in imagery part. Thus if you heavy
> relay on imagery part of GRASS GIS, please find some time to give
> small feedback.
> 
> GRASS 7.8.0 imagery groups gained functionality of fully qualified
> maps and thus could be used from other mapsets, still some issues
> popped up.
> 
> #1 Should there be subgroups at all?
> There has been a call to completely eliminate subgroups [1] and stick
> only with groups. If you are using subgroups, this is the right moment
> to share your user story (and not hypothetical one!).

Subgroups used to be very useful when imagery came without 
georeferencing. One would import the data into XY, and georeference all 
bands contained in one group. In the projected location one could then 
define subgroups to do the actual work on them.

In other word, they were (are?) useful when you have different parts of 
your workflow where one part concerns all bands while other parts only a 
subset of these bands.

As most imagery comes georeferenced nowadays, this workflow is much less 
frequent nowadays and for most of my usage of subgroups today, it could 
be replaced without any problem by the use of groups.


> #2 Should i.maxlik add its output to the group?
> Current implementation of i.maxlik adds classification result to the
> input group [2]. This prevents use of i.maxlik with imagery group from
> other mapset. I would vote to remove such feature. If you have a use
> case where such functionality is needed, speak now, or forever hold
> your peace.

+1 to remove this functionality.


> #3 Should signature files be handled similarly to raster colors?
> i.cluster, i.gensig and i.gensigset write signature files to imagery
> subrgoup. This is not possible if group is located in other mapset. My
> proposal — handle signatures as raster colours — signatures are always
> saved in current mapset. Thus signatures created for a group in other
> mapset would be not visible in other mapsets.

I do think that mapset-specific groups make sense and that for me 
personally I see a lot of potential for chaos if I could have signature 
files in a mapset that pertain to groups in other mapsets. It is so easy 
to create a group that I'm not sure what the significant added value 
would be.

So, I'm more skeptical about this one, without having a clear-cut opinion.

Moritz