[QGIS-Developer] Projects without a CRS

[Andreas Neumann]

Hi, 

I am wondering about projects without a CRS. While a new project now
always comes with a CRS (depending on the global CRS settings), the user
can still explicitly disable a definition of a CRS in Menu "Project" -->
"Properties" --> "CRS" 

I have the following questions about projects without a CRS: 

- what are the restrictions/limitations of projects without a CRS? 

- assuming that a layer has a CRS (e.g. a Postgis layer that has a CRS)
is loaded into a project that explictly has no CRS set - does QGIS still
know the CRS of the Postgis layer or would it treat it as a CRS-less
layer? 

- does it still make sense to support projects without a CRS? If yes,
what are the use cases? 

- will it still be possible to have projects without a CRS or will this
one day be deprecated 

I personally do understand that it is not a good idea to have projects
with no CRS defined, but I am trying to understand and convince my
colleagues at my workplace that projects without a CRS are an absolute
nogo. But maybe I am wrong and it still makes sense to support projects
without a CRS. 

One use case I could think of for projects without a CRS, is using QGIS
for something that is planar, but not geographic in nature, e.g. a
non-GIS topic, such as examining an image (let's say the enlarged view
of an electron microscope of some small thing) where the user might want
to "map" certain characteristics of the image, but the object itself is
"mobile" (can move around) and is not fixed to a fixed position of the
earth. 

What are your thoughts about projects without a CRS? 

Greetings, 

Andreas
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