[QGIS-Developer] Projects without a CRS

[Andreas Neumann]

Hi Harrissou, 

Thanks - I should trust our documentation better ;-) 

Indeed this already answers many of my questions. 

So with this documentation in mind, I can assume that the "no
projection" setting is here to stay and won't be removed in the future -
right? 

But still, when dealing with geographic data, a "no projection" project
should be discouraged ... 

Personally I think that the "no projection" option shouldn't be on the
top (both in the project setting and in the documentation), to really
discourage users from using "no projection". It should be somewhere
below or above the datum transformations, to indicate it that this is an
advanced thing where you really should know what you are doing. 

Thanks, 

Andreas 

On 2019-07-01 08:59, Harrissou wrote:

> Hi Andreas
> 
> I think there are some (partial?) answers in docs, in case you didn't read it yet.
> https://docs.qgis.org/testing/en/docs/user_manual/introduction/qgis_configuration.html#crs-properties
> 
> Regards,
> Harrissou
> 
> Le 1 juillet 2019 08:46:03 GMT+02:00, Andreas Neumann <a.neumann at carto.net> a écrit : 
> 
>> 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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