[GRASS-dev] importing & projecting

[Paulo van Breugel]

On 22-09-15 14:19, Moritz Lennert wrote:
> On 18/09/15 13:34, Paulo van Breugel wrote:
>> I imported raster layers in a projected mapset, while the data layers
>> were in latlon. I used the r.in.gdal from the menu (i.e., not command
>> line), importing all geotif files in a directory.
>>
>> I would have assumed that GRASS would throw an error as the layers were
>> not in the correct projection. Instead GRASS just imported the layers,
>> projecting the layers 'on the fly'.
>>
>> A very convenient option , but I wonder if it shouldn't be an option
>> that should be explicitly selected by the user?
>
> I very strongly agree and I think that such an important decision 
> should have been discussed on the ML (if it was, sorry, I must have 
> missed it). The relevant changes, AFAICT, are r65751 (v.import) and 
> r65917 (r.import).
>
> I don't have a strong opinion on this, but I think that there is some 
> advantage to GRASS telling the user that the file she is trying to 
> import is in a different projection than the location and that 
> explicit use of v./r.import would necessary.
The explicit choice could still be included in the GUI, but should, I 
think, be off by default.
>
> Now the import wizard just silently imports anything without even 
> informing the user that reprojection is happening. 
I can't remember the exact words, but a line is shown telling that the 
data has been projected when the import is finished. Easy to miss 
though, especially for users not really aware their data is in another 
projection.

> This does not always make sense and is a potential path to many 
> disasters...

I would say it is a sure path to disasters.. not always, but there will 
be some
>
> Projection handling is not easy, but IMHO it is one of the strengths 
> of GRASS to force the user to think about it. I agree that r./v.import 
> are a very nice convenience, but their use should at least result from 
> a conscious decision, not out of ignorance...
>
> Moritz