[gdal-dev] Spatial references and geometry operations

[adamgutonski]

Thank you for the response Paul, it sounds like I'll be safe as long as I include the SRS :)

Cheers,
Adam

Sent with [Proton Mail](https://proton.me/) secure email.

------- Original Message -------
On Friday, September 29th, 2023 at 4:20 AM, Paul Harwood <runette at gmail.com> wrote:

> As a very general response, you probably need to differentiate between two possible questions that you are asking, either:
>
> 1 Does the operation fail with an error, or
> 2 Is the result correct or meaningful?
>
> I don't know about 1). My guess and experience is that, in most cases, it won't fail.
>
> However, I would make the case that most operations are undefined if the system is making (possibly) unknown assumptions about the CRS. If you are asking for the point at a distance along a line or a buffer then you are implicitly or explicitly giving the system an input distance, so you are making assumptions about the CRS of your input. If your assumptions do not match the system's assumptions for the CRS, then the result will be wrong. I would say that it is always better to make the definition of the CRS explicit and then the result is defined.
>
> On Fri, 29 Sept 2023 at 03:32, adamgutonski via gdal-dev <gdal-dev at lists.osgeo.org> wrote:
>
>> Hello,
>>
>> I am using geometry object functions like Buffer and Value. I am wondering if and when it is necessary to assign a spatial reference to an ogr.Geometry before calling these functions? For example if I want to get a point along the line using Value is the output affected by whether or not the ogr line geometry has an assigned spatial reference? Is there a way to tell what geometry functions are affected by this or not?
>>
>> Thanks,
>> Adam Gutonski
>>
>> Sent with [Proton Mail](https://proton.me/) secure email.
>> _______________________________________________
>> gdal-dev mailing list
>> gdal-dev at lists.osgeo.org
>> https://lists.osgeo.org/mailman/listinfo/gdal-dev
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/gdal-dev/attachments/20230929/d7a1548a/attachment.htm>