[PROJ] Determine "cut line" for arbitrary projection

[Nyall Dawson]

On Sun, 9 Mar 2025 at 04:06, Javier Jimenez Shaw <j1 at jimenezshaw.com> wrote:
>
> If you mean in a generic way, I think the answer is no.
> Each projection has its own peculiarities and behaviours. Spilhaus (by the way, not yet in PROJ, but coming in 9.6.0) is a good example.

Testing Spilhaus in QGIS was actually the motivation for this
question. It works fine for rasters, but for vectors there's extreme
artifacts caused by rendering features crossing the boundaries of this
projection.

>
> "... latitude (or projected x coordinate) " Do you mean longitude? See that the longitude you are looking for may depend on the latitude.

🤦 of course! (*although for the above mentioned Spilhaus projection I
guess we'd need something more complex than a single line longitude
line anyway!)

Nyall

>
>
> On Sat, 8 Mar 2025 at 07:30, Nyall Dawson via PROJ <proj at lists.osgeo.org> wrote:
>>
>> Hi list,
>>
>> A question: given an arbitrary projection/CRS, is it possible to determine the latitude (or projected x coordinate) at which features would need to be "cut" in order to avoid artifacts when those features wrap around the projection extremes.
>>
>> Eg if it was EPSG:4326, we'd need to cut the features at +/- 180. But if it's another projection... say mercator or spilhaus or ... is there any way to reliably determine this cutting line?
>>
>> Nyall
>>
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