possible mapping issue over Antarctica

[tricaric]

maplibre-gl-js version: 5.1.0

browser: Chrome/Safari/Firefox on Mac, Safari/iOS

Steps to Trigger Behavior

This bug was originally reported here: hyperknot/openfreemap#59

When using a "globe" projection, there's seems to be a tiling issue over Antarctica, most easily visible when using the openfreemap with

style: "https://tiles.openfreemap.org/styles/positron"

Alternatively, this issue can also be observed with the example: https://maplibre.org/maplibre-gl-js/docs/examples/globe-zoom-planet-size-function/

Similar issue in the same spot, see attached images.

Link to Demonstration

[HarelM]

Yeah, the mathematics around the poles is problematic...
Feel free to investigate.

[kubapelc]

There is no data in the map source outside the web mercator range, so globe has to fill in the blanks somehow. It interpolates anything it finds on the edge towards the poles. This effect is nicely visible if you use raster maps, such as satellite. That blue spike is just a part of the ocean that crosses the edge of web mercator around ~85° latitude, so it gets interpolated all the way to the pole.

[HarelM]

@kubapelc can we add this information to the globe.md readme? I think this is a valuable information.
Thanks for looking into this!