Conclusion:

From below

Ok so this is a bug in pymartini in rescale_positions. Specifically, when you set column_row=False you're using a different transposed matrix for the Martini errors step and for the terrain lookup step!

So basically column_row should always be True so that you're using the same axis ordering for generating the mesh and the terrain lookup, and just add better documentation about whether a .T is needed before passing the tile to pymartini.

Todo:

• Remove column_row option; make it always True
• Add docs about needing to transpose input matrix

This tile has a way higher mesh max error than it should.

It should be easy to find this tile's OSM index from the example viewer, then it could be anywhere in:

• Terrarium tile (unlikely) Ruled out here
• Decoding (unlikely)
• Mesh generation (possible)
• Encoding (possible)
• Decoding (unlikely)
• Rendering (unlikely) Ruled out here