Tile coordinate scheme

[jvntf]

Hi thanks for the great work with tin-terrain! I am just a bit confused as to how the tile indices are calculated. The X and Z coordinates seem to match up with with the OSM spec but the Y coord does not align. Is it possible that I have just done something wrong in the generation of my tiles? I reprojected my DEM raster to 3857, and then ran the tin-terrain tool as instructed in the README. Thanks in advance for any guidance!

If it helps, I am trying to load terrain mesh tiles and render them with deck.gl.