Implementing the QTM discrete global grid system (DGGS)

QTM Generator is a tool to make a Quaternary Triangular Mesh (QTM) to tessellate the planet geodetically into a discrete global grid system (DGGS) based on an octohedron. Each triangular facet resursively subdivides into four smaller ones to build a hierarchical mesh. It directly implements the geometry and tile indexing scheme developed by Geoffrey Dutton, and described in Dutton, Geoffrey H. "Planetary Modelling via Hierarchical Tessellation." In Procedings of the AutoCarto 9 Conference, 462–71. Baltimore, MD, 1989.