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QTM Generator

This script makes 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. We directly implement the geometry and tile indexing scheme developed by Geoffrey Dutton, and described in the following publication:

Dutton, Geoffrey H. "Planetary Modelling via Hierarchical Tessellation." In Procedings of the AutoCarto 9 Conference, 462–71. Baltimore, MD, 1989. https://pdfs.semanticscholar.org/875e/12ce948012b3eced58c0f1470dba51ef87ef.pdf

Written by Paulo Raposo (pauloj.raposo [at] outlook.com) and Randall Brown (ranbrown8448 [at] gmail.com) at the Department of Geography, University of Tennessee, Knoxville.

Usage:

All geometry is defined in WGS 84. The script outputs to a GeoJSON file for each hierarchical level in the QTM, making as many levels as the user requests.

The output folder specified must pre-exist. Output files are named qtmlvlX.geojson, where X is the integer number of the level, 0 or higher.

Examples on the command line:

Unix-like: python qtmgenerator.py /home/username/qtmfolder 12

Dependencies: