{
  "retrieved": "2026-10-28",
  "sources": [
    {
      "title": "Terrain Tiles \u2014 AWS Open Data Registry",
      "url": "https://registry.opendata.aws/terrain-tiles/",
      "license": "Open mosaic with per-source attribution, not a single blanket license."
    },
    {
      "title": "Mapzen/Tilenzen Terrarium format",
      "url": "https://github.com/tilezen/joerd/blob/master/docs/formats.md"
    },
    {
      "title": "Terrain data source attribution and licensing",
      "url": "https://github.com/tilezen/joerd/blob/master/docs/attribution.md",
      "local_copy": "ATTRIBUTION-source.txt"
    },
    {
      "title": "Three.js r180",
      "url": "https://github.com/mrdoob/three.js/tree/r180",
      "license": "MIT",
      "local_license": "../shared-viewer/vendor/THREE-LICENSE.txt"
    },
    {
      "title": "USGS 3DEP",
      "url": "https://elevation.nationalmap.gov/arcgis/rest/services/3DEPElevation/ImageServer",
      "license": "Public domain",
      "license_url": "https://data.usgs.gov/datacatalog/data/USGS%3A3a81321b-c153-416f-98b7-cc8e5f0e17c3",
      "local_copy": "new-york-usgs.tif"
    }
  ],
  "notes": [
    "DEM describes ground surface, not underground cave chambers.",
    "128\u00d7128 grid is a display generalization, not a survey or navigation model.",
    "Vertical exaggeration changes the visual scale only and is always labeled.",
    "Straight connecting lines show the order of overview stops; they are not GPS tracks or access routes."
  ]
}