# Terrain attribution and method

Source: Mapzen / Tilezen Terrain Tiles, anonymous AWS `elevation-tiles-prod` bucket. Registry: https://registry.opendata.aws/terrain-tiles/

Global SRTM and GMTED2010 terrain data courtesy of the U.S. Geological Survey. Global ETOPO1 terrain data: U.S. National Oceanic and Atmospheric Administration. Mapzen / Tilezen assembled the terrain tile service. The documented source datasets are public government data with their own source terms. The provider's full current attribution and data-source documents are authoritative; no blanket license is asserted over every possible upstream tile source.

- Attribution and source-specific terms: https://github.com/tilezen/joerd/blob/master/docs/attribution.md
- Source mosaic and footprints: https://github.com/tilezen/joerd/blob/master/docs/data-sources.md
- RGB encoding / projection: https://github.com/tilezen/joerd/blob/master/docs/formats.md
- SRTM: https://www.usgs.gov/centers/eros/science/usgs-eros-archive-digital-elevation-shuttle-radar-topography-mission-srtm-1

Reviewed 2026-10-27. SRTM and GMTED2010 are documented global land inputs. Exact contributing source rasters for each pixel have not been independently resolved from the footprints database. Do not describe these rendered windows as exclusively NASA SRTM or as a survey.

The art is original topographic contour linework, not copied recipe artwork. The generator bilinearly samples source tiles into a local equirectangular grid and triangulates that measured heightfield. It uses the unchanged float32 vertices and faces with a schematic plinth and 5x vertical exaggeration. Horizontal plane/triangle intersections produce real 100 m elevation contours. An isometric orthographic projection and depth buffer remove hidden lines; visible paths are simplified within 0.35 SVG pixels. Cut-wall hatching is schematic material shading, not geological strata. The north arrow follows the projection. Both device sizes use vector lines; themes invert ink/paper without changing geometry. Consult manifest.json for bounds, source URLs/hashes, sampling distances, projection, contour interval/levels and sampled elevation range. Printing remains inactive; earlier local exports are preserved as historical artifacts.

Windows are editorial selections near the named origin, not legal geographical-indication boundaries, farm locations or coffee planting coverage. DEM heights do not establish coffee-growing elevations. These data are unsuitable for navigation or engineering work.

An invalid negative source spike in the initial Huehuetenango candidate was rejected. The delivered southern window excludes that artifact; no heights were patched. Its choice is documented in `data/origins.json` and `manifest.json`.