{
  "name": "China DEM, bilinearly resampled from Mapzen Terrain Tiles zoom 6",
  "width": 1800,
  "height": 1240,
  "bounds": {
    "west": 72.5,
    "east": 135.5,
    "south": 17.0,
    "north": 54.5
  },
  "crs": "EPSG:4326 (regular longitude/latitude sample grid)",
  "sampleAlignment": "inclusive bounds: lon=west+x/(width-1)*(east-west), lat=north-y/(height-1)*(north-south)",
  "rows": "north to south",
  "columns": "west to east",
  "heightUnit": "metres",
  "elevationMin": -7623.084850623729,
  "elevationMax": 8037.795035848649,
  "retainsNegativeElevationsAndOceanBathymetry": true,
  "source": {
    "provider": "Mapzen / Tilezen Terrain Tiles, AWS Open Data",
    "tileUrl": "https://s3.amazonaws.com/elevation-tiles-prod/terrarium/{z}/{x}/{y}.png",
    "zoom": 6,
    "tileSize": 256,
    "crs": "EPSG:3857",
    "tileBounds": {
      "xMin": 44,
      "xMax": 56,
      "yMin": 20,
      "yMax": 28
    },
    "tileCount": 117,
    "downloadBytes": 8976950,
    "accessedAt": "2026-09-27T10:35:29.825605+00:00",
    "dataSourcesAtZoom6": {
      "land": "USGS GMTED2010",
      "ocean": "NOAA ETOPO1"
    },
    "nominalPixelSpacingMetresAtLatitude35": 2003.6335353336838,
    "sourceDocumentation": "https://github.com/tilezen/joerd/blob/master/docs/data-sources.md",
    "formatDocumentation": "https://github.com/tilezen/joerd/blob/master/docs/formats.md",
    "attributionDocumentation": "https://github.com/tilezen/joerd/blob/master/docs/attribution.md",
    "registry": "https://registry.opendata.aws/terrain-tiles/"
  },
  "processing": "Decode source Terrarium RGB to elevation metres, mosaic 256x256 tiles, bilinearly resample elevations to an inclusive EPSG:4326 regular grid. No fabricated terrain, smoothing, sea-level clipping, or vertical exaggeration has been applied.",
  "files": {
    "china-dem-1800x1240-terrarium.png": {
      "encoding": "RGB Terrarium",
      "decode": "R*256+G+B/256-32768",
      "maximumQuantizationErrorMetres": 0.001953125
    },
    "china-dem-1800x1240-u16le.bin": {
      "encoding": "Uint16 little-endian, row-major",
      "decode": "value-32768",
      "maximumQuantizationErrorMetres": 0.5
    },
    "china-dem-1800x1240-height16.png": {
      "encoding": "16-bit grayscale PNG",
      "decode": "value-32768",
      "maximumQuantizationErrorMetres": 0.5,
      "browserWarning": "Canvas getImageData typically returns 8-bit channels; use a Terrarium RGB PNG for browser decoding, not this grayscale PNG."
    },
    "china-dem-1800x1240-terrarium-metre.png": {
      "encoding": "RGB Terrarium with integer metre precision",
      "decode": "R*256+G+B/256-32768",
      "maximumQuantizationErrorMetres": 0.5,
      "recommendedForBrowser": true
    }
  },
  "attribution": "Terrain data: Mapzen / Tilezen; GMTED2010 courtesy of the U.S. Geological Survey; ETOPO1 from NOAA / NCEI. Resampled to a longitude/latitude grid for this visualization.",
  "attributionChinese": "地形数据：Mapzen / Tilezen；陆地高程来自美国地质调查局 GMTED2010，海底地形来自 NOAA / NCEI ETOPO1。本图已重采样为经纬度网格。",
  "limitations": "Zoom 6 is about 2 km per pixel at 35 degrees latitude. The 1800x1240 image is resampled and does not create additional source detail. Suitable for national-scale relief, not local engineering, navigation or fine geological measurement. Elevation data provide surface relief only and do not establish geology or strata ages."
}