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README.md

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+---
+license: other
+license_name: copernicus
+license_link: https://copernicus.eu/user-license
+task_categories:
+  - other
+tags:
+  - elevation
+  - dem
+  - copernicus
+  - terrain
+  - geospatial
+size_categories:
+  - 100K<n<1M
+---
+
+# Copernicus GLO-30 DEM Chunks
+
+Global Digital Elevation Model (DEM) tiles from the Copernicus GLO-30 dataset,
+pre-processed into 256x256 chunks in OZCHNK01 merged format for efficient
+web serving.
+
+## Source
+
+Copernicus DEM GLO-30 (30-meter resolution) from the European Space Agency.
+Original COG tiles downloaded from AWS Open Data:
+https://copernicus-dem-30m.s3.eu-central-1.amazonaws.com/
+
+## License
+
+Copernicus Licence (free for most uses). See: https://copernicus.eu/user-license
+
+## Format
+
+Binary merged format (OZCHNK01):
+
+- **Magic**: 8 bytes "OZCHNK01"
+- **Version**: 2 (Copernicus = Float32)
+- **Grid**: Variable ROWS x COLS (depends on tile dimensions)
+- **Index**: Array of [4-byte offset, 4-byte size] per chunk
+- **Data**: Concatenated zlib-compressed 256x256 Float32 chunks
+
+### Tile Grid
+
+- Internal COG tiles: 1024x1024 pixels
+- Each split into 4x4 = 16 chunks of 256x256
+- Edge tiles may have fewer chunks
+- Data type: Float32 (4 bytes/pixel)
+
+### File Naming
+
+Files are organized by latitude band:
+
+- Path: `{lat_dir}/{basename}.merged`
+- Example: `N00/COPDEM_N00_00_E006_00_DEM.merged`
+
+## Coverage
+
+Global land areas at 30m resolution (~90GB total, ~26,450 tiles).
+
+## Usage
+
+For use with OpenZenith elevation API. Each merged file contains all 256x256
+chunks for one Copernicus tile, allowing efficient range requests to fetch
+individual chunks.
+
+To read a chunk:
+
+1. Open the merged file
+2. Read the 12-byte header (magic + version + rows + cols)
+3. Read the index: rows*cols entries of [offset, size]
+4. Seek to the chunk offset, read size bytes
+5. Decompress with zlib to get 256x256 Float32 pixel data
+6. Elevation value = float32 at row*256 + col