NASA Digital Elevation Model (NASADEM)

Load and query NASADEM/SRTM tiles for earth elevation data. NASADEM is a refinement over the original SRTM dataset collected during the STS-99 Space Suttle mission. The file format (.hgt) is identical between the orignal SRTM and NASADEM datasets, and this library handles both transparently.

Usage

use nasadem::{geo::Coord, Tile};

/// Sample tile included in this repo.
let tile_path = format!(
    "{}/../data/nasadem/1arcsecond/N38W105.hgt",
    env!("CARGO_MANIFEST_DIR")
);

let tile = Tile::load(tile_path).unwrap();

// Query the tile with a absolute geograpic
// coordinates and assert the elevation is 3772 meters.
assert_eq!(
    tile.get(Coord {
        x: -104.993_472_222_222_22,
        y: 38.790_972_222_222_22,
    }),
    Some(3772)
);

// Query the tile with a linear index and
// assert the elevation is 3772 meters.
assert_eq!(tile.get(2_707_976), Some(3772));

// Query the tile with a relative cartesian
// index and assert the elevation is 3772 meters.
assert_eq!(tile.get((24, 752)), Some(3772));

Helpful Resources:

• 30-Meter SRTM Tile Downloader
• HGT File Layout
• Archive Team HGT Format
• SRTM Collection User Guide

Tile Layout

NASADEM height .hgt files use a simple, headerless binary format with no metadata. The only variable parameter—resolution—can be inferred from the file size.

Example: N51W001.hgt

For this example, a 3-arcsecond resolution tile (1201x1201) might be named N51W001.hgt. In this case, the bottom-left (southwest) corner of the tile is located at 51°N, 1°W. The the non-header values in the following table represent the linear offset of each i16 elevation value in the flat memory array.

Note that while NASADEM filenames correspond to the southwest corner of a tile, the first elevation value in a .hgt file is the northwest corner.

License

This project is licensed under one of the following licenses:

• Apache License 2.0 (LICENSE-APACHE or Apache License 2.0)
• MIT License (LICENSE-MIT or MIT License)

Contributions

By default, contributions you make to this project are considered dual-licensed under both the Apache 2.0 License and the MIT License, with no additional conditions.