Crate nasadem 

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.

	Col 0	Col 1	Col 2	Col 3	…	Col 1200
Row 0	(52°N, 1°W) 0	1	2	3	…	(52°N, 0°) 1200
Row 1	1201	1202	1203	1204	…	2400
Row 2	2401	2402	2403	2404	…	3600
Row 3	3601	3602	3603	3604	…	4800
…	…	…	…	…	…	…
Row 1200	(51°N, 1°W) 1441200	1441201	1441202	1441203	…	(51°N, 0°) 1442400

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.

Re-exports

pub use geo;

Structs

Sample

A NASADEM elevation sample.

Tile

A NASADEM tile.

Enums

NasademError

TileIndex

Represents various ways to index into a Tile.

Type Aliases

C

Base floating point type used for all coordinates and calculations.

Elev

Bit representation of elevation samples.