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geographiclib-rs

A subset of geographiclib implemented in Rust.

Currently this implements the direct and the inverse geodesic calculations.

If instead you are looking for Rust bindings to Karney's C++ implementation, see https://crates.io/geographiclib.

Examples

// Determine the point 10000 km NE of JFK - the "direct" geodesic calculation.
use geographiclib_rs::{Geodesic, DirectGeodesic};

let g = Geodesic::wgs84();
let jfk_lat = 40.64;
let jfk_lon = -73.78;
let northeast_azimuth = 45.0;

let (lat, lon, az) = g.direct(jfk_lat, jfk_lon, northeast_azimuth, 10e6);

use approx::assert_relative_eq;
assert_relative_eq!(lat, 32.621100463725796);
assert_relative_eq!(lon, 49.05248709295982);
assert_relative_eq!(az,  140.4059858768007);

// Determine the distance between two points - the "inverse" geodesic calculation.
use geographiclib_rs::{Geodesic, InverseGeodesic};

let g = Geodesic::wgs84();
let p1 = (34.095925, -118.2884237);
let p2 = (59.4323439, 24.7341649);
let s12: f64 = g.inverse(p1.0, p1.1, p2.0, p2.1);

use approx::assert_relative_eq;
assert_relative_eq!(s12, 9094718.72751138);

// Determine the perimeter and area of a polygon.
use geographiclib_rs::{Geodesic, PolygonArea, Winding};

let g = Geodesic::wgs84();
let mut pa = PolygonArea::new(&g, Winding::CounterClockwise);
pa.add_point(0.0, 0.0);
pa.add_point(0.0, 1.0);
pa.add_point(1.0, 1.0);
pa.add_point(1.0, 0.0);

let (perimeter_m, area_m_squared, num_points) = pa.compute(false);

use approx::assert_relative_eq;
assert_relative_eq!(perimeter_m, 443770.91724830196);
assert_relative_eq!(area_m_squared, 12308778361.469452);
assert_eq!(num_points, 4);

// Determine the distance between rovers Pathfinder and Curiosity on Mars
use geographiclib_rs::{Geodesic, InverseGeodesic};

let mars = Geodesic::new(3396190.0, 1.0 / 169.8944472);
let pathfinder = (19.26, 326.75);
let curiosity = (-4.765700445, 137.39820983);
let distance_m: f64 = mars.inverse(curiosity.0, curiosity.1, pathfinder.0, pathfinder.1);

assert_eq!(distance_m.round(), 9639113.0);

Features

accurate: Enabled by default. Use the accurate crate to provide high accuracy polygon areas and perimeters in PolygonArea. Can be disabled for better performance or when PolygonArea is not being used.

Benchmarking

To compare the direct and inverse geodesic calculation against the geographiclib c bindings, run:

cargo bench

Which produces output like:

direct (c wrapper)/default
                        time:   [24.046 µs 24.071 µs 24.099 µs]

direct (rust impl)/default
                        time:   [26.129 µs 26.168 µs 26.211 µs]

inverse (c wrapper)/default
                        time:   [45.061 µs 45.141 µs 45.227 µs]

inverse (rust impl)/default
                        time:   [67.739 µs 67.796 µs 67.865 µs]

Showing that, at least in this benchmark, the Rust implementation is 10-50% slower than the c bindings.