geo/algorithm/
haversine_distance.rs

1use crate::{CoordFloat, Point, MEAN_EARTH_RADIUS};
2use num_traits::FromPrimitive;
3
4/// Determine the distance between two geometries using the [haversine formula].
5///
6/// [haversine formula]: https://en.wikipedia.org/wiki/Haversine_formula
7///
8/// *Note*: this implementation uses a mean earth radius of 6371.088 km, based on the [recommendation of
9/// the IUGG](ftp://athena.fsv.cvut.cz/ZFG/grs80-Moritz.pdf)
10pub trait HaversineDistance<T, Rhs = Self> {
11    /// Determine the distance between two geometries using the [haversine
12    /// formula].
13    ///
14    /// # Units
15    ///
16    /// - return value: meters
17    ///
18    /// # Examples
19    ///
20    /// ```
21    /// use geo::prelude::*;
22    /// use geo::point;
23    ///
24    /// // New York City
25    /// let p1 = point!(x: -74.006f64, y: 40.7128f64);
26    ///
27    /// // London
28    /// let p2 = point!(x: -0.1278f64, y: 51.5074f64);
29    ///
30    /// let distance = p1.haversine_distance(&p2);
31    ///
32    /// assert_eq!(
33    ///     5_570_230., // meters
34    ///     distance.round()
35    /// );
36    /// ```
37    ///
38    /// [haversine formula]: https://en.wikipedia.org/wiki/Haversine_formula
39    fn haversine_distance(&self, rhs: &Rhs) -> T;
40}
41
42impl<T> HaversineDistance<T, Point<T>> for Point<T>
43where
44    T: CoordFloat + FromPrimitive,
45{
46    fn haversine_distance(&self, rhs: &Point<T>) -> T {
47        let two = T::one() + T::one();
48        let theta1 = self.y().to_radians();
49        let theta2 = rhs.y().to_radians();
50        let delta_theta = (rhs.y() - self.y()).to_radians();
51        let delta_lambda = (rhs.x() - self.x()).to_radians();
52        let a = (delta_theta / two).sin().powi(2)
53            + theta1.cos() * theta2.cos() * (delta_lambda / two).sin().powi(2);
54        let c = two * a.sqrt().asin();
55        T::from(MEAN_EARTH_RADIUS).unwrap() * c
56    }
57}
58
59#[cfg(test)]
60mod test {
61    use crate::HaversineDistance;
62    use crate::Point;
63
64    #[test]
65    fn distance1_test() {
66        let a = Point::new(0., 0.);
67        let b = Point::new(1., 0.);
68        assert_relative_eq!(
69            a.haversine_distance(&b),
70            111195.0802335329_f64,
71            epsilon = 1.0e-6
72        );
73    }
74
75    #[test]
76    fn distance2_test() {
77        let a = Point::new(-72.1235, 42.3521);
78        let b = Point::new(72.1260, 70.612);
79        assert_relative_eq!(
80            a.haversine_distance(&b),
81            7130580.307935911_f64,
82            epsilon = 1.0e-6
83        );
84    }
85
86    #[test]
87    fn distance3_test() {
88        // this input comes from issue #100
89        let a = Point::new(-77.036585, 38.897448);
90        let b = Point::new(-77.009080, 38.889825);
91        assert_relative_eq!(
92            a.haversine_distance(&b),
93            2526.823504306046_f64,
94            epsilon = 1.0e-6
95        );
96    }
97
98    #[test]
99    fn distance3_test_f32() {
100        // this input comes from issue #100
101        let a = Point::<f32>::new(-77.03658, 38.89745);
102        let b = Point::<f32>::new(-77.00908, 38.889825);
103        assert_relative_eq!(a.haversine_distance(&b), 2526.8354_f32, epsilon = 1.0e-6);
104    }
105}
geo/algorithm/haversine_distance.rs

geo/algorithm/
haversine_distance.rs
