geo/algorithm/
geodesic_bearing.rs

1use crate::Point;
2use geo_types::CoordNum;
3use geographiclib_rs::{Geodesic, InverseGeodesic};
4
5/// Returns the bearing to another Point in degrees on a geodesic.
6///
7/// This uses the geodesic methods given by [Karney (2013)].
8///
9/// [Karney (2013)]:  https://arxiv.org/pdf/1109.4448.pdf
10pub trait GeodesicBearing<T: CoordNum> {
11    /// Returns the bearing to another Point in degrees, where North is 0° and East is 90°.
12    ///
13    /// # Examples
14    ///
15    /// ```
16    /// # #[macro_use] extern crate approx;
17    /// #
18    /// use geo::GeodesicBearing;
19    /// use geo::Point;
20    ///
21    /// let p_1 = Point::new(9.177789688110352, 48.776781529534965);
22    /// let p_2 = Point::new(9.27411867078536, 48.8403266058781);
23    /// let bearing = p_1.geodesic_bearing(p_2);
24    /// assert_relative_eq!(bearing, 45., epsilon = 1.0e-6);
25    /// ```
26    fn geodesic_bearing(&self, point: Point<T>) -> T;
27
28    /// Returns the bearing and distance to another Point in a (bearing, distance) tuple.
29    ///
30    /// # Units
31    ///
32    /// - `bearing`: degrees, zero degrees is north. East is 90°.
33    /// - `distance`: meters
34    ///
35    /// # Examples
36    ///
37    /// ```
38    /// # #[macro_use] extern crate approx;
39    /// #
40    /// use geo::GeodesicBearing;
41    /// use geo::Point;
42    ///
43    /// let p_1 = Point::new(9.177789688110352, 48.776781529534965);
44    /// let p_2 = Point::new(9.27411867078536, 48.8403266058781);
45    /// let (bearing, distance) = p_1.geodesic_bearing_distance(p_2);
46    /// assert_relative_eq!(bearing, 45., epsilon = 1.0e-6);
47    /// assert_relative_eq!(distance, 10000., epsilon = 1.0e-6);
48    /// ```
49    fn geodesic_bearing_distance(&self, point: Point<T>) -> (T, T);
50}
51
52impl GeodesicBearing<f64> for Point<f64> {
53    fn geodesic_bearing(&self, rhs: Point<f64>) -> f64 {
54        let (azi1, _, _) = Geodesic::wgs84().inverse(self.y(), self.x(), rhs.y(), rhs.x());
55        azi1
56    }
57
58    fn geodesic_bearing_distance(&self, rhs: Point<f64>) -> (f64, f64) {
59        let (distance, azi1, _, _) =
60            Geodesic::wgs84().inverse(self.y(), self.x(), rhs.y(), rhs.x());
61        (azi1, distance)
62    }
63}
64
65#[cfg(test)]
66mod test {
67    use super::*;
68    use crate::point;
69
70    #[test]
71    fn north_bearing() {
72        let p_1 = point!(x: 9., y: 47.);
73        let p_2 = point!(x: 9., y: 48.);
74        let bearing = p_1.geodesic_bearing(p_2);
75        assert_relative_eq!(bearing, 0.);
76    }
77
78    #[test]
79    fn east_bearing() {
80        let p_1 = point!(x: 9., y: 10.);
81        let p_2 = point!(x: 18.118501133357412, y: 9.875322179340463);
82        let bearing = p_1.geodesic_bearing(p_2);
83        assert_relative_eq!(bearing, 90.);
84    }
85
86    #[test]
87    fn northeast_bearing() {
88        let p_1 = point!(x: 9.177789688110352f64, y: 48.776781529534965);
89        let p_2 = point!(x: 9.27411867078536, y: 48.8403266058781);
90        let bearing = p_1.geodesic_bearing(p_2);
91        assert_relative_eq!(bearing, 45., epsilon = 1.0e-11);
92    }
93
94    #[test]
95    fn consistent_with_destination() {
96        use crate::algorithm::GeodesicDestination;
97        let p_1 = point!(x: 9.177789688110352, y: 48.776781529534965);
98        let p_2 = p_1.geodesic_destination(45., 10000.);
99        let (bearing, distance) = p_1.geodesic_bearing_distance(p_2);
100        assert_relative_eq!(bearing, 45., epsilon = 1.0e-11);
101        assert_relative_eq!(distance, 10000.0, epsilon = 1.0e-9);
102    }
103}
geo/algorithm/geodesic_bearing.rs

geo/algorithm/
geodesic_bearing.rs
