geo 0.29.3

Geospatial primitives and algorithms
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130

use super::Distance;
use crate::{CoordFloat, Line, LineString, MultiLineString, Point};

/// Calculate the length of a `Line`, `LineString`, or `MultiLineString` in a given [metric space](crate::algorithm::line_measures::metric_spaces).
///
/// # Examples
/// ```
/// use geo::algorithm::line_measures::{Length, Euclidean, Haversine};
///
/// let line_string = geo::wkt!(LINESTRING(
///     0.0 0.0,
///     3.0 4.0,
///     3.0 5.0
/// ));
/// assert_eq!(line_string.length::<Euclidean>(), 6.);
///
/// let line_string_lon_lat = geo::wkt!(LINESTRING (
///     -47.9292 -15.7801f64,
///     -58.4173 -34.6118,
///     -70.6483 -33.4489
/// ));
/// assert_eq!(line_string_lon_lat.length::<Haversine>().round(), 3_474_956.0);
/// ```
pub trait Length<F: CoordFloat> {
    fn length<MetricSpace: Distance<F, Point<F>, Point<F>>>(&self) -> F;
}

impl<F: CoordFloat> Length<F> for Line<F> {
    fn length<MetricSpace: Distance<F, Point<F>, Point<F>>>(&self) -> F {
        MetricSpace::distance(self.start_point(), self.end_point())
    }
}

impl<F: CoordFloat> Length<F> for LineString<F> {
    fn length<MetricSpace: Distance<F, Point<F>, Point<F>>>(&self) -> F {
        let mut length = F::zero();
        for line in self.lines() {
            length = length + line.length::<MetricSpace>();
        }
        length
    }
}

impl<F: CoordFloat> Length<F> for MultiLineString<F> {
    fn length<MetricSpace: Distance<F, Point<F>, Point<F>>>(&self) -> F {
        let mut length = F::zero();
        for line in self {
            length = length + line.length::<MetricSpace>();
        }
        length
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{coord, Euclidean, Geodesic, Haversine, Rhumb};

    #[test]
    fn lines() {
        // london to paris
        let line = Line::new(
            coord!(x: -0.1278f64, y: 51.5074),
            coord!(x: 2.3522, y: 48.8566),
        );

        assert_eq!(
            343_923., // meters
            line.length::<Geodesic>().round()
        );
        assert_eq!(
            341_088., // meters
            line.length::<Rhumb>().round()
        );
        assert_eq!(
            343_557., // meters
            line.length::<Haversine>().round()
        );

        // computing Euclidean length of an unprojected (lng/lat) line gives a nonsense answer
        assert_eq!(
            4., // nonsense!
            line.length::<Euclidean>().round()
        );
        // london to paris in EPSG:3035
        let projected_line = Line::new(
            coord!(x: 3620451.74f64, y: 3203901.44),
            coord!(x: 3760771.86, y: 2889484.80),
        );
        assert_eq!(344_307., projected_line.length::<Euclidean>().round());
    }

    #[test]
    fn line_strings() {
        let line_string = LineString::new(vec![
            coord!(x: -58.3816f64, y: -34.6037), // Buenos Aires, Argentina
            coord!(x: -77.0428, y: -12.0464),    // Lima, Peru
            coord!(x: -47.9292, y: -15.7801),    // Brasília, Brazil
        ]);

        assert_eq!(
            6_302_220., // meters
            line_string.length::<Geodesic>().round()
        );
        assert_eq!(
            6_332_790., // meters
            line_string.length::<Rhumb>().round()
        );
        assert_eq!(
            6_304_387., // meters
            line_string.length::<Haversine>().round()
        );

        // computing Euclidean length of an unprojected (lng/lat) gives a nonsense answer
        assert_eq!(
            59., // nonsense!
            line_string.length::<Euclidean>().round()
        );
        // EPSG:102033
        let projected_line_string = LineString::from(vec![
            coord!(x: 143042.46f64, y: -1932485.45), // Buenos Aires, Argentina
            coord!(x: -1797084.08, y: 583528.84),    // Lima, Peru
            coord!(x: 1240052.27, y: 207169.12),     // Brasília, Brazil
        ]);
        assert_eq!(
            6_237_538.,
            projected_line_string.length::<Euclidean>().round()
        );
    }
}