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use crate::GeodesicDistance;
use crate::{Line, LineString, MultiLineString};
/// Determine the length of a geometry on an ellipsoidal model of the earth.
///
/// This uses the geodesic measurement methods given by [Karney (2013)]. As opposed to older methods
/// like Vincenty, this method is accurate to a few nanometers and always converges.
///
/// [Karney (2013)]: https://arxiv.org/pdf/1109.4448.pdf
pub trait GeodesicLength<T, RHS = Self> {
/// Determine the length of a geometry on an ellipsoidal model of the earth.
///
/// This uses the geodesic measurement methods given by [Karney (2013)]. As opposed to older methods
/// like Vincenty, this method is accurate to a few nanometers and always converges.
///
///
/// # Units
///
/// - return value: meters
///
/// # Examples
///
/// ```
/// use geo::prelude::*;
/// use geo::LineString;
///
/// let linestring = LineString::from(vec![
/// // New York City
/// (-74.006, 40.7128),
/// // London
/// (-0.1278, 51.5074),
/// // Osaka
/// (135.5244559, 34.687455)
/// ]);
///
/// let length = linestring.geodesic_length();
///
/// assert_eq!(
/// 15_109_158., // meters
/// length.round()
/// );
/// ```
///
/// [Karney (2013)]: https://arxiv.org/pdf/1109.4448.pdf
fn geodesic_length(&self) -> T;
}
impl GeodesicLength<f64> for Line {
/// The units of the returned value is meters.
fn geodesic_length(&self) -> f64 {
let (start, end) = self.points();
start.geodesic_distance(&end)
}
}
impl GeodesicLength<f64> for LineString {
fn geodesic_length(&self) -> f64 {
let mut length = 0.0;
for line in self.lines() {
length += line.geodesic_length();
}
length
}
}
impl GeodesicLength<f64> for MultiLineString {
fn geodesic_length(&self) -> f64 {
let mut length = 0.0;
for line_string in &self.0 {
length += line_string.geodesic_length();
}
length
}
}