Function simplify_douglas_peucker 

pub fn simplify_douglas_peucker(
    coords: &[GeoCoord],
    epsilon: f64,
) -> Vec<GeoCoord>

Simplify a polyline using the Douglas-Peucker algorithm.

epsilon is the maximum allowed perpendicular distance in degrees (see module docs for the coordinate-space rationale). Smaller values retain more detail; zero retains every vertex.

Returns

A new Vec<GeoCoord> containing only the vertices that exceed the tolerance threshold, plus the first and last vertices which are always retained.

Edge cases

Input	Result
empty slice	empty Vec
1 vertex	that vertex (copied)
2 vertices	both vertices (copied)
epsilon <= 0.0	all vertices (no simplification)
epsilon is NaN	all vertices (no simplification – NaN comparisons always false)

Example

use rustial_engine::simplify_douglas_peucker;
use rustial_engine::GeoCoord;

let line = vec![
    GeoCoord::from_lat_lon(0.0, 0.0),
    GeoCoord::from_lat_lon(0.0, 0.5),  // collinear -- will be removed
    GeoCoord::from_lat_lon(0.0, 1.0),
];
let simplified = simplify_douglas_peucker(&line, 0.01);
assert_eq!(simplified.len(), 2);