Function arc 

pub fn arc(
    center: &GeoCoord,
    radius_m: f64,
    start_bearing: f64,
    end_bearing: f64,
    segments: usize,
) -> Vec<GeoCoord>

Generate an arc (partial circle) as a polyline.

Arguments

• center – centre point.
• radius_m – radius in meters.
• start_bearing – start angle in degrees (0 = north, 90 = east).
• end_bearing – end angle in degrees (swept clockwise from start).
• segments – number of segments in the arc (clamped to min 2).

Returns a list of points along the arc from start_bearing to end_bearing. Does not close the ring.