/** Mean Earth radius in kilometres (the `haversine` default). */
export declare const EARTH_RADIUS_KM = 6371.0088;
/**
 * Great-circle (haversine) distance between two latitude/longitude points given
 * in **degrees**. Returns the distance in the units of `radius` (default: km on
 * mean-Earth-radius).
 */
export declare function haversine(lat1: number, lon1: number, lat2: number, lon2: number, radius?: number): number;
type Vec3 = readonly [number, number, number] | readonly number[];
type Quat = readonly [number, number, number, number] | readonly number[];
/**
 * Spherical linear interpolation between two vectors (treated as directions on a
 * sphere). `t ∈ [0,1]`; result has interpolated direction and magnitude. Falls back
 * to linear interpolation when the vectors are nearly parallel.
 */
export declare function slerp(v0: readonly number[], v1: readonly number[], t: number): number[];
/** Hamilton product of two quaternions `[w, x, y, z]`. */
export declare function quaternionMultiply(q1: Quat, q2: Quat): number[];
/** Quaternion conjugate `[w, −x, −y, −z]`. */
export declare function quaternionConjugate(q: Quat): number[];
/** Unit-normalize a quaternion. */
export declare function quaternionNormalize(q: Quat): number[];
/** Unit quaternion for a rotation of `angle` radians about (unit-normalized) `axis`. */
export declare function quaternionFromAxisAngle(axis: Vec3, angle: number): number[];
/** Rotate a 3-vector by a (unit) quaternion: `q · [0,v] · q⁻¹`. */
export declare function quaternionRotate(q: Quat, v: Vec3): number[];
/** 3×3 rotation matrix for a (unit) quaternion `[w, x, y, z]`. */
export declare function quaternionToRotationMatrix(q: Quat): number[][];
export {};
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