aman-backend/src/math/wgs84.ts

import { Angle } from './angle';

const EarthRadius = 6371000;

export class WGS84 {
  /// @brief Calculates the Haversine distance
  /// @param coordinate0 The first coordinate
  /// @param coordinate1 The second coordinate
  /// @return The haversine distance in metres
  static distance(
    coordinate0: { lat: number; lon: number },
    coordinate1: { lat: number; lon: number },
  ): number {
    const lat0 = Angle.deg2rad(coordinate0.lat);
    const lon0 = Angle.deg2rad(coordinate0.lon);
    const lat1 = Angle.deg2rad(coordinate1.lat);
    const lon1 = Angle.deg2rad(coordinate1.lon);

    const a =
      0.5 -
      Math.cos(lat1 - lat0) * 0.5 +
      Math.cos(lat0) * Math.cos(lat1) * (1 - Math.cos(lon1 - lon0) * 0.5);

    return 2 * EarthRadius * Math.asin(Math.sqrt(a));
  }

  /// @brief Projects coordinate based on the distance and bearing
  /// @param coordinate The root coordinate
  /// @param distance The distance in metres
  /// @param bearing The bearing in degree
  static project(
    coordinate: { lat: number; lon: number },
    distance: number,
    bearing: number,
  ): { lat: number; lon: number } {
    const lat0 = Angle.deg2rad(coordinate.lat);
    const lon0 = Angle.deg2rad(coordinate.lon);
    const radians = Angle.deg2rad(bearing);

    const lat1 = Math.asin(
      Math.sin(lat0) * Math.cos(distance / EarthRadius) +
        Math.cos(lat0) * Math.sin(distance / EarthRadius) * Math.cos(radians),
    );
    const lon1 =
      lon0 +
      Math.atan2(
        Math.sin(radians) * Math.sin(distance / EarthRadius) * Math.cos(lat0),
        Math.cos(distance / EarthRadius) - Math.sin(lat0) * Math.sin(lat1),
      );

    return { lat: Angle.rad2deg(lat1), lon: Angle.rad2deg(lon1) };
  }
}