atriusmaps-node-sdk/dist/cjs/src/utils/geodesy.js

This project provides an API to Atrius Personal Wayfinder maps within a Node environment. See the README.md for more information

'use strict';

/*
  This utility module contains a set of functions dealing with "Geodesy" - measurements of
  the earth, its surface and related geometry.

  For a more cohesive set of functions, see https://github.com/chrisveness/geodesy
*/

// degrees to radians
const toRadians = d => (d * Math.PI) / 180;

/**
 * Haversine formula for finding distance between two lat/lng points.
 * from https://www.movable-type.co.uk/scripts/latlong.html
 * @param {float} lat1 latitutde of point 1
 * @param {float} lng1 longitude of point 1
 * @param {float} lat2 latitutde of point 2
 * @param {float} lng2 longitude of point 2
 * @returns number (in meters) between p1 and p2
 */
function distance(lat1, lng1, lat2, lng2) {
  const R = 6371000; // approx. earth radius (meters)
  const φ1 = toRadians(lat1);
  const φ2 = toRadians(lat2);
  const Δφ = toRadians(lat2 - lat1);
  const Δλ = toRadians(lng2 - lng1);

  const a = Math.sin(Δφ / 2) * Math.sin(Δφ / 2) + Math.cos(φ1) * Math.cos(φ2) * Math.sin(Δλ / 2) * Math.sin(Δλ / 2);
  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

  return R * c;
}

function bearingToDirection(deg, T) {
  const names = [
    T('wayfinder:north'), // 0
    T('wayfinder:northeast'), // 45
    T('wayfinder:east'), // 90
    T('wayfinder:southeast'), // 135
    T('wayfinder:south'), // 180 / -180
    T('wayfinder:southwest'), // -135
    T('wayfinder:west'), // -90
    T('wayfinder:northwest'), // -45
  ];
  // normalize -180..180
  const d = ((deg + 180) % 360) - 180;

  const index = Math.round(d / 45);
  return names[(index + 8) % 8];
}

exports.bearingToDirection = bearingToDirection;
exports.distance = distance;
exports.toRadians = toRadians;