Distance Between GPS Points

distance-between-gps-points.js

/*
* get DMS from DD
*/
function getDms(val) {
  let degrees, minutes, seconds, result;

  val = Math.abs(val);

  degrees = Math.floor(val);
  result = degrees + "º ";

  minutes = Math.floor((val - degrees) * 60);
  result += minutes + "' ";

  seconds = Math.round((val - degrees - minutes / 60) * 3600 * 1000) / 1000;
  result += seconds + '" ';

  return result;
}

/*
* finalize conversion from DD to DMS
* returns coordinates as a string in format X-XX° X-XX′ X-XX″ (N|S), X-XX° X-XX′ X-XX″ (E|W)
*/
function ddToDms(lat, lng) {
   let latDMS, lngDMS, resultDMS;

   lat = parseFloat(lat);  
   lng = parseFloat(lng);

   latDMS = getDms(lat);
   latDMS += (lat >= 0)? 'N' : 'S';

   lngDMS = getDms(lng);
   lngDMS += (lng >= 0)? 'E' : 'W';

   resultDMS = latDMS + ', ' + lngDMS;

   return resultDMS;
}

/*
* get distance between two GPS coordinates
* returns distance between GPS coordinates in kilometers
* coordinates should be provided in format X-XX° X-XX′ X-XX″ (N|S), X-XX° X-XX′ X-XX″ (E|W)
*/
function getDistance(coord1, coord2) {
  coord1 = coord1.split(', ').map(item => unescape(item).split(/[º'"]\s/));
  coord2 = coord2.split(', ').map(item => unescape(item).split(/[º'"]\s/));
  const R = 6371;
  let lat1 = (coord1[0][3] === 'S') ? -1 : 1;
  let lat2 = (coord2[0][3] === 'S') ? -1 : 1;
  let lon1 = (coord1[1][3] === 'W') ? -1 : 1;
  let lon2 = (coord2[1][3] === 'W') ? -1 : 1;

  coord1 = coord1.map(item => item.map(itm => parseInt(itm)));
  coord2 = coord2.map(item => item.map(itm => parseInt(itm)));
  
  lat1 = lat1 * (coord1[0][0] + (coord1[0][1] + coord1[0][2] / 60) / 60);
  lat2 = lat2 * (coord2[0][0] + (coord2[0][1] + coord2[0][2] / 60) / 60);
  lon1 = lon1 * (coord1[1][0] + (coord1[1][1] + coord1[1][2] / 60) / 60);
  lon2 = lon2 * (coord2[1][0] + (coord2[1][1] + coord2[1][2] / 60) / 60);
  
  const latDiff = (lat2 - lat1) * Math.PI / 180;
  const lonDiff = (lon2 - lon1) * Math.PI / 180;
  
  lat1 = lat1 * Math.PI / 180;
  lat2 = lat2 * Math.PI / 180;
  lon1 = lon1 * Math.PI / 180;
  lon2 = lon2 * Math.PI / 180;
  
  const x = Math.pow(Math.sin(latDiff/2), 2) + Math.pow(Math.sin(lonDiff/2), 2) * Math.cos(lat1) * Math.cos(lat2); 
  const y = 2 * Math.atan2(Math.sqrt(x), Math.sqrt(1 - x));
  const distance = R * y;
  return distance;
}

/*
* TEST 1
*/
let coord1 = '47° 28′ 0″ N, 13° 2′ 0″ E';
let coord2 = '47° 28′ 0″ N, 13° 2′ 0″ E';

const distance1 = getDistance(coord1, coord2); // 0
console.log('distance1:', distance1);

/*
* TEST 2
* convert given DD coordinates to DMS first, then get distance
*/
const lat1 = 90;
const lng1 = 81;
const lat2 = 45;
const lng2 = 93;

const dmsCoords1 = ddToDms(lat1, lng1);
const dmsCoords2 = ddToDms(lat2, lng2);
console.log('dmsCoords1:', dmsCoords1);
console.log('dmsCoords2:', dmsCoords2);

const distance2 = getDistance(dmsCoords1, dmsCoords2);
console.log('distance2:', distance2);

DistanceBetweenGPSPoints.markdown

Distance Between GPS Points

Function getDistance(coord1, coord2) returns distance between GPS coordinates in kilometers.

Coordinates should be provided in format X-XX° X-XX′ X-XX″ (N|S), X-XX° X-XX′ X-XX″ (E|W).

To calculate distance between GPS coordinates in DD format, first convert it to DMS by using a function ddtoDms(lat, lng) and provide result for getDistance function, i.e. getDistance(ddToDms(lat1, lng1), ddToDms(lat2, lng2))

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