I am searching to know the concept behind this since last month and till now I got these resources
- How do I calculate distance between two latitude-longitude points?
- geolib.js
- Function to calculate distance between two coordinates shows wrong
- Calculate distance, bearing and more between Latitude/Longitude points
But I still can't figure out the right distance between specified coordinates
As an instance, I have two coordinates
Start lat: 26.26594 Start long: 78.2095508 Destination lat: 21.24386 Destination long: 81.611
and I got the result as 655.358 KM, but actually (I had measured it using my bike's odometer) those are just ~3 KM far, then why I am getting this answer.
I had even checked for my implementation on that geolib.js (2nd item I have specified in the list items), it is also showing the same result (655.358).
I can't figure it out
JS
// initialising the distance calculation
function geoLocationInit() {
$('.fd-loc-err').html(''); // empty the error shown, if there is any already
$('.fd-dist-rest-user').html('<img src="/images/loader.gif" alt="loading"/>'); // loader
var options = {timeout:120000};
if (navigator.geolocation) {
navigator.geolocation.watchPosition(getLocation, gotError, options);
}
else {
locationError = 'Your Browser does not support geolocation';
showLocationError(locationError);
}
}
//finding the coordinates of user
function getLocation(current) {
var userLat = current.coords.latitude, userLong = current.coords.longitude;
var distance = getDistance(userLat, userLong, restLatitude, restLongitude);
$('.fd-dist-rest-user').html('~' + (distance/1000).toFixed(2) + ' km away'); // fd-dist-rest-user is the <div> tag where i have show the distance calculated
}
function toRad(value) {
return value * Math.PI / 180;
}
// calculating distance using Vincenty Formula
function getDistance(lat1, lon1, lat2, lon2) {
var a = 6378137, b = 6356752.314245, f = 1/298.257223563;
var L = toRad(lon2-lon1);
var U1 = Math.atan((1-f) * Math.tan(toRad(lat1)));
var U2 = Math.atan((1-f) * Math.tan(toRad(lat2)));
var sinU1 = Math.sin(U1), cosU1 = Math.cos(U1);
var sinU2 = Math.sin(U2), cosU2 = Math.cos(U2);
var lambda = L, lambdaP, iterLimit = 100;
do
{
var sinLambda = Math.sin(lambda), cosLambda = Math.cos(lambda);
var sinSigma = Math.sqrt((cosU2*sinLambda) * (cosU2*sinLambda) + (cosU1*sinU2-sinU1*cosU2*cosLambda) * (cosU1*sinU2-sinU1*cosU2*cosLambda));
if (sinSigma==0) return 0;
var cosSigma = sinU1*sinU2 + cosU1*cosU2*cosLambda;
var sigma = Math.atan2(sinSigma, cosSigma);
var sinAlpha = cosU1 * cosU2 * sinLambda / sinSigma;
var cosSqAlpha = 1 - sinAlpha*sinAlpha;
var cos2SigmaM = cosSigma - 2*sinU1*sinU2/cosSqAlpha;
if (isNaN(cos2SigmaM)) cos2SigmaM = 0;
var C = f/16*cosSqAlpha*(4+f*(4-3*cosSqAlpha));
lambdaP = lambda;
lambda = L + (1-C) * f * sinAlpha * (sigma + C*sinSigma*(cos2SigmaM+C*cosSigma*(-1+2*cos2SigmaM*cos2SigmaM)));
} while (Math.abs(lambda-lambdaP) > 1e-12 && --iterLimit>0);
if (iterLimit==0) return NaN
var uSq = cosSqAlpha * (a*a - b*b) / (b*b);
var A = 1 + uSq/16384*(4096+uSq*(-768+uSq*(320-175*uSq)));
var B = uSq/1024 * (256+uSq*(-128+uSq*(74-47*uSq)));
var deltaSigma = B*sinSigma*(cos2SigmaM+B/4*(cosSigma*(-1+2*cos2SigmaM*cos2SigmaM)-B/6*cos2SigmaM*(-3+4*sinSigma*sinSigma)*(-3+4*cos2SigmaM*cos2SigmaM)));
var s = b*A*(sigma-deltaSigma);
return s;
}
// Error handling for the geolocation
function gotError(error) {
switch(error.code) {
case 1:
locationError = 'You need to give the permission to use your location to calculate the distances between this restaurant and you <button class="btn btn-danger fd-detect-lctn-try-agn">Please try again</button>';
break;
case 2:
locationError = 'TIME OUT - You need to give permission to use your location to show the distance of this restaurant from your current position <button class="btn btn-danger fd-detect-lctn-try-agn">Please try again</button>';
break;
case 3:
locationError = 'It took to long getting your position, <button class="btn btn-danger fd-detect-lctn">Please try again</button>';
break;
default:
locationError = 'An unknown error has occurred, <button class="btn btn-danger fd-detect-lctn">Please try again</button>';
}
showLocationError(locationError);
}
function showLocationError(msg) {
$('.fd-loc-err').html(msg);
$('.fd-dist-rest-user').html('');
}
I am getting the latitude and longitude from my database then calling the geoLocationInit function on a button click (below is the following code)
restLongitude = response['longitude'];
restLatitude = response['latitude'];
geoLocationInit(); /* getting location initialisation */