Get a distance from a location using HTML geolocation

distance.js

var calculateDistance = function(location1, location2) {
    // this is where we want to calculate the distance from. You can of course split this out so that the function 
    var origin = {longitude:50,latitude:1};

    // first calculate the locations into radians.
    var radlat1 = Math.PI * location1.latitude/180;
    var radlat2 = Math.PI * location2.latitude/180;
    var radlon1 = Math.PI * location1.longitude/180;
    var radlon2 = Math.PI * location2.longitude/180;
    var theta = location2.longitude-location1.latitude;
    var radtheta = Math.PI * theta/180

    // this is where we do the SOHCAHTOA trigonometry bits
    var distance = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
    distance = Math.acos(distance)
    distance = distance * 180/Math.PI

    // 1.1515 is to take into account the curvature of the earth
    // the only works on small distances due to the earth not being spherical
    distance = distance * 60 * 1.1515

    // distance is now in miles
    return distance;
}


navigator.geolocation.getCurrentPosition(function(result) {
    var location = data.coords;

    // get the distance to a specific a location
    var origin = {longitude: 50, latitude:1};
    var distance = calculateDistance(location,origin);

    // run your logic on distance
});

Hi!

I tried to use your script but I think (after comparing with other code) you have to edit theta:

var theta = location2.longitude-location1.longitude;

I know it's been a long time, but I came across this page after looking for an algorithm on google.