The default radius is Earth’s radius of 6378137 meters. But Mike in the Haversine above uses 6371km instead.

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If you want to calculate it yourself, then you can use the Haversine formula:

var rad = function(x) { return x * Math.PI / 180; }; var getDistance = function(p1, p2) { var R = 6378137; // Earthâ€™s mean radius in meter var dLat = rad(p2.lat() - p1.lat()); var dLong = rad(p2.lng() - p1.lng()); var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) + Math.cos(rad(p1.lat())) * Math.cos(rad(p2.lat())) * Math.sin(dLong / 2) * Math.sin(dLong / 2); var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a)); var d = R * c; return d; // returns the distance in meter };

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There actually seems to be a method in GMap3. It’s a static method of the google.maps.geometry.spherical namespace.

It takes as arguments two LatLng objects and will utilize a default Earth radius of 6378137 meters, although the default radius can be overridden with a custom value if necessary.

Make sure you include:

<script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=false&v=3&libraries=geometry"></script>

in your head section.

The call will be:

google.maps.geometry.spherical.computeDistanceBetween (latLngA, latLngB);

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Just add this to the beginning of your JavaScript code:

google.maps.LatLng.prototype.distanceFrom = function(latlng) { var lat = [this.lat(), latlng.lat()] var lng = [this.lng(), latlng.lng()] var R = 6378137; var dLat = (lat[1]-lat[0]) * Math.PI / 180; var dLng = (lng[1]-lng[0]) * Math.PI / 180; var a = Math.sin(dLat/2) * Math.sin(dLat/2) + Math.cos(lat[0] * Math.PI / 180 ) * Math.cos(lat[1] * Math.PI / 180 ) * Math.sin(dLng/2) * Math.sin(dLng/2); var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a)); var d = R * c; return Math.round(d); }

and then use the function like this:

var loc1 = new GLatLng(52.5773139, 1.3712427); var loc2 = new GLatLng(52.4788314, 1.7577444); var dist = loc2.distanceFrom(loc1); alert(dist/1000);

reff: https://stackoverflow.com/questions/1502590/calculate-distance-between-two-points-in-google-maps-v3