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yanbab/distance.js

Created May 16, 2014 12:56
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distance between 2 lat/long coord
Raw
distance.js
/* This function calculates distance with the Haversine formula, t
his formula assumes that our Earth is spherical,
but it isn’t since it’s more like a big orange fruit also compresses at poles.
I’ve read that this function has an error about + o – 3 meters (it depends),
but it’s a small error for many purposes.
http://snipplr.com/view/25479/
*/
function distance(lat1,lon1,lat2,lon2) {
var R = 6371; // km (change this constant to get miles)
var dLat = (lat2-lat1) * Math.PI / 180;
var dLon = (lon2-lon1) * Math.PI / 180;
var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(lat1 * Math.PI / 180 ) * Math.cos(lat2 * Math.PI / 180 ) *
Math.sin(dLon/2) * Math.sin(dLon/2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c;
if (d>1) return Math.round(d)+"km";
else if (d<=1) return Math.round(d*1000)+"m";
return d;
}
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