Calculate distance based on two-point latitude and longitude

function Getgreatcircledistance (lat1,lng1,lat2,lng2) {if (!LAT1 | |!lng1 | |!lat2 | |!lng2) {return-1;}    var v = 0;    var radLat1 = Getrad (LAT1);    var radLat2 = Getrad (LAT2);    var a = RADLAT1-RADLAT2;    var B = Getrad (lng1)-Getrad (LNG2); var s = 2*math.asin (Math.sqrt (Math.pow (Math.sin (A/2), 2) +Math.Cos (RADLAT1) *math.cos (RADLAT2) *math.pow (Math.sin (B/2), 2));    s = S*earth_radius;    s = Math.Round (s); if (s<1000) {v = s.tofixed (0) + ' m '; } else{s = s/1000;v = s.tofixed (1) + ' km '; } return v;} var lat1 =//Current latitude var lng1 =//Current longitude var lat2 =//target latitude var lng2 =//target Longitude v = getgreatcircledistance (lat1,lng1,lat2,lng2)

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Calculate distance based on two-point latitude and longitude