Created
August 21, 2014 00:30
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Functions for computing geographical distances
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| var GeoDistance = (function () { | |
| var _d = {}; | |
| // Earth Radius, in Miles | |
| _d.RADIUS = 3958.7615; | |
| _d.RAD_LAT = 3963.1906; | |
| _d.RAD_LNG = 3949.9028; | |
| _d.rad = function ( x ) { | |
| return ( x * ( Math.PI / 180 ) ); | |
| } | |
| var _rad = _d.rad; | |
| //------------------------------------------------------------------------ | |
| // haversine | |
| _d.haversine = function ( lat1, lng1, lat2, lng2 ) { | |
| var R = _d.RADIUS; | |
| var pLat1 = _rad( lat1 ), | |
| pLat2 = _rad( lat2 ), | |
| dLat = _rad( lat2 - lat1 ), | |
| dLng = _rad( lng2 - lng1 ); | |
| var a = ( Math.sin( dLat / 2 ) * Math.sin( dLat / 2 ) + | |
| Math.cos( pLat1 ) * Math.cos( pLat2 ) * | |
| 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 d; | |
| } | |
| //------------------------------------------------------------------------ | |
| // law of cosines | |
| _d.cosines = function ( lat1, lng1, lat2, lng2 ) { | |
| var R = _d.RADIUS, | |
| pLat1 = _rad( lat1 ), | |
| pLat2 = _rad( lat2 ), | |
| dLng = _rad( lng2 - lng1 ); | |
| var c = Math.acos( Math.sin( pLat1 ) * Math.sin( pLat2 ) + | |
| Math.cos( pLat1 ) * Math.cos( pLat2 ) * | |
| Math.cos( dLng ) ); | |
| var d = c * R; | |
| return d; | |
| } | |
| //======================================================================== | |
| // google SQL example | |
| _d.haversql = function ( lat1, lng1, lat2, lng2 ) { | |
| return ( _d.RADIUS * | |
| Math.acos( Math.cos( _rad( lat2 ) ) * | |
| Math.cos( _rad( lat1 ) ) * | |
| Math.cos( _rad( lng1 ) - _rad( lng2 ) ) + | |
| Math.sin( _rad( lat2 ) ) * | |
| Math.sin( _rad( lat1 ) ) ) ); | |
| } | |
| //------------------------------------------------------------------------ | |
| // google example, with asin | |
| _d.ahaversine = function ( lat1, lng1, lat2, lng2 ) { | |
| var R = _d.RADIUS; | |
| var pLat1 = _rad( lat1 ), | |
| pLat2 = _rad( lat2 ), | |
| dLat = _rad( lat2 - lat1 ), | |
| dLng = _rad( lng2 - lng1 ); | |
| var a = ( Math.sin( dLat / 2 ) * Math.sin( dLat / 2 ) + | |
| Math.cos( pLat1 ) * Math.cos( pLat2 ) * | |
| Math.sin( dLng / 2 ) * Math.sin( dLng / 2 ) ); | |
| var c = 2 * Math.asin( Math.sqrt( a ) ); | |
| var d = R * c; | |
| return d; | |
| } | |
| //======================================================================== | |
| // export | |
| return _d; | |
| })(); |
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