44 lines
1.7 KiB
JavaScript
44 lines
1.7 KiB
JavaScript
/*
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* extend Leaflet's LatLng class
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* giving it the ability to calculate the bearing to another LatLng
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* Usage example:
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* here = map.getCenter(); / some latlng
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* there = L.latlng([37.7833,-122.4167]);
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* var whichway = here.bearingWordTo(there);
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* var howfar = (here.distanceTo(there) / 1609.34).toFixed(2);
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* alert("San Francisco is " + howfar + " miles, to the " + whichway );
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*
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* Greg Allensworth <greg.allensworth@gmail.com>
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* No license, use as you will, kudos welcome but not required, etc.
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*/
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L.LatLng.prototype.bearingTo = function(other) {
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var d2r = L.LatLng.DEG_TO_RAD;
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var r2d = L.LatLng.RAD_TO_DEG;
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var lat1 = this.lat * d2r;
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var lat2 = other.lat * d2r;
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var dLon = (other.lng-this.lng) * d2r;
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var y = Math.sin(dLon) * Math.cos(lat2);
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var x = Math.cos(lat1)*Math.sin(lat2) - Math.sin(lat1)*Math.cos(lat2)*Math.cos(dLon);
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var brng = Math.atan2(y, x);
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brng = parseInt( brng * r2d );
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brng = (brng + 360) % 360;
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return brng;
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};
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L.LatLng.prototype.bearingWordTo = function(other) {
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var bearing = this.bearingTo(other);
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var bearingword = '';
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if (bearing >= 22 && bearing <= 67) bearingword = 'NE';
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else if (bearing >= 67 && bearing <= 112) bearingword = 'E';
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else if (bearing >= 112 && bearing <= 157) bearingword = 'SE';
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else if (bearing >= 157 && bearing <= 202) bearingword = 'S';
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else if (bearing >= 202 && bearing <= 247) bearingword = 'SW';
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else if (bearing >= 247 && bearing <= 292) bearingword = 'W';
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else if (bearing >= 292 && bearing <= 337) bearingword = 'NW';
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else if (bearing >= 337 || bearing <= 22) bearingword = 'N';
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return bearingword;
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};
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