20 lines
710 B
TypeScript
20 lines
710 B
TypeScript
export type Lng =number|null|undefined
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export type Lat =number|null|undefined
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export type LatLng = {
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lat: Lat
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lng: Lng
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}
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/** optimization by https://stackoverflow.com/questions/5260423/torad-javascript-function-throwing-error/21623256#21623256 **/
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export function haversine_distance(lat1:Lat, lon1: Lng, lat2:Lat, lon2:Lng) {
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if(lat1 && lon1 && lat2 && lon2) {
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var R = 6371 // Radius of the earth in km
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var dLat = (lat2 - lat1) * Math.PI / 180 // deg2rad below
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var dLon = (lon2 - lon1) * Math.PI / 180
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var a = 0.5 - Math.cos(dLat)/2 +
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Math.cos(lat1 * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) * (1 - Math.cos(dLon))/2
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return R * 2 * Math.asin(Math.sqrt(a))
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}
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}
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