50 lines
2.9 KiB
JavaScript
50 lines
2.9 KiB
JavaScript
//:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
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//::: :::
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//::: This routine calculates the distance between two points (given the :::
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//::: latitude/longitude of those points). It is being used to calculate :::
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//::: the distance between two locations using GeoDataSource (TM) prodducts :::
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//::: :::
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//::: Definitions: :::
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//::: South latitudes are negative, east longitudes are positive :::
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//::: :::
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//::: Passed to function: :::
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//::: lat1, lon1 = Latitude and Longitude of point 1 (in decimal degrees) :::
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//::: lat2, lon2 = Latitude and Longitude of point 2 (in decimal degrees) :::
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//::: unit = the unit you desire for results :::
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//::: where: 'M' is statute miles (default) :::
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//::: 'K' is kilometers :::
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//::: 'N' is nautical miles :::
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//::: :::
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//::: Worldwide cities and other features databases with latitude longitude :::
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//::: are available at https://www.geodatasource.com :::
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//::: :::
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//::: For enquiries, please contact sales@geodatasource.com :::
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//::: :::
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//::: Official Web site: https://www.geodatasource.com :::
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//::: :::
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//::: GeoDataSource.com (C) All Rights Reserved 2017 :::
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//::: :::
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//:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
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function getDistance(lat1, lon1, lat2, lon2, unit) {
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var radlat1 = Math.PI * lat1/180
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var radlat2 = Math.PI * lat2/180
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var theta = lon1-lon2
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var radtheta = Math.PI * theta/180
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var dist = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
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if (dist > 1) {
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dist = 1;
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}
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dist = Math.acos(dist)
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dist = dist * 180/Math.PI
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dist = dist * 60 * 1.1515
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if (unit=="K") { dist = dist * 1.609344 }
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if (unit=="N") { dist = dist * 0.8684 }
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return dist
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}
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// https://stackoverflow.com/questions/10756313/javascript-jquery-map-a-range-of-numbers-to-another-range-of-numbers
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function scale(num, in_min, in_max, out_min, out_max) {
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return (num - in_min ) * (out_max - out_min) / (in_max - in_min) + out_min;
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}
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