79 lines
3.1 KiB
JavaScript
79 lines
3.1 KiB
JavaScript
/**
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* Function to calculate distance between two coordinates using the haversine algorithm (less precise).
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* @param coord1 first set of coordinates.
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* @param coord2 second set of coordinates.
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* @returns {number} distance between the two points in meters.
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*/
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function distanceInMetersBetweenEarthCoordinates(coord1, coord2) {
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let long1 = coord1[0]
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let lat1 = coord1[1]
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let long2 = coord2[0]
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let lat2 = coord2[1]
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let earthRadiusM = 6371000
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let phi1 = lat1 * Math.PI / 180
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let phi2 = lat2 * Math.PI / 180
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let dlat = (lat2-lat1) * Math.PI / 180
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let dlong = (long2 - long1) * Math.PI / 180
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let a = Math.sin(dlat/2) * Math.sin(dlat/2) +
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Math.cos(phi1) * Math.cos(phi2) *
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Math.sin(dlong/2) * Math.sin(dlong/2)
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let c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a))
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return earthRadiusM * c
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}
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Number.prototype.toRad = function () { return this * Math.PI / 180; }
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/**
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* Function to calculate distance between two coordinates using the vincenty algorithm (more precise).
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* @param coord1 first set of coordinates.
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* @param coord2 second set of coordinates.
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* @returns {string|number} distance between the two point is meters.
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*/
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function distVincenty(coord1, coord2) {
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const lon1 = coord1[0]
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const lat1 = coord1[1]
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const lon2 = coord2[0]
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const lat2 = coord2[1]
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var a = 6378137, b = 6356752.314245, f = 1/298.257223563; // WGS-84 ellipsoid params
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var L = (lon2-lon1).toRad()
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var U1 = Math.atan((1-f) * Math.tan(lat1.toRad()));
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var U2 = Math.atan((1-f) * Math.tan(lat2.toRad()));
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var sinU1 = Math.sin(U1), cosU1 = Math.cos(U1);
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var sinU2 = Math.sin(U2), cosU2 = Math.cos(U2);
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var lambda = L, lambdaP, iterLimit = 100;
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do {
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var sinLambda = Math.sin(lambda), cosLambda = Math.cos(lambda);
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var sinSigma = Math.sqrt((cosU2*sinLambda) * (cosU2*sinLambda) +
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(cosU1*sinU2-sinU1*cosU2*cosLambda) * (cosU1*sinU2-sinU1*cosU2*cosLambda));
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if (sinSigma===0) return 0; // co-incident points
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var cosSigma = sinU1*sinU2 + cosU1*cosU2*cosLambda;
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var sigma = Math.atan2(sinSigma, cosSigma);
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var sinAlpha = cosU1 * cosU2 * sinLambda / sinSigma;
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var cosSqAlpha = 1 - sinAlpha*sinAlpha;
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var cos2SigmaM = cosSigma - 2*sinU1*sinU2/cosSqAlpha;
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if (isNaN(cos2SigmaM)) cos2SigmaM = 0; // equatorial line: cosSqAlpha=0 (§6)
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var C = f/16*cosSqAlpha*(4+f*(4-3*cosSqAlpha));
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lambdaP = lambda;
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lambda = L + (1-C) * f * sinAlpha *
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(sigma + C*sinSigma*(cos2SigmaM+C*cosSigma*(-1+2*cos2SigmaM*cos2SigmaM)));
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} while (Math.abs(lambda-lambdaP) > 1e-12 && --iterLimit>0);
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if (iterLimit===0) return NaN // formula failed to converge
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var uSq = cosSqAlpha * (a*a - b*b) / (b*b);
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var A = 1 + uSq/16384*(4096+uSq*(-768+uSq*(320-175*uSq)));
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var B = uSq/1024 * (256+uSq*(-128+uSq*(74-47*uSq)));
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var deltaSigma = B*sinSigma*(cos2SigmaM+B/4*(cosSigma*(-1+2*cos2SigmaM*cos2SigmaM)-
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B/6*cos2SigmaM*(-3+4*sinSigma*sinSigma)*(-3+4*cos2SigmaM*cos2SigmaM)));
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var s = b*A*(sigma-deltaSigma);
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s = s.toFixed(3); // round to 1mm precision
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return s;
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}
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