333 lines
9.9 KiB
JavaScript
333 lines
9.9 KiB
JavaScript
/*
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(c) 2011-2015, Vladimir Agafonkin
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SunCalc is a JavaScript library for calculating sun/moon position and light phases.
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https://github.com/mourner/suncalc
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Copyright (c) 2014, Vladimir Agafonkin
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All rights reserved.
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Redistribution and use in source and binary forms, with or without modification, are
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permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice, this list of
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conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice, this list
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of conditions and the following disclaimer in the documentation and/or other materials
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provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
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TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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(function () { 'use strict';
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// shortcuts for easier to read formulas
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var PI = Math.PI,
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sin = Math.sin,
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cos = Math.cos,
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tan = Math.tan,
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asin = Math.asin,
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atan = Math.atan2,
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acos = Math.acos,
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rad = PI / 180;
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// sun calculations are based on http://aa.quae.nl/en/reken/zonpositie.html formulas
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// date/time constants and conversions
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var dayMs = 1000 * 60 * 60 * 24,
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J1970 = 2440588,
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J2000 = 2451545;
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function toJulian(date) { return date.valueOf() / dayMs - 0.5 + J1970; }
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function fromJulian(j) { return new Date((j + 0.5 - J1970) * dayMs); }
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function toDays(date) { return toJulian(date) - J2000; }
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// general calculations for position
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var e = rad * 23.4397; // obliquity of the Earth
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function rightAscension(l, b) { return atan(sin(l) * cos(e) - tan(b) * sin(e), cos(l)); }
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function declination(l, b) { return asin(sin(b) * cos(e) + cos(b) * sin(e) * sin(l)); }
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function azimuth(H, phi, dec) { return atan(sin(H), cos(H) * sin(phi) - tan(dec) * cos(phi)); }
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function altitude(H, phi, dec) { return asin(sin(phi) * sin(dec) + cos(phi) * cos(dec) * cos(H)); }
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function siderealTime(d, lw) { return rad * (280.16 + 360.9856235 * d) - lw; }
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function astroRefraction(h) {
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if (h < 0) // the following formula works for positive altitudes only.
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h = 0; // if h = -0.08901179 a div/0 would occur.
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// formula 16.4 of "Astronomical Algorithms" 2nd edition by Jean Meeus (Willmann-Bell, Richmond) 1998.
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// 1.02 / tan(h + 10.26 / (h + 5.10)) h in degrees, result in arc minutes -> converted to rad:
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return 0.0002967 / Math.tan(h + 0.00312536 / (h + 0.08901179));
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}
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// general sun calculations
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function solarMeanAnomaly(d) { return rad * (357.5291 + 0.98560028 * d); }
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function eclipticLongitude(M) {
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var C = rad * (1.9148 * sin(M) + 0.02 * sin(2 * M) + 0.0003 * sin(3 * M)), // equation of center
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P = rad * 102.9372; // perihelion of the Earth
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return M + C + P + PI;
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}
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function sunCoords(d) {
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var M = solarMeanAnomaly(d),
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L = eclipticLongitude(M);
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return {
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dec: declination(L, 0),
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ra: rightAscension(L, 0)
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};
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}
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var SunCalc = {};
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// calculates sun position for a given date and latitude/longitude
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SunCalc.getPosition = function (date, lat, lng) {
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var lw = rad * -lng,
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phi = rad * lat,
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d = toDays(date),
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c = sunCoords(d),
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H = siderealTime(d, lw) - c.ra;
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return {
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azimuth: azimuth(H, phi, c.dec),
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altitude: altitude(H, phi, c.dec)
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};
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};
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// sun times configuration (angle, morning name, evening name)
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var times = SunCalc.times = [
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[-0.833, 'sunrise', 'sunset' ],
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[ -0.3, 'sunriseEnd', 'sunsetStart' ],
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[ -6, 'dawn', 'dusk' ],
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[ -12, 'nauticalDawn', 'nauticalDusk'],
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[ -18, 'nightEnd', 'night' ],
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[ 6, 'goldenHourEnd', 'goldenHour' ]
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];
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// adds a custom time to the times config
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SunCalc.addTime = function (angle, riseName, setName) {
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times.push([angle, riseName, setName]);
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};
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// calculations for sun times
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var J0 = 0.0009;
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function julianCycle(d, lw) { return Math.round(d - J0 - lw / (2 * PI)); }
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function approxTransit(Ht, lw, n) { return J0 + (Ht + lw) / (2 * PI) + n; }
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function solarTransitJ(ds, M, L) { return J2000 + ds + 0.0053 * sin(M) - 0.0069 * sin(2 * L); }
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function hourAngle(h, phi, d) { return acos((sin(h) - sin(phi) * sin(d)) / (cos(phi) * cos(d))); }
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// returns set time for the given sun altitude
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function getSetJ(h, lw, phi, dec, n, M, L) {
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var w = hourAngle(h, phi, dec),
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a = approxTransit(w, lw, n);
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return solarTransitJ(a, M, L);
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}
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// calculates sun times for a given date and latitude/longitude
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SunCalc.getTimes = function (date, lat, lng) {
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var lw = rad * -lng,
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phi = rad * lat,
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d = toDays(date),
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n = julianCycle(d, lw),
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ds = approxTransit(0, lw, n),
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M = solarMeanAnomaly(ds),
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L = eclipticLongitude(M),
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dec = declination(L, 0),
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Jnoon = solarTransitJ(ds, M, L),
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i, len, time, Jset, Jrise;
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var result = {
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solarNoon: fromJulian(Jnoon),
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nadir: fromJulian(Jnoon - 0.5)
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};
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for (i = 0, len = times.length; i < len; i += 1) {
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time = times[i];
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Jset = getSetJ(time[0] * rad, lw, phi, dec, n, M, L);
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Jrise = Jnoon - (Jset - Jnoon);
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result[time[1]] = fromJulian(Jrise);
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result[time[2]] = fromJulian(Jset);
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}
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return result;
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};
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// moon calculations, based on http://aa.quae.nl/en/reken/hemelpositie.html formulas
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function moonCoords(d) { // geocentric ecliptic coordinates of the moon
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var L = rad * (218.316 + 13.176396 * d), // ecliptic longitude
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M = rad * (134.963 + 13.064993 * d), // mean anomaly
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F = rad * (93.272 + 13.229350 * d), // mean distance
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l = L + rad * 6.289 * sin(M), // longitude
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b = rad * 5.128 * sin(F), // latitude
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dt = 385001 - 20905 * cos(M); // distance to the moon in km
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return {
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ra: rightAscension(l, b),
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dec: declination(l, b),
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dist: dt
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};
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}
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SunCalc.getMoonPosition = function (date, lat, lng) {
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var lw = rad * -lng,
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phi = rad * lat,
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d = toDays(date),
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c = moonCoords(d),
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H = siderealTime(d, lw) - c.ra,
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h = altitude(H, phi, c.dec),
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// formula 14.1 of "Astronomical Algorithms" 2nd edition by Jean Meeus (Willmann-Bell, Richmond) 1998.
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pa = atan(sin(H), tan(phi) * cos(c.dec) - sin(c.dec) * cos(H));
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h = h + astroRefraction(h); // altitude correction for refraction
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return {
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azimuth: azimuth(H, phi, c.dec),
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altitude: h,
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distance: c.dist,
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parallacticAngle: pa
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};
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};
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// calculations for illumination parameters of the moon,
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// based on http://idlastro.gsfc.nasa.gov/ftp/pro/astro/mphase.pro formulas and
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// Chapter 48 of "Astronomical Algorithms" 2nd edition by Jean Meeus (Willmann-Bell, Richmond) 1998.
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SunCalc.getMoonIllumination = function (date) {
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var d = toDays(date || new Date()),
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s = sunCoords(d),
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m = moonCoords(d),
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sdist = 149598000, // distance from Earth to Sun in km
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phi = acos(sin(s.dec) * sin(m.dec) + cos(s.dec) * cos(m.dec) * cos(s.ra - m.ra)),
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inc = atan(sdist * sin(phi), m.dist - sdist * cos(phi)),
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angle = atan(cos(s.dec) * sin(s.ra - m.ra), sin(s.dec) * cos(m.dec) -
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cos(s.dec) * sin(m.dec) * cos(s.ra - m.ra));
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return {
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fraction: (1 + cos(inc)) / 2,
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phase: 0.5 + 0.5 * inc * (angle < 0 ? -1 : 1) / Math.PI,
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angle: angle
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};
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};
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function hoursLater(date, h) {
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return new Date(date.valueOf() + h * dayMs / 24);
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}
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// calculations for moon rise/set times are based on http://www.stargazing.net/kepler/moonrise.html article
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SunCalc.getMoonTimes = function (date, lat, lng, inUTC) {
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var t = new Date(date);
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if (inUTC) t.setUTCHours(0, 0, 0, 0);
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else t.setHours(0, 0, 0, 0);
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var hc = 0.133 * rad,
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h0 = SunCalc.getMoonPosition(t, lat, lng).altitude - hc,
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h1, h2, rise, set, a, b, xe, ye, d, roots, x1, x2, dx;
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// go in 2-hour chunks, each time seeing if a 3-point quadratic curve crosses zero (which means rise or set)
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for (var i = 1; i <= 24; i += 2) {
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h1 = SunCalc.getMoonPosition(hoursLater(t, i), lat, lng).altitude - hc;
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h2 = SunCalc.getMoonPosition(hoursLater(t, i + 1), lat, lng).altitude - hc;
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a = (h0 + h2) / 2 - h1;
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b = (h2 - h0) / 2;
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xe = -b / (2 * a);
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ye = (a * xe + b) * xe + h1;
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d = b * b - 4 * a * h1;
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roots = 0;
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if (d >= 0) {
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dx = Math.sqrt(d) / (Math.abs(a) * 2);
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x1 = xe - dx;
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x2 = xe + dx;
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if (Math.abs(x1) <= 1) roots++;
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if (Math.abs(x2) <= 1) roots++;
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if (x1 < -1) x1 = x2;
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}
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if (roots === 1) {
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if (h0 < 0) rise = i + x1;
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else set = i + x1;
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} else if (roots === 2) {
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rise = i + (ye < 0 ? x2 : x1);
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set = i + (ye < 0 ? x1 : x2);
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}
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if (rise && set) break;
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h0 = h2;
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}
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var result = {};
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if (rise) result.rise = hoursLater(t, rise);
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if (set) result.set = hoursLater(t, set);
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if (!rise && !set) result[ye > 0 ? 'alwaysUp' : 'alwaysDown'] = true;
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return result;
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};
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// export as Node module / AMD module / browser variable
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if (typeof exports === 'object' && typeof module !== 'undefined') module.exports = SunCalc;
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else if (typeof define === 'function' && define.amd) define(SunCalc);
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else window.SunCalc = SunCalc;
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}());
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