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ICU-1325 various fixes and cleanup; add 2 variant algorithms for sunrise and sunset

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X-SVN-Rev: 10877
This commit is contained in:
Alan Liu 2003-01-20 20:03:53 +00:00
parent e5d724909c
commit dbb4a89263
1 changed files with 375 additions and 31 deletions
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icu4j/src/com/ibm/icu/util/CalendarAstronomer.java
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@ -5,8 +5,8 @@
*******************************************************************************
*
* $Source: /xsrl/Nsvn/icu/icu4j/src/com/ibm/icu/util/Attic/CalendarAstronomer.java,v $
* $Date: 2002/12/18 19:31:44 $
* $Revision: 1.12 $
* $Date: 2003/01/20 20:03:53 $
* $Revision: 1.13 $
*
*****************************************************************************************
*/
@ -169,6 +169,28 @@ public class CalendarAstronomer {
*/
public static final long JULIAN_EPOCH_MS = -210866760000000L;
// static {
// Calendar cal = new GregorianCalendar(TimeZone.getTimeZone("GMT"));
// cal.clear();
// cal.set(cal.ERA, 0);
// cal.set(cal.YEAR, 4713);
// cal.set(cal.MONTH, cal.JANUARY);
// cal.set(cal.DATE, 1);
// cal.set(cal.HOUR_OF_DAY, 12);
// System.out.println("1.5 Jan 4713 BC = " + cal.getTime().getTime());
// cal.clear();
// cal.set(cal.YEAR, 2000);
// cal.set(cal.MONTH, cal.JANUARY);
// cal.set(cal.DATE, 1);
// cal.add(cal.DATE, -1);
// System.out.println("0.0 Jan 2000 = " + cal.getTime().getTime());
// }
/**
* Milliseconds value for 0.0 January 2000 AD.
*/
static final long EPOCH_2000_MS = 946598400000L;
//-------------------------------------------------------------------------
// Assorted private data used for conversions
@ -506,18 +528,63 @@ public class CalendarAstronomer {
//-------------------------------------------------------------------------
// The Sun
//-------------------------------------------------------------------------
//
// Parameters of the Sun's orbit as of 1/1/1990
// Parameters of the Sun's orbit as of the epoch Jan 0.0 1990
// Angles are in radians (after multiplying by PI/180)
//
double jdnEpoch = 2447891.5; // JDN of epoch (Jan 0.0 1990)
static final double JD_EPOCH = 2447891.5; // Julian day of epoch
double sunEtaG = 279.403303 * PI/180; // Ecliptic longitude at epoch
double sunOmegaG = 282.768422 * PI/180; // Ecliptic longitude of perigee
double sunE = 0.016713; // Eccentricity of orbit
double sunR0 = 1.495585e8; // Semi-major axis in KM
double sunTheta0 = 0.533128 * PI/180; // Angular diameter at R0
static final double SUN_ETA_G = 279.403303 * PI/180; // Ecliptic longitude at epoch
static final double SUN_OMEGA_G = 282.768422 * PI/180; // Ecliptic longitude of perigee
static final double SUN_E = 0.016713; // Eccentricity of orbit
//double sunR0 = 1.495585e8; // Semi-major axis in KM
//double sunTheta0 = 0.533128 * PI/180; // Angular diameter at R0
// The following three methods, which compute the sun parameters
// given above for an arbitrary epoch (whatever time the object is
// set to), make only a small difference as compared to using the
// above constants. E.g., Sunset times might differ by ~12
// seconds. Furthermore, the eta-g computation is befuddled by
// Duffet-Smith's incorrect coefficients (p.86). I've corrected
// the first-order coefficient but the others may be off too - no
// way of knowing without consulting another source.
// /**
// * Return the sun's ecliptic longitude at perigee for the current time.
// * See Duffett-Smith, p. 86.
// * @return radians
// */
// private double getSunOmegaG() {
// double T = getJulianCentury();
// return (281.2208444 + (1.719175 + 0.000452778*T)*T) * DEG_RAD;
// }
// /**
// * Return the sun's ecliptic longitude for the current time.
// * See Duffett-Smith, p. 86.
// * @return radians
// */
// private double getSunEtaG() {
// double T = getJulianCentury();
// //return (279.6966778 + (36000.76892 + 0.0003025*T)*T) * DEG_RAD;
// //
// // The above line is from Duffett-Smith, and yields manifestly wrong
// // results. The below constant is derived empirically to match the
// // constant he gives for the 1990 EPOCH.
// //
// return (279.6966778 + (-0.3262541582718024 + 0.0003025*T)*T) * DEG_RAD;
// }
// /**
// * Return the sun's eccentricity of orbit for the current time.
// * See Duffett-Smith, p. 86.
// * @return double
// */
// private double getSunE() {
// double T = getJulianCentury();
// return 0.01675104 - (0.0000418 + 0.000000126*T)*T;
// }
/**
* The longitude of the sun at the time specified by this object.
@ -537,23 +604,37 @@ public class CalendarAstronomer {
// by Peter Duffet-Smith, for details on the algorithm.
if (sunLongitude == INVALID) {
double day = getJulianDay() - jdnEpoch; // Days since epoch
// Find the angular distance the sun in a fictitious
// circular orbit has travelled since the epoch.
double epochAngle = norm2PI(PI2/TROPICAL_YEAR*day);
// The epoch wasn't at the sun's perigee; find the angular distance
// since perigee, which is called the "mean anomaly"
meanAnomalySun = norm2PI(epochAngle + sunEtaG - sunOmegaG);
// Now find the "true anomaly", e.g. the real solar longitude
// by solving Kepler's equation for an elliptical orbit
sunLongitude = norm2PI(trueAnomaly(meanAnomalySun, sunE) + sunOmegaG);
double[] result = getSunLongitude(getJulianDay());
sunLongitude = result[0];
meanAnomalySun = result[1];
}
return sunLongitude;
}
public double[] getSunLongitude(double julianDay)
{
// See page 86 of "Practial Astronomy with your Calculator",
// by Peter Duffet-Smith, for details on the algorithm.
double day = julianDay - JD_EPOCH; // Days since epoch
// Find the angular distance the sun in a fictitious
// circular orbit has travelled since the epoch.
double epochAngle = norm2PI(PI2/TROPICAL_YEAR*day);
// The epoch wasn't at the sun's perigee; find the angular distance
// since perigee, which is called the "mean anomaly"
double meanAnomaly = norm2PI(epochAngle + SUN_ETA_G - SUN_OMEGA_G);
// Now find the "true anomaly", e.g. the real solar longitude
// by solving Kepler's equation for an elliptical orbit
// NOTE: The 3rd ed. of the book lists omega_g and eta_g in different
// equations; omega_g is to be correct.
return new double[] {
norm2PI(trueAnomaly(meanAnomaly, SUN_E) + SUN_OMEGA_G),
meanAnomaly
};
}
/**
* The position of the sun at this object's current date and time,
* in equatorial coordinates.
@ -649,7 +730,267 @@ public class CalendarAstronomer {
rise,
.533 * DEG_RAD, // Angular Diameter
34 /60.0 * DEG_RAD, // Refraction correction
MINUTE_MS); // Desired accuracy
MINUTE_MS / 12); // Desired accuracy
}
//-------------------------------------------------------------------------
// Alternate Sun Rise/Set
// See Duffett-Smith p.93
//-------------------------------------------------------------------------
// This yields worse results (as compared to USNO data) than getSunRiseSet().
public long getSunRiseSet2(boolean rise) {
// 1. Calculate coordinates of the sun's center for midnight
double jd = Math.floor(getJulianDay() - 0.5) + 0.5;
double[] sl = getSunLongitude(jd);
double lambda1 = sl[0];
Equatorial pos1 = eclipticToEquatorial(lambda1, 0);
// 2. Add ... to lambda to get position 24 hours later
double lambda2 = lambda1 + 0.985647*DEG_RAD;
Equatorial pos2 = eclipticToEquatorial(lambda2, 0);
// 3. Calculate LSTs of rising and setting for these two positions
double tanL = Math.tan(fLatitude);
double H = Math.acos(-tanL * Math.tan(pos1.declination));
double lst1r = (PI2 + pos1.ascension - H) * 24 / PI2;
double lst1s = (pos1.ascension + H) * 24 / PI2;
H = Math.acos(-tanL * Math.tan(pos2.declination));
double lst2r = (PI2-H + pos2.ascension ) * 24 / PI2;
double lst2s = (H + pos2.ascension ) * 24 / PI2;
if (lst1r > 24) lst1r -= 24;
if (lst1s > 24) lst1s -= 24;
if (lst2r > 24) lst2r -= 24;
if (lst2s > 24) lst2s -= 24;
// 4. Convert LSTs to GSTs. If GST1 > GST2, add 24 to GST2.
double gst1r = lstToGst(lst1r);
double gst1s = lstToGst(lst1s);
double gst2r = lstToGst(lst2r);
double gst2s = lstToGst(lst2s);
if (gst1r > gst2r) gst2r += 24;
if (gst1s > gst2s) gst2s += 24;
// 5. Calculate GST at 0h UT of this date
double t00 = utToGst(0);
// 6. Calculate GST at 0h on the observer's longitude
double offset = Math.round(fLongitude*12/PI); // p.95 step 6; he _rounds_ to nearest 15 deg.
double t00p = t00 - offset*1.002737909;
if (t00p < 0) t00p += 24; // do NOT normalize
// 7. Adjust
if (gst1r < t00p) {
gst1r += 24;
gst2r += 24;
}
if (gst1s < t00p) {
gst1s += 24;
gst2s += 24;
}
// 8.
double gstr = (24.07*gst1r-t00*(gst2r-gst1r))/(24.07+gst1r-gst2r);
double gsts = (24.07*gst1s-t00*(gst2s-gst1s))/(24.07+gst1s-gst2s);
// 9. Correct for parallax, refraction, and sun's diameter
double dec = (pos1.declination + pos2.declination) / 2;
double psi = Math.acos(Math.sin(fLatitude) / Math.cos(dec));
double x = 0.830725 * DEG_RAD; // parallax+refraction+diameter
double y = Math.asin(Math.sin(x) / Math.sin(psi)) * RAD_DEG;
double delta_t = 240 * y / Math.cos(dec) / 3600; // hours
// 10. Add correction to GSTs, subtract from GSTr
gstr -= delta_t;
gsts += delta_t;
// 11. Convert GST to UT and then to local civil time
double ut = gstToUt(rise ? gstr : gsts);
//System.out.println((rise?"rise=":"set=") + ut + ", delta_t=" + delta_t);
long midnight = DAY_MS * (time / DAY_MS); // Find UT midnight on this day
return midnight + (long) (ut * 3600000);
}
/**
* Convert local sidereal time to Greenwich sidereal time.
* Section 15. Duffett-Smith p.21
* @param lst in hours (0..24)
* @return GST in hours (0..24)
*/
double lstToGst(double lst) {
double delta = fLongitude * 24 / PI2;
return normalize(lst - delta, 24);
}
/**
* Convert UT to GST on this date.
* Section 12. Duffett-Smith p.17
* @param ut in hours
* @return GST in hours
*/
double utToGst(double ut) {
return normalize(getT0() + ut*1.002737909, 24);
}
/**
* Convert GST to UT on this date.
* Section 13. Duffett-Smith p.18
* @param gst in hours
* @return UT in hours
*/
double gstToUt(double gst) {
return normalize(gst - getT0(), 24) * 0.9972695663;
}
double getT0() {
// Common computation for UT <=> GST
// Find JD for 0h UT
double jd = Math.floor(getJulianDay() - 0.5) + 0.5;
double s = jd - 2451545.0;
double t = s / 36525.0;
double t0 = 6.697374558 + (2400.051336 + 0.000025862*t)*t;
return t0;
}
//-------------------------------------------------------------------------
// Alternate Sun Rise/Set
// See sci.astro FAQ
// http://www.faqs.org/faqs/astronomy/faq/part3/section-5.html
//-------------------------------------------------------------------------
// Note: This method appears to produce inferior accuracy as
// compared to getSunRiseSet().
public long getSunRiseSet3(boolean rise) {
// Compute day number for 0.0 Jan 2000 epoch
double d = (double)(time - EPOCH_2000_MS) / DAY_MS;
// Now compute the Local Sidereal Time, LST:
//
double LST = 98.9818 + 0.985647352 * d + /*UT*15 + long*/
fLongitude*RAD_DEG;
//
// (east long. positive). Note that LST is here expressed in degrees,
// where 15 degrees corresponds to one hour. Since LST really is an angle,
// it's convenient to use one unit---degrees---throughout.
// COMPUTING THE SUN'S POSITION
// ----------------------------
//
// To be able to compute the Sun's rise/set times, you need to be able to
// compute the Sun's position at any time. First compute the "day
// number" d as outlined above, for the desired moment. Next compute:
//
double oblecl = 23.4393 - 3.563E-7 * d;
//
double w = 282.9404 + 4.70935E-5 * d;
double M = 356.0470 + 0.9856002585 * d;
double e = 0.016709 - 1.151E-9 * d;
//
// This is the obliquity of the ecliptic, plus some of the elements of
// the Sun's apparent orbit (i.e., really the Earth's orbit): w =
// argument of perihelion, M = mean anomaly, e = eccentricity.
// Semi-major axis is here assumed to be exactly 1.0 (while not strictly
// true, this is still an accurate approximation). Next compute E, the
// eccentric anomaly:
//
double E = M + e*(180/PI) * Math.sin(M*DEG_RAD) * ( 1.0 + e*Math.cos(M*DEG_RAD) );
//
// where E and M are in degrees. This is it---no further iterations are
// needed because we know e has a sufficiently small value. Next compute
// the true anomaly, v, and the distance, r:
//
/* r * cos(v) = */ double A = Math.cos(E*DEG_RAD) - e;
/* r * sin(v) = */ double B = Math.sqrt(1 - e*e) * Math.sin(E*DEG_RAD);
//
// and
//
// r = sqrt( A*A + B*B )
double v = Math.atan2( B, A )*RAD_DEG;
//
// The Sun's true longitude, slon, can now be computed:
//
double slon = v + w;
//
// Since the Sun is always at the ecliptic (or at least very very close to
// it), we can use simplified formulae to convert slon (the Sun's ecliptic
// longitude) to sRA and sDec (the Sun's RA and Dec):
//
// sin(slon) * cos(oblecl)
// tan(sRA) = -------------------------
// cos(slon)
//
// sin(sDec) = sin(oblecl) * sin(slon)
//
// As was the case when computing az, the Azimuth, if possible use an
// atan2() function to compute sRA.
double sRA = Math.atan2(Math.sin(slon*DEG_RAD) * Math.cos(oblecl*DEG_RAD), Math.cos(slon*DEG_RAD))*RAD_DEG;
double sin_sDec = Math.sin(oblecl*DEG_RAD) * Math.sin(slon*DEG_RAD);
double sDec = Math.asin(sin_sDec)*RAD_DEG;
// COMPUTING RISE AND SET TIMES
// ----------------------------
//
// To compute when an object rises or sets, you must compute when it
// passes the meridian and the HA of rise/set. Then the rise time is
// the meridian time minus HA for rise/set, and the set time is the
// meridian time plus the HA for rise/set.
//
// To find the meridian time, compute the Local Sidereal Time at 0h local
// time (or 0h UT if you prefer to work in UT) as outlined above---name
// that quantity LST0. The Meridian Time, MT, will now be:
//
// MT = RA - LST0
double MT = normalize(sRA - LST, 360);
//
// where "RA" is the object's Right Ascension (in degrees!). If negative,
// add 360 deg to MT. If the object is the Sun, leave the time as it is,
// but if it's stellar, multiply MT by 365.2422/366.2422, to convert from
// sidereal to solar time. Now, compute HA for rise/set, name that
// quantity HA0:
//
// sin(h0) - sin(lat) * sin(Dec)
// cos(HA0) = ---------------------------------
// cos(lat) * cos(Dec)
//
// where h0 is the altitude selected to represent rise/set. For a purely
// mathematical horizon, set h0 = 0 and simplify to:
//
// cos(HA0) = - tan(lat) * tan(Dec)
//
// If you want to account for refraction on the atmosphere, set h0 = -35/60
// degrees (-35 arc minutes), and if you want to compute the rise/set times
// for the Sun's upper limb, set h0 = -50/60 (-50 arc minutes).
//
double h0 = -50/60 * DEG_RAD;
double HA0 = Math.acos(
(Math.sin(h0) - Math.sin(fLatitude) * sin_sDec) /
(Math.cos(fLatitude) * Math.cos(sDec*DEG_RAD)))*RAD_DEG;
// When HA0 has been computed, leave it as it is for the Sun but multiply
// by 365.2422/366.2422 for stellar objects, to convert from sidereal to
// solar time. Finally compute:
//
// Rise time = MT - HA0
// Set time = MT + HA0
//
// convert the times from degrees to hours by dividing by 15.
//
// If you'd like to check that your calculations are accurate or just
// need a quick result, check the USNO's Sun or Moon Rise/Set Table,
// <URL:http://aa.usno.navy.mil/AA/data/docs/RS_OneYear.html>.
double result = MT + (rise ? -HA0 : HA0); // in degrees
// Find UT midnight on this day
long midnight = DAY_MS * (time / DAY_MS);
return midnight + (long) (result * 3600000 / 15);
}
//-------------------------------------------------------------------------
@ -688,7 +1029,7 @@ public class CalendarAstronomer {
// Find the # of days since the epoch of our orbital parameters.
// TODO: Convert the time of day portion into ephemeris time
//
double day = getJulianDay() - jdnEpoch; // Days since epoch
double day = getJulianDay() - JD_EPOCH; // Days since epoch
// Calculate the mean longitude and anomaly of the moon, based on
// a circular orbit. Similar to the corresponding solar calculation.
@ -990,7 +1331,7 @@ public class CalendarAstronomer {
setTime(newTime);
}
while (++ count < 5 && Math.abs(deltaT) > epsilon);
// Calculate the correction due to refraction and the object's angular diameter
double cosD = Math.cos(pos.declination);
double psi = Math.acos(Math.sin(fLatitude) / cosD);
@ -1005,6 +1346,10 @@ public class CalendarAstronomer {
// Other utility methods
//-------------------------------------------------------------------------
/***
* Given 'value', add or subtract 'range' until 0 <= 'value' < range.
* The modulus operator.
*/
private static final double normalize(double value, double range) {
return value - range * Math.floor(value / range);
}
@ -1041,20 +1386,19 @@ public class CalendarAstronomer {
private double trueAnomaly(double meanAnomaly, double eccentricity)
{
// First, solve Kepler's equation iteratively
// Duffett-Smith, p.90
double delta;
double E = meanAnomaly;
do {
delta = E - eccentricity * Math.sin(E) - meanAnomaly;
E = E - delta / (1 - eccentricity * Math.cos(E));
}
while (Math.abs(delta) > accuracy);
while (Math.abs(delta) > 1e-5); // epsilon = 1e-5 rad
return 2.0 * Math.atan( Math.tan(E/2) * Math.sqrt( (1+eccentricity)
/(1-eccentricity) ) );
}
static private final double accuracy = 0.01 * PI/180; // 0.01 degrees
/**
* Return the obliquity of the ecliptic (the angle between the ecliptic
* and the earth's equator) at the current time. This varies due to
@ -1071,8 +1415,8 @@ public class CalendarAstronomer {
eclipObliquity = 23.439292
- 46.815/3600 * T
- 0.0006 * T*T
+ 0.00181 * T*T*T;
- 0.0006/3600 * T*T
+ 0.00181/3600 * T*T*T;
eclipObliquity *= DEG_RAD;
}