/
eart2000.cpp
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/
eart2000.cpp
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/* eart2000.cpp: functions for computing Earth coordinates
Copyright (C) 2010, Project Pluto
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA. */
#include <math.h>
/* EART2000.CPP
This computes a heliocentric J2000 position of the Earth, using
the VSOP theory. I don't use it very often, since the VSOP theory
for all the planets is given in the file VSOP.BIN on the Guide CD-ROM.
(This is the truncated VSOP used in Meeus' _Astronomical Algorithms_.
The full VSOP is in BIG_VSOP.BIN.)
The input is a time in millennia from J2000 = JD 2451545. The
output fills an array of six doubles with the X, Y, Z, ecliptic
longitude, ecliptic latitude, and distance, all in J2000 coords. */
int get_earth_loc( const double t_millennia, double *results);
static const int count[18] = {64, 34, 20, 7, 2, 0, /* 127 */
5, 7, 4, 3, 2, 0, /* +21 = 148 */
40, 10, 6, 2, 1, 0}; /* +59 = 207 */
static const double coeffs[207 * 3] = {
175347046., 0.000000000, 0.000000000,
3341656., 4.669256804, 6283.075849991,
34894., 4.626102422, 12566.151699983,
3497., 2.744117834, 5753.384884897,
3418., 2.828865798, 3.523118349,
3136., 3.627670418, 77713.771468121,
2676., 4.418083454, 7860.419392439,
2343., 6.135162144, 3930.209696220,
1324., 0.742463417, 11506.769769794,
1273., 2.037096579, 529.690965095,
1199., 1.109629462, 1577.343542448,
990., 5.232680721, 5884.926846583,
902., 2.045054465, 26.298319800,
857., 3.508491523, 398.149003408,
780., 1.178826820, 5223.693919802,
753., 2.533390528, 5507.553238667,
505., 4.582926000, 18849.227549974,
492., 4.205057118, 775.522611324,
357., 2.919541145, 0.067310303,
317., 5.849019485, 11790.629088659,
284., 1.898692409, 796.298006816,
271., 0.314862554, 10977.078804699,
243., 0.344814459, 5486.777843175,
206., 4.806466315, 2544.314419883,
205., 1.869537703, 5573.142801433,
202., 2.457677902, 6069.776754553,
156., 0.833060846, 213.299095438,
132., 3.411182927, 2942.463423292,
126., 1.082954595, 20.775395492,
115., 0.645449117, 0.980321068,
103., 0.635998456, 4694.002954708,
102., 0.975692803, 15720.838784878,
102., 4.266798020, 7.113547001,
99., 6.209929269, 2146.165416475,
98., 0.681013424, 155.420399434,
86., 5.983226313, 161000.685737674,
85., 1.298707648, 6275.962302991,
85., 3.670800930, 71430.695618129,
80., 1.807912871, 17260.154654690,
79., 3.036974587, 12036.460734888,
75., 1.755089133, 5088.628839767,
74., 3.503194150, 3154.687084896,
74., 4.679266339, 801.820931124,
70., 0.832976214, 9437.762934887,
62., 3.977639128, 8827.390269875,
61., 1.818398930, 7084.896781115,
57., 2.784304586, 6286.598968340,
56., 4.386948654, 14143.495242431,
56., 3.470060599, 6279.552731642,
52., 0.189149472, 12139.553509107,
52., 1.332827399, 1748.016413067,
51., 0.283068329, 5856.477659115,
49., 0.487350142, 1194.447010225,
41., 5.368175929, 8429.241266467,
41., 2.398509387, 19651.048481098,
39., 6.168330210, 10447.387839604,
37., 6.041338632, 10213.285546211,
37., 2.569574818, 1059.381930189,
36., 1.708758088, 2352.866153772,
36., 1.775968892, 6812.766815086,
33., 0.593102786, 17789.845619785,
30., 0.442944642, 83996.847318112,
30., 2.739751241, 1349.867409659,
25., 3.164708917, 4690.479836359,
628307584999., 0.000000000, 0.000000000,
206059., 2.678234558, 6283.075849991,
4303., 2.635122335, 12566.151699983,
425., 1.590469820, 3.523118349,
119., 5.795557656, 26.298319800,
109., 2.966310107, 1577.343542448,
93., 2.592111095, 18849.227549974,
72., 1.138405812, 529.690965095,
68., 1.874533003, 398.149003408,
67., 4.409328320, 5507.553238667,
59., 2.888157906, 5223.693919802,
56., 2.174717400, 155.420399434,
45., 0.397995029, 796.298006816,
36., 0.468754372, 775.522611324,
29., 2.647322546, 7.113547001,
21., 5.341382751, 0.980321068,
19., 1.846283760, 5486.777843175,
19., 4.968551795, 213.299095438,
17., 2.991167606, 6275.962302991,
16., 0.032165873, 2544.314419883,
16., 1.430493013, 2146.165416475,
15., 1.204697937, 10977.078804699,
12., 2.834322821, 1748.016413067,
12., 3.258050820, 5088.628839767,
12., 5.273797604, 1194.447010225,
12., 2.075020801, 4694.002954708,
11., 0.766147230, 553.569402842,
10., 1.302634234, 6286.598968340,
10., 4.239258653, 1349.867409659,
9., 2.699568270, 242.728603974,
9., 5.644760860, 951.718406251,
8., 5.300561729, 2352.866153772,
6., 2.650345140, 9437.762934887,
6., 4.666337263, 4690.479836359,
8722., 1.072536356, 6283.075849991,
991., 3.141592654, 0.000000000,
295., 0.437173503, 12566.151699983,
27., 0.052956361, 3.523118349,
16., 5.188202157, 26.298319800,
16., 3.685047122, 155.420399434,
9., 0.296671147, 18849.227549974,
9., 2.057063196, 77713.771468121,
7., 0.826915410, 775.522611324,
5., 4.662432317, 1577.343542448,
4., 1.030670323, 7.113547001,
4., 3.440433695, 5573.142801433,
3., 5.140212246, 796.298006816,
3., 6.054793185, 5507.553238667,
3., 1.192400085, 242.728603974,
3., 6.117058654, 529.690965095,
3., 0.303632482, 398.149003408,
3., 2.279664343, 553.569402842,
2., 4.376661180, 5223.693919802,
2., 3.754350955, 0.980321068,
289., 5.841731497, 6283.075849991,
21., 6.049839390, 12566.151699983,
3., 5.195605796, 155.420399434,
3., 3.141592654, 0.000000000,
1., 4.721976120, 3.523118349,
1., 5.969048992, 242.728603974,
1., 5.541829032, 18849.227549974,
8., 4.141173214, 6283.075849991,
1., 3.275736442, 12566.151699983,
280., 3.198701560, 84334.661581308,
102., 5.422486193, 5507.553238667,
80., 3.880132045, 5223.693919802,
44., 3.704446898, 2352.866153772,
32., 4.000263698, 1577.343542448,
227778., 3.413766205, 6283.075849991,
3806., 3.370634238, 12566.151699983,
3620., 0.000000000, 0.000000000,
72., 3.327775497, 18849.227549974,
8., 3.891904036, 5507.553238667,
8., 1.794896072, 5223.693919802,
6., 5.197894248, 2352.866153772,
9721., 5.151928099, 6283.075849991,
233., 3.141592654, 0.000000000,
134., 0.644062130, 12566.151699983,
7., 1.073333978, 18849.227549974,
276., 0.594800971, 6283.075849991,
17., 3.141592654, 0.000000000,
4., 0.117505753, 12566.151699983,
6., 2.267340298, 6283.075849991,
1., 0.000000000, 0.000000000,
100013989., 0.000000000, 0.000000000,
1670700., 3.098463503, 6283.075849991,
13956., 3.055246095, 12566.151699983,
3084., 5.198466744, 77713.771468121,
1628., 1.173875581, 5753.384884897,
1576., 2.846852149, 7860.419392439,
925., 5.452922367, 11506.769769794,
542., 4.564091515, 3930.209696220,
472., 3.661000221, 5884.926846583,
346., 0.963686273, 5507.553238667,
329., 5.899836861, 5223.693919802,
307., 0.298671395, 5573.142801433,
243., 4.273495308, 11790.629088659,
212., 5.847144613, 1577.343542448,
186., 5.021997107, 10977.078804699,
175., 3.011936367, 18849.227549974,
110., 5.055106359, 5486.777843175,
98., 0.886813113, 6069.776754553,
87., 5.689564189, 15720.838784878,
86., 1.270791253, 161000.685737674,
65., 0.272513414, 17260.154654690,
63., 0.921770540, 529.690965095,
57., 2.013742922, 83996.847318112,
56., 5.241597992, 71430.695618129,
49., 3.245012404, 2544.314419883,
47., 2.577998532, 775.522611324,
45., 5.537156638, 9437.762934887,
43., 6.011102580, 6275.962302991,
39., 5.360638329, 4694.002954708,
38., 2.392553440, 8827.390269875,
37., 0.829612818, 19651.048481098,
37., 4.901075873, 12139.553509107,
36., 1.674471358, 12036.460734888,
35., 1.842706933, 2942.463423292,
33., 0.243702217, 7084.896781115,
32., 0.183682999, 5088.628839767,
32., 1.777756421, 398.149003408,
28., 1.213448875, 6286.598968340,
28., 1.899344278, 6279.552731642,
26., 4.588968631, 10447.387839604,
103019., 1.107489682, 6283.075849991,
1721., 1.064423004, 12566.151699983,
702., 3.141592654, 0.000000000,
32., 1.021685833, 18849.227549974,
31., 2.843584440, 5507.553238667,
25., 1.319065703, 5223.693919802,
18., 1.424287091, 1577.343542448,
10., 5.913852484, 10977.078804699,
9., 1.420468544, 6275.962302991,
9., 0.271581929, 5486.777843175,
4359., 5.784551338, 6283.075849991,
124., 5.579354280, 12566.151699983,
12., 3.141592654, 0.000000000,
9., 3.627778931, 77713.771468121,
6., 1.869589051, 5573.142801433,
3., 5.470348797, 18849.227549974,
145., 4.273194339, 6283.075849991,
7., 3.917062617, 12566.151699983,
4., 2.563890163, 6283.075849991 };
int get_earth_loc( const double t_millennia, double *results)
{
int i, j, k;
double const *tptr = coeffs;
double power, sum;
double val[3];
for( i = 0; i < 3; i++)
{
val[i] = 0;
power = 1.;
for( j = 0; j < 6; j++)
{
sum = 0.;
for( k = 0; k < count[j + i * 6]; k++, tptr += 3)
sum += tptr[0] * cos( tptr[1] + tptr[2] * t_millennia);
val[i] += sum * power;
power *= t_millennia;
}
val[i] *= 1.e-8;
}
*results++ = val[2] * cos( val[0]) * cos( val[1]);
*results++ = val[2] * sin( val[0]) * cos( val[1]);
*results++ = val[2] * sin( val[1]);
*results++ = val[0];
*results++ = val[1];
*results++ = val[2];
return( 0);
}