222 lines
6.2 KiB
C
222 lines
6.2 KiB
C
/**************************************************************************
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* orbits.c - calculates the orbital elements of the sun, moon and planets.
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* For inclusion in flight gear
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*
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* Written 1997 by Durk Talsma, started October 19, 1997.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* $Id$
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* (Log is kept at end of this file)
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**************************************************************************/
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#include <math.h>
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#include <string.h>
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#include <Astro/orbits.h>
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#include <Include/fg_constants.h>
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#include <Include/general.h>
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#include <Time/fg_time.h>
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#include <Main/fg_debug.h>
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struct OrbElements pltOrbElements[9];
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//double fgCalcActTime(struct fgTIME t)
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//{
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// double
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// actTime, UT;
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// int year;
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//
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// /* a hack. This one introduces the 2000 problem into the program */
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// year = t.gmt->tm_year + 1900;
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//
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// /* calculate the actual time, remember to add 1 to tm_mon! */
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// actTime = 367 * year - 7 *
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// (year + ((t.gmt->tm_mon+1) + 9) / 12) / 4 + 275 *
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// (t.gmt->tm_mon+1) / 9 + t.gmt->tm_mday - 730530;
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//
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// UT = t.gmt->tm_hour + ((double) t.gmt->tm_min / 60);
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// /*printf("UT = %f\n", UT); */
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// actTime += (UT / 24.0);
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// #define DEBUG 1
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// #ifdef DEBUG
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// /* printf(" Actual Time:\n"); */
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// /* printf(" current day = %f\t", actTime); */
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// /* printf(" GMT = %d, %d, %d, %d, %d, %d\n",
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// year, t.gmt->tm_mon, t.gmt->tm_mday,
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// t.gmt->tm_hour, t.gmt->tm_min, t.gmt->tm_sec); */
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// #endif
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// return actTime;
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//}
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double fgCalcActTime(struct fgTIME t)
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{
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return (t.mjd - 36523.5);
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}
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/* convert degrees to radians */
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/*
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double fgDegToRad(double angle)
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{
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return (angle * PIOVER180);
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}
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*/
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double fgCalcEccAnom(double M, double e)
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{
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double
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eccAnom, E0, E1, diff;
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eccAnom = M + e * sin(M) * (1.0 + e * cos(M));
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/* iterate to achieve a greater precision for larger eccentricities */
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if (e > 0.05)
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{
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E0 = eccAnom;
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do
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{
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E1 = E0 - (E0 - e * sin(E0) - M) / (1 - e * cos(E0));
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diff = fabs(E0 - E1);
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E0 = E1;
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}
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while (diff > (DEG_TO_RAD * 0.001));
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return E0;
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}
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return eccAnom;
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}
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void fgReadOrbElements(struct OrbElements *dest, FILE *src)
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{
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char line[256];
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int i,j;
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j = 0;
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do
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{
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fgets(line, 256,src);
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for (i = 0; i < 256; i++)
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{
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if (line[i] == '#')
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line[i] = 0;
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}
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/*printf("Reading line %d\n", j++); */
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}
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while (!(strlen(line)));
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sscanf(line, "%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf\n",
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&dest->NFirst, &dest->NSec,
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&dest->iFirst, &dest->iSec,
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&dest->wFirst, &dest->wSec,
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&dest->aFirst, &dest->aSec,
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&dest->eFirst, &dest->eSec,
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&dest->MFirst, &dest->MSec);
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}
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void fgSolarSystemInit(struct fgTIME t)
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{
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struct fgGENERAL *g;
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char path[80];
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int i;
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FILE *data;
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fgPrintf( FG_ASTRO, FG_INFO, "Initializing solar system\n");
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/* build the full path name to the orbital elements database file */
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g = &general;
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path[0] = '\0';
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strcat(path, g->root_dir);
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strcat(path, "/Scenery/");
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strcat(path, "Planets.dat");
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if ( (data = fopen(path, "r")) == NULL )
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{
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fgPrintf( FG_ASTRO, FG_ALERT,
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"Cannot open data file: '%s'\n", path);
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return;
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}
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fgPrintf( FG_ASTRO, FG_INFO, " reading datafile %s\n", path);
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/* for all the objects... */
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for (i = 0; i < 9; i ++)
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{
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/* ...read from the data file ... */
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fgReadOrbElements(&pltOrbElements[i], data);
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/* ...and calculate the actual values */
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fgSolarSystemUpdate(&pltOrbElements[i], t);
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}
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}
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void fgSolarSystemUpdate(struct OrbElements *planet, struct fgTIME t)
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{
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double
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actTime;
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actTime = fgCalcActTime(t);
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/* calculate the actual orbital elements */
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planet->M = DEG_TO_RAD * (planet->MFirst + (planet->MSec * actTime)); // angle in radians
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planet->w = DEG_TO_RAD * (planet->wFirst + (planet->wSec * actTime)); // angle in radians
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planet->N = DEG_TO_RAD * (planet->NFirst + (planet->NSec * actTime)); // angle in radians
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planet->i = DEG_TO_RAD * (planet->iFirst + (planet->iSec * actTime)); // angle in radians
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planet->e = planet->eFirst + (planet->eSec * actTime);
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planet->a = planet->aFirst + (planet->aSec * actTime);
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}
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/* $Log$
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/* Revision 1.5 1998/02/02 20:53:22 curt
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/* To version 0.29
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/*
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* Revision 1.4 1998/01/27 00:47:47 curt
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* Incorporated Paul Bleisch's <bleisch@chromatic.com> new debug message
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* system and commandline/config file processing code.
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*
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* Revision 1.3 1998/01/22 02:59:27 curt
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* Changed #ifdef FILE_H to #ifdef _FILE_H
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*
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* Revision 1.2 1998/01/19 19:26:58 curt
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* Merged in make system changes from Bob Kuehne <rpk@sgi.com>
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* This should simplify things tremendously.
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*
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* Revision 1.1 1998/01/07 03:16:17 curt
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* Moved from .../Src/Scenery/ to .../Src/Astro/
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*
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* Revision 1.6 1997/12/30 20:47:52 curt
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* Integrated new event manager with subsystem initializations.
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*
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* Revision 1.5 1997/12/15 23:55:02 curt
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* Add xgl wrappers for debugging.
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* Generate terrain normals on the fly.
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*
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* Revision 1.4 1997/12/10 22:37:51 curt
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* Prepended "fg" on the name of all global structures that didn't have it yet.
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* i.e. "struct WEATHER {}" became "struct fgWEATHER {}"
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*
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* Revision 1.3 1997/11/25 23:20:44 curt
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* Changed planets.dat Planets.dat
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*
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* Revision 1.2 1997/11/25 19:25:36 curt
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* Changes to integrate Durk's moon/sun code updates + clean up.
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*
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* Revision 1.1 1997/10/25 03:16:10 curt
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* Initial revision of code contributed by Durk Talsma.
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*
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*/
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