/************************************************************************** * fg_time.c -- data structures and routines for managing time related stuff. * * Written by Curtis Olson, started August 1997. * * Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com * * 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., 675 Mass Ave, Cambridge, MA 02139, USA. * * $Id$ * (Log is kept at end of this file) **************************************************************************/ #include #include #include #include #ifdef WIN32 #include /* for gettimeofday() */ #include /* for gettimeofday() */ #endif #include "fg_time.h" #include "../constants.h" #include "../Flight/flight.h" #include "../Time/fg_time.h" #define DEGHR(x) ((x)/15.) #define RADHR(x) DEGHR(x*RAD_TO_DEG) struct fgTIME cur_time_params; /* Initialize the time dependent variables */ void fgTimeInit(struct fgTIME *t) { t->gst_diff = -9999.0; } /* given a date in months, mn, days, dy, years, yr, return the * modified Julian date (number of days elapsed since 1900 jan 0.5), * mjd. Adapted from Xephem. */ double cal_mjd (int mn, double dy, int yr) { static double last_mjd, last_dy; double mjd; static int last_mn, last_yr; int b, d, m, y; long c; if (mn == last_mn && yr == last_yr && dy == last_dy) { mjd = last_mjd; return(mjd); } m = mn; y = (yr < 0) ? yr + 1 : yr; if (mn < 3) { m += 12; y -= 1; } if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) { b = 0; } else { int a; a = y/100; b = 2 - a + a/4; } if (y < 0) { c = (long)((365.25*y) - 0.75) - 694025L; } else { c = (long)(365.25*y) - 694025L; } d = 30.6001*(m+1); mjd = b + c + d + dy - 0.5; last_mn = mn; last_dy = dy; last_yr = yr; last_mjd = mjd; return(mjd); } /* given an mjd, return greenwich mean siderial time, gst */ double utc_gst (double mjd) { double gst; double day = floor(mjd-0.5)+0.5; double hr = (mjd-day)*24.0; double T, x; T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0; x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T; x /= 3600.0; gst = (1.0/SIDRATE)*hr + x; printf("gst => %.4f\n", gst); return(gst); } /* given Julian Date and Longitude (decimal degrees West) compute and * return Local Sidereal Time, in decimal hours. * * Provided courtesy of ecdowney@noao.edu (Elwood Downey) */ double sidereal_precise (double mjd, double lng) { double gst; double lst; /* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ", mjd + MJD0, lng); */ /* convert to required internal units */ lng *= DEG_TO_RAD; /* compute LST and print */ gst = utc_gst (mjd); lst = gst - RADHR (lng); lst -= 24.0*floor(lst/24.0); /* printf ("%7.4f\n", lst); */ /* that's all */ return (lst); } /* return a courser but cheaper estimate of sidereal time */ double sidereal_course(struct tm *gmt, time_t now, double lng) { time_t start, start_gmt; struct tm mt; long int offset; double diff, part, days, hours, lst; #ifdef WIN32 int daylight; long int timezone; struct timeval tv; struct timezone tz; #endif printf("COURSE: GMT = %d/%d/%2d %d:%02d:%02d\n", gmt->tm_mon, gmt->tm_mday, gmt->tm_year, gmt->tm_hour, gmt->tm_min, gmt->tm_sec); mt.tm_mon = 2; mt.tm_mday = 21; mt.tm_year = gmt->tm_year; mt.tm_hour = 12; mt.tm_min = 0; mt.tm_sec = 0; start = mktime(&mt); #ifdef WIN32 daylight = mt.tm_isdst; gettimeofday(&tv, &tz); timezone = tz.tz_minuteswest * 60; #endif if ( daylight > 0 ) { daylight = 1; } else if ( daylight < 0 ) { printf("OOOPS, big time problem in fg_time.c, no daylight savings info.\n"); } offset = -(timezone / 3600 - daylight); printf("Raw time zone offset = %ld\n", timezone); printf("Daylight Savings = %d\n", daylight); printf("Local hours from GMT = %ld\n", offset); start_gmt = start - timezone + (daylight * 3600); printf("March 21 noon (CST) = %ld\n", start); printf("March 21 noon (GMT) = %ld\n", start_gmt); diff = (now - start_gmt) / (3600.0 * 24.0); printf("Time since 3/21/%2d GMT = %.2f\n", gmt->tm_year, diff); part = fmod(diff, 1.0); days = diff - part; hours = gmt->tm_hour + gmt->tm_min/60.0 + gmt->tm_sec/3600.0; lst = (days - lng)/15.0 + hours - 12; while ( lst < 0.0 ) { lst += 24.0; } printf("days = %.1f hours = %.2f lon = %.2f lst = %.2f\n", days, hours, lng, lst); return(lst); } /* Update the time dependent variables */ void fgTimeUpdate(struct FLIGHT *f, struct fgTIME *t) { double gst_precise, gst_course; static long int warp = 0; /* get current Unix calendar time (in seconds) */ warp += 60; /* warp = 0; */ t->cur_time = time(NULL) + (0) * 60 * 60; t->cur_time += warp; printf("Current Unix calendar time = %ld warp = %ld\n", t->cur_time, warp); /* get GMT break down for current time */ t->gmt = gmtime(&t->cur_time); printf("Current GMT = %d/%d/%2d %d:%02d:%02d\n", t->gmt->tm_mon+1, t->gmt->tm_mday, t->gmt->tm_year, t->gmt->tm_hour, t->gmt->tm_min, t->gmt->tm_sec); /* calculate modified Julian date */ t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday, (int)(t->gmt->tm_year + 1900)); /* add in partial day */ t->mjd += (t->gmt->tm_hour / 24.0) + (t->gmt->tm_min / (24.0 * 60.0)) + (t->gmt->tm_sec / (24.0 * 60.0 * 60.0)); /* convert "back" to Julian date + partial day (as a fraction of one) */ t->jd = t->mjd + MJD0; printf("Current Julian Date = %.5f\n", t->jd); printf("Current Longitude = %.3f\n", FG_Longitude * RAD_TO_DEG); /* Calculate local side real time */ if ( t->gst_diff < -100.0 ) { /* first time through do the expensive calculation & cheap calculation to get the difference. */ printf("First time, doing precise gst\n"); t->gst = gst_precise = sidereal_precise(t->mjd, 0.00); gst_course = sidereal_course(t->gmt, t->cur_time, 0.00); t->gst_diff = gst_precise - gst_course; t->lst = sidereal_course(t->gmt, t->cur_time, -(FG_Longitude * RAD_TO_DEG)) + t->gst_diff; } else { /* course + difference should drift off very slowly */ t->gst = sidereal_course(t->gmt, t->cur_time, 0.00) + t->gst_diff; t->lst = sidereal_course(t->gmt, t->cur_time, -(FG_Longitude * RAD_TO_DEG)) + t->gst_diff; } /* printf("Current lon=0.00 Sidereal Time = %.3f\n", t->gst); */ /* printf("Current LOCAL Sidereal Time = %.3f (%.3f) (diff = %.3f)\n", t->lst, sidereal_precise(t->mjd, -(FG_Longitude * RAD_TO_DEG)), t->gst_diff); */ } /* $Log$ /* Revision 1.11 1997/11/25 19:25:40 curt /* Changes to integrate Durk's moon/sun code updates + clean up. /* * Revision 1.10 1997/11/15 18:16:42 curt * minor tweaks. * * Revision 1.9 1997/11/14 00:26:50 curt * Transform scenery coordinates earlier in pipeline when scenery is being * created, not when it is being loaded. Precalculate normals for each node * as average of the normals of each containing polygon so Garoude shading is * now supportable. * * Revision 1.8 1997/10/25 03:30:08 curt * Misc. tweaks. * * Revision 1.7 1997/09/23 00:29:50 curt * Tweaks to get things to compile with gcc-win32. * * Revision 1.6 1997/09/20 03:34:34 curt * Still trying to get those durned stars aligned properly. * * Revision 1.5 1997/09/16 22:14:52 curt * Tweaked time of day lighting equations. Don't draw stars during the day. * * Revision 1.4 1997/09/16 15:50:31 curt * Working on star alignment and time issues. * * Revision 1.3 1997/09/13 02:00:08 curt * Mostly working on stars and generating sidereal time for accurate star * placement. * * Revision 1.2 1997/08/27 03:30:35 curt * Changed naming scheme of basic shared structures. * * Revision 1.1 1997/08/13 21:55:59 curt * Initial revision. * */