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GMST update

feature/19
Daniel Warner 2018-08-30 18:59:43 +01:00 committed by Daniel Warner
parent 6982421275
commit 52dcd7f0f5
1 changed files with 8 additions and 8 deletions
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16
libsgp4/DateTime.h
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@ -605,17 +605,17 @@ public:
*/ */
double ToGreenwichSiderealTime() const double ToGreenwichSiderealTime() const
{ {
// t = Julian centuries from 2000 Jan. 1 12h UT1 // julian date of previous midnight
const double t = (ToJulian() - 2451545.0) / 36525.0; double jd0 = floor(ToJulian() + 0.5) - 0.5;
// julian centuries since epoch
double t = (jd0 - 2451545.0) / 36525.0;
double jdf = ToJulian() - jd0;
// Rotation angle in arcseconds double gt = 24110.54841 + t * (8640184.812866 + t * (0.093104 - t * 6.2E-6));
double theta = 67310.54841 gt += jdf * 1.00273790935 * 86400.0;
+ (876600.0 * 3600.0 + 8640184.812866) * t
+ 0.093104 * t * t
- 0.0000062 * t * t * t;
// 360.0 / 86400.0 = 1.0 / 240.0 // 360.0 / 86400.0 = 1.0 / 240.0
return Util::WrapTwoPI(Util::DegreesToRadians(theta / 240.0)); return Util::WrapTwoPI(Util::DegreesToRadians(gt / 240.0));
} }
/** /**