66 lines
1.7 KiB
C++
66 lines
1.7 KiB
C++
#include "Observer.h"
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#include "Globals.h"
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/*
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* calculate lookangle between the observer and the passed in Eci object
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*/
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CoordTopographic Observer::GetLookAngle(const Eci &eci) {
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/*
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* update the observers Eci to match the time of the Eci passed in
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* if necessary
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*/
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UpdateObserversEci(eci.GetDate());
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/*
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* calculate differences
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*/
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Vector range_rate = eci.GetVelocity().Subtract(observers_eci_.GetVelocity());
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Vector range = eci.GetPosition().Subtract(observers_eci_.GetPosition());
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range.w = range.GetMagnitude();
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/*
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* Calculate Local Mean Sidereal Time for observers longitude
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*/
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double theta = eci.GetDate().ToLocalMeanSiderealTime(geo_.longitude);
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double sin_lat = sin(geo_.latitude);
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double cos_lat = cos(geo_.latitude);
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double sin_theta = sin(theta);
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double cos_theta = cos(theta);
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double top_s = sin_lat * cos_theta * range.x +
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sin_lat * sin_theta * range.y -
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cos_lat * range.z;
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double top_e = -sin_theta * range.x +
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cos_theta * range.y;
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double top_z = cos_lat * cos_theta * range.x +
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cos_lat * sin_theta * range.y +
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sin_lat * range.z;
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double az = atan(-top_e / top_s);
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if (top_s > 0.0)
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az += kPI;
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if (az < 0.0)
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az += 2.0 * kPI;
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double el = asin(top_z / range.w);
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double rate = range.Dot(range_rate) / range.w;
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/*
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* azimuth in radians
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* elevation in radians
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* range in km
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* range rate in km/s
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*/
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CoordTopographic topo(az,
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el,
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range.w,
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rate);
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return topo;
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}
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