43 lines
1.0 KiB
C++
43 lines
1.0 KiB
C++
#include "SphericalGravityModel.h"
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#include "utils/math/Constants.h"
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#include <cmath>
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namespace sim
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{
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SphericalGravityModel::SphericalGravityModel()
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{
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}
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SphericalGravityModel::~SphericalGravityModel()
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{
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}
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TripletD SphericalGravityModel::getAccel(double x, double y, double z)
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{
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// Convert x, y, z from meters to km. This is to avoid potential precision losses
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// with using the earth's gravitation parameter in meters (14 digit number).
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// GM in kilometers is much more manageable.
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// An alternative is to use quadruple precision, but that may
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// take a lot more computation time and I think this will be fine.
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double x_km = x / 1000.0;
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double y_km = y / 1000.0;
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double z_km = z / 1000.0;
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double r_km = std::sqrt(x_km * x_km + y_km * y_km + z_km * z_km);
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double accelFactor = - utils::math::Constants::earthGM_km / std::sqrt(r_km * r_km * r_km);
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double ax = accelFactor * x_km * 1000.0;
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double ay = accelFactor * y_km * 1000.0;
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double az = accelFactor * z_km * 1000.0;
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return TripletD(ax, ay, az);
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}
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}
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