ATT_math.c File Reference

LAT attitude processing mathematical functions. More...

#include <ATT/ATT.h>
#include <ATT_private.h>
#include <math.h>

Functions
static void	vector_2_longlat (const double *v, double *longitude, double *latitude)
	Routine to convert cartesian coordinates to longitude-latitude like angular coordinates.
Vector Transform Functions
void	ATT_xform_vec_by_quat (double *Ve, const double *Q, const double *Vl)
	Tranform vector coordinates from LAT to J2000.
Quaternion Utility Functions
void	ATT_quat_multiply (double *Qr, const double *Qa, const double *Qb)
	Multiply two quaternions.
double	ATT_quat_magnitude (const double *Q)
	Get a quaternion magnitude.
void	ATT_quat_normalize (double *Q)
	Normallize a quaternion.
void	ATT_quat_conjugate (double *Qr, const double *Qa)
	Get a quaternion conjugate.
Vector Utility Functions
double	ATT_vec_magnitude (const double *V)
	Get a vector magnitude.
void	ATT_vec_normalize (double *V)
	Normallize a vector.
void	ATT_vec_cart_to_sphr_deg (const double *Vc, double *Vs)
	Transform a cartesian vector to spherical (ra,dec) coordinates (degrees).
void	ATT_vec_cart_to_sphr_rad (const double *Vc, double *Vs)
	Transform a cartesian vector to spherical (ra,dec) coordinates (radians).

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Detailed Description

LAT attitude processing mathematical functions.

Author:

D.L. Wood

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Function Documentation

void ATT_quat_conjugate	(	double *	Qr,
		const double *	Qa
	)

Get a quaternion conjugate.

Returns the conjugate of quaternion Qa in Qr.

Parameters:

	Qa	Input quaternion. Qa[0] = q1 (x) Qa[1] = q2 (y) Qa[2] = q3 (z) Qa[3] = q4 (w)
	Qr	Output conjugate quaternion. Qr[0] = q1 (x) Qr[1] = q2 (y) Qr[2] = q3 (z) Qr[3] = q4 (w)

Referenced by ATT_xform_vec_by_quat().

double ATT_quat_magnitude

(

const double *

Q

)

Get a quaternion magnitude.

Returns the magnitude of quaternion Q.

Parameters:

Q

Input quaternion. Q[0] = q1 (x) Q[1] = q2 (y) Q[2] = q3 (z) Q[3] = q4 (w)

Returns:

The magnitude of Q.

Referenced by ATT_quat_normalize().

void ATT_quat_multiply	(	double *	Qr,
		const double *	Qa,
		const double *	Qb
	)

Multiply two quaternions.

Multilplies the quaternion Qa by quaternion Qb and stores the result in Qr. Qr = Qb x Qa. This operation is not commutative.

Parameters:

	Qa	Input quaternion. Qa[0] = q1 (x) Qa[1] = q2 (y) Qa[2] = q3 (z) Qa[3] = q4 (w)
	Qb	Input quaternion. Qb[0] = q1 (x) Qb[1] = q2 (y) Qb[2] = q3 (z) Qb[3] = q4 (w)
	Qr	Output quaternion product. Qr[0] = q1 (x) Qr[1] = q2 (y) Qr[2] = q3 (z) Qr[3] = q4 (w)

Referenced by ATT_update(), and ATT_xform_vec_by_quat().

void ATT_quat_normalize

(

double *

Q

)

Normallize a quaternion.

Modifies quaternion Q so that the result has magnitude '1'. This function works in place.

Parameters:

Q

Input quaternion. Q[0] = q1 (x) Q[1] = q2 (y) Q[2] = q3 (z) Q[3] = q4 (w)

References ATT_quat_magnitude().

void ATT_vec_cart_to_sphr_deg	(	const double *	Vc,
		double *	Vs
	)

Transform a cartesian vector to spherical (ra,dec) coordinates (degrees).

Transforms the vector Vc in (x,y,z) cartesian coordinates into the vector Vs in (ra,dec) spherical coordinates. Vs is returned in degrees.

Parameters:

	Vc	The input vector in cartisian coordinates. Vc[0] = x Vc[1] = y Vc[2] = z
	Vs	The output vector in spherical coordinates. Vs[0] = ra Vs[1] = dec

References M_PI, and vector_2_longlat().

void ATT_vec_cart_to_sphr_rad	(	const double *	Vc,
		double *	Vs
	)

Transform a cartesian vector to spherical (ra,dec) coordinates (radians).

Transforms the vector Vc in (x,y,z) cartesian coordinates into the vector Vs in (ra,dec) spherical coordinates. Vs is returned in radians.

Parameters:

	Vc	The input vector in cartisian coordinates. Vc[0] = x Vc[1] = y Vc[2] = z
	Vs	The output vector in spherical coordinates. Vs[0] = ra Vs[1] = dec

References vector_2_longlat().

double ATT_vec_magnitude

(

const double *

V

)

Get a vector magnitude.

Returns the magnitude of vector V.

Parameters:

V

Input vector. V[0] = x V[1] = y V[2] = z

Returns:

The magnitude of V.

Referenced by ATT_vec_normalize().

void ATT_vec_normalize

(

double *

V

)

Normallize a vector.

Modifies vector V so that the result has magnitude '1'. This function works in place.

Parameters:

V

Input vector. V[0] = x V[1] = y V[2] = z

References ATT_vec_magnitude().

unsigned int ATT_xform_vec_by_quat	(	double *	Ve,
		const double *	Q,
		const double *	Vl
	)

Tranform vector coordinates from LAT to J2000.

Performs coordinate transformation on the vector Vl, which is assumed to be a cartiesian vector in LAT instrument local coordinates (SC body coordinates). The information in quaternion Q is used to transform the vector coordinates into J2000 (ECI) coordinates. The resulting vector coordinates are stored in Ve.

Parameters:

	Q	Input quaternion. Q[0] = q1 (x) Q[1] = q2 (y) Q[2] = q3 (z) Q[3] = q4 (w)
	Vl	Input vector in LAT coordinates. Vl[0] = x Vl[1] = y Vl[2] = z
	Ve	Output vector in J2000 coordinates. Ve[0] = x Ve[1] = y Ve[2] = z

References ATT_quat_conjugate(), and ATT_quat_multiply().

Referenced by ATT_xform().

static void vector_2_longlat	(	const double *	v,
		double *	longitude,
		double *	latitude
	)			[static]

Routine to convert cartesian coordinates to longitude-latitude like angular coordinates.

Adopted from ARGOS/USA ground processing code.

Parameters:

	v	The input vector in cartisian coordinates. Vc[0] = x Vc[1] = y Vc[2] = z
	longitude	Stores the output "longitude" coordinate.
	latitude	Stores the output "latitude" coordinate.

References M_PI.

Referenced by ATT_vec_cart_to_sphr_deg(), and ATT_vec_cart_to_sphr_rad().