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/**
******************************************************************************
*
* @file WorldMagModel.c
* @author The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
* @brief Source file for the World Magnetic Model
* This is a port of code available from the US NOAA.
* The hard coded coefficients should be valid until 2015.
* Major changes include:
* - No geoid model (altitude must be geodetic WGS-84)
* - Floating point calculation (not double precision)
* - Hard coded coefficients for model
* - Elimination of user interface
* - Elimination of dynamic memory allocation
*
* @see The GNU Public License (GPL) Version 3
*
*****************************************************************************/
/*
* 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 3 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.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <stdint.h>
#include "WorldMagModel.h"
#include "WMMInternal.h"
WMMtype_Ellipsoid Ellip;
WMMtype_MagneticModel MagneticModel;
/**************************************************************************************
* Example use - very simple - only two exposed functions
*
* WMM_Initialize(); // Set default values and constants
*
* WMM_GetMagVector(float Lat, float Lon, float Alt, uint16_t Month, uint16_t Day, uint16_t Year, float B[3]);
* e.g. Iceland in may of 2012 = WMM_GetMagVector(65.0, -20.0, 0.0, 5, 5, 2012, B);
* Alt is above the WGS-84 Ellipsoid
* B is the NED (XYZ) magnetic vector in nTesla
**************************************************************************************/
void WMM_Initialize()
// Sets default values for WMM subroutines.
// UPDATES : Ellip and MagneticModel
{
float coeffs[NUMTERMS][6];
// Sets WGS-84 parameters
Ellip.a = 6378.137; // semi-major axis of the ellipsoid in km
Ellip.b = 6356.7523142; // semi-minor axis of the ellipsoid in km
Ellip.fla = 1/298.257223563; // flattening
Ellip.eps = sqrt(1- (Ellip.b*Ellip.b)/(Ellip.a*Ellip.a )); // first eccentricity
Ellip.epssq = (Ellip.eps*Ellip.eps); // first eccentricity squared
Ellip.re = 6371.2; // Earth's radius in km
// Sets Magnetic Model parameters
MagneticModel.nMax = WMM_MAX_MODEL_DEGREES;
MagneticModel.nMaxSecVar = WMM_MAX_SECULAR_VARIATION_MODEL_DEGREES;
MagneticModel.SecularVariationUsed = 0;
// Really, Really needs to be read from a file - out of date in 2015 at latest
MagneticModel.EditionDate = 5.7863328170559505e-307;
MagneticModel.epoch = 2010.0;
sprintf(MagneticModel.ModelName, "WMM-2010");
WMM_Set_Coeff_Array(coeffs);
for(uint16_t i=0; i<NUMTERMS; i++){
MagneticModel.Main_Field_Coeff_G[i]=coeffs[i][2];
MagneticModel.Main_Field_Coeff_H[i]=coeffs[i][3];
MagneticModel.Secular_Var_Coeff_G[i]=coeffs[i][4];
MagneticModel.Secular_Var_Coeff_H[i]=coeffs[i][5];
}
}
void WMM_GetMagVector(float Lat, float Lon, float AltEllipsoid, uint16_t Month, uint16_t Day, uint16_t Year, float B[3])
{
char Error_Message[255];
WMMtype_MagneticModel TimedMagneticModel;
WMMtype_CoordSpherical CoordSpherical;
WMMtype_CoordGeodetic CoordGeodetic;
WMMtype_Date Date;
WMMtype_GeoMagneticElements GeoMagneticElements;
CoordGeodetic.lambda = Lon;
CoordGeodetic.phi = Lat;
CoordGeodetic.HeightAboveEllipsoid = AltEllipsoid;
WMM_GeodeticToSpherical(Ellip, CoordGeodetic, &CoordSpherical); /*Convert from geodeitic to Spherical Equations: 17-18, WMM Technical report*/
Date.Month=Month;
Date.Day=Day;
Date.Year=Year;
WMM_DateToYear (&Date, Error_Message);
WMM_TimelyModifyMagneticModel(Date, &MagneticModel, &TimedMagneticModel); /* Time adjust the coefficients, Equation 19, WMM Technical report */
WMM_Geomag(Ellip, CoordSpherical, CoordGeodetic, &TimedMagneticModel, &GeoMagneticElements); /* Computes the geoMagnetic field elements and their time change*/
B[0]=GeoMagneticElements.X;
B[1]=GeoMagneticElements.Y;
B[2]=GeoMagneticElements.Z;
}
uint16_t WMM_Geomag(WMMtype_Ellipsoid Ellip, WMMtype_CoordSpherical CoordSpherical, WMMtype_CoordGeodetic CoordGeodetic,
WMMtype_MagneticModel *TimedMagneticModel, WMMtype_GeoMagneticElements *GeoMagneticElements)
/*
The main subroutine that calls a sequence of WMM sub-functions to calculate the magnetic field elements for a single point.
The function expects the model coefficients and point coordinates as input and returns the magnetic field elements and
their rate of change. Though, this subroutine can be called successively to calculate a time series, profile or grid
of magnetic field, these are better achieved by the subroutine WMM_Grid.
INPUT: Ellip
CoordSpherical
CoordGeodetic
TimedMagneticModel
OUTPUT : GeoMagneticElements
CALLS: WMM_ComputeSphericalHarmonicVariables( Ellip, CoordSpherical, TimedMagneticModel->nMax, &SphVariables); (Compute Spherical Harmonic variables )
WMM_AssociatedLegendreFunction(CoordSpherical, TimedMagneticModel->nMax, LegendreFunction); Compute ALF
WMM_Summation(LegendreFunction, TimedMagneticModel, SphVariables, CoordSpherical, &MagneticResultsSph); Accumulate the spherical harmonic coefficients
WMM_SecVarSummation(LegendreFunction, TimedMagneticModel, SphVariables, CoordSpherical, &MagneticResultsSphVar); Sum the Secular Variation Coefficients
WMM_RotateMagneticVector(CoordSpherical, CoordGeodetic, MagneticResultsSph, &MagneticResultsGeo); Map the computed Magnetic fields to Geodeitic coordinates
WMM_RotateMagneticVector(CoordSpherical, CoordGeodetic, MagneticResultsSphVar, &MagneticResultsGeoVar); Map the secular variation field components to Geodetic coordinates
WMM_CalculateGeoMagneticElements(&MagneticResultsGeo, GeoMagneticElements); Calculate the Geomagnetic elements
WMM_CalculateSecularVariation(MagneticResultsGeoVar, GeoMagneticElements); Calculate the secular variation of each of the Geomagnetic elements
*/
{
WMMtype_LegendreFunction LegendreAllocate, *LegendreFunction;
LegendreFunction = &LegendreAllocate;
WMMtype_SphericalHarmonicVariables SphVariables;
WMMtype_MagneticResults MagneticResultsSph, MagneticResultsGeo, MagneticResultsSphVar, MagneticResultsGeoVar;
WMM_ComputeSphericalHarmonicVariables( Ellip, CoordSpherical, TimedMagneticModel->nMax, &SphVariables); /* Compute Spherical Harmonic variables */
WMM_AssociatedLegendreFunction(CoordSpherical, TimedMagneticModel->nMax, LegendreFunction); /* Compute ALF */
WMM_Summation(LegendreFunction, TimedMagneticModel, SphVariables, CoordSpherical, &MagneticResultsSph); /* Accumulate the spherical harmonic coefficients*/
WMM_SecVarSummation(LegendreFunction, TimedMagneticModel, SphVariables, CoordSpherical, &MagneticResultsSphVar); /*Sum the Secular Variation Coefficients */
WMM_RotateMagneticVector(CoordSpherical, CoordGeodetic, MagneticResultsSph, &MagneticResultsGeo); /* Map the computed Magnetic fields to Geodeitic coordinates */
WMM_RotateMagneticVector(CoordSpherical, CoordGeodetic, MagneticResultsSphVar, &MagneticResultsGeoVar); /* Map the secular variation field components to Geodetic coordinates*/
WMM_CalculateGeoMagneticElements(&MagneticResultsGeo, GeoMagneticElements); /* Calculate the Geomagnetic elements, Equation 18 , WMM Technical report */
WMM_CalculateSecularVariation(MagneticResultsGeoVar, GeoMagneticElements); /*Calculate the secular variation of each of the Geomagnetic elements*/
return TRUE;
}
uint16_t WMM_ComputeSphericalHarmonicVariables(WMMtype_Ellipsoid Ellip, WMMtype_CoordSpherical CoordSpherical, uint16_t nMax, WMMtype_SphericalHarmonicVariables *SphVariables)
/* Computes Spherical variables
Variables computed are (a/r)^(n+2), cos_m(lamda) and sin_m(lambda) for spherical harmonic
summations. (Equations 10-12 in the WMM Technical Report)
INPUT Ellip data structure with the following elements
float a; semi-major axis of the ellipsoid
float b; semi-minor axis of the ellipsoid
float fla; flattening
float epssq; first eccentricity squared
float eps; first eccentricity
float re; mean radius of ellipsoid
CoordSpherical A data structure with the following elements
float lambda; ( longitude)
float phig; ( geocentric latitude )
float r; ( distance from the center of the ellipsoid)
nMax integer ( Maxumum degree of spherical harmonic secular model)\
OUTPUT SphVariables Pointer to the data structure with the following elements
float RelativeRadiusPower[WMM_MAX_MODEL_DEGREES+1]; [earth_reference_radius_km sph. radius ]^n
float cos_mlambda[WMM_MAX_MODEL_DEGREES+1]; cp(m) - cosine of (mspherical coord. longitude)
float sin_mlambda[WMM_MAX_MODEL_DEGREES+1]; sp(m) - sine of (mspherical coord. longitude)
CALLS : none
*/
{
float cos_lambda, sin_lambda;
uint16_t m, n;
cos_lambda = cos(DEG2RAD(CoordSpherical.lambda));
sin_lambda = sin(DEG2RAD(CoordSpherical.lambda));
/* for n = 0 ... model_order, compute (Radius of Earth / Spherica radius r)^(n+2)
for n 1..nMax-1 (this is much faster than calling pow MAX_N+1 times). */
SphVariables->RelativeRadiusPower[0] = (Ellip.re / CoordSpherical.r) * (Ellip.re / CoordSpherical.r);
for (n = 1; n <= nMax; n++)
{
SphVariables->RelativeRadiusPower[n] = SphVariables->RelativeRadiusPower[n-1] * (Ellip.re / CoordSpherical.r);
}
/*
Compute cos(m*lambda), sin(m*lambda) for m = 0 ... nMax
cos(a + b) = cos(a)*cos(b) - sin(a)*sin(b)
sin(a + b) = cos(a)*sin(b) + sin(a)*cos(b)
*/
SphVariables->cos_mlambda[0] = 1.0;
SphVariables->sin_mlambda[0] = 0.0;
SphVariables->cos_mlambda[1] = cos_lambda;
SphVariables->sin_mlambda[1] = sin_lambda;
for (m = 2; m <= nMax; m++)
{
SphVariables->cos_mlambda[m] = SphVariables->cos_mlambda[m-1]*cos_lambda - SphVariables->sin_mlambda[m-1]*sin_lambda;
SphVariables->sin_mlambda[m] = SphVariables->cos_mlambda[m-1]*sin_lambda + SphVariables->sin_mlambda[m-1]*cos_lambda;
}
return TRUE;
} /*WMM_ComputeSphericalHarmonicVariables*/
uint16_t WMM_AssociatedLegendreFunction(WMMtype_CoordSpherical CoordSpherical, uint16_t nMax, WMMtype_LegendreFunction *LegendreFunction)
/* Computes all of the Schmidt-semi normalized associated Legendre
functions up to degree nMax. If nMax <= 16, function WMM_PcupLow is used.
Otherwise WMM_PcupHigh is called.
INPUT CoordSpherical A data structure with the following elements
float lambda; ( longitude)
float phig; ( geocentric latitude )
float r; ( distance from the center of the ellipsoid)
nMax integer ( Maxumum degree of spherical harmonic secular model)
LegendreFunction Pointer to data structure with the following elements
float *Pcup; ( pointer to store Legendre Function )
float *dPcup; ( pointer to store Derivative of Lagendre function )
OUTPUT LegendreFunction Calculated Legendre variables in the data structure
*/
{
float sin_phi;
uint16_t FLAG = 1;
sin_phi = sin ( DEG2RAD ( CoordSpherical.phig ) ); /* sin (geocentric latitude) */
if (nMax <= 16 || (1 - fabs(sin_phi)) < 1.0e-10 ) /* If nMax is less tha 16 or at the poles */
FLAG = WMM_PcupLow(LegendreFunction->Pcup,LegendreFunction->dPcup,sin_phi, nMax);
else FLAG = WMM_PcupHigh(LegendreFunction->Pcup,LegendreFunction->dPcup,sin_phi, nMax);
if (FLAG == 0) /* Error while computing Legendre variables*/
return FALSE;
return TRUE;
} /*WMM_AssociatedLegendreFunction */
uint16_t WMM_Summation(WMMtype_LegendreFunction *LegendreFunction, WMMtype_MagneticModel *MagneticModel, WMMtype_SphericalHarmonicVariables SphVariables, WMMtype_CoordSpherical CoordSpherical, WMMtype_MagneticResults *MagneticResults)
{
/* Computes Geomagnetic Field Elements X, Y and Z in Spherical coordinate system using
spherical harmonic summation.
The vector Magnetic field is given by -grad V, where V is Geomagnetic scalar potential
The gradient in spherical coordinates is given by:
dV ^ 1 dV ^ 1 dV ^
grad V = -- r + - -- t + -------- -- p
dr r dt r sin(t) dp
INPUT : LegendreFunction
MagneticModel
SphVariables
CoordSpherical
OUTPUT : MagneticResults
CALLS : WMM_SummationSpecial
Manoj Nair, June, 2009 Manoj.C.Nair@Noaa.Gov
*/
uint16_t m, n, index;
float cos_phi;
MagneticResults->Bz = 0.0;
MagneticResults->By = 0.0;
MagneticResults->Bx = 0.0;
for (n = 1; n <= MagneticModel->nMax; n++)
{
for (m=0;m<=n;m++)
{
index = (n * (n + 1) / 2 + m);
/* nMax (n+2) n m m m
Bz = -SUM (a/r) (n+1) SUM [g cos(m p) + h sin(m p)] P (sin(phi))
n=1 m=0 n n n */
/* Equation 12 in the WMM Technical report. Derivative with respect to radius.*/
MagneticResults->Bz -= SphVariables.RelativeRadiusPower[n] *
( MagneticModel->Main_Field_Coeff_G[index]*SphVariables.cos_mlambda[m] +
MagneticModel->Main_Field_Coeff_H[index]*SphVariables.sin_mlambda[m] )
* (float) (n+1) * LegendreFunction-> Pcup[index];
/* 1 nMax (n+2) n m m m
By = SUM (a/r) (m) SUM [g cos(m p) + h sin(m p)] dP (sin(phi))
n=1 m=0 n n n */
/* Equation 11 in the WMM Technical report. Derivative with respect to longitude, divided by radius. */
MagneticResults->By += SphVariables.RelativeRadiusPower[n] *
( MagneticModel->Main_Field_Coeff_G[index]*SphVariables.sin_mlambda[m] -
MagneticModel->Main_Field_Coeff_H[index]*SphVariables.cos_mlambda[m] )
* (float) (m) * LegendreFunction-> Pcup[index];
/* nMax (n+2) n m m m
Bx = - SUM (a/r) SUM [g cos(m p) + h sin(m p)] dP (sin(phi))
n=1 m=0 n n n */
/* Equation 10 in the WMM Technical report. Derivative with respect to latitude, divided by radius. */
MagneticResults->Bx -= SphVariables.RelativeRadiusPower[n] *
( MagneticModel->Main_Field_Coeff_G[index]*SphVariables.cos_mlambda[m] +
MagneticModel->Main_Field_Coeff_H[index]*SphVariables.sin_mlambda[m] )
* LegendreFunction-> dPcup[index];
}
}
cos_phi = cos ( DEG2RAD ( CoordSpherical.phig ) );
if ( fabs(cos_phi) > 1.0e-10 )
{
MagneticResults->By = MagneticResults->By / cos_phi ;
}
else
/* Special calculation for component - By - at Geographic poles.
* If the user wants to avoid using this function, please make sure that
* the latitude is not exactly +/-90. An option is to make use the function
* WMM_CheckGeographicPoles.
*/
{
WMM_SummationSpecial(MagneticModel, SphVariables, CoordSpherical, MagneticResults);
}
return TRUE;
}/*WMM_Summation */
uint16_t WMM_SecVarSummation(WMMtype_LegendreFunction *LegendreFunction, WMMtype_MagneticModel *MagneticModel, WMMtype_SphericalHarmonicVariables SphVariables, WMMtype_CoordSpherical CoordSpherical, WMMtype_MagneticResults *MagneticResults)
{
/*This Function sums the secular variation coefficients to get the secular variation of the Magnetic vector.
INPUT : LegendreFunction
MagneticModel
SphVariables
CoordSpherical
OUTPUT : MagneticResults
CALLS : WMM_SecVarSummationSpecial
*/
uint16_t m, n, index;
float cos_phi;
MagneticModel->SecularVariationUsed = TRUE;
MagneticResults->Bz = 0.0;
MagneticResults->By = 0.0;
MagneticResults->Bx = 0.0;
for (n = 1; n <= MagneticModel->nMaxSecVar; n++)
{
for (m=0;m<=n;m++)
{
index = (n * (n + 1) / 2 + m);
/* nMax (n+2) n m m m
Bz = -SUM (a/r) (n+1) SUM [g cos(m p) + h sin(m p)] P (sin(phi))
n=1 m=0 n n n */
/* Derivative with respect to radius.*/
MagneticResults->Bz -= SphVariables.RelativeRadiusPower[n] *
( MagneticModel->Secular_Var_Coeff_G[index]*SphVariables.cos_mlambda[m] +
MagneticModel->Secular_Var_Coeff_H[index]*SphVariables.sin_mlambda[m] )
* (float) (n+1) * LegendreFunction-> Pcup[index];
/* 1 nMax (n+2) n m m m
By = SUM (a/r) (m) SUM [g cos(m p) + h sin(m p)] dP (sin(phi))
n=1 m=0 n n n */
/* Derivative with respect to longitude, divided by radius. */
MagneticResults->By += SphVariables.RelativeRadiusPower[n] *
( MagneticModel->Secular_Var_Coeff_G[index]*SphVariables.sin_mlambda[m] -
MagneticModel->Secular_Var_Coeff_H[index]*SphVariables.cos_mlambda[m] )
* (float) (m) * LegendreFunction-> Pcup[index];
/* nMax (n+2) n m m m
Bx = - SUM (a/r) SUM [g cos(m p) + h sin(m p)] dP (sin(phi))
n=1 m=0 n n n */
/* Derivative with respect to latitude, divided by radius. */
MagneticResults->Bx -= SphVariables.RelativeRadiusPower[n] *
( MagneticModel->Secular_Var_Coeff_G[index]*SphVariables.cos_mlambda[m] +
MagneticModel->Secular_Var_Coeff_H[index]*SphVariables.sin_mlambda[m] )
* LegendreFunction-> dPcup[index];
}
}
cos_phi = cos ( DEG2RAD ( CoordSpherical.phig ) );
if ( fabs(cos_phi) > 1.0e-10 )
{
MagneticResults->By = MagneticResults->By / cos_phi ;
}
else
/* Special calculation for component By at Geographic poles */
{
WMM_SecVarSummationSpecial(MagneticModel, SphVariables, CoordSpherical, MagneticResults);
}
return TRUE;
} /*WMM_SecVarSummation*/
uint16_t WMM_RotateMagneticVector(WMMtype_CoordSpherical CoordSpherical, WMMtype_CoordGeodetic CoordGeodetic, WMMtype_MagneticResults MagneticResultsSph, WMMtype_MagneticResults *MagneticResultsGeo)
/* Rotate the Magnetic Vectors to Geodetic Coordinates
Manoj Nair, June, 2009 Manoj.C.Nair@Noaa.Gov
Equation 16, WMM Technical report
INPUT : CoordSpherical : Data structure WMMtype_CoordSpherical with the following elements
float lambda; ( longitude)
float phig; ( geocentric latitude )
float r; ( distance from the center of the ellipsoid)
CoordGeodetic : Data structure WMMtype_CoordGeodetic with the following elements
float lambda; (longitude)
float phi; ( geodetic latitude)
float HeightAboveEllipsoid; (height above the ellipsoid (HaE) )
float HeightAboveGeoid;(height above the Geoid )
MagneticResultsSph : Data structure WMMtype_MagneticResults with the following elements
float Bx; North
float By; East
float Bz; Down
OUTPUT: MagneticResultsGeo Pointer to the data structure WMMtype_MagneticResults, with the following elements
float Bx; North
float By; East
float Bz; Down
CALLS : none
*/
{
float Psi;
/* Difference between the spherical and Geodetic latitudes */
Psi = ( M_PI/180 ) * ( CoordSpherical.phig - CoordGeodetic.phi );
/* Rotate spherical field components to the Geodeitic system */
MagneticResultsGeo->Bz = MagneticResultsSph.Bx * sin(Psi) + MagneticResultsSph.Bz * cos(Psi);
MagneticResultsGeo->Bx = MagneticResultsSph.Bx * cos(Psi) - MagneticResultsSph.Bz * sin(Psi);
MagneticResultsGeo->By = MagneticResultsSph.By;
return TRUE;
} /*WMM_RotateMagneticVector*/
uint16_t WMM_CalculateGeoMagneticElements(WMMtype_MagneticResults *MagneticResultsGeo, WMMtype_GeoMagneticElements *GeoMagneticElements)
/* Calculate all the Geomagnetic elements from X,Y and Z components
INPUT MagneticResultsGeo Pointer to data structure with the following elements
float Bx; ( North )
float By; ( East )
float Bz; ( Down )
OUTPUT GeoMagneticElements Pointer to data structure with the following elements
float Decl; (Angle between the magnetic field vector and true north, positive east)
float Incl; Angle between the magnetic field vector and the horizontal plane, positive down
float F; Magnetic Field Strength
float H; Horizontal Magnetic Field Strength
float X; Northern component of the magnetic field vector
float Y; Eastern component of the magnetic field vector
float Z; Downward component of the magnetic field vector
CALLS : none
*/
{
GeoMagneticElements->X = MagneticResultsGeo->Bx;
GeoMagneticElements->Y = MagneticResultsGeo->By;
GeoMagneticElements->Z = MagneticResultsGeo->Bz;
GeoMagneticElements->H = sqrt (MagneticResultsGeo->Bx* MagneticResultsGeo->Bx + MagneticResultsGeo->By * MagneticResultsGeo->By);
GeoMagneticElements->F = sqrt (GeoMagneticElements->H*GeoMagneticElements->H + MagneticResultsGeo->Bz * MagneticResultsGeo->Bz);
GeoMagneticElements->Decl = RAD2DEG(atan2 (GeoMagneticElements->Y , GeoMagneticElements->X));
GeoMagneticElements->Incl = RAD2DEG(atan2 (GeoMagneticElements->Z , GeoMagneticElements->H));
return TRUE;
} /*WMM_CalculateGeoMagneticElements */
uint16_t WMM_CalculateSecularVariation(WMMtype_MagneticResults MagneticVariation, WMMtype_GeoMagneticElements *MagneticElements)
/*This takes the Magnetic Variation in x, y, and z and uses it to calculate the secular variation of each of the Geomagnetic elements.
INPUT MagneticVariation Data structure with the following elements
float Bx; ( North )
float By; ( East )
float Bz; ( Down )
OUTPUT MagneticElements Pointer to the data structure with the following elements updated
float Decldot; Yearly Rate of change in declination
float Incldot; Yearly Rate of change in inclination
float Fdot; Yearly rate of change in Magnetic field strength
float Hdot; Yearly rate of change in horizontal field strength
float Xdot; Yearly rate of change in the northern component
float Ydot; Yearly rate of change in the eastern component
float Zdot; Yearly rate of change in the downward component
float GVdot;Yearly rate of chnage in grid variation
CALLS : none
*/
{
MagneticElements->Xdot = MagneticVariation.Bx;
MagneticElements->Ydot = MagneticVariation.By;
MagneticElements->Zdot = MagneticVariation.Bz;
MagneticElements->Hdot = (MagneticElements->X * MagneticElements->Xdot + MagneticElements->Y * MagneticElements->Ydot) / MagneticElements->H; //See equation 19 in the WMM technical report
MagneticElements->Fdot = (MagneticElements->X * MagneticElements->Xdot + MagneticElements->Y * MagneticElements->Ydot + MagneticElements->Z * MagneticElements->Zdot) / MagneticElements->F;
MagneticElements->Decldot = 180.0 / M_PI * (MagneticElements->X * MagneticElements->Ydot - MagneticElements->Y * MagneticElements->Xdot) / (MagneticElements->H * MagneticElements->H);
MagneticElements->Incldot = 180.0 / M_PI * (MagneticElements->H * MagneticElements->Zdot - MagneticElements->Z * MagneticElements->Hdot) / (MagneticElements->F * MagneticElements->F);
MagneticElements->GVdot = MagneticElements->Decldot;
return TRUE;
} /*WMM_CalculateSecularVariation*/
uint16_t WMM_PcupHigh(float *Pcup, float *dPcup, float x, uint16_t nMax)
/* This function evaluates all of the Schmidt-semi normalized associated Legendre
functions up to degree nMax. The functions are initially scaled by
10^280 sin^m in order to minimize the effects of underflow at large m
near the poles (see Holmes and Featherstone 2002, J. Geodesy, 76, 279-299).
Note that this function performs the same operation as WMM_PcupLow.
However this function also can be used for high degree (large nMax) models.
Calling Parameters:
INPUT
nMax: Maximum spherical harmonic degree to compute.
x: cos(colatitude) or sin(latitude).
OUTPUT
Pcup: A vector of all associated Legendgre polynomials evaluated at
x up to nMax. The lenght must by greater or equal to (nMax+1)*(nMax+2)/2.
dPcup: Derivative of Pcup(x) with respect to latitude
CALLS : none
Notes:
Adopted from the FORTRAN code written by Mark Wieczorek September 25, 2005.
Manoj Nair, Nov, 2009 Manoj.C.Nair@Noaa.Gov
Change from the previous version
The prevous version computes the derivatives as
dP(n,m)(x)/dx, where x = sin(latitude) (or cos(colatitude) ).
However, the WMM Geomagnetic routines requires dP(n,m)(x)/dlatitude.
Hence the derivatives are multiplied by sin(latitude).
Removed the options for CS phase and normalizations.
Note: In geomagnetism, the derivatives of ALF are usually found with
respect to the colatitudes. Here the derivatives are found with respect
to the latitude. The difference is a sign reversal for the derivative of
the Associated Legendre Functions.
The derivates can't be computed for latitude = |90| degrees.
*/
{
float pm2, pm1, pmm, plm, rescalem, z, scalef;
float f1[NUMPCUP], f2[NUMPCUP], PreSqr[NUMPCUP];
uint16_t k, kstart, m, n;
if (fabs(x) == 1.0)
{
// printf("Error in PcupHigh: derivative cannot be calculated at poles\n");
return FALSE;
}
scalef = 1.0e-280;
for(n = 0 ; n <= 2*nMax+1 ; ++n )
{
PreSqr[n] = sqrt((float)(n));
}
k = 2;
for(n=2 ; n<=nMax ; n++)
{
k = k + 1;
f1[k] = (float)(2*n-1) /(float)(n);
f2[k] = (float)(n-1) /(float)(n);
for(m=1 ; m<=n-2 ; m++)
{
k = k+1;
f1[k] = (float)(2*n-1) / PreSqr[n+m] / PreSqr[n-m];
f2[k] = PreSqr[n-m-1] * PreSqr[n+m-1] / PreSqr[n+m] / PreSqr[n-m];
}
k = k + 2;
}
/*z = sin (geocentric latitude) */
z = sqrt((1.0-x)*(1.0+x));
pm2 = 1.0;
Pcup[0] = 1.0;
dPcup[0] = 0.0;
if (nMax == 0)
return FALSE;
pm1 = x;
Pcup[1] = pm1;
dPcup[1] = z;
k = 1;
for(n = 2; n <= nMax; n++ )
{
k = k+n;
plm = f1[k]*x*pm1-f2[k]*pm2;
Pcup[k] = plm;
dPcup[k] = (float)(n) * (pm1 - x * plm) / z;
pm2 = pm1;
pm1 = plm;
}
pmm = PreSqr[2]*scalef;
rescalem = 1.0/scalef;
kstart = 0;
for(m = 1; m <= nMax - 1; ++m)
{
rescalem = rescalem*z;
/* Calculate Pcup(m,m)*/
kstart = kstart+m+1;
pmm = pmm * PreSqr[2*m+1] / PreSqr[2*m];
Pcup[kstart] = pmm*rescalem / PreSqr[2*m+1];
dPcup[kstart] = -((float)(m) * x * Pcup[kstart] / z);
pm2 = pmm/PreSqr[2*m+1];
/* Calculate Pcup(m+1,m)*/
k = kstart+m+1 ;
pm1 = x * PreSqr[2*m+1] * pm2;
Pcup[k] = pm1*rescalem;
dPcup[k] = ((pm2*rescalem) * PreSqr[2*m+1] - x * (float)(m+1) * Pcup[k]) / z;
/* Calculate Pcup(n,m)*/
for(n = m+2; n <= nMax; ++n)
{
k = k+n;
plm = x*f1[k]*pm1-f2[k]*pm2;
Pcup[k] = plm*rescalem;
dPcup[k] = (PreSqr[n+m] * PreSqr[n-m] * (pm1 * rescalem) - (float)(n) * x * Pcup[k] ) / z;
pm2 = pm1;
pm1 = plm;
}
}
/* Calculate Pcup(nMax,nMax)*/
rescalem = rescalem*z;
kstart = kstart+m+1;
pmm = pmm / PreSqr[2*nMax];
Pcup[kstart] = pmm * rescalem;
dPcup[kstart] = -(float)(nMax) * x * Pcup[kstart] / z;
return TRUE ;
} /* WMM_PcupHigh */
uint16_t WMM_PcupLow( float *Pcup, float *dPcup, float x, uint16_t nMax)
/* This function evaluates all of the Schmidt-semi normalized associated Legendre
functions up to degree nMax.
Calling Parameters:
INPUT
nMax: Maximum spherical harmonic degree to compute.
x: cos(colatitude) or sin(latitude).
OUTPUT
Pcup: A vector of all associated Legendgre polynomials evaluated at
x up to nMax.
dPcup: Derivative of Pcup(x) with respect to latitude
Notes: Overflow may occur if nMax > 20 , especially for high-latitudes.
Use WMM_PcupHigh for large nMax.
Writted by Manoj Nair, June, 2009 . Manoj.C.Nair@Noaa.Gov.
Note: In geomagnetism, the derivatives of ALF are usually found with
respect to the colatitudes. Here the derivatives are found with respect
to the latitude. The difference is a sign reversal for the derivative of
the Associated Legendre Functions.
*/
{
uint16_t n, m, index, index1, index2;
float k, z, schmidtQuasiNorm[NUMPCUP];
Pcup[0] = 1.0;
dPcup[0] = 0.0;
/*sin (geocentric latitude) - sin_phi */
z = sqrt( ( 1.0 - x ) * ( 1.0 + x ) ) ;
/* First, Compute the Gauss-normalized associated Legendre functions*/
for (n = 1; n <= nMax; n++)
{
for (m=0;m<=n;m++)
{
index = (n * (n + 1) / 2 + m);
if (n == m)
{
index1 = ( n - 1 ) * n / 2 + m -1;
Pcup [index] = z * Pcup[index1];
dPcup[index] = z * dPcup[index1] + x * Pcup[index1];
}
else if (n == 1 && m == 0)
{
index1 = ( n - 1 ) * n / 2 + m;
Pcup[index] = x * Pcup[index1];
dPcup[index] = x * dPcup[index1] - z * Pcup[index1];
}
else if (n > 1 && n != m)
{
index1 = ( n - 2 ) * ( n - 1 ) / 2 + m;
index2 = ( n - 1) * n / 2 + m;
if (m > n - 2)
{
Pcup[index] = x * Pcup[index2];
dPcup[index] = x * dPcup[index2] - z * Pcup[index2];
}
else
{
k = (float)( ( ( n - 1 ) * ( n - 1 ) ) - ( m * m ) ) / ( float ) ( ( 2 * n - 1 ) * ( 2 * n - 3 ) );
Pcup[index] = x * Pcup[index2] - k * Pcup[index1];
dPcup[index] = x * dPcup[index2] - z * Pcup[index2] - k * dPcup[index1];
}
}
}
}
/*Compute the ration between the Gauss-normalized associated Legendre
functions and the Schmidt quasi-normalized version. This is equivalent to
sqrt((m==0?1:2)*(n-m)!/(n+m!))*(2n-1)!!/(n-m)! */
schmidtQuasiNorm[0] = 1.0;
for (n = 1; n <= nMax; n++)
{
index = (n * (n + 1) / 2);
index1 = (n - 1) * n / 2 ;
/* for m = 0 */
schmidtQuasiNorm[index] = schmidtQuasiNorm[index1] * (float) (2 * n - 1) / (float) n;
for ( m = 1; m <= n; m++)
{
index = (n * (n + 1) / 2 + m);
index1 = (n * (n + 1) / 2 + m - 1);
schmidtQuasiNorm[index] = schmidtQuasiNorm[index1] * sqrt( (float) ((n - m + 1) * (m == 1 ? 2 : 1)) / (float) (n + m));
}
}
/* Converts the Gauss-normalized associated Legendre
functions to the Schmidt quasi-normalized version using pre-computed
relation stored in the variable schmidtQuasiNorm */
for (n = 1; n <= nMax; n++)
{
for (m=0;m<=n;m++)
{
index = (n * (n + 1) / 2 + m);
Pcup[index] = Pcup[index] * schmidtQuasiNorm[index];
dPcup[index] = - dPcup[index] * schmidtQuasiNorm[index];
/* The sign is changed since the new WMM routines use derivative with respect to latitude
insted of co-latitude */
}
}
return TRUE;
} /*WMM_PcupLow */
uint16_t WMM_SummationSpecial(WMMtype_MagneticModel *MagneticModel, WMMtype_SphericalHarmonicVariables SphVariables, WMMtype_CoordSpherical CoordSpherical, WMMtype_MagneticResults *MagneticResults)
/* Special calculation for the component By at Geographic poles.
Manoj Nair, June, 2009 manoj.c.nair@noaa.gov
INPUT: MagneticModel
SphVariables
CoordSpherical
OUTPUT: MagneticResults
CALLS : none
See Section 1.4, "SINGULARITIES AT THE GEOGRAPHIC POLES", WMM Technical report
*/
{
uint16_t n, index;
float k, sin_phi, PcupS[NUMPCUPS], schmidtQuasiNorm1, schmidtQuasiNorm2, schmidtQuasiNorm3;
PcupS[0] = 1;
schmidtQuasiNorm1 = 1.0;
MagneticResults->By = 0.0;
sin_phi = sin ( DEG2RAD ( CoordSpherical.phig ) );
for (n = 1; n <= MagneticModel->nMax; n++)
{
/*Compute the ration between the Gauss-normalized associated Legendre
functions and the Schmidt quasi-normalized version. This is equivalent to
sqrt((m==0?1:2)*(n-m)!/(n+m!))*(2n-1)!!/(n-m)! */
index = (n * (n + 1) / 2 + 1);
schmidtQuasiNorm2 = schmidtQuasiNorm1 * (float) (2 * n - 1) / (float) n;
schmidtQuasiNorm3 = schmidtQuasiNorm2 * sqrt( (float) (n * 2) / (float) (n + 1));
schmidtQuasiNorm1 = schmidtQuasiNorm2;
if (n == 1)
{
PcupS[n] = PcupS[n-1];
}
else
{
k = (float)( ( (n - 1) * (n - 1) ) - 1) / ( float ) ( (2 * n - 1) * (2 * n - 3) );
PcupS[n] = sin_phi * PcupS[n-1] - k * PcupS[n-2];
}
/* 1 nMax (n+2) n m m m
By = SUM (a/r) (m) SUM [g cos(m p) + h sin(m p)] dP (sin(phi))
n=1 m=0 n n n */
/* Equation 11 in the WMM Technical report. Derivative with respect to longitude, divided by radius. */
MagneticResults->By += SphVariables.RelativeRadiusPower[n] *
( MagneticModel->Main_Field_Coeff_G[index]*SphVariables.sin_mlambda[1] -
MagneticModel->Main_Field_Coeff_H[index]*SphVariables.cos_mlambda[1] )
* PcupS[n] * schmidtQuasiNorm3;
}
return TRUE;
}/*WMM_SummationSpecial */
uint16_t WMM_SecVarSummationSpecial(WMMtype_MagneticModel *MagneticModel, WMMtype_SphericalHarmonicVariables SphVariables, WMMtype_CoordSpherical CoordSpherical, WMMtype_MagneticResults *MagneticResults)
{
/*Special calculation for the secular variation summation at the poles.
INPUT: MagneticModel
SphVariables
CoordSpherical
OUTPUT: MagneticResults
CALLS : none
*/
uint16_t n, index;
float k, sin_phi, PcupS[NUMPCUPS], schmidtQuasiNorm1, schmidtQuasiNorm2, schmidtQuasiNorm3;
PcupS[0] = 1;
schmidtQuasiNorm1 = 1.0;
MagneticResults->By = 0.0;
sin_phi = sin ( DEG2RAD ( CoordSpherical.phig ) );
for (n = 1; n <= MagneticModel->nMaxSecVar; n++)
{
index = (n * (n + 1) / 2 + 1);
schmidtQuasiNorm2 = schmidtQuasiNorm1 * (float) (2 * n - 1) / (float) n;
schmidtQuasiNorm3 = schmidtQuasiNorm2 * sqrt( (float) (n * 2) / (float) (n + 1));
schmidtQuasiNorm1 = schmidtQuasiNorm2;
if (n == 1)
{
PcupS[n] = PcupS[n-1];
}
else
{
k = (float)( ( (n - 1) * (n - 1) ) - 1) / ( float ) ( (2 * n - 1) * (2 * n - 3) );
PcupS[n] = sin_phi * PcupS[n-1] - k * PcupS[n-2];
}
/* 1 nMax (n+2) n m m m
By = SUM (a/r) (m) SUM [g cos(m p) + h sin(m p)] dP (sin(phi))
n=1 m=0 n n n */
/* Derivative with respect to longitude, divided by radius. */
MagneticResults->By += SphVariables.RelativeRadiusPower[n] *
( MagneticModel->Secular_Var_Coeff_G[index]*SphVariables.sin_mlambda[1] -
MagneticModel->Secular_Var_Coeff_H[index]*SphVariables.cos_mlambda[1] )
* PcupS[n] * schmidtQuasiNorm3;
}
return TRUE;
}/*SecVarSummationSpecial*/
void WMM_TimelyModifyMagneticModel(WMMtype_Date UserDate, WMMtype_MagneticModel *MagneticModel, WMMtype_MagneticModel *TimedMagneticModel)
// Time change the Model coefficients from the base year of the model using secular variation coefficients.
// Store the coefficients of the static model with their values advanced from epoch t0 to epoch t.
// Copy the SV coefficients. If input "t" is the same as "t0", then this is merely a copy operation.
// If the address of "TimedMagneticModel" is the same as the address of "MagneticModel", then this procedure overwrites
// the given item "MagneticModel".
{
uint16_t n, m, index, a, b;
TimedMagneticModel->EditionDate = MagneticModel->EditionDate;
TimedMagneticModel->epoch = MagneticModel->epoch;
TimedMagneticModel->nMax = MagneticModel->nMax;
TimedMagneticModel->nMaxSecVar = MagneticModel->nMaxSecVar;
a = TimedMagneticModel->nMaxSecVar;
b = (a * (a + 1) / 2 + a);
strcpy(TimedMagneticModel->ModelName,MagneticModel->ModelName);
for (n = 1; n <= MagneticModel->nMax; n++)
{
for (m=0;m<=n;m++)
{
index = (n * (n + 1) / 2 + m);
if(index <= b)
{
TimedMagneticModel->Main_Field_Coeff_H[index] = MagneticModel->Main_Field_Coeff_H[index] + (UserDate.DecimalYear - MagneticModel->epoch) * MagneticModel->Secular_Var_Coeff_H[index];
TimedMagneticModel->Main_Field_Coeff_G[index] = MagneticModel->Main_Field_Coeff_G[index] + (UserDate.DecimalYear - MagneticModel->epoch) * MagneticModel->Secular_Var_Coeff_G[index];
TimedMagneticModel->Secular_Var_Coeff_H[index] = MagneticModel->Secular_Var_Coeff_H[index]; // We need a copy of the secular var coef to calculate secular change
TimedMagneticModel->Secular_Var_Coeff_G[index] = MagneticModel->Secular_Var_Coeff_G[index];
}
else
{
TimedMagneticModel->Main_Field_Coeff_H[index] = MagneticModel->Main_Field_Coeff_H[index];
TimedMagneticModel->Main_Field_Coeff_G[index] = MagneticModel->Main_Field_Coeff_G[index];
}
}
}
} /* WMM_TimelyModifyMagneticModel */
uint16_t WMM_DateToYear (WMMtype_Date *CalendarDate, char *Error)
// Converts a given calendar date into a decimal year
{
uint16_t temp = 0; // Total number of days
uint16_t MonthDays[13] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
uint16_t ExtraDay = 0;
uint16_t i;
if((CalendarDate->Year%4 == 0 && CalendarDate->Year%100 != 0) || CalendarDate->Year%400 == 0)
ExtraDay=1;
MonthDays[2] += ExtraDay;
/******************Validation********************************/
if(CalendarDate->Month <= 0 || CalendarDate->Month > 12)
{
strcpy(Error, "\nError: The Month entered is invalid, valid months are '1 to 12'\n");
return 0;
}
if(CalendarDate->Day <= 0 || CalendarDate->Day > MonthDays[CalendarDate->Month])
{
// printf("\nThe number of days in month %d is %d\n", CalendarDate->Month, MonthDays[CalendarDate->Month]);
strcpy(Error, "\nError: The day entered is invalid\n");
return 0;
}
/****************Calculation of t***************************/
for(i = 1; i <= CalendarDate->Month; i++)
temp+=MonthDays[i-1];
temp+=CalendarDate->Day;
CalendarDate->DecimalYear = CalendarDate->Year + (temp-1)/(365.0 + ExtraDay);
return 1;
} /*WMM_DateToYear*/
void WMM_GeodeticToSpherical(WMMtype_Ellipsoid Ellip, WMMtype_CoordGeodetic CoordGeodetic, WMMtype_CoordSpherical *CoordSpherical)
// Converts Geodetic coordinates to Spherical coordinates
// Convert geodetic coordinates, (defined by the WGS-84
// reference ellipsoid), to Earth Centered Earth Fixed Cartesian
// coordinates, and then to spherical coordinates.
{
float CosLat, SinLat, rc, xp, zp; // all local variables
CosLat = cos(DEG2RAD(CoordGeodetic.phi));
SinLat = sin(DEG2RAD(CoordGeodetic.phi));
// compute the local radius of curvature on the WGS-84 reference ellipsoid
rc = Ellip.a / sqrt(1.0 - Ellip.epssq * SinLat * SinLat);
// compute ECEF Cartesian coordinates of specified point (for longitude=0)
xp = (rc + CoordGeodetic.HeightAboveEllipsoid) * CosLat;
zp = (rc*(1.0 - Ellip.epssq) + CoordGeodetic.HeightAboveEllipsoid) * SinLat;
// compute spherical radius and angle lambda and phi of specified point
CoordSpherical->r = sqrt(xp * xp + zp * zp);
CoordSpherical->phig = RAD2DEG(asin(zp / CoordSpherical->r)); // geocentric latitude
CoordSpherical->lambda = CoordGeodetic.lambda; // longitude
}// WMM_GeodeticToSpherical
void WMM_Set_Coeff_Array(float coeffs[][6])
{
float CoeffFile[91][6] =
{{0, 0, 0, 0, 0, 0},
{1, 0, -29496.6, 0.0, 11.6, 0.0},
{1, 1, -1586.3, 4944.4, 16.5, -25.9},
{2, 0, -2396.6, 0.0, -12.1, 0.0},
{2, 1, 3026.1, -2707.7, -4.4, -22.5},
{2, 2, 1668.6, -576.1, 1.9, -11.8},
{3, 0, 1340.1, 0.0, 0.4, 0.0},
{3, 1, -2326.2, -160.2, -4.1, 7.3},
{3, 2, 1231.9, 251.9, -2.9, -3.9},
{3, 3, 634.0, -536.6, -7.7, -2.6},
{4, 0, 912.6, 0.0, -1.8, 0.0},
{4, 1, 808.9, 286.4, 2.3, 1.1},
{4, 2, 166.7, -211.2, -8.7, 2.7},
{4, 3, -357.1, 164.3, 4.6, 3.9},
{4, 4, 89.4, -309.1, -2.1, -0.8},
{5, 0, -230.9, 0.0, -1.0, 0.0},
{5, 1, 357.2, 44.6, 0.6, 0.4},
{5, 2, 200.3, 188.9, -1.8, 1.8},
{5, 3, -141.1, -118.2, -1.0, 1.2},
{5, 4, -163.0, 0.0, 0.9, 4.0},
{5, 5, -7.8, 100.9, 1.0, -0.6},
{6, 0, 72.8, 0.0, -0.2, 0.0},
{6, 1, 68.6, -20.8, -0.2, -0.2},
{6, 2, 76.0, 44.1, -0.1, -2.1},
{6, 3, -141.4, 61.5, 2.0, -0.4},
{6, 4, -22.8, -66.3, -1.7, -0.6},
{6, 5, 13.2, 3.1, -0.3, 0.5},
{6, 6, -77.9, 55.0, 1.7, 0.9},
{7, 0, 80.5, 0.0, 0.1, 0.0},
{7, 1, -75.1, -57.9, -0.1, 0.7},
{7, 2, -4.7, -21.1, -0.6, 0.3},
{7, 3, 45.3, 6.5, 1.3, -0.1},
{7, 4, 13.9, 24.9, 0.4, -0.1},
{7, 5, 10.4, 7.0, 0.3, -0.8},
{7, 6, 1.7, -27.7, -0.7, -0.3},
{7, 7, 4.9, -3.3, 0.6, 0.3},
{8, 0, 24.4, 0.0, -0.1, 0.0},
{8, 1, 8.1, 11.0, 0.1, -0.1},
{8, 2, -14.5, -20.0, -0.6, 0.2},
{8, 3, -5.6, 11.9, 0.2, 0.4},
{8, 4, -19.3, -17.4, -0.2, 0.4},
{8, 5, 11.5, 16.7, 0.3, 0.1},
{8, 6, 10.9, 7.0, 0.3, -0.1},
{8, 7, -14.1, -10.8, -0.6, 0.4},
{8, 8, -3.7, 1.7, 0.2, 0.3},
{9, 0, 5.4, 0.0, 0.0, 0.0},
{9, 1, 9.4, -20.5, -0.1, 0.0},
{9, 2, 3.4, 11.5, 0.0, -0.2},
{9, 3, -5.2, 12.8, 0.3, 0.0},
{9, 4, 3.1, -7.2, -0.4, -0.1},
{9, 5, -12.4, -7.4, -0.3, 0.1},
{9, 6, -0.7, 8.0, 0.1, 0.0},
{9, 7, 8.4, 2.1, -0.1, -0.2},
{9, 8, -8.5, -6.1, -0.4, 0.3},
{9, 9, -10.1, 7.0, -0.2, 0.2},
{10, 0, -2.0, 0.0, 0.0, 0.0},
{10, 1, -6.3, 2.8, 0.0, 0.1},
{10, 2, 0.9, -0.1, -0.1, -0.1},
{10, 3, -1.1, 4.7, 0.2, 0.0},
{10, 4, -0.2, 4.4, 0.0, -0.1},
{10, 5, 2.5, -7.2, -0.1, -0.1},
{10, 6, -0.3, -1.0, -0.2, 0.0},
{10, 7, 2.2, -3.9, 0.0, -0.1},
{10, 8, 3.1, -2.0, -0.1, -0.2},
{10, 9, -1.0, -2.0, -0.2, 0.0},
{10, 10, -2.8, -8.3, -0.2, -0.1},
{11, 0, 3.0, 0.0, 0.0, 0.0},
{11, 1, -1.5, 0.2, 0.0, 0.0},
{11, 2, -2.1, 1.7, 0.0, 0.1},
{11, 3, 1.7, -0.6, 0.1, 0.0},
{11, 4, -0.5, -1.8, 0.0, 0.1},
{11, 5, 0.5, 0.9, 0.0, 0.0},
{11, 6, -0.8, -0.4, 0.0, 0.1},
{11, 7, 0.4, -2.5, 0.0, 0.0},
{11, 8, 1.8, -1.3, 0.0, -0.1},
{11, 9, 0.1, -2.1, 0.0, -0.1},
{11, 10, 0.7, -1.9, -0.1, 0.0},
{11, 11, 3.8, -1.8, 0.0, -0.1},
{12, 0, -2.2, 0.0, 0.0, 0.0},
{12, 1, -0.2, -0.9, 0.0, 0.0},
{12, 2, 0.3, 0.3, 0.1, 0.0},
{12, 3, 1.0, 2.1, 0.1, 0.0},
{12, 4, -0.6, -2.5, -0.1, 0.0},
{12, 5, 0.9, 0.5, 0.0, 0.0},
{12, 6, -0.1, 0.6, 0.0, 0.1},
{12, 7, 0.5, 0.0, 0.0, 0.0},
{12, 8, -0.4, 0.1, 0.0, 0.0},
{12, 9, -0.4, 0.3, 0.0, 0.0},
{12, 10, 0.2, -0.9, 0.0, 0.0},
{12, 11, -0.8, -0.2, -0.1, 0.0},
{12, 12, 0.0, 0.9, 0.1, 0.0}};
for(uint16_t i=0; i<NUMTERMS; i++){
for(uint16_t j=0; j<6; j++)
coeffs[i][j]=CoeffFile[i][j];
}
}

176
flight/AHRS/inc/WMMInternal.h Normal file
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/**
******************************************************************************
*
* @file WMMInternal.h
* @author The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
* @brief Include file of the WorldMagModel internal functionality.
*
* @see The GNU Public License (GPL) Version 3
*
*****************************************************************************/
/*
* 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 3 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.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef WMMINTERNAL_H_
#define WMMINTERNAL_H_
// internal constants
#define TRUE ((uint16_t)1)
#define FALSE ((uint16_t)0)
#define WMM_MAX_MODEL_DEGREES 12
#define WMM_MAX_SECULAR_VARIATION_MODEL_DEGREES 12
#define NUMTERMS 91 // ((WMM_MAX_MODEL_DEGREES+1)*(WMM_MAX_MODEL_DEGREES+2)/2);
#define NUMPCUP 92 // NUMTERMS +1
#define NUMPCUPS 13 // WMM_MAX_MODEL_DEGREES +1
#define RAD2DEG(rad) ((rad)*(180.0L/M_PI))
#define DEG2RAD(deg) ((deg)*(M_PI/180.0L))
// internal structure definitions
typedef struct {
float EditionDate;
float epoch; //Base time of Geomagnetic model epoch (yrs)
char ModelName[20];
float Main_Field_Coeff_G[NUMTERMS]; // C - Gauss coefficients of main geomagnetic model (nT)
float Main_Field_Coeff_H[NUMTERMS]; // C - Gauss coefficients of main geomagnetic model (nT)
float Secular_Var_Coeff_G[NUMTERMS]; // CD - Gauss coefficients of secular geomagnetic model (nT/yr)
float Secular_Var_Coeff_H[NUMTERMS]; // CD - Gauss coefficients of secular geomagnetic model (nT/yr)
uint16_t nMax; // Maximum degree of spherical harmonic model
uint16_t nMaxSecVar; // Maxumum degree of spherical harmonic secular model
uint16_t SecularVariationUsed; // Whether or not the magnetic secular variation vector will be needed by program
} WMMtype_MagneticModel;
typedef struct {
float a; // semi-major axis of the ellipsoid
float b; // semi-minor axis of the ellipsoid
float fla; // flattening
float epssq; // first eccentricity squared
float eps; // first eccentricity
float re; // mean radius of ellipsoid
} WMMtype_Ellipsoid;
typedef struct {
float lambda; // longitude
float phi; // geodetic latitude
float HeightAboveEllipsoid; // height above the ellipsoid (HaE)
} WMMtype_CoordGeodetic;
typedef struct {
float lambda; // longitude
float phig; // geocentric latitude
float r; // distance from the center of the ellipsoid
} WMMtype_CoordSpherical;
typedef struct {
uint16_t Year;
uint16_t Month;
uint16_t Day;
float DecimalYear;
} WMMtype_Date;
typedef struct {
float Pcup[NUMPCUP]; // Legendre Function
float dPcup[NUMPCUP]; // Derivative of Lagendre fn
} WMMtype_LegendreFunction;
typedef struct {
float Bx; // North
float By; // East
float Bz; // Down
} WMMtype_MagneticResults;
typedef struct {
float RelativeRadiusPower[WMM_MAX_MODEL_DEGREES+1]; // [earth_reference_radius_km / sph. radius ]^n
float cos_mlambda[WMM_MAX_MODEL_DEGREES+1]; // cp(m) - cosine of (m*spherical coord. longitude
float sin_mlambda[WMM_MAX_MODEL_DEGREES+1]; // sp(m) - sine of (m*spherical coord. longitude)
} WMMtype_SphericalHarmonicVariables;
typedef struct {
float Decl; /* 1. Angle between the magnetic field vector and true north, positive east*/
float Incl; /*2. Angle between the magnetic field vector and the horizontal plane, positive down*/
float F; /*3. Magnetic Field Strength*/
float H; /*4. Horizontal Magnetic Field Strength*/
float X; /*5. Northern component of the magnetic field vector*/
float Y; /*6. Eastern component of the magnetic field vector*/
float Z; /*7. Downward component of the magnetic field vector*/
float GV; /*8. The Grid Variation*/
float Decldot; /*9. Yearly Rate of change in declination*/
float Incldot; /*10. Yearly Rate of change in inclination*/
float Fdot; /*11. Yearly rate of change in Magnetic field strength*/
float Hdot; /*12. Yearly rate of change in horizontal field strength*/
float Xdot; /*13. Yearly rate of change in the northern component*/
float Ydot; /*14. Yearly rate of change in the eastern component*/
float Zdot; /*15. Yearly rate of change in the downward component*/
float GVdot; /*16. Yearly rate of chnage in grid variation*/
} WMMtype_GeoMagneticElements;
// Internal Function Prototypes
void WMM_Set_Coeff_Array(float coeffs[][6]);
void WMM_GeodeticToSpherical(WMMtype_Ellipsoid Ellip, WMMtype_CoordGeodetic CoordGeodetic, WMMtype_CoordSpherical *CoordSpherical);
uint16_t WMM_DateToYear (WMMtype_Date *CalendarDate, char *Error);
void WMM_TimelyModifyMagneticModel(WMMtype_Date UserDate, WMMtype_MagneticModel *MagneticModel, WMMtype_MagneticModel *TimedMagneticModel);
uint16_t WMM_Geomag(WMMtype_Ellipsoid Ellip,
WMMtype_CoordSpherical CoordSpherical,
WMMtype_CoordGeodetic CoordGeodetic,
WMMtype_MagneticModel *TimedMagneticModel,
WMMtype_GeoMagneticElements *GeoMagneticElements);
uint16_t WMM_AssociatedLegendreFunction( WMMtype_CoordSpherical CoordSpherical, uint16_t nMax, WMMtype_LegendreFunction *LegendreFunction);
uint16_t WMM_CalculateGeoMagneticElements(WMMtype_MagneticResults *MagneticResultsGeo, WMMtype_GeoMagneticElements *GeoMagneticElements);
uint16_t WMM_CalculateSecularVariation(WMMtype_MagneticResults MagneticVariation, WMMtype_GeoMagneticElements *MagneticElements);
uint16_t WMM_ComputeSphericalHarmonicVariables( WMMtype_Ellipsoid Ellip,
WMMtype_CoordSpherical CoordSpherical,
uint16_t nMax,
WMMtype_SphericalHarmonicVariables * SphVariables);
uint16_t WMM_PcupLow( float *Pcup, float *dPcup, float x, uint16_t nMax);
uint16_t WMM_PcupHigh( float *Pcup, float *dPcup, float x, uint16_t nMax);
uint16_t WMM_RotateMagneticVector(WMMtype_CoordSpherical ,
WMMtype_CoordGeodetic CoordGeodetic,
WMMtype_MagneticResults MagneticResultsSph,
WMMtype_MagneticResults *MagneticResultsGeo);
uint16_t WMM_SecVarSummation(WMMtype_LegendreFunction *LegendreFunction,
WMMtype_MagneticModel *MagneticModel,
WMMtype_SphericalHarmonicVariables SphVariables,
WMMtype_CoordSpherical CoordSpherical,
WMMtype_MagneticResults *MagneticResults);
uint16_t WMM_SecVarSummationSpecial(WMMtype_MagneticModel *MagneticModel,
WMMtype_SphericalHarmonicVariables SphVariables,
WMMtype_CoordSpherical CoordSpherical,
WMMtype_MagneticResults *MagneticResults);
uint16_t WMM_Summation( WMMtype_LegendreFunction *LegendreFunction,
WMMtype_MagneticModel *MagneticModel,
WMMtype_SphericalHarmonicVariables SphVariables,
WMMtype_CoordSpherical CoordSpherical,
WMMtype_MagneticResults *MagneticResults);
uint16_t WMM_SummationSpecial(WMMtype_MagneticModel *MagneticModel,
WMMtype_SphericalHarmonicVariables SphVariables,
WMMtype_CoordSpherical CoordSpherical,
WMMtype_MagneticResults *MagneticResults);
#endif /* WMMINTERNAL_H_ */

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/**
******************************************************************************
*
* @file WorldMagModel.h
* @author The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
* @brief Include file of the WorldMagModel exposed functionality.
*
* @see The GNU Public License (GPL) Version 3
*
*****************************************************************************/
/*
* 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 3 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.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef WORLDMAGMODEL_H_
#define WORLDMAGMODEL_H_
// Exposed Function Prototypes
void WMM_Initialize();
void WMM_GetMagVector(float Lat, float Lon, float AltEllipsoid, uint16_t Month, uint16_t Day, uint16_t Year, float B[3]);
#endif /* WORLDMAGMODEL_H_ */