Detailed Description

FGLocation holds an arbitrary location in the Earth centered Earth fixed reference frame (ECEF).

The coordinate frame ECEF has its center in the middle of the earth. The X-axis points from the center of the Earth towards a location with zero latitude and longitude on the Earth surface. The Y-axis points from the center of the Earth towards a location with zero latitude and 90 deg East longitude on the Earth surface. The Z-axis points from the Earth center to the geographic north pole.

This class provides access functions to set and get the location as either the simple X, Y and Z values in ft or longitude/latitude and the radial distance of the location from the Earth center.

It is common to associate a parent frame with a location. This frame is usually called the local horizontal frame or simply the local frame. It is also called the NED frame (North, East, Down), as well as the Navigation frame. This frame has its X/Y plane parallel to the surface of the Earth. The X-axis points towards north, the Y-axis points east and the Z-axis is normal to the reference spheroid (WGS84 for Earth).

Since the local frame is determined by the location (and NOT by the orientation of the vehicle IN any frame), this class also provides the rotation matrices required to transform from the Earth centered (ECEF) frame to the local horizontal frame and back. This class "owns" the transformations that go from the ECEF frame to and from the local frame. Again, this is because the ECEF, and local frames do not involve the actual orientation of the vehicle - only the location on the Earth surface. There are conversion functions for conversion of position vectors given in the one frame to positions in the other frame.

The Earth centered reference frame is NOT an inertial frame since it rotates with the Earth.

The cartesian coordinates (X,Y,Z) in the Earth centered frame are the master values. All other values are computed from these master values and are cached as long as the location is changed by access through a non-const member function. Values are cached to improve performance. It is best practice to work with a natural set of master values. Other parameters that are derived from these master values are calculated only when needed, and IF they are needed and calculated, then they are cached (stored and remembered) so they do not need to be re-calculated until the master values they are derived from are themselves changed (and become stale).

Accuracy and round off

Given,

that we model a vehicle near the Earth
that the Earth surface average radius is about 2*10^7, ft
that we use double values for the representation of the location

we have an accuracy of about

1e-16*2e7ft/1 = 2e-9 ft

left. This should be sufficient for our needs. Note that this is the same relative accuracy we would have when we compute directly with lon/lat/radius. For the radius value this is clear. For the lon/lat pair this is easy to see. Take for example KSFO located at about 37.61 deg north 122.35 deg west, which corresponds to 0.65642 rad north and 2.13541 rad west. Both values are of magnitude of about 1. But 1 ft corresponds to about 1/(2e7*2*pi) = 7.9577e-09 rad. So the left accuracy with this representation is also about 1*1e-16/7.9577e-09 = 1.2566e-08 which is of the same magnitude as the representation chosen here.

The advantage of this representation is that it is a linear space without singularities. The singularities are the north and south pole and most notably the non-steady jump at -pi to pi. It is harder to track this jump correctly especially when we need to work with error norms and derivatives of the equations of motion within the time-stepping code. Also, the rate of change is of the same magnitude for all components in this representation which is an advantage for numerical stability in implicit time-stepping.

Note: Both GEOCENTRIC and GEODETIC latitudes can be used. In order to get best matching relative to a map, geodetic latitude must be used.

See also: Stevens and Lewis, "Aircraft Control and Simulation", Second edition; W. C. Durham "Aircraft Dynamics & Control", section 2.2

Author: Mathias Froehlich

Definition at line 151 of file FGLocation.h.

#include <FGLocation.h>

Inheritance diagram for FGLocation:

Collaboration diagram for FGLocation:

Public Member Functions
	FGLocation (const FGColumnVector3 &lv)
	Constructor to initialize the location with the cartesian coordinates (X,Y,Z) contained in the input FGColumnVector3.

	FGLocation (const FGLocation &l)
	Copy constructor.

	FGLocation (double lon, double lat, double radius)
	Constructor to set the longitude, latitude and the distance from the center of the earth.

	FGLocation (void)
	Default constructor.

double &	Entry (unsigned int idx)
	Write access the entries of the vector.

double	Entry (unsigned int idx) const
	Read access the entries of the vector.

double	GetCosLongitude () const
	Get the cosine of Longitude.

double	GetDistanceTo (double target_longitude, double target_latitude) const
	Get the geodetic distance between the current location and a given location.

double	GetGeodAltitude (void) const
	Gets the geodetic altitude in feet.

double	GetGeodLatitudeDeg (void) const
	Get the GEODETIC latitude in degrees.

double	GetGeodLatitudeRad (void) const
	Get the GEODETIC latitude in radians.

double	GetHeadingTo (double target_longitude, double target_latitude) const
	Get the heading that should be followed from the current location to a given location along the shortest path.

double	GetLatitude () const
	Get the GEOCENTRIC latitude in radians.

double	GetLatitudeDeg () const
	Get the GEOCENTRIC latitude in degrees.

double	GetLongitude () const
	Get the longitude.

double	GetLongitudeDeg () const
	Get the longitude.

double	GetRadius () const
	Get the distance from the center of the earth in feet.

double	GetSeaLevelRadius (void) const
	Get the sea level radius in feet below the current location.

double	GetSinLongitude () const
	Get the sine of Longitude.

const FGMatrix33 &	GetTec2l (void) const
	Transform matrix from the earth centered to local horizontal frame.

const FGMatrix33 &	GetTl2ec (void) const
	Transform matrix from local horizontal to earth centered frame.

FGLocation	LocalToLocation (const FGColumnVector3 &lvec) const
	Conversion from Local frame coordinates to a location in the earth centered and fixed frame.

FGColumnVector3	LocationToLocal (const FGColumnVector3 &ecvec) const
	Conversion from a location in the earth centered and fixed frame to local horizontal frame coordinates.

	operator const FGColumnVector3 & () const
	Cast to a simple 3d vector.

bool	operator!= (const FGLocation &l) const
	This operator returns true if the ECEF location vectors for the two location objects are not equal.

double &	operator() (unsigned int idx)
	Write access the entries of the vector.

double	operator() (unsigned int idx) const
	Read access the entries of the vector.

FGLocation	operator* (double scalar) const
	This operator scales an ECEF position vector.

const FGLocation &	operator*= (double scalar)
	This operator scales the ECEF position vector.

FGLocation	operator+ (const FGLocation &l) const
	This operator adds two ECEF position vectors.

const FGLocation &	operator+= (const FGLocation &l)
	This operator adds the ECEF position vectors.

FGLocation	operator- (const FGLocation &l) const
	This operator substracts two ECEF position vectors.

const FGLocation &	operator-= (const FGLocation &l)
	This operator substracts the ECEF position vectors.

const FGLocation &	operator/= (double scalar)
	This operator scales the ECEF position vector.

const FGLocation &	operator= (const FGColumnVector3 &v)
	Sets this location via the supplied vector.

FGLocation &	operator= (const FGLocation &l)
	Sets this location via the supplied location object.

bool	operator== (const FGLocation &l) const
	This operator returns true if the ECEF location vectors for the two location objects are equal.

void	SetEllipse (double semimajor, double semiminor)
	Sets the semimajor and semiminor axis lengths for this planet.

void	SetLatitude (double latitude)
	Set the GEOCENTRIC latitude.

void	SetLongitude (double longitude)
	Set the longitude.

void	SetPosition (double lon, double lat, double radius)
	Sets the longitude, latitude and the distance from the center of the earth.

void	SetPositionGeodetic (double lon, double lat, double height)
	Sets the longitude, latitude and the distance above the reference spheroid.

void	SetRadius (double radius)
	Set the distance from the center of the earth.

Public Member Functions inherited from FGJSBBase
	FGJSBBase ()
	Constructor for FGJSBBase.

virtual	~FGJSBBase ()
	Destructor for FGJSBBase.

void	disableHighLighting (void)
	Disables highlighting in the console output.

Additional Inherited Members
Public Types inherited from FGJSBBase
enum	{ eL = 1 , eM , eN }
	Moments L, M, N. More...

enum	{ eP = 1 , eQ , eR }
	Rates P, Q, R. More...

enum	{ eU = 1 , eV , eW }
	Velocities U, V, W. More...

enum	{ eX = 1 , eY , eZ }
	Positions X, Y, Z. More...

enum	{ ePhi = 1 , eTht , ePsi }
	Euler angles Phi, Theta, Psi. More...

enum	{ eDrag = 1 , eSide , eLift }
	Stability axis forces, Drag, Side force, Lift. More...

enum	{ eRoll = 1 , ePitch , eYaw }
	Local frame orientation Roll, Pitch, Yaw. More...

enum	{ eNorth = 1 , eEast , eDown }
	Local frame position North, East, Down. More...

enum	{ eLat = 1 , eLong , eRad }
	Locations Radius, Latitude, Longitude. More...

enum	{ inNone = 0 , inDegrees , inRadians , inMeters , inFeet }
	Conversion specifiers. More...

Static Public Member Functions inherited from FGJSBBase
static const std::string &	GetVersion (void)
	Returns the version number of JSBSim.

static constexpr double	KelvinToFahrenheit (double kelvin)
	Converts from degrees Kelvin to degrees Fahrenheit.

static constexpr double	CelsiusToRankine (double celsius)
	Converts from degrees Celsius to degrees Rankine.

static constexpr double	RankineToCelsius (double rankine)
	Converts from degrees Rankine to degrees Celsius.

static constexpr double	KelvinToRankine (double kelvin)
	Converts from degrees Kelvin to degrees Rankine.

static constexpr double	RankineToKelvin (double rankine)
	Converts from degrees Rankine to degrees Kelvin.

static constexpr double	FahrenheitToCelsius (double fahrenheit)
	Converts from degrees Fahrenheit to degrees Celsius.

static constexpr double	CelsiusToFahrenheit (double celsius)
	Converts from degrees Celsius to degrees Fahrenheit.

static constexpr double	CelsiusToKelvin (double celsius)
	Converts from degrees Celsius to degrees Kelvin.

static constexpr double	KelvinToCelsius (double kelvin)
	Converts from degrees Kelvin to degrees Celsius.

static constexpr double	FeetToMeters (double measure)
	Converts from feet to meters.

static bool	EqualToRoundoff (double a, double b)
	Finite precision comparison.

static bool	EqualToRoundoff (float a, float b)
	Finite precision comparison.

static bool	EqualToRoundoff (float a, double b)
	Finite precision comparison.

static bool	EqualToRoundoff (double a, float b)
	Finite precision comparison.

static constexpr double	Constrain (double min, double value, double max)
	Constrain a value between a minimum and a maximum value.

static constexpr double	sign (double num)

Static Public Attributes inherited from FGJSBBase
static char	highint [5] = {27, '[', '1', 'm', '\0' }
	highlights text

static char	halfint [5] = {27, '[', '2', 'm', '\0' }
	low intensity text

static char	normint [6] = {27, '[', '2', '2', 'm', '\0' }
	normal intensity text

static char	reset [5] = {27, '[', '0', 'm', '\0' }
	resets text properties

static char	underon [5] = {27, '[', '4', 'm', '\0' }
	underlines text

static char	underoff [6] = {27, '[', '2', '4', 'm', '\0' }
	underline off

static char	fgblue [6] = {27, '[', '3', '4', 'm', '\0' }
	blue text

static char	fgcyan [6] = {27, '[', '3', '6', 'm', '\0' }
	cyan text

static char	fgred [6] = {27, '[', '3', '1', 'm', '\0' }
	red text

static char	fggreen [6] = {27, '[', '3', '2', 'm', '\0' }
	green text

static char	fgdef [6] = {27, '[', '3', '9', 'm', '\0' }
	default text

static short	debug_lvl = 1

Static Protected Member Functions inherited from FGJSBBase
static std::string	CreateIndexedPropertyName (const std::string &Property, int index)

Static Protected Attributes inherited from FGJSBBase
static constexpr double	radtodeg = 180. / M_PI

static constexpr double	degtorad = M_PI / 180.

static constexpr double	hptoftlbssec = 550.0

static constexpr double	psftoinhg = 0.014138

static constexpr double	psftopa = 47.88

static constexpr double	fttom = 0.3048

static constexpr double	ktstofps = 1852./(3600*fttom)

static constexpr double	fpstokts = 1.0 / ktstofps

static constexpr double	inchtoft = 1.0/12.0

static constexpr double	m3toft3 = 1.0/(fttomfttomfttom)

static constexpr double	in3tom3 = inchtoftinchtoftinchtoft/m3toft3

static constexpr double	inhgtopa = 3386.38

static constexpr double	slugtolb = 32.174049
	Note that definition of lbtoslug by the inverse of slugtolb and not to a different constant you can also get from some tables will make lbtoslug*slugtolb == 1 up to the magnitude of roundoff.

static constexpr double	lbtoslug = 1.0/slugtolb

static constexpr double	kgtolb = 2.20462

static constexpr double	kgtoslug = 0.06852168

static const std::string	needed_cfg_version = "2.0"

static const std::string	JSBSim_version = JSBSIM_VERSION " " __DATE__ " " __TIME__

Constructor & Destructor Documentation

◆ FGLocation() [1/4]

FGLocation ( void )

Default constructor.

Definition at line 56 of file FGLocation.cpp.

  : mECLoc(1.0, 0.0, 0.0), mCacheValid(false)
{
  e2 = c = 0.0;
  a = ec = ec2 = 1.0;
 
  mLon = mLat = mRadius = 0.0;
  mGeodLat = GeodeticAltitude = 0.0;
 
  mTl2ec.InitMatrix();
  mTec2l.InitMatrix();
}

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◆ FGLocation() [2/4]

FGLocation	(	double	lon,
		double	lat,
		double	radius
	)

Constructor to set the longitude, latitude and the distance from the center of the earth.

Parameters

lon	longitude
lat	GEOCENTRIC latitude
radius	distance from center of earth to vehicle in feet

Definition at line 71 of file FGLocation.cpp.

  : mCacheValid(false)
{
  e2 = c = 0.0;
  a = ec = ec2 = 1.0;
 
  mLon = mLat = mRadius = 0.0;
  mGeodLat = GeodeticAltitude = 0.0;
 
  mTl2ec.InitMatrix();
  mTec2l.InitMatrix();
 
  double sinLat = sin(lat);
  double cosLat = cos(lat);
  double sinLon = sin(lon);
  double cosLon = cos(lon);
  mECLoc = { radius*cosLat*cosLon,
             radius*cosLat*sinLon,
             radius*sinLat };
}

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◆ FGLocation() [3/4]

FGLocation ( const FGColumnVector3 & lv )

Constructor to initialize the location with the cartesian coordinates (X,Y,Z) contained in the input FGColumnVector3.

Distances are in feet, the position is expressed in the ECEF frame.

Parameters

lv	vector that contain the cartesian coordinates

Definition at line 94 of file FGLocation.cpp.

  : mECLoc(lv), mCacheValid(false)
{
  e2 = c = 0.0;
  a = ec = ec2 = 1.0;
 
  mLon = mLat = mRadius = 0.0;
  mGeodLat = GeodeticAltitude = 0.0;
 
  mTl2ec.InitMatrix();
  mTec2l.InitMatrix();
}

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◆ FGLocation() [4/4]

FGLocation ( const FGLocation & l )

Copy constructor.

Definition at line 109 of file FGLocation.cpp.

  : mECLoc(l.mECLoc), mCacheValid(l.mCacheValid)
{
  a = l.a;
  e2 = l.e2;
  c = l.c;
  ec = l.ec;
  ec2 = l.ec2;
  mEllipseSet = l.mEllipseSet;
 
  /*ag
   * if the cache is not valid, all of the following values are unset.
   * They will be calculated once ComputeDerivedUnconditional is called.
   * If unset, they may possibly contain NaN and could thus trigger floating
   * point exceptions.
   */
  if (!mCacheValid) return;
 
  mLon = l.mLon;
  mLat = l.mLat;
  mRadius = l.mRadius;
 
  mTl2ec = l.mTl2ec;
  mTec2l = l.mTec2l;
 
  mGeodLat = l.mGeodLat;
  GeodeticAltitude = l.GeodeticAltitude;
}

Member Function Documentation

◆ Entry() [1/2]

double & Entry ( unsigned int idx )

inline

Write access the entries of the vector.

Parameters

idx	the component index.

Returns: a reference to the vector entry at the given index. Indices are counted starting with 1. This function is just a shortcut for the double& operator()(unsigned int idx) function. It is used internally to access the elements in a more convenient way. Note that the index given in the argument is unchecked.

Definition at line 374 of file FGLocation.h.

                                  {
    mCacheValid = false; return mECLoc.Entry(idx);
  }

◆ Entry() [2/2]

double Entry ( unsigned int idx ) const

inline

Read access the entries of the vector.

Parameters

idx	the component index.

Returns: the value of the matrix entry at the given index. Indices are counted starting with 1. This function is just a shortcut for the double operator()(unsigned int idx) const function. It is used internally to access the elements in a more convenient way. Note that the index given in the argument is unchecked.

Definition at line 364 of file FGLocation.h.

364{ return mECLoc.Entry(idx); }

◆ GetCosLongitude()

double GetCosLongitude ( ) const

inline

Get the cosine of Longitude.

Definition at line 246 of file FGLocation.h.

246{ ComputeDerived(); return mTec2l(2,2); }

◆ GetDistanceTo()

double GetDistanceTo	(	double	target_longitude,
		double	target_latitude
	)		const

Get the geodetic distance between the current location and a given location.

This corresponds to the shortest distance between the two locations. Earth curvature is taken into account.

Parameters

target_longitude	the target longitude in radians
target_latitude	the target geodetic latitude in radians

Returns: The geodetic distance in feet between the two locations

Definition at line 377 of file FGLocation.cpp.

{
  assert(mEllipseSet);
  ComputeDerived();
  GeographicLib::Geodesic geod(a, 1 - ec);
  GeographicLib::Math::real distance;
  geod.Inverse(mGeodLat * radtodeg, mLon * radtodeg, target_latitude * radtodeg,
               target_longitude * radtodeg, distance);
 
  return distance;
}

◆ GetGeodAltitude()

double GetGeodAltitude ( void ) const

inline

Gets the geodetic altitude in feet.

Definition at line 279 of file FGLocation.h.

                                     {
    assert(mEllipseSet);
    ComputeDerived(); return GeodeticAltitude;
  }

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◆ GetGeodLatitudeDeg()

double GetGeodLatitudeDeg ( void ) const

inline

Get the GEODETIC latitude in degrees.

Returns: the geodetic latitude in degrees of the location represented by this class instance. The returned value is in the range between -90 <= lon <= 90. Latitude is positive north and negative south.

Definition at line 273 of file FGLocation.h.

                                        {
    assert(mEllipseSet);
    ComputeDerived(); return radtodeg*mGeodLat;
  }

◆ GetGeodLatitudeRad()

double GetGeodLatitudeRad ( void ) const

inline

Get the GEODETIC latitude in radians.

Returns: the geodetic latitude in rad of the location represented with this class instance. The returned values are in the range between -pi/2 <= lon <= pi/2. Latitude is positive north and negative south.

Definition at line 258 of file FGLocation.h.

                                        {
    assert(mEllipseSet);
    ComputeDerived(); return mGeodLat;
  }

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◆ GetHeadingTo()

double GetHeadingTo	(	double	target_longitude,
		double	target_latitude
	)		const

Get the heading that should be followed from the current location to a given location along the shortest path.

Earth curvature is taken into account.

Parameters

target_longitude	the target longitude in radians
target_latitude	the target geodetic latitude in radians

Returns: The heading in radians that should be followed to reach the targeted location along the shortest path

Definition at line 392 of file FGLocation.cpp.

{
  assert(mEllipseSet);
  ComputeDerived();
  GeographicLib::Geodesic geod(a, 1 - ec);
  GeographicLib::Math::real heading, azimuth2;
  geod.Inverse(mGeodLat * radtodeg, mLon * radtodeg, target_latitude * radtodeg,
               target_longitude * radtodeg, heading, azimuth2);
 
  return heading * degtorad;
}

◆ GetLatitude()

double GetLatitude ( ) const

inline

Get the GEOCENTRIC latitude in radians.

Returns: the geocentric latitude in rad of the location represented with this class instance. The returned values are in the range between -pi/2 <= lon <= pi/2. Latitude is positive north and negative south.

Definition at line 252 of file FGLocation.h.

252{ ComputeDerived(); return mLat; }

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◆ GetLatitudeDeg()

double GetLatitudeDeg ( ) const

inline

Get the GEOCENTRIC latitude in degrees.

Returns: the geocentric latitude in deg of the location represented with this class instance. The returned value is in the range between -90 <= lon <= 90. Latitude is positive north and negative south.

Definition at line 267 of file FGLocation.h.

267{ ComputeDerived(); return radtodeg*mLat; }

◆ GetLongitude()

double GetLongitude ( ) const

inline

Get the longitude.

Returns: the longitude in rad of the location represented with this class instance. The returned values are in the range between -pi <= lon <= pi. Longitude is positive east and negative west.

Definition at line 234 of file FGLocation.h.

234{ ComputeDerived(); return mLon; }

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◆ GetLongitudeDeg()

double GetLongitudeDeg ( ) const

inline

Get the longitude.

Returns: the longitude in deg of the location represented with this class instance. The returned values are in the range between -180 <= lon <= 180. Longitude is positive east and negative west.

Definition at line 240 of file FGLocation.h.

240{ ComputeDerived(); return radtodeg*mLon; }

◆ GetRadius()

double GetRadius ( ) const

inline

Get the distance from the center of the earth in feet.

Returns: the distance of the location represented with this class instance to the center of the earth in ft. The radius value is always positive.

Definition at line 291 of file FGLocation.h.

291{ ComputeDerived(); return mRadius; }

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◆ GetSeaLevelRadius()

double GetSeaLevelRadius ( void ) const

Get the sea level radius in feet below the current location.

Definition at line 273 of file FGLocation.cpp.

{
  assert(mEllipseSet);
  ComputeDerived();
  double cosLat = cos(mLat);
  return a*ec/sqrt(1.0-e2*cosLat*cosLat);
}

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◆ GetSinLongitude()

double GetSinLongitude ( ) const

inline

Get the sine of Longitude.

Definition at line 243 of file FGLocation.h.

243{ ComputeDerived(); return -mTec2l(2,1); }

◆ GetTec2l()

const FGMatrix33 & GetTec2l ( void ) const

inline

Transform matrix from the earth centered to local horizontal frame.

Returns: a const reference to the rotation matrix of the transform from the earth centered frame to the local horizontal frame.

Definition at line 301 of file FGLocation.h.

301{ ComputeDerived(); return mTec2l; }

◆ GetTl2ec()

const FGMatrix33 & GetTl2ec ( void ) const

inline

Transform matrix from local horizontal to earth centered frame.

Returns: a const reference to the rotation matrix of the transform from the local horizontal frame to the earth centered frame.

Definition at line 296 of file FGLocation.h.

296{ ComputeDerived(); return mTl2ec; }

◆ LocalToLocation()

FGLocation LocalToLocation ( const FGColumnVector3 & lvec ) const

inline

Conversion from Local frame coordinates to a location in the earth centered and fixed frame.

This function calculates the FGLocation of an object which position relative to the vehicle is given as in input.

Parameters

lvec	Vector in the local horizontal coordinate frame

Returns: The location in the earth centered and fixed frame

Definition at line 326 of file FGLocation.h.

                                                                {
    ComputeDerived(); return mTl2ec*lvec + mECLoc;
  }

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◆ LocationToLocal()

FGColumnVector3 LocationToLocal ( const FGColumnVector3 & ecvec ) const

inline

Conversion from a location in the earth centered and fixed frame to local horizontal frame coordinates.

This function calculates the relative position between the vehicle and the input vector and returns the result expressed in the local frame.

Parameters

ecvec Vector in the earth centered and fixed frame

Returns: The vector in the local horizontal coordinate frame

Definition at line 336 of file FGLocation.h.

                                                                      {
    ComputeDerived(); return mTec2l*(ecvec - mECLoc);
  }

◆ operator const FGColumnVector3 &()

operator const FGColumnVector3 & ( ) const

inline

Cast to a simple 3d vector.

Definition at line 476 of file FGLocation.h.

                                          {
    return mECLoc;
  }

◆ operator!=()

bool operator!= ( const FGLocation & l ) const

inline

This operator returns true if the ECEF location vectors for the two location objects are not equal.

Definition at line 407 of file FGLocation.h.

407{ return ! operator==(l); }

JSBSim::FGLocation::operator==

bool operator==(const FGLocation &l) const

This operator returns true if the ECEF location vectors for the two location objects are equal.

Definition FGLocation.h:401

◆ operator()() [1/2]

double & operator() ( unsigned int idx )

inline

Write access the entries of the vector.

Parameters

idx	the component index.

Returns: a reference to the vector entry at the given index. Indices are counted starting with 1. Note that the index given in the argument is unchecked.

Definition at line 354 of file FGLocation.h.

354{ mCacheValid = false; return mECLoc.Entry(idx); }

◆ operator()() [2/2]

double operator() ( unsigned int idx ) const

inline

Read access the entries of the vector.

Parameters

idx	the component index. Return the value of the matrix entry at the given index. Indices are counted starting with 1. Note that the index given in the argument is unchecked.

Definition at line 347 of file FGLocation.h.

347{ return mECLoc.Entry(idx); }

◆ operator*()

FGLocation operator* ( double scalar ) const

inline

This operator scales an ECEF position vector.

A new object is returned that defines a position made of the cartesian coordinates of the provided ECEF position scaled by the supplied scalar value.

Definition at line 469 of file FGLocation.h.

                                            {
    FGLocation result(scalar*mECLoc);
    if (mEllipseSet) result.SetEllipse(a, ec*a);
    return result;
  }

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◆ operator*=()

const FGLocation & operator*= ( double scalar )

inline

This operator scales the ECEF position vector.

The cartesian coordinates of the ECEF position vector on the left side of the equality are scaled by the supplied value (right side), and a reference to this object is returned.

Definition at line 433 of file FGLocation.h.

                                              {
    mCacheValid = false;
    mECLoc *= scalar;
    return *this;
  }

◆ operator+()

FGLocation operator+ ( const FGLocation & l ) const

inline

This operator adds two ECEF position vectors.

A new object is returned that defines a position which is the sum of the cartesian coordinates of the two positions provided.

Definition at line 450 of file FGLocation.h.

                                                  {
    FGLocation result(mECLoc + l.mECLoc);
    if (mEllipseSet) result.SetEllipse(a, ec*a);
    return result;
  }

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◆ operator+=()

const FGLocation & operator+= ( const FGLocation & l )

inline

This operator adds the ECEF position vectors.

The cartesian coordinates of the supplied vector (right side) are added to the ECEF position vector on the left side of the equality, and a reference to this object is returned.

Definition at line 413 of file FGLocation.h.

                                                    {
    mCacheValid = false;
    mECLoc += l.mECLoc;
    return *this;
  }

◆ operator-()

FGLocation operator- ( const FGLocation & l ) const

inline

This operator substracts two ECEF position vectors.

A new object is returned that defines a position which is the difference of the cartesian coordinates of the two positions provided.

Definition at line 459 of file FGLocation.h.

                                                  {
    FGLocation result(mECLoc - l.mECLoc);
    if (mEllipseSet) result.SetEllipse(a, ec*a);
    return result;
  }

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◆ operator-=()

const FGLocation & operator-= ( const FGLocation & l )

inline

This operator substracts the ECEF position vectors.

The cartesian coordinates of the supplied vector (right side) are substracted from the ECEF position vector on the left side of the equality, and a reference to this object is returned.

Definition at line 423 of file FGLocation.h.

                                                    {
    mCacheValid = false;
    mECLoc -= l.mECLoc;
    return *this;
  }

◆ operator/=()

const FGLocation & operator/= ( double scalar )

inline

This operator scales the ECEF position vector.

The cartesian coordinates of the ECEF position vector on the left side of the equality are scaled by the inverse of the supplied value (right side), and a reference to this object is returned.

Definition at line 443 of file FGLocation.h.

                                              {
    return operator*=(1.0/scalar);
  }

◆ operator=() [1/2]

const FGLocation & operator= ( const FGColumnVector3 & v )

inline

Sets this location via the supplied vector.

The location can be set by an Earth-centered, Earth-fixed (ECEF) frame position vector. The cache is marked as invalid, so any future requests for selected important data will cause the parameters to be calculated.

Parameters

v	the ECEF column vector in feet.

Returns: a reference to the FGLocation object.

Definition at line 384 of file FGLocation.h.

  {
    mECLoc(eX) = v(eX);
    mECLoc(eY) = v(eY);
    mECLoc(eZ) = v(eZ);
    mCacheValid = false;
    //ComputeDerived();
    return *this;
  }

◆ operator=() [2/2]

FGLocation & operator= ( const FGLocation & l )

Sets this location via the supplied location object.

Parameters

l	A location object reference.

Returns: a reference to the FGLocation object.

Definition at line 140 of file FGLocation.cpp.

{
  mECLoc = l.mECLoc;
  mCacheValid = l.mCacheValid;
  mEllipseSet = l.mEllipseSet;
 
  a = l.a;
  e2 = l.e2;
  c = l.c;
  ec = l.ec;
  ec2 = l.ec2;
 
  //ag See comment in constructor above
  if (!mCacheValid) return *this;
 
  mLon = l.mLon;
  mLat = l.mLat;
  mRadius = l.mRadius;
 
  mTl2ec = l.mTl2ec;
  mTec2l = l.mTec2l;
 
  mGeodLat = l.mGeodLat;
  GeodeticAltitude = l.GeodeticAltitude;
 
  return *this;
}

◆ operator==()

bool operator== ( const FGLocation & l ) const

inline

This operator returns true if the ECEF location vectors for the two location objects are equal.

Definition at line 401 of file FGLocation.h.

                                             {
    return mECLoc == l.mECLoc;
  }

◆ SetEllipse()

void SetEllipse	(	double	semimajor,
		double	semiminor
	)

Sets the semimajor and semiminor axis lengths for this planet.

The eccentricity and flattening are calculated from the semimajor and semiminor axis lengths.

Parameters

semimajor	planet semi-major axis in ft.
semiminor	planet semi-minor axis in ft.

Definition at line 259 of file FGLocation.cpp.

{
  mCacheValid = false;
  mEllipseSet = true;
 
  a = semimajor;
  ec = semiminor/a;
  ec2 = ec * ec;
  e2 = 1.0 - ec2;
  c = a * e2;
}

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◆ SetLatitude()

void SetLatitude ( double latitude )

Set the GEOCENTRIC latitude.

Parameters

latitude GEOCENTRIC latitude in rad to set. Sets the latitude of the location represented with this class instance to the value of the given argument. The value is meant to be in rad. The longitude and the radius value are preserved with this call with the exception of radius being equal to zero. If the radius is previously set to zero it is changed to be equal to 1.0 past this call. Latitude is positive north and negative south. The arguments should be within the bounds of -pi/2 <= lat <= pi/2. The behavior of this function with arguments outside this range is left as an exercise to the gentle reader ...

Definition at line 190 of file FGLocation.cpp.

{
  mCacheValid = false;
 
  double r = mECLoc.Magnitude();
  if (r == 0.0) {
    mECLoc(eX) = 1.0;
    r = 1.0;
  }
 
  double rtmp = mECLoc.Magnitude(eX, eY);
  if (rtmp != 0.0) {
    double fac = r/rtmp*cos(latitude);
    mECLoc(eX) *= fac;
    mECLoc(eY) *= fac;
  } else {
    mECLoc(eX) = r*cos(latitude);
    mECLoc(eY) = 0.0;
  }
  mECLoc(eZ) = r*sin(latitude);
}

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◆ SetLongitude()

void SetLongitude ( double longitude )

Set the longitude.

Parameters

longitude Longitude in rad to set. Sets the longitude of the location represented with this class instance to the value of the given argument. The value is meant to be in rad. The latitude and the radius value are preserved with this call with the exception of radius being equal to zero. If the radius is previously set to zero it is changed to be equal to 1.0 past this call. Longitude is positive east and negative west. The arguments should be within the bounds of -pi <= lon <= pi. The behavior of this function with arguments outside this range is left as an exercise to the gentle reader ...

Definition at line 170 of file FGLocation.cpp.

{
  double rtmp = mECLoc.Magnitude(eX, eY);
  // Check if we have zero radius.
  // If so set it to 1, so that we can set a position
  if (0.0 == mECLoc.Magnitude())
    rtmp = 1.0;
 
  // Fast return if we are on the north or south pole ...
  if (rtmp == 0.0)
    return;
 
  mCacheValid = false;
 
  mECLoc(eX) = rtmp*cos(longitude);
  mECLoc(eY) = rtmp*sin(longitude);
}

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◆ SetPosition()

void SetPosition	(	double	lon,
		double	lat,
		double	radius
	)

Sets the longitude, latitude and the distance from the center of the earth.

Parameters

lon	longitude in radians
lat	GEOCENTRIC latitude in radians
radius	distance from center of earth to vehicle in feet

Definition at line 227 of file FGLocation.cpp.

{
  mCacheValid = false;
 
  double sinLat = sin(lat);
  double cosLat = cos(lat);
  double sinLon = sin(lon);
  double cosLon = cos(lon);
 
  mECLoc = { radius*cosLat*cosLon,
             radius*cosLat*sinLon,
             radius*sinLat };
}

◆ SetPositionGeodetic()

void SetPositionGeodetic	(	double	lon,
		double	lat,
		double	height
	)

Sets the longitude, latitude and the distance above the reference spheroid.

Parameters

lon	longitude in radians
lat	GEODETIC latitude in radians
height	distance above the reference ellipsoid to vehicle in feet

Definition at line 243 of file FGLocation.cpp.

{
  assert(mEllipseSet);
  mCacheValid = false;
 
  double slat = sin(lat);
  double clat = cos(lat);
  double RN = a / sqrt(1.0 - e2*slat*slat);
 
  mECLoc(eX) = (RN + height)*clat*cos(lon);
  mECLoc(eY) = (RN + height)*clat*sin(lon);
  mECLoc(eZ) = ((1 - e2)*RN + height)*slat;
}

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◆ SetRadius()

void SetRadius ( double radius )

Set the distance from the center of the earth.

Parameters

radius Radius in ft to set. Sets the radius of the location represented with this class instance to the value of the given argument. The value is meant to be in ft. The latitude and longitude values are preserved with this call with the exception of radius being equal to zero. If the radius is previously set to zero, latitude and longitude is set equal to zero past this call. The argument should be positive. The behavior of this function called with a negative argument is left as an exercise to the gentle reader ...

Definition at line 214 of file FGLocation.cpp.

{
  mCacheValid = false;
 
  double rold = mECLoc.Magnitude();
  if (rold == 0.0)
    mECLoc(eX) = radius;
  else
    mECLoc *= radius/rold;
}

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The documentation for this class was generated from the following files:

Detailed Description

Public Member Functions

Additional Inherited Members

Constructor & Destructor Documentation

◆ FGLocation() [1/4]

◆ FGLocation() [2/4]

◆ FGLocation() [3/4]

◆ FGLocation() [4/4]

Member Function Documentation

◆ Entry() [1/2]

◆ Entry() [2/2]

◆ GetCosLongitude()

◆ GetDistanceTo()

◆ GetGeodAltitude()

◆ GetGeodLatitudeDeg()

◆ GetGeodLatitudeRad()

◆ GetHeadingTo()

◆ GetLatitude()

◆ GetLatitudeDeg()

◆ GetLongitude()

◆ GetLongitudeDeg()

◆ GetRadius()

◆ GetSeaLevelRadius()

◆ GetSinLongitude()

◆ GetTec2l()

◆ GetTl2ec()

◆ LocalToLocation()

◆ LocationToLocal()

◆ operator const FGColumnVector3 &()

◆ operator!=()

◆ operator()() [1/2]

◆ operator()() [2/2]

◆ operator*()

◆ operator*=()

◆ operator+()

◆ operator+=()

◆ operator-()

◆ operator-=()

◆ operator/=()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ operator==()

◆ SetEllipse()

◆ SetLatitude()

◆ SetLongitude()

◆ SetPosition()

◆ SetPositionGeodetic()

◆ SetRadius()