/usr/include/GeographicLib/GeodesicExact.hpp is in libgeographic-dev 1.45-2.
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* \file GeodesicExact.hpp
* \brief Header for GeographicLib::GeodesicExact class
*
* Copyright (c) Charles Karney (2012-2015) <charles@karney.com> and licensed
* under the MIT/X11 License. For more information, see
* http://geographiclib.sourceforge.net/
**********************************************************************/
#if !defined(GEOGRAPHICLIB_GEODESICEXACT_HPP)
#define GEOGRAPHICLIB_GEODESICEXACT_HPP 1
#include <GeographicLib/Constants.hpp>
#include <GeographicLib/EllipticFunction.hpp>
#if !defined(GEOGRAPHICLIB_GEODESICEXACT_ORDER)
/**
* The order of the expansions used by GeodesicExact.
**********************************************************************/
# define GEOGRAPHICLIB_GEODESICEXACT_ORDER 30
#endif
namespace GeographicLib {
class GeodesicLineExact;
/**
* \brief Exact geodesic calculations
*
* The equations for geodesics on an ellipsoid can be expressed in terms of
* incomplete elliptic integrals. The Geodesic class expands these integrals
* in a series in the flattening \e f and this provides an accurate solution
* for \e f ∈ [-0.01, 0.01]. The GeodesicExact class computes the
* ellitpic integrals directly and so provides a solution which is valid for
* all \e f. However, in practice, its use should be limited to about
* <i>b</i>/\e a ∈ [0.01, 100] or \e f ∈ [-99, 0.99].
*
* For the WGS84 ellipsoid, these classes are 2--3 times \e slower than the
* series solution and 2--3 times \e less \e accurate (because it's less easy
* to control round-off errors with the elliptic integral formulation); i.e.,
* the error is about 40 nm (40 nanometers) instead of 15 nm. However the
* error in the series solution scales as <i>f</i><sup>7</sup> while the
* error in the elliptic integral solution depends weakly on \e f. If the
* quarter meridian distance is 10000 km and the ratio <i>b</i>/\e a = 1
* − \e f is varied then the approximate maximum error (expressed as a
* distance) is <pre>
* 1 - f error (nm)
* 1/128 387
* 1/64 345
* 1/32 269
* 1/16 210
* 1/8 115
* 1/4 69
* 1/2 36
* 1 15
* 2 25
* 4 96
* 8 318
* 16 985
* 32 2352
* 64 6008
* 128 19024
* </pre>
*
* The computation of the area in these classes is via a 30th order series.
* This gives accurate results for <i>b</i>/\e a ∈ [1/2, 2]; the
* accuracy is about 8 decimal digits for <i>b</i>/\e a ∈ [1/4, 4].
*
* See \ref geodellip for the formulation. See the documentation on the
* Geodesic class for additional information on the geodesic problems.
*
* Example of use:
* \include example-GeodesicExact.cpp
*
* <a href="GeodSolve.1.html">GeodSolve</a> is a command-line utility
* providing access to the functionality of GeodesicExact and
* GeodesicLineExact (via the -E option).
**********************************************************************/
class GEOGRAPHICLIB_EXPORT GeodesicExact {
private:
typedef Math::real real;
friend class GeodesicLineExact;
static const int nC4_ = GEOGRAPHICLIB_GEODESICEXACT_ORDER;
static const int nC4x_ = (nC4_ * (nC4_ + 1)) / 2;
static const unsigned maxit1_ = 20;
unsigned maxit2_;
real tiny_, tol0_, tol1_, tol2_, tolb_, xthresh_;
enum captype {
CAP_NONE = 0U,
CAP_E = 1U<<0,
// Skip 1U<<1 for compatibility with Geodesic (not required)
CAP_D = 1U<<2,
CAP_H = 1U<<3,
CAP_C4 = 1U<<4,
CAP_ALL = 0x1FU,
CAP_MASK = CAP_ALL,
OUT_ALL = 0x7F80U,
OUT_MASK = 0xFF80U, // Includes LONG_UNROLL
};
static real CosSeries(real sinx, real cosx, const real c[], int n);
static real Astroid(real x, real y);
real _a, _f, _f1, _e2, _ep2, _n, _b, _c2, _etol2;
real _C4x[nC4x_];
void Lengths(const EllipticFunction& E,
real sig12,
real ssig1, real csig1, real dn1,
real ssig2, real csig2, real dn2,
real cbet1, real cbet2, unsigned outmask,
real& s12s, real& m12a, real& m0,
real& M12, real& M21) const;
real InverseStart(EllipticFunction& E,
real sbet1, real cbet1, real dn1,
real sbet2, real cbet2, real dn2,
real lam12,
real& salp1, real& calp1,
real& salp2, real& calp2, real& dnm) const;
real Lambda12(real sbet1, real cbet1, real dn1,
real sbet2, real cbet2, real dn2,
real salp1, real calp1,
real& salp2, real& calp2, real& sig12,
real& ssig1, real& csig1, real& ssig2, real& csig2,
EllipticFunction& E,
real& omg12, bool diffp, real& dlam12) const;
// These are Maxima generated functions to provide series approximations to
// the integrals for the area.
void C4coeff();
void C4f(real k2, real c[]) const;
// Large coefficients are split so that lo contains the low 52 bits and hi
// the rest. This choice avoids double rounding with doubles and higher
// precision types. float coefficients will suffer double rounding;
// however the accuracy is already lousy for floats.
static Math::real inline reale(long long hi, long long lo) {
using std::ldexp;
return ldexp(real(hi), 52) + lo;
}
public:
/**
* Bit masks for what calculations to do. These masks do double duty.
* They signify to the GeodesicLineExact::GeodesicLineExact constructor and
* to GeodesicExact::Line what capabilities should be included in the
* GeodesicLineExact object. They also specify which results to return in
* the general routines GeodesicExact::GenDirect and
* GeodesicExact::GenInverse routines. GeodesicLineExact::mask is a
* duplication of this enum.
**********************************************************************/
enum mask {
/**
* No capabilities, no output.
* @hideinitializer
**********************************************************************/
NONE = 0U,
/**
* Calculate latitude \e lat2. (It's not necessary to include this as a
* capability to GeodesicLineExact because this is included by default.)
* @hideinitializer
**********************************************************************/
LATITUDE = 1U<<7 | CAP_NONE,
/**
* Calculate longitude \e lon2.
* @hideinitializer
**********************************************************************/
LONGITUDE = 1U<<8 | CAP_H,
/**
* Calculate azimuths \e azi1 and \e azi2. (It's not necessary to
* include this as a capability to GeodesicLineExact because this is
* included by default.)
* @hideinitializer
**********************************************************************/
AZIMUTH = 1U<<9 | CAP_NONE,
/**
* Calculate distance \e s12.
* @hideinitializer
**********************************************************************/
DISTANCE = 1U<<10 | CAP_E,
/**
* Allow distance \e s12 to be used as input in the direct geodesic
* problem.
* @hideinitializer
**********************************************************************/
DISTANCE_IN = 1U<<11 | CAP_E,
/**
* Calculate reduced length \e m12.
* @hideinitializer
**********************************************************************/
REDUCEDLENGTH = 1U<<12 | CAP_D,
/**
* Calculate geodesic scales \e M12 and \e M21.
* @hideinitializer
**********************************************************************/
GEODESICSCALE = 1U<<13 | CAP_D,
/**
* Calculate area \e S12.
* @hideinitializer
**********************************************************************/
AREA = 1U<<14 | CAP_C4,
/**
* Unroll \e lon2 in the direct calculation. (This flag used to be
* called LONG_NOWRAP.)
* @hideinitializer
**********************************************************************/
LONG_UNROLL = 1U<<15,
/// \cond SKIP
LONG_NOWRAP = LONG_UNROLL,
/// \endcond
/**
* All capabilities, calculate everything. (LONG_UNROLL is not
* included in this mask.)
* @hideinitializer
**********************************************************************/
ALL = OUT_ALL| CAP_ALL,
};
/** \name Constructor
**********************************************************************/
///@{
/**
* Constructor for a ellipsoid with
*
* @param[in] a equatorial radius (meters).
* @param[in] f flattening of ellipsoid. Setting \e f = 0 gives a sphere.
* Negative \e f gives a prolate ellipsoid.
* @exception GeographicErr if \e a or (1 − \e f) \e a is not
* positive.
**********************************************************************/
GeodesicExact(real a, real f);
///@}
/** \name Direct geodesic problem specified in terms of distance.
**********************************************************************/
///@{
/**
* Perform the direct geodesic calculation where the length of the geodesic
* is specified in terms of distance.
*
* @param[in] lat1 latitude of point 1 (degrees).
* @param[in] lon1 longitude of point 1 (degrees).
* @param[in] azi1 azimuth at point 1 (degrees).
* @param[in] s12 distance between point 1 and point 2 (meters); it can be
* signed.
* @param[out] lat2 latitude of point 2 (degrees).
* @param[out] lon2 longitude of point 2 (degrees).
* @param[out] azi2 (forward) azimuth at point 2 (degrees).
* @param[out] m12 reduced length of geodesic (meters).
* @param[out] M12 geodesic scale of point 2 relative to point 1
* (dimensionless).
* @param[out] M21 geodesic scale of point 1 relative to point 2
* (dimensionless).
* @param[out] S12 area under the geodesic (meters<sup>2</sup>).
* @return \e a12 arc length of between point 1 and point 2 (degrees).
*
* \e lat1 should be in the range [−90°, 90°]. The values of
* \e lon2 and \e azi2 returned are in the range [−180°,
* 180°).
*
* If either point is at a pole, the azimuth is defined by keeping the
* longitude fixed, writing \e lat = ±(90° − ε),
* and taking the limit ε → 0+. An arc length greater that
* 180° signifies a geodesic which is not a shortest path. (For a
* prolate ellipsoid, an additional condition is necessary for a shortest
* path: the longitudinal extent must not exceed of 180°.)
*
* The following functions are overloaded versions of GeodesicExact::Direct
* which omit some of the output parameters. Note, however, that the arc
* length is always computed and returned as the function value.
**********************************************************************/
Math::real Direct(real lat1, real lon1, real azi1, real s12,
real& lat2, real& lon2, real& azi2,
real& m12, real& M12, real& M21, real& S12)
const {
real t;
return GenDirect(lat1, lon1, azi1, false, s12,
LATITUDE | LONGITUDE | AZIMUTH |
REDUCEDLENGTH | GEODESICSCALE | AREA,
lat2, lon2, azi2, t, m12, M12, M21, S12);
}
/**
* See the documentation for GeodesicExact::Direct.
**********************************************************************/
Math::real Direct(real lat1, real lon1, real azi1, real s12,
real& lat2, real& lon2)
const {
real t;
return GenDirect(lat1, lon1, azi1, false, s12,
LATITUDE | LONGITUDE,
lat2, lon2, t, t, t, t, t, t);
}
/**
* See the documentation for GeodesicExact::Direct.
**********************************************************************/
Math::real Direct(real lat1, real lon1, real azi1, real s12,
real& lat2, real& lon2, real& azi2)
const {
real t;
return GenDirect(lat1, lon1, azi1, false, s12,
LATITUDE | LONGITUDE | AZIMUTH,
lat2, lon2, azi2, t, t, t, t, t);
}
/**
* See the documentation for GeodesicExact::Direct.
**********************************************************************/
Math::real Direct(real lat1, real lon1, real azi1, real s12,
real& lat2, real& lon2, real& azi2, real& m12)
const {
real t;
return GenDirect(lat1, lon1, azi1, false, s12,
LATITUDE | LONGITUDE | AZIMUTH | REDUCEDLENGTH,
lat2, lon2, azi2, t, m12, t, t, t);
}
/**
* See the documentation for GeodesicExact::Direct.
**********************************************************************/
Math::real Direct(real lat1, real lon1, real azi1, real s12,
real& lat2, real& lon2, real& azi2,
real& M12, real& M21)
const {
real t;
return GenDirect(lat1, lon1, azi1, false, s12,
LATITUDE | LONGITUDE | AZIMUTH | GEODESICSCALE,
lat2, lon2, azi2, t, t, M12, M21, t);
}
/**
* See the documentation for GeodesicExact::Direct.
**********************************************************************/
Math::real Direct(real lat1, real lon1, real azi1, real s12,
real& lat2, real& lon2, real& azi2,
real& m12, real& M12, real& M21)
const {
real t;
return GenDirect(lat1, lon1, azi1, false, s12,
LATITUDE | LONGITUDE | AZIMUTH |
REDUCEDLENGTH | GEODESICSCALE,
lat2, lon2, azi2, t, m12, M12, M21, t);
}
///@}
/** \name Direct geodesic problem specified in terms of arc length.
**********************************************************************/
///@{
/**
* Perform the direct geodesic calculation where the length of the geodesic
* is specified in terms of arc length.
*
* @param[in] lat1 latitude of point 1 (degrees).
* @param[in] lon1 longitude of point 1 (degrees).
* @param[in] azi1 azimuth at point 1 (degrees).
* @param[in] a12 arc length between point 1 and point 2 (degrees); it can
* be signed.
* @param[out] lat2 latitude of point 2 (degrees).
* @param[out] lon2 longitude of point 2 (degrees).
* @param[out] azi2 (forward) azimuth at point 2 (degrees).
* @param[out] s12 distance between point 1 and point 2 (meters).
* @param[out] m12 reduced length of geodesic (meters).
* @param[out] M12 geodesic scale of point 2 relative to point 1
* (dimensionless).
* @param[out] M21 geodesic scale of point 1 relative to point 2
* (dimensionless).
* @param[out] S12 area under the geodesic (meters<sup>2</sup>).
*
* \e lat1 should be in the range [−90°, 90°]. The values of
* \e lon2 and \e azi2 returned are in the range [−180°,
* 180°).
*
* If either point is at a pole, the azimuth is defined by keeping the
* longitude fixed, writing \e lat = ±(90° − ε),
* and taking the limit ε → 0+. An arc length greater that
* 180° signifies a geodesic which is not a shortest path. (For a
* prolate ellipsoid, an additional condition is necessary for a shortest
* path: the longitudinal extent must not exceed of 180°.)
*
* The following functions are overloaded versions of GeodesicExact::Direct
* which omit some of the output parameters.
**********************************************************************/
void ArcDirect(real lat1, real lon1, real azi1, real a12,
real& lat2, real& lon2, real& azi2, real& s12,
real& m12, real& M12, real& M21, real& S12)
const {
GenDirect(lat1, lon1, azi1, true, a12,
LATITUDE | LONGITUDE | AZIMUTH | DISTANCE |
REDUCEDLENGTH | GEODESICSCALE | AREA,
lat2, lon2, azi2, s12, m12, M12, M21, S12);
}
/**
* See the documentation for GeodesicExact::ArcDirect.
**********************************************************************/
void ArcDirect(real lat1, real lon1, real azi1, real a12,
real& lat2, real& lon2) const {
real t;
GenDirect(lat1, lon1, azi1, true, a12,
LATITUDE | LONGITUDE,
lat2, lon2, t, t, t, t, t, t);
}
/**
* See the documentation for GeodesicExact::ArcDirect.
**********************************************************************/
void ArcDirect(real lat1, real lon1, real azi1, real a12,
real& lat2, real& lon2, real& azi2) const {
real t;
GenDirect(lat1, lon1, azi1, true, a12,
LATITUDE | LONGITUDE | AZIMUTH,
lat2, lon2, azi2, t, t, t, t, t);
}
/**
* See the documentation for GeodesicExact::ArcDirect.
**********************************************************************/
void ArcDirect(real lat1, real lon1, real azi1, real a12,
real& lat2, real& lon2, real& azi2, real& s12)
const {
real t;
GenDirect(lat1, lon1, azi1, true, a12,
LATITUDE | LONGITUDE | AZIMUTH | DISTANCE,
lat2, lon2, azi2, s12, t, t, t, t);
}
/**
* See the documentation for GeodesicExact::ArcDirect.
**********************************************************************/
void ArcDirect(real lat1, real lon1, real azi1, real a12,
real& lat2, real& lon2, real& azi2,
real& s12, real& m12) const {
real t;
GenDirect(lat1, lon1, azi1, true, a12,
LATITUDE | LONGITUDE | AZIMUTH | DISTANCE |
REDUCEDLENGTH,
lat2, lon2, azi2, s12, m12, t, t, t);
}
/**
* See the documentation for GeodesicExact::ArcDirect.
**********************************************************************/
void ArcDirect(real lat1, real lon1, real azi1, real a12,
real& lat2, real& lon2, real& azi2, real& s12,
real& M12, real& M21) const {
real t;
GenDirect(lat1, lon1, azi1, true, a12,
LATITUDE | LONGITUDE | AZIMUTH | DISTANCE |
GEODESICSCALE,
lat2, lon2, azi2, s12, t, M12, M21, t);
}
/**
* See the documentation for GeodesicExact::ArcDirect.
**********************************************************************/
void ArcDirect(real lat1, real lon1, real azi1, real a12,
real& lat2, real& lon2, real& azi2, real& s12,
real& m12, real& M12, real& M21) const {
real t;
GenDirect(lat1, lon1, azi1, true, a12,
LATITUDE | LONGITUDE | AZIMUTH | DISTANCE |
REDUCEDLENGTH | GEODESICSCALE,
lat2, lon2, azi2, s12, m12, M12, M21, t);
}
///@}
/** \name General version of the direct geodesic solution.
**********************************************************************/
///@{
/**
* The general direct geodesic calculation. GeodesicExact::Direct and
* GeodesicExact::ArcDirect are defined in terms of this function.
*
* @param[in] lat1 latitude of point 1 (degrees).
* @param[in] lon1 longitude of point 1 (degrees).
* @param[in] azi1 azimuth at point 1 (degrees).
* @param[in] arcmode boolean flag determining the meaning of the second
* parameter.
* @param[in] s12_a12 if \e arcmode is false, this is the distance between
* point 1 and point 2 (meters); otherwise it is the arc length between
* point 1 and point 2 (degrees); it can be signed.
* @param[in] outmask a bitor'ed combination of GeodesicExact::mask values
* specifying which of the following parameters should be set.
* @param[out] lat2 latitude of point 2 (degrees).
* @param[out] lon2 longitude of point 2 (degrees).
* @param[out] azi2 (forward) azimuth at point 2 (degrees).
* @param[out] s12 distance between point 1 and point 2 (meters).
* @param[out] m12 reduced length of geodesic (meters).
* @param[out] M12 geodesic scale of point 2 relative to point 1
* (dimensionless).
* @param[out] M21 geodesic scale of point 1 relative to point 2
* (dimensionless).
* @param[out] S12 area under the geodesic (meters<sup>2</sup>).
* @return \e a12 arc length of between point 1 and point 2 (degrees).
*
* The GeodesicExact::mask values possible for \e outmask are
* - \e outmask |= GeodesicExact::LATITUDE for the latitude \e lat2;
* - \e outmask |= GeodesicExact::LONGITUDE for the latitude \e lon2;
* - \e outmask |= GeodesicExact::AZIMUTH for the latitude \e azi2;
* - \e outmask |= GeodesicExact::DISTANCE for the distance \e s12;
* - \e outmask |= GeodesicExact::REDUCEDLENGTH for the reduced length \e
* m12;
* - \e outmask |= GeodesicExact::GEODESICSCALE for the geodesic scales \e
* M12 and \e M21;
* - \e outmask |= GeodesicExact::AREA for the area \e S12;
* - \e outmask |= GeodesicExact::ALL for all of the above;
* - \e outmask |= GeodesicExact::LONG_UNROLL to unroll \e lon2 instead of
* wrapping it into the range [−180°, 180°).
* .
* The function value \e a12 is always computed and returned and this
* equals \e s12_a12 is \e arcmode is true. If \e outmask includes
* GeodesicExact::DISTANCE and \e arcmode is false, then \e s12 = \e
* s12_a12. It is not necessary to include GeodesicExact::DISTANCE_IN in
* \e outmask; this is automatically included is \e arcmode is false.
*
* With the GeodesicExact::LONG_UNROLL bit set, the quantity \e lon2
* − \e lon1 indicates how many times and in what sense the geodesic
* encircles the ellipsoid.
**********************************************************************/
Math::real GenDirect(real lat1, real lon1, real azi1,
bool arcmode, real s12_a12, unsigned outmask,
real& lat2, real& lon2, real& azi2,
real& s12, real& m12, real& M12, real& M21,
real& S12) const;
///@}
/** \name Inverse geodesic problem.
**********************************************************************/
///@{
/**
* Perform the inverse geodesic calculation.
*
* @param[in] lat1 latitude of point 1 (degrees).
* @param[in] lon1 longitude of point 1 (degrees).
* @param[in] lat2 latitude of point 2 (degrees).
* @param[in] lon2 longitude of point 2 (degrees).
* @param[out] s12 distance between point 1 and point 2 (meters).
* @param[out] azi1 azimuth at point 1 (degrees).
* @param[out] azi2 (forward) azimuth at point 2 (degrees).
* @param[out] m12 reduced length of geodesic (meters).
* @param[out] M12 geodesic scale of point 2 relative to point 1
* (dimensionless).
* @param[out] M21 geodesic scale of point 1 relative to point 2
* (dimensionless).
* @param[out] S12 area under the geodesic (meters<sup>2</sup>).
* @return \e a12 arc length of between point 1 and point 2 (degrees).
*
* \e lat1 and \e lat2 should be in the range [−90°, 90°].
* The values of \e azi1 and \e azi2 returned are in the range
* [−180°, 180°).
*
* If either point is at a pole, the azimuth is defined by keeping the
* longitude fixed, writing \e lat = ±(90° − ε),
* and taking the limit ε → 0+.
*
* The following functions are overloaded versions of GeodesicExact::Inverse
* which omit some of the output parameters. Note, however, that the arc
* length is always computed and returned as the function value.
**********************************************************************/
Math::real Inverse(real lat1, real lon1, real lat2, real lon2,
real& s12, real& azi1, real& azi2, real& m12,
real& M12, real& M21, real& S12) const {
return GenInverse(lat1, lon1, lat2, lon2,
DISTANCE | AZIMUTH |
REDUCEDLENGTH | GEODESICSCALE | AREA,
s12, azi1, azi2, m12, M12, M21, S12);
}
/**
* See the documentation for GeodesicExact::Inverse.
**********************************************************************/
Math::real Inverse(real lat1, real lon1, real lat2, real lon2,
real& s12) const {
real t;
return GenInverse(lat1, lon1, lat2, lon2,
DISTANCE,
s12, t, t, t, t, t, t);
}
/**
* See the documentation for GeodesicExact::Inverse.
**********************************************************************/
Math::real Inverse(real lat1, real lon1, real lat2, real lon2,
real& azi1, real& azi2) const {
real t;
return GenInverse(lat1, lon1, lat2, lon2,
AZIMUTH,
t, azi1, azi2, t, t, t, t);
}
/**
* See the documentation for GeodesicExact::Inverse.
**********************************************************************/
Math::real Inverse(real lat1, real lon1, real lat2, real lon2,
real& s12, real& azi1, real& azi2)
const {
real t;
return GenInverse(lat1, lon1, lat2, lon2,
DISTANCE | AZIMUTH,
s12, azi1, azi2, t, t, t, t);
}
/**
* See the documentation for GeodesicExact::Inverse.
**********************************************************************/
Math::real Inverse(real lat1, real lon1, real lat2, real lon2,
real& s12, real& azi1, real& azi2, real& m12)
const {
real t;
return GenInverse(lat1, lon1, lat2, lon2,
DISTANCE | AZIMUTH | REDUCEDLENGTH,
s12, azi1, azi2, m12, t, t, t);
}
/**
* See the documentation for GeodesicExact::Inverse.
**********************************************************************/
Math::real Inverse(real lat1, real lon1, real lat2, real lon2,
real& s12, real& azi1, real& azi2,
real& M12, real& M21) const {
real t;
return GenInverse(lat1, lon1, lat2, lon2,
DISTANCE | AZIMUTH | GEODESICSCALE,
s12, azi1, azi2, t, M12, M21, t);
}
/**
* See the documentation for GeodesicExact::Inverse.
**********************************************************************/
Math::real Inverse(real lat1, real lon1, real lat2, real lon2,
real& s12, real& azi1, real& azi2, real& m12,
real& M12, real& M21) const {
real t;
return GenInverse(lat1, lon1, lat2, lon2,
DISTANCE | AZIMUTH |
REDUCEDLENGTH | GEODESICSCALE,
s12, azi1, azi2, m12, M12, M21, t);
}
///@}
/** \name General version of inverse geodesic solution.
**********************************************************************/
///@{
/**
* The general inverse geodesic calculation. GeodesicExact::Inverse is
* defined in terms of this function.
*
* @param[in] lat1 latitude of point 1 (degrees).
* @param[in] lon1 longitude of point 1 (degrees).
* @param[in] lat2 latitude of point 2 (degrees).
* @param[in] lon2 longitude of point 2 (degrees).
* @param[in] outmask a bitor'ed combination of GeodesicExact::mask values
* specifying which of the following parameters should be set.
* @param[out] s12 distance between point 1 and point 2 (meters).
* @param[out] azi1 azimuth at point 1 (degrees).
* @param[out] azi2 (forward) azimuth at point 2 (degrees).
* @param[out] m12 reduced length of geodesic (meters).
* @param[out] M12 geodesic scale of point 2 relative to point 1
* (dimensionless).
* @param[out] M21 geodesic scale of point 1 relative to point 2
* (dimensionless).
* @param[out] S12 area under the geodesic (meters<sup>2</sup>).
* @return \e a12 arc length of between point 1 and point 2 (degrees).
*
* The GeodesicExact::mask values possible for \e outmask are
* - \e outmask |= GeodesicExact::DISTANCE for the distance \e s12;
* - \e outmask |= GeodesicExact::AZIMUTH for the latitude \e azi2;
* - \e outmask |= GeodesicExact::REDUCEDLENGTH for the reduced length \e
* m12;
* - \e outmask |= GeodesicExact::GEODESICSCALE for the geodesic scales \e
* M12 and \e M21;
* - \e outmask |= GeodesicExact::AREA for the area \e S12;
* - \e outmask |= GeodesicExact::ALL for all of the above.
* .
* The arc length is always computed and returned as the function value.
**********************************************************************/
Math::real GenInverse(real lat1, real lon1, real lat2, real lon2,
unsigned outmask,
real& s12, real& azi1, real& azi2,
real& m12, real& M12, real& M21, real& S12)
const;
///@}
/** \name Interface to GeodesicLineExact.
**********************************************************************/
///@{
/**
* Set up to compute several points on a single geodesic.
*
* @param[in] lat1 latitude of point 1 (degrees).
* @param[in] lon1 longitude of point 1 (degrees).
* @param[in] azi1 azimuth at point 1 (degrees).
* @param[in] caps bitor'ed combination of GeodesicExact::mask values
* specifying the capabilities the GeodesicLineExact object should
* possess, i.e., which quantities can be returned in calls to
* GeodesicLineExact::Position.
* @return a GeodesicLineExact object.
*
* \e lat1 should be in the range [−90°, 90°].
*
* The GeodesicExact::mask values are
* - \e caps |= GeodesicExact::LATITUDE for the latitude \e lat2; this is
* added automatically;
* - \e caps |= GeodesicExact::LONGITUDE for the latitude \e lon2;
* - \e caps |= GeodesicExact::AZIMUTH for the azimuth \e azi2; this is
* added automatically;
* - \e caps |= GeodesicExact::DISTANCE for the distance \e s12;
* - \e caps |= GeodesicExact::REDUCEDLENGTH for the reduced length \e m12;
* - \e caps |= GeodesicExact::GEODESICSCALE for the geodesic scales \e M12
* and \e M21;
* - \e caps |= GeodesicExact::AREA for the area \e S12;
* - \e caps |= GeodesicExact::DISTANCE_IN permits the length of the
* geodesic to be given in terms of \e s12; without this capability the
* length can only be specified in terms of arc length;
* - \e caps |= GeodesicExact::ALL for all of the above.
* .
* The default value of \e caps is GeodesicExact::ALL which turns on all
* the capabilities.
*
* If the point is at a pole, the azimuth is defined by keeping \e lon1
* fixed, writing \e lat1 = ±(90 − ε), and taking the
* limit ε → 0+.
**********************************************************************/
GeodesicLineExact Line(real lat1, real lon1, real azi1, unsigned caps = ALL)
const;
///@}
/** \name Inspector functions.
**********************************************************************/
///@{
/**
* @return \e a the equatorial radius of the ellipsoid (meters). This is
* the value used in the constructor.
**********************************************************************/
Math::real MajorRadius() const { return _a; }
/**
* @return \e f the flattening of the ellipsoid. This is the
* value used in the constructor.
**********************************************************************/
Math::real Flattening() const { return _f; }
/// \cond SKIP
/**
* <b>DEPRECATED</b>
* @return \e r the inverse flattening of the ellipsoid.
**********************************************************************/
Math::real InverseFlattening() const { return 1/_f; }
/// \endcond
/**
* @return total area of ellipsoid in meters<sup>2</sup>. The area of a
* polygon encircling a pole can be found by adding
* GeodesicExact::EllipsoidArea()/2 to the sum of \e S12 for each side of
* the polygon.
**********************************************************************/
Math::real EllipsoidArea() const
{ return 4 * Math::pi() * _c2; }
///@}
/**
* A global instantiation of GeodesicExact with the parameters for the WGS84
* ellipsoid.
**********************************************************************/
static const GeodesicExact& WGS84();
};
} // namespace GeographicLib
#endif // GEOGRAPHICLIB_GEODESICEXACT_HPP
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