GeographicLib::PolarStereographic Class Reference

Polar stereographic projection. More...

#include <PolarStereographic.hpp>

Public Member Functions
void	Forward (bool northp, real lat, real lon, real &x, real &y) const
void	Forward (bool northp, real lat, real lon, real &x, real &y, real &gamma, real &k) const
	PolarStereographic (real a, real f, real k0)
void	Reverse (bool northp, real x, real y, real &lat, real &lon) const
void	Reverse (bool northp, real x, real y, real &lat, real &lon, real &gamma, real &k) const
void	SetScale (real lat, real k=real(1))
Inspector functions
Math::real	MajorRadius () const
Math::real	Flattening () const
Math::real	CentralScale () const

Static Public Member Functions
static const PolarStereographic &	UPS ()

Private Types
typedef Math::real	real

Private Attributes
real	_a
real	_c
real	_e2
real	_e2m
real	_es
real	_f
real	_k0

Detailed Description

Polar stereographic projection.

Implementation taken from the report,

• J. P. Snyder, Map Projections: A Working Manual, USGS Professional Paper 1395 (1987), pp. 160–163.

This is a straightforward implementation of the equations in Snyder except that Newton's method is used to invert the projection.

This class also returns the meridian convergence gamma and scale k. The meridian convergence is the bearing of grid north (the y axis) measured clockwise from true north.

Example of use:

// Example of using the GeographicLib::PolarStereographic class
 
#include <iostream>
#include <iomanip>
#include <exception>
#include <GeographicLib/PolarStereographic.hpp>
 
using namespace std;
using namespace GeographicLib;
 
int main() {
  try {
    PolarStereographic proj(Constants::WGS84_a(), Constants::WGS84_f(),
                            Constants::UPS_k0());
    // Alternatively:
    // const PolarStereographic& proj = PolarStereographic::UPS();
    bool northp = true;
    {
      // Sample forward calculation
      double lat = 61.2, lon = -149.9; // Anchorage
      double x, y;
      proj.Forward(northp, lat, lon, x, y);
      cout << x << " " << y << "\n";
    }
    {
      // Sample reverse calculation
      double x = -1637e3, y = 2824e3;
      double lat, lon;
      proj.Reverse(northp, x, y, lat, lon);
      cout << lat << " " << lon << "\n";
    }
  }
  catch (const exception& e) {
    cerr << "Caught exception: " << e.what() << "\n";
    return 1;
  }
}

Definition at line 36 of file PolarStereographic.hpp.

Member Typedef Documentation

real

typedef Math::real GeographicLib::PolarStereographic::real

private

Definition at line 38 of file PolarStereographic.hpp.

Constructor & Destructor Documentation

PolarStereographic()

GeographicLib::PolarStereographic::PolarStereographic	(	real	a,
		real	f,
		real	k0
	)

Constructor for a ellipsoid with

Parameters

[in]	a	equatorial radius (meters).
[in]	f	flattening of ellipsoid. Setting f = 0 gives a sphere. Negative f gives a prolate ellipsoid.
[in]	k0	central scale factor.

Exceptions

GeographicErr

if a, (1 − f) a, or k0 is not positive.

Definition at line 16 of file src/PolarStereographic.cpp.

Member Function Documentation

CentralScale()

Math::real GeographicLib::PolarStereographic::CentralScale ( ) const

inline

The central scale for the projection. This is the value of k0 used in the constructor and is the scale at the pole unless overridden by PolarStereographic::SetScale.

Definition at line 141 of file PolarStereographic.hpp.

Flattening()

Math::real GeographicLib::PolarStereographic::Flattening ( ) const

inline

Returns

f the flattening of the ellipsoid. This is the value used in the constructor.

Definition at line 134 of file PolarStereographic.hpp.

Forward() [1/2]

void GeographicLib::PolarStereographic::Forward ( bool  northp, real  lat, real  lon, real &  x, real &  y  ) const

inline

PolarStereographic::Forward without returning the convergence and scale.

Definition at line 106 of file PolarStereographic.hpp.

Forward() [2/2]

void GeographicLib::PolarStereographic::Forward	(	bool	northp,
		real	lat,
		real	lon,
		real &	x,
		real &	y,
		real &	gamma,
		real &	k
	)		const

Forward projection, from geographic to polar stereographic.

Parameters

[in]	northp	the pole which is the center of projection (true means north, false means south).
[in]	lat	latitude of point (degrees).
[in]	lon	longitude of point (degrees).
[out]	x	easting of point (meters).
[out]	y	northing of point (meters).
[out]	gamma	meridian convergence at point (degrees).
[out]	k	scale of projection at point.

No false easting or northing is added. lat should be in the range (−90°, 90°] for northp = true and in the range [−90°, 90°) for northp = false.

Definition at line 61 of file src/PolarStereographic.cpp.

MajorRadius()

Math::real GeographicLib::PolarStereographic::MajorRadius ( ) const

inline

Returns

a the equatorial radius of the ellipsoid (meters). This is the value used in the constructor.

Definition at line 128 of file PolarStereographic.hpp.

Reverse() [1/2]

void GeographicLib::PolarStereographic::Reverse ( bool  northp, real  x, real  y, real &  lat, real &  lon  ) const

inline

PolarStereographic::Reverse without returning the convergence and scale.

Definition at line 115 of file PolarStereographic.hpp.

Reverse() [2/2]

void GeographicLib::PolarStereographic::Reverse	(	bool	northp,
		real	x,
		real	y,
		real &	lat,
		real &	lon,
		real &	gamma,
		real &	k
	)		const

Reverse projection, from polar stereographic to geographic.

Parameters

[in]	northp	the pole which is the center of projection (true means north, false means south).
[in]	x	easting of point (meters).
[in]	y	northing of point (meters).
[out]	lat	latitude of point (degrees).
[out]	lon	longitude of point (degrees).
[out]	gamma	meridian convergence at point (degrees).
[out]	k	scale of projection at point.

No false easting or northing is added. The value of lon returned is in the range [−180°, 180°].

Definition at line 81 of file src/PolarStereographic.cpp.

SetScale()

void GeographicLib::PolarStereographic::SetScale	(	real	lat,
		real	k = real(1)
	)

Set the scale for the projection.

Parameters

[in]	lat	(degrees) assuming northp = true.
[in]	k	scale at latitude lat (default 1).

Exceptions

GeographicErr	k is not positive.
GeographicErr	if lat is not in (−90°, 90°].

Definition at line 98 of file src/PolarStereographic.cpp.

UPS()

const PolarStereographic & GeographicLib::PolarStereographic::UPS ( )

static

A global instantiation of PolarStereographic with the WGS84 ellipsoid and the UPS scale factor. However, unlike UPS, no false easting or northing is added.

Definition at line 33 of file src/PolarStereographic.cpp.

Member Data Documentation

_a

real GeographicLib::PolarStereographic::_a

private

Definition at line 39 of file PolarStereographic.hpp.

_c

real GeographicLib::PolarStereographic::_c

private

Definition at line 39 of file PolarStereographic.hpp.

_e2

real GeographicLib::PolarStereographic::_e2

private

Definition at line 39 of file PolarStereographic.hpp.

_e2m

real GeographicLib::PolarStereographic::_e2m

private

Definition at line 39 of file PolarStereographic.hpp.

_es

real GeographicLib::PolarStereographic::_es

private

Definition at line 39 of file PolarStereographic.hpp.

_f

real GeographicLib::PolarStereographic::_f

private

Definition at line 39 of file PolarStereographic.hpp.

_k0

real GeographicLib::PolarStereographic::_k0

private

Definition at line 40 of file PolarStereographic.hpp.

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

• PolarStereographic.hpp
• src/PolarStereographic.cpp