GeographicLib  1.21
Public Member Functions
GeographicLib::LocalCartesian Class Reference

Local Cartesian coordinates. More...

#include <GeographicLib/LocalCartesian.hpp>

List of all members.

Public Member Functions

 LocalCartesian (real lat0, real lon0, real h0=0, const Geocentric &earth=Geocentric::WGS84) throw ()
 LocalCartesian (const Geocentric &earth=Geocentric::WGS84) throw ()
void Reset (real lat0, real lon0, real h0=0) throw ()
void Forward (real lat, real lon, real h, real &x, real &y, real &z) const throw ()
void Forward (real lat, real lon, real h, real &x, real &y, real &z, std::vector< real > &M) const throw ()
void Reverse (real x, real y, real z, real &lat, real &lon, real &h) const throw ()
void Reverse (real x, real y, real z, real &lat, real &lon, real &h, std::vector< real > &M) const throw ()
Inspector functions
Math::real LatitudeOrigin () const throw ()
Math::real LongitudeOrigin () const throw ()
Math::real HeightOrigin () const throw ()
Math::real MajorRadius () const throw ()
Math::real Flattening () const throw ()

Detailed Description

Local Cartesian coordinates.

Convert between geodetic coordinates latitude = lat, longitude = lon, height = h (measured vertically from the surface of the ellipsoid) to local cartesian coordinates (x, y, z). The origin of local cartesian coordinate system is at lat = lat0, lon = lon0, h = h0. The z axis is normal to the ellipsoid; the y axis points due north. The plane z = - h0 is tangent to the ellipsoid.

The conversions all take place via geocentric coordinates using a Geocentric object (by default Geocentric::WGS84).

Example of use:

// Example of using the GeographicLib::LocalCartesian class
// $Id: 0fd182a359b17d3b76ccd55f405b272a327a42e8 $

#include <iostream>
#include <exception>
#include <cmath>
#include <GeographicLib/Geocentric.hpp>
#include <GeographicLib/LocalCartesian.hpp>

using namespace std;
using namespace GeographicLib;

int main() {
  try {
    Geocentric earth(Constants::WGS84_a(), Constants::WGS84_f());
    // Alternatively: const Geocentric& earth = Geocentric::WGS84;
    const double lat0 = 48 + 50/60.0, lon0 = 2 + 20/60.0; // Paris
    LocalCartesian proj(lat0, lon0, 0, earth);
    {
      // Sample forward calculation
      double lat = 50.9, lon = 1.8, h = 0; // Calais
      double x, y, z;
      proj.Forward(lat, lon, h, x, y, z);
      cout << x << " " << y << " " << z << "\n";
    }
    {
      // Sample reverse calculation
      double x = -38e3, y = 230e3, z = -4e3;
      double lat, lon, h;
      proj.Reverse(x, y, z, lat, lon, h);
      cout << lat << " " << lon << " " << h << "\n";
    }
  }
  catch (const exception& e) {
    cerr << "Caught exception: " << e.what() << "\n";
    return 1;
  }
  return 0;
}

CartConvert is a command-line utility providing access to the functionality of Geocentric and LocalCartesian.


Constructor & Destructor Documentation

GeographicLib::LocalCartesian::LocalCartesian ( real  lat0,
real  lon0,
real  h0 = 0,
const Geocentric earth = Geocentric::WGS84 
) throw () [inline]

Constructor setting the origin.

Parameters:
[in]lat0latitude at origin (degrees).
[in]lon0longitude at origin (degrees).
[in]h0height above ellipsoid at origin (meters); default 0.
[in]earthGeocentric object for the transformation; default Geocentric::WGS84.

Definition at line 63 of file LocalCartesian.hpp.

GeographicLib::LocalCartesian::LocalCartesian ( const Geocentric earth = Geocentric::WGS84) throw () [inline, explicit]

Default constructor.

Parameters:
[in]earthGeocentric object for the transformation; default Geocentric::WGS84.

Sets lat0 = 0, lon0 = 0, h0 = 0.

Definition at line 76 of file LocalCartesian.hpp.


Member Function Documentation

void GeographicLib::LocalCartesian::Reset ( real  lat0,
real  lon0,
real  h0 = 0 
) throw ()

Reset the origin.

Parameters:
[in]lat0latitude at origin (degrees).
[in]lon0longitude at origin (degrees).
[in]h0height above ellipsoid at origin (meters); default 0.

Definition at line 22 of file LocalCartesian.cpp.

void GeographicLib::LocalCartesian::Forward ( real  lat,
real  lon,
real  h,
real &  x,
real &  y,
real &  z 
) const throw () [inline]

Convert from geodetic to local cartesian coordinates.

Parameters:
[in]latlatitude of point (degrees).
[in]lonlongitude of point (degrees).
[in]hheight of point above the ellipsoid (meters).
[out]xlocal cartesian coordinate (meters).
[out]ylocal cartesian coordinate (meters).
[out]zlocal cartesian coordinate (meters).

lat should be in the range [-90, 90]; lon and lon0 should be in the range [-180, 360].

Definition at line 104 of file LocalCartesian.hpp.

Referenced by main().

void GeographicLib::LocalCartesian::Forward ( real  lat,
real  lon,
real  h,
real &  x,
real &  y,
real &  z,
std::vector< real > &  M 
) const throw () [inline]

Convert from geodetic to local cartesian coordinates and return rotation matrix.

Parameters:
[in]latlatitude of point (degrees).
[in]lonlongitude of point (degrees).
[in]hheight of point above the ellipsoid (meters).
[out]xlocal cartesian coordinate (meters).
[out]ylocal cartesian coordinate (meters).
[out]zlocal cartesian coordinate (meters).
[out]Mif the length of the vector is 9, fill with the rotation matrix in row-major order.

Let v be a unit vector located at (lat, lon, h). We can express v as column vectors in one of two ways

  • in east, north, up coordinates (where the components are relative to a local coordinate system at (lat, lon, h)); call this representation v1.
  • in x, y, z coordinates (where the components are relative to the local coordinate system at (lat0, lon0, h0)); call this representation v0.

Then we have v0 = M . v1.

Definition at line 133 of file LocalCartesian.hpp.

void GeographicLib::LocalCartesian::Reverse ( real  x,
real  y,
real  z,
real &  lat,
real &  lon,
real &  h 
) const throw () [inline]

Convert from local cartesian to geodetic coordinates.

Parameters:
[in]xlocal cartesian coordinate (meters).
[in]ylocal cartesian coordinate (meters).
[in]zlocal cartesian coordinate (meters).
[out]latlatitude of point (degrees).
[out]lonlongitude of point (degrees).
[out]hheight of point above the ellipsoid (meters).

The value of lon returned is in the range [-180, 180).

Definition at line 156 of file LocalCartesian.hpp.

Referenced by main().

void GeographicLib::LocalCartesian::Reverse ( real  x,
real  y,
real  z,
real &  lat,
real &  lon,
real &  h,
std::vector< real > &  M 
) const throw () [inline]

Convert from local cartesian to geodetic coordinates and return rotation matrix.

Parameters:
[in]xlocal cartesian coordinate (meters).
[in]ylocal cartesian coordinate (meters).
[in]zlocal cartesian coordinate (meters).
[out]latlatitude of point (degrees).
[out]lonlongitude of point (degrees).
[out]hheight of point above the ellipsoid (meters).
[out]Mif the length of the vector is 9, fill with the rotation matrix in row-major order.

Let v be a unit vector located at (lat, lon, h). We can express v as column vectors in one of two ways

  • in east, north, up coordinates (where the components are relative to a local coordinate system at (lat, lon, h)); call this representation v1.
  • in x, y, z coordinates (where the components are relative to the local coordinate system at (lat0, lon0, h0)); call this representation v0.

Then we have v1 = M^T . v0, where M^T is the transpose of M.

Definition at line 186 of file LocalCartesian.hpp.

Math::real GeographicLib::LocalCartesian::LatitudeOrigin ( ) const throw () [inline]
Returns:
latitude of the origin (degrees).

Definition at line 203 of file LocalCartesian.hpp.

Math::real GeographicLib::LocalCartesian::LongitudeOrigin ( ) const throw () [inline]
Returns:
longitude of the origin (degrees).

Definition at line 208 of file LocalCartesian.hpp.

Math::real GeographicLib::LocalCartesian::HeightOrigin ( ) const throw () [inline]
Returns:
height of the origin (meters).

Definition at line 213 of file LocalCartesian.hpp.

Math::real GeographicLib::LocalCartesian::MajorRadius ( ) const throw () [inline]
Returns:
a the equatorial radius of the ellipsoid (meters). This is the value of a inherited from the Geocentric object used in the constructor.

Definition at line 220 of file LocalCartesian.hpp.

Math::real GeographicLib::LocalCartesian::Flattening ( ) const throw () [inline]
Returns:
f the flattening of the ellipsoid. This is the value inherited from the Geocentric object used in the constructor.

Definition at line 226 of file LocalCartesian.hpp.


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