GeographicLib::Georef Class Reference

Conversions for the World Geographic Reference System (georef) More...

#include <GeographicLib/Georef.hpp>

Static Public Member Functions
static void	Forward (real lat, real lon, int prec, std::string &georef)
static void	Reverse (const std::string &georef, real &lat, real &lon, int &prec, bool centerp=true)
static Math::real	Resolution (int prec)
static int	Precision (real res)

Detailed Description

Conversions for the World Geographic Reference System (georef)

The World Geographic Reference System is described in

• https://en.wikipedia.org/wiki/Georef
• https://web.archive.org/web/20161214054445/http://earth-info.nga.mil/GandG/coordsys/grids/georef.pdf

It provides a compact string representation of a geographic area (expressed as latitude and longitude). The classes GARS and Geohash implement similar compact representations.

Example of use:

// Example of using the GeographicLib::GARS class
 
#include <iostream>
#include <iomanip>
#include <exception>
#include <string>
#include <GeographicLib/Georef.hpp>
 
using namespace std;
using namespace GeographicLib;
 
int main() {
  try {
    {
      // Sample forward calculation
      double lat = 57.64911, lon = 10.40744; // Jutland
      string georef;
      for (int prec = -1; prec <= 11; ++prec) {
        Georef::Forward(lat, lon, prec, georef);
        cout << prec << " " << georef << "\n";
      }
    }
    {
      // Sample reverse calculation
      string georef = "NKLN2444638946";
      double lat, lon;
      int prec;
      cout << fixed;
      Georef::Reverse(georef.substr(0, 2), lat, lon, prec);
      cout << prec << " " << lat << " " << lon << "\n";
      Georef::Reverse(georef.substr(0, 4), lat, lon, prec);
      cout << prec << " " << lat << " " << lon << "\n";
      Georef::Reverse(georef, lat, lon, prec);
      cout << prec << " " << lat << " " << lon << "\n";
    }
  }
  catch (const exception& e) {
    cerr << "Caught exception: " << e.what() << "\n";
    return 1;
  }
}

Definition at line 38 of file Georef.hpp.

Member Function Documentation

Forward()

void GeographicLib::Georef::Forward ( real  lat, real  lon, int  prec, std::string &  georef  )

static

Convert from geographic coordinates to georef.

Parameters

[in]	lat	latitude of point (degrees).
[in]	lon	longitude of point (degrees).
[in]	prec	the precision of the resulting georef.
[out]	georef	the georef string.

Exceptions

GeographicErr	if lat is not in [−90°, 90°].
std::bad_alloc	if memory for georef can't be allocated.

prec specifies the precision of georef as follows:

• prec = −1 (min), 15°
• prec = 0, 1°
• prec = 1, converted to prec = 2
• prec = 2, 1'
• prec = 3, 0.1'
• prec = 4, 0.01'
• prec = 5, 0.001'
• …
• prec = 11 (max), 10⁻⁹'

If lat or lon is NaN, then georef is set to "INVALID".

Definition at line 27 of file Georef.cpp.

References GeographicLib::Math::AngNormalize(), GeographicLib::Math::qd, and GeographicLib::Utility::str().

Reverse()

void GeographicLib::Georef::Reverse ( const std::string &  georef, real &  lat, real &  lon, int &  prec, bool  centerp = true  )

static

Convert from Georef to geographic coordinates.

Parameters

[in]	georef	the Georef.
[out]	lat	latitude of point (degrees).
[out]	lon	longitude of point (degrees).
[out]	prec	the precision of georef.
[in]	centerp	if true (the default) return the center georef, otherwise return the south-west corner.

Exceptions

GeographicErr

if georef is illegal.

The case of the letters in georef is ignored. prec is in the range [−1, 11] and gives the precision of georef as follows:

• prec = −1 (min), 15°
• prec = 0, 1°
• prec = 1, not returned
• prec = 2, 1'
• prec = 3, 0.1'
• prec = 4, 0.01'
• prec = 5, 0.001'
• …
• prec = 11 (max), 10⁻⁹'

If the first 3 characters of georef are "INV", then lat and lon are set to NaN and prec is unchanged.

Definition at line 70 of file Georef.cpp.

References GeographicLib::Utility::lookup(), GeographicLib::Math::NaN(), and GeographicLib::Utility::str().

Resolution()

static Math::real GeographicLib::Georef::Resolution ( int  prec )

inlinestatic

The angular resolution of a Georef.

Parameters

[in]

prec

the precision of the Georef.

Returns

the latitude-longitude resolution (degrees).

Internally, prec is first put in the range [−1, 11].

Definition at line 133 of file Georef.hpp.

Precision()

static int GeographicLib::Georef::Precision ( real  res )

inlinestatic

The Georef precision required to meet a given geographic resolution.

Parameters

[in]

res

the minimum of resolution in latitude and longitude (degrees).

Returns

Georef precision.

The returned length is in the range [0, 11].

Definition at line 154 of file Georef.hpp.

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

• Georef.hpp
• Georef.cpp