GeographicLib::GARS Class Reference

Conversions for the Global Area Reference System (GARS) More...

#include <GeographicLib/GARS.hpp>

Static Public Member Functions
static void	Forward (real lat, real lon, int prec, std::string &gars)
static void	Reverse (const std::string &gars, 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 Global Area Reference System (GARS)

The Global Area Reference System is described in

• https://en.wikipedia.org/wiki/Global_Area_Reference_System
• https://earth-info.nga.mil/index.php?dir=coordsys&action=coordsys#tab_gars

It provides a compact string representation of a geographic area (expressed as latitude and longitude). The classes Georef 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/GARS.hpp>
 
using namespace std;
using namespace GeographicLib;
 
int main() {
  try {
    {
      // Sample forward calculation
      double lat = 57.64911, lon = 10.40744; // Jutland
      string gars;
      for (int prec = 0; prec <= 2; ++prec) {
        GARS::Forward(lat, lon, prec, gars);
        cout << prec << " " << gars << "\n";
      }
    }
    {
      // Sample reverse calculation
      string gars = "381NH45";
      double lat, lon;
      cout << fixed;
      for (int len = 5; len <= int(gars.size()); ++len) {
        int prec;
        GARS::Reverse(gars.substr(0, len), 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 GARS.hpp.

Member Function Documentation

Forward()

void GeographicLib::GARS::Forward ( real  lat, real  lon, int  prec, std::string &  gars  )

static

Convert from geographic coordinates to GARS.

Parameters

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

Exceptions

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

prec specifies the precision of gars as follows:

• prec = 0 (min), 30' precision, e.g., 006AG;
• prec = 1, 15' precision, e.g., 006AG3;
• prec = 2 (max), 5' precision, e.g., 006AG39.

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

Definition at line 25 of file GARS.cpp.

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

Reverse()

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

static

Convert from GARS to geographic coordinates.

Parameters

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

Exceptions

GeographicErr

if gars is illegal.

The case of the letters in gars is ignored. prec is in the range [0, 2] and gives the precision of gars as follows:

• prec = 0 (min), 30' precision, e.g., 006AG;
• prec = 1, 15' precision, e.g., 006AG3;
• prec = 2 (max), 5' precision, e.g., 006AG39.

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

Definition at line 65 of file GARS.cpp.

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

Resolution()

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

inlinestatic

The angular resolution of a GARS.

Parameters

[in]

prec

the precision of the GARS.

Returns

the latitude-longitude resolution (degrees).

Internally, prec is first put in the range [0, 2].

Definition at line 125 of file GARS.hpp.

Precision()

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

inlinestatic

The GARS precision required to meet a given geographic resolution.

Parameters

[in]

res

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

Returns

GARS precision.

The returned length is in the range [0, 2].

Definition at line 139 of file GARS.hpp.

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

• GARS.hpp
• GARS.cpp