.NET wrapper for GeographicLib::Geohash. More...

#include <Geohash.h>

Static Public Member Functions
static int	DecimalPrecision (int len)

static void	Forward (double lat, double lon, int len, [System::Runtime::InteropServices::Out] System::String^%geohash)

static int	GeohashLength (double res)

static int	GeohashLength (double latres, double lonres)

static double	LatitudeResolution (int len)

static double	LongitudeResolution (int len)

static void	Reverse (System::String^geohash, [System::Runtime::InteropServices::Out] double%lat, [System::Runtime::InteropServices::Out] double%lon, [System::Runtime::InteropServices::Out] int%len, bool centerp)

Private Member Functions
	Geohash ()

Detailed Description

.NET wrapper for GeographicLib::Geohash.

Geohashes are described in

https://en.wikipedia.org/wiki/Geohash
http://geohash.org/ (this link is broken as of 2012-12-11)

They provide a compact string representation of a particular geographic location (expressed as latitude and longitude), with the property that if trailing characters are dropped from the string the geographic location remains nearby.

C# Example:

using System;
using NETGeographicLib;
namespace example_Geohash
{
    class Program
    {
        static void Main(string[] args)
        {
            try {
                {
                    // Sample forward calculation
                    double lat = 57.64911, lon = 10.40744; // Jutland (the wikipedia example)
                    string geohash;
                    int maxlen = Geohash.GeohashLength(1.0e-5);
                    for (int len = 0; len <= maxlen; ++len) {
                        Geohash.Forward(lat, lon, len, out geohash);
                        Console.WriteLine( geohash );
                    }
                }
                {
                    // Sample reverse calculation
                    string geohash = "u4pruydqqvj";
                    double lat, lon;
                    for (int i = 0; i <= geohash.Length; ++i) {
                        int len;
                        Geohash.Reverse(geohash.Substring(0, i), out lat, out lon, out len, true);
                        Console.WriteLine(String.Format("Length: {0} Latitude: {1} Longitude: {2}", len, lat, lon ) );
                    }
                }
            }
            catch (GeographicErr e) {
                Console.WriteLine(String.Format("Caught exception: {0}", e.Message));
            }
        }
    }
}

Managed C++ Example:

// Example of using the GeographicLib::Geohash class
#include <iostream>
#include <iomanip>
#include <exception>
#include <string>
#include <GeographicLib/Geohash.hpp>
using namespace std;
using namespace GeographicLib;
int main() {
  try {
    {
      // Sample forward calculation
      double lat = 57.64911, lon = 10.40744; // Jutland (the wikipedia example)
      string geohash;
      int maxlen = Geohash::GeohashLength(1.0e-5);
      for (int len = 0; len <= maxlen; ++len) {
        Geohash::Forward(lat, lon, len, geohash);
        cout << len << " " << geohash << "\n";
      }
    }
    {
      // Sample reverse calculation
      string geohash = "u4pruydqqvj";
      double lat, lon;
      cout << fixed;
      for (unsigned i = 0; i <= geohash.length(); ++i) {
        int len;
        Geohash::Reverse(geohash.substr(0, i), lat, lon, len);
        cout << setprecision(max(0, Geohash::DecimalPrecision(len)))
             << len << " " << lat << " " << lon << "\n";
      }
    }
  }
  catch (const exception& e) {
    cerr << "Caught exception: " << e.what() << "\n";
    return 1;
  }
}

Visual Basic Example:

Imports NETGeographicLib
Module example_Geohash
    Sub Main()
        Try
            ' Sample forward calculation
            Dim lat As Double = 57.64911, lon = 10.40744 ' Jutland (the wikipedia example)
            Dim ghash As String
            Dim maxlen As Integer = Geohash.GeohashLength(0.00001)
            For len As Integer = 0 To maxlen
                Geohash.Forward(lat, lon, len, ghash)
                Console.WriteLine(ghash)
            Next
            ' Sample reverse calculation
            ghash = "u4pruydqqvj"
            For i As Integer = 0 To ghash.Length - 1
                Dim len As Integer
                Geohash.Reverse(ghash.Substring(0, i), lat, lon, len, True)
                Console.WriteLine(String.Format("Length: {0} Latitude: {1} Longitude: {2}", len, lat, lon))
            Next
        Catch ex As GeographicErr
            Console.WriteLine(String.Format("Caught exception: {0}", ex.Message))
        End Try
    End Sub
End Module

Definition at line 34 of file Geohash.h.

Constructor & Destructor Documentation

NETGeographicLib::Geohash::Geohash ( )

inlineprivate

Definition at line 38 of file Geohash.h.

Member Function Documentation

int Geohash::DecimalPrecision ( int len )

static

The decimal geographic precision required to match a given geohash length. This is the number of digits needed after decimal point in a decimal degrees representation.

Parameters

[in] len the length of the geohash.

Returns: the decimal precision (may be negative).

Internally, len is first put in the range [0, 18]. The returned decimal precision is in the range [−2, 12].

Definition at line 81 of file dotnet/NETGeographicLib/Geohash.cpp.

void Geohash::Forward	(	double	lat,
		double	lon,
		int	len,
		[System::Runtime::InteropServices::Out] System::String^%	geohash
	)

static

Convert from geographic coordinates to a geohash.

Parameters

[in]	lat	latitude of point (degrees).
[in]	lon	longitude of point (degrees).
[in]	len	the length of the resulting geohash.
[out]	geohash	the geohash.

Exceptions

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

Internally, len is first put in the range [0, 18].

If lat or lon is NaN, the returned geohash is "nan".

Definition at line 19 of file dotnet/NETGeographicLib/Geohash.cpp.

int Geohash::GeohashLength ( double res )

static

The geohash length required to meet a given geographic resolution.

Parameters

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

Returns: geohash length.

The returned length is in the range [0, 18].

Definition at line 69 of file dotnet/NETGeographicLib/Geohash.cpp.

int Geohash::GeohashLength	(	double	latres,
		double	lonres
	)

static

The geohash length required to meet a given geographic resolution.

Parameters

[in]	latres	the resolution in latitude (degrees).
[in]	lonres	the resolution in longitude (degrees).

Returns: geohash length.

The returned length is in the range [0, 18].

Definition at line 75 of file dotnet/NETGeographicLib/Geohash.cpp.

double Geohash::LatitudeResolution ( int len )

static

The latitude resolution of a geohash.

Parameters

[in] len the length of the geohash.

Returns: the latitude resolution (degrees).

Internally, len is first put in the range [0, 18].

Definition at line 57 of file dotnet/NETGeographicLib/Geohash.cpp.

double Geohash::LongitudeResolution ( int len )

static

The longitude resolution of a geohash.

Parameters

[in] len the length of the geohash.

Returns: the longitude resolution (degrees).

Internally, len is first put in the range [0, 18].

Definition at line 63 of file dotnet/NETGeographicLib/Geohash.cpp.

void Geohash::Reverse	(	System::String^	geohash,
		[System::Runtime::InteropServices::Out] double%	lat,
		[System::Runtime::InteropServices::Out] double%	lon,
		[System::Runtime::InteropServices::Out] int%	len,
		bool	centerp
	)

static

Convert from a geohash to geographic coordinates.

Parameters

[in]	geohash	the geohash.
[out]	lat	latitude of point (degrees).
[out]	lon	longitude of point (degrees).
[out]	len	the length of the geohash.
[in]	centerp	if true (the default) return the center of the geohash location, otherwise return the south-west corner.

Exceptions

GeographicErr if geohash contains illegal characters.

Only the first 18 characters for geohash are considered. The case of the letters in geohash is ignored.

If the first three characters in geohash are "nan", then lat and lon are set to NaN.

Definition at line 34 of file dotnet/NETGeographicLib/Geohash.cpp.

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

Static Public Member Functions

Private Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation