.NET wrapper for GeographicLib::PolygonArea and PolygonAreaExact. More...

#include <PolygonArea.h>

Public Member Functions
void	AddEdge (double azi, double s)

void	AddPoint (double lat, double lon)

void	Clear ()

unsigned	Compute (bool reverse, bool sign, [System::Runtime::InteropServices::Out] double%perimeter, [System::Runtime::InteropServices::Out] double%area)

	PolygonArea (Geodesic^earth, bool polyline)

	PolygonArea (const bool polyline)

unsigned	TestEdge (double azi, double s, bool reverse, bool sign, [System::Runtime::InteropServices::Out] double%perimeter, [System::Runtime::InteropServices::Out] double%area)

unsigned	TestPoint (double lat, double lon, bool reverse, bool sign, [System::Runtime::InteropServices::Out] double%perimeter, [System::Runtime::InteropServices::Out] double%area)

	~PolygonArea ()

Private Member Functions
	!PolygonArea (void)

Private Attributes
GeographicLib::PolygonArea *	m_pPolygonArea

Inspector functions
property double	MajorRadius { double get()

property double	Flattening { double get()

void	CurrentPoint ([System::Runtime::InteropServices::Out] double%lat, [System::Runtime::InteropServices::Out] double%lon)

Detailed Description

.NET wrapper for GeographicLib::PolygonArea and PolygonAreaExact.

This class allows .NET applications to access GeographicLib::PolygonArea.

This computes the area of a geodesic polygon using the method given Section 6 of

C. F. F. Karney, Algorithms for geodesics, J. Geodesy 87, 43–55 (2013); DOI: 10.1007/s00190-012-0578-z; addenda: geod-addenda.html.

This class lets you add vertices one at a time to the polygon. The area and perimeter are accumulated in two times the standard floating point precision to guard against the loss of accuracy with many-sided polygons. At any point you can ask for the perimeter and area so far. There's an option to treat the points as defining a polyline instead of a polygon; in that case, only the perimeter is computed.

C# Example:

using System;
using NETGeographicLib;
namespace example_PolygonArea
{
    class Program
    {
        static void Main(string[] args)
        {
            try {
                Geodesic geod = new Geodesic();  // WGS84
                PolygonArea poly = new PolygonArea(geod, true);
                poly.AddPoint( 52,  0);     // London
                poly.AddPoint( 41,-74);     // New York
                poly.AddPoint(-23,-43);     // Rio de Janeiro
                poly.AddPoint(-26, 28);     // Johannesburg
                double perimeter, area;
                uint n = poly.Compute(false, true, out perimeter, out area);
                Console.WriteLine(String.Format("{0} {1} {2}", n, perimeter, area));
            }
            catch (GeographicErr e) {
                Console.WriteLine(String.Format("Caught exception: {0}", e.Message));
            }
        }
    }
}

Managed C++ Example:

// Example of using the GeographicLib::PolygonArea class
#include <iostream>
#include <exception>
#include <GeographicLib/PolygonArea.hpp>
#include <GeographicLib/Geodesic.hpp>
#include <GeographicLib/Constants.hpp>
using namespace std;
using namespace GeographicLib;
int main() {
  try {
    Geodesic geod(Constants::WGS84_a(), Constants::WGS84_f());
    // Alternatively: const Geodesic& geod = Geodesic::WGS84();
    PolygonArea poly(geod);
    poly.AddPoint( 52,  0);     // London
    poly.AddPoint( 41,-74);     // New York
    poly.AddPoint(-23,-43);     // Rio de Janeiro
    poly.AddPoint(-26, 28);     // Johannesburg
    double perimeter, area;
    unsigned n = poly.Compute(false, true, perimeter, area);
    cout << n << " " << perimeter << " " << area << "\n";
  }
  catch (const exception& e) {
    cerr << "Caught exception: " << e.what() << "\n";
    return 1;
  }
}

Visual Basic Example:

Imports NETGeographicLib
Module example_PolygonArea
    Sub Main()
        Try
            Dim geod As Geodesic = New Geodesic()  ' WGS84
            Dim poly As PolygonArea = New PolygonArea(geod, True)
            poly.AddPoint(52, 0)     ' London
            poly.AddPoint(41, -74)   ' New York
            poly.AddPoint(-23, -43)  ' Rio de Janeiro
            poly.AddPoint(-26, 28)   ' Johannesburg
            Dim perimeter, area As Double
            Dim n As UInteger = poly.Compute(False, True, perimeter, area)
            Console.WriteLine(String.Format("{0} {1} {2}", n, perimeter, area))
        Catch ex As GeographicErr
            Console.WriteLine(String.Format("Caught exception: {0}", ex.Message))
        End Try
    End Sub
End Module

INTERFACE DIFFERENCES:
The MajorRadius and Flattening functions are implemented as properties.

Definition at line 49 of file PolygonArea.h.

Constructor & Destructor Documentation

PolygonArea::!PolygonArea ( void )

private

Definition at line 24 of file dotnet/NETGeographicLib/PolygonArea.cpp.

PolygonArea::PolygonArea	(	Geodesic^	earth,
		bool	polyline
	)

Constructor for PolygonArea.

Parameters

[in]	earth	the Geodesic object to use for geodesic calculations.
[in]	polyline	if true that treat the points as defining a polyline instead of a polygon.

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

PolygonArea::PolygonArea ( const bool polyline )

Constructor for PolygonArea that assumes a WGS84 ellipsoid.

Parameters

[in] polyline if true that treat the points as defining a polyline instead of a polygon.

Definition at line 50 of file dotnet/NETGeographicLib/PolygonArea.cpp.

NETGeographicLib::PolygonArea::~PolygonArea ( )

inline

The destructor calls the finalizer.

Definition at line 79 of file PolygonArea.h.

Member Function Documentation

void PolygonArea::AddEdge	(	double	azi,
		double	s
	)

Add an edge to the polygon or polyline.

Parameters

[in]	azi	azimuth at current point (degrees).
[in]	s	distance from current point to next point (meters).

This does nothing if no points have been added yet. Use PolygonArea::CurrentPoint to determine the position of the new vertex.

Definition at line 73 of file dotnet/NETGeographicLib/PolygonArea.cpp.

void PolygonArea::AddPoint	(	double	lat,
		double	lon
	)

Add a point to the polygon or polyline.

Parameters

[in]	lat	the latitude of the point (degrees).
[in]	lon	the longitude of the point (degrees).

lat should be in the range [−90°, 90°].

Definition at line 67 of file dotnet/NETGeographicLib/PolygonArea.cpp.

void PolygonArea::Clear ( )

Clear PolygonArea, allowing a new polygon to be started.

Definition at line 64 of file dotnet/NETGeographicLib/PolygonArea.cpp.

unsigned PolygonArea::Compute	(	bool	reverse,
		bool	sign,
		[System::Runtime::InteropServices::Out] double%	perimeter,
		[System::Runtime::InteropServices::Out] double%	area
	)

Return the results so far.

Parameters

[in]	reverse	if true then clockwise (instead of counter-clockwise) traversal counts as a positive area.
[in]	sign	if true then return a signed result for the area if the polygon is traversed in the "wrong" direction instead of returning the area for the rest of the earth.
[out]	perimeter	the perimeter of the polygon or length of the polyline (meters).
[out]	area	the area of the polygon (meters²); only set if polyline is false in the constructor.

Returns: the number of points.

Definition at line 79 of file dotnet/NETGeographicLib/PolygonArea.cpp.

void PolygonArea::CurrentPoint	(	[System::Runtime::InteropServices::Out] double%	lat,
		[System::Runtime::InteropServices::Out] double%	lon
	)

Report the previous vertex added to the polygon or polyline.

Parameters

[out]	lat	the latitude of the point (degrees).
[out]	lon	the longitude of the point (degrees).

If no points have been added, then NaNs are returned. Otherwise, lon will be in the range [−180°, 180°).

Definition at line 115 of file dotnet/NETGeographicLib/PolygonArea.cpp.

unsigned PolygonArea::TestEdge	(	double	azi,
		double	s,
		bool	reverse,
		bool	sign,
		[System::Runtime::InteropServices::Out] double%	perimeter,
		[System::Runtime::InteropServices::Out] double%	area
	)

Return the results assuming a tentative final test point is added via an azimuth and distance; however, the data for the test point is not saved. This lets you report a running result for the perimeter and area as the user moves the mouse cursor. Ordinary floating point arithmetic is used to accumulate the data for the test point; thus the area and perimeter returned are less accurate than if PolygonArea::AddEdge and PolygonArea::Compute are used.

Parameters

[in]	azi	azimuth at current point (degrees).
[in]	s	distance from current point to final test point (meters).
[in]	reverse	if true then clockwise (instead of counter-clockwise) traversal counts as a positive area.
[in]	sign	if true then return a signed result for the area if the polygon is traversed in the "wrong" direction instead of returning the area for the rest of the earth.
[out]	perimeter	the approximate perimeter of the polygon or length of the polyline (meters).
[out]	area	the approximate area of the polygon (meters²); only set if polyline is false in the constructor.

Returns: the number of points.

Definition at line 103 of file dotnet/NETGeographicLib/PolygonArea.cpp.

unsigned PolygonArea::TestPoint	(	double	lat,
		double	lon,
		bool	reverse,
		bool	sign,
		[System::Runtime::InteropServices::Out] double%	perimeter,
		[System::Runtime::InteropServices::Out] double%	area
	)

Return the results assuming a tentative final test point is added; however, the data for the test point is not saved. This lets you report a running result for the perimeter and area as the user moves the mouse cursor. Ordinary floating point arithmetic is used to accumulate the data for the test point; thus the area and perimeter returned are less accurate than if PolygonArea::AddPoint and PolygonArea::Compute are used.

Parameters

[in]	lat	the latitude of the test point (degrees).
[in]	lon	the longitude of the test point (degrees).
[in]	reverse	if true then clockwise (instead of counter-clockwise) traversal counts as a positive area.
[in]	sign	if true then return a signed result for the area if the polygon is traversed in the "wrong" direction instead of returning the area for the rest of the earth.
[out]	perimeter	the approximate perimeter of the polygon or length of the polyline (meters).
[out]	area	the approximate area of the polygon (meters²); only set if polyline is false in the constructor.

Returns: the number of points.

lat should be in the range [−90°, 90°].

Definition at line 91 of file dotnet/NETGeographicLib/PolygonArea.cpp.

Member Data Documentation

property double NETGeographicLib::PolygonArea::Flattening { double get()

Returns: f the flattening of the ellipsoid. This is the value inherited from the Geodesic object used in the constructor.

Definition at line 196 of file PolygonArea.h.

GeographicLib::PolygonArea* NETGeographicLib::PolygonArea::m_pPolygonArea

private

Definition at line 53 of file PolygonArea.h.

property double NETGeographicLib::PolygonArea::MajorRadius { double get()

Returns: a the equatorial radius of the ellipsoid (meters). This is the value inherited from the Geodesic object used in the constructor.

Definition at line 190 of file PolygonArea.h.

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

Public Member Functions

Private Member Functions

Private Attributes

Inspector functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation