用经纬度计算多边形的面积

问题描述

我有这个代码，用这个编写:

我的测试结果是:期望值为 10000，但发现值为 1.28153883377486E+48.

知道我的代码有什么问题吗?

解决方案

我很确定这个声明:

area = area * R * R/2;

应该放在顶点上的循环之后，而不是在每次迭代中重复.

I have this code, written using this: source1 and this: source 2

public static double CalculatePolygonArea(IList<GpsLocation> coordinates)
    {
        double area = 0;

        if (coordinates.Count > 2)
        {
            for (var i = 0; i < coordinates.Count-1; i++)
            {
                GpsLocation p1, p2;
                p1 = coordinates[i];
                p2 = coordinates[i + 1];
                area += ToRad(p2.Longitude - p1.Longitude) * (2 + Math.Sin(ToRad(p1.Latitude))
                   + Math.Sin(ToRad(p2.Latitude)));

                area = area * R * R / 2;
            }
        }

        return Math.Abs(area);
    }

Here is my test code:

[Fact]
    public void GpsPolygonAreaTest()
    {
        var poly = new List<GpsLocation>();
        var p1 = new GpsLocation(0, 0);
        poly.Add(p1);
        var p2 = GpsHelper.CreateLocationBasedOnBearingDistance(p1, 5, 100);
        poly.Add(p2);
        var p3 = GpsHelper.CreateLocationBasedOnBearingDistance(p2, 95, 100);
        poly.Add(p3);
        var p4 = GpsHelper.CreateLocationBasedOnBearingDistance(p3, 185, 100);
        poly.Add(p4);
        poly.Add(p1);

        var area = GpsHelper.CalculatePolygonArea(poly);

        area.Should().Be(10000);
    }

I confirmed that my polygon is 100m x 100m, see image:

My test result is: Expected value to be 10000, but found 1.28153883377486E+48.

Any ideas what wrong with my code?

解决方案

I'm pretty sure this statement:

area = area * R * R / 2;

should be placed after the loop over the vertices, rather than repeated on each iteration.

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