备用
一、背景:
如何判断一个指定的经纬度点是否落在一个多边形区域内？
二、实现代码(delphi)
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C#算法：
/// <summary>
/// 判断指定的经纬度坐标点是否落在指定的多边形区域内
/// </summary>
/// <param name="ALon">指定点的经度</param>
/// <param name="ALat">指定点的纬度</param>
/// <param name="APoints">指定多边形区域各个节点坐标</param>
/// <returns>True 落在范围内 False 不在范围内</returns>
public bool isPtInPoly(double ALon, double ALat, Point[] APoints)
{
int iSum, iCount, iIndex;
double dLon1, dLon2, dLat1, dLat2, dLon;
if (APoints.Length < 3)
{
return false;
}
iSum = 0;
iCount = APoints.Length;
for (iIndex = 0; iIndex < iCount - 1; iIndex++)
{
if (iIndex == iCount - 1)
{
dLon1 = APoints[iIndex].X;
dLat1 = APoints[iIndex].Y;
dLon2 = APoints[0].X;
dLat2 = APoints[0].Y;
}
else
{
dLon1 = APoints[iIndex].X;
dLat1 = APoints[iIndex].Y;
dLon2 = APoints[iIndex + 1].X;
dLat2 = APoints[iIndex + 1].Y;
}
if (((ALat >= dLat1) && (ALat < dLat2)) || ((ALat >= dLat2) && (ALat < dLat1)))
{
if (Math.Abs(dLat1 - dLat2) > 0)
{
dLon = dLon1 - ((dLon1 - dLon2) * (dLat1 - ALat)) / (dLat1 - dLat2);
if (dLon < ALon)
iSum++;
}
}
}
if ((iSum % 2) != 0)
return true;
return false;
}