点到折线最短距离所在点距离折线起点的累积距离

  1 using System;

  2 using System.Collections.Generic;

  3 using System.Linq;

  4 using System.Text;

  5 using ESRI.ArcGIS.Geometry;

  6 using RGeos.Geometry

  7 

  8 namespace RGeos.Geometry

  9 {

 10     public class CulmulateDistance

 11     {

 12         /// <summary>

 13         /// 点到折线最短距离处距离折线起点的累积距离

 14         /// </summary>

 15         /// <param name="P">任意一点</param>

 16         /// <param name="polyline">折线</param>

 17         /// <returns></returns>

 18         public static double CulmulateDist_Point_to_Polyline(IPoint P, IPolyline polyline)

 19         {

 20             ISegmentCollection segs = polyline as ISegmentCollection;

 21             double min = double.MaxValue;

 22             int segIndex = -1;//最短距离所在档的索引

 23             for (int i = 0; i < segs.SegmentCount; i++)

 24             {

 25                 //点到每条线段的最短距离

 26                 double dis = Dist_Point_to_Segment(P, segs.get_Segment(i));

 27                 if (dis < min)

 28                 {

 29                     min = dis;

 30                     segIndex = i;//取出最小的一个

 31                 }

 32             }

 33             double culmulateDis = 0;

 34             for (int i = 0; i < segs.SegmentCount; i++)

 35             {

 36                 if (segIndex != i)

 37                 {

 38                     culmulateDis += segs.get_Segment(i).Length;

 39                 }

 40                 else

 41                 {

 42                     ISegment current = segs.get_Segment(i);

 43                     Vector3d v = new Vector3d();

 44                     v.X = current.ToPoint.X - current.FromPoint.X;

 45                     v.Y = current.ToPoint.Y - current.FromPoint.Y;

 46 

 47                     Vector3d w = new Vector3d();

 48                     w.X = P.X - current.FromPoint.X;

 49                     w.Y = P.Y - current.FromPoint.Y;

 50 

 51                     double c1 = dot(w, v);//投影长度

 52                     if (c1 <= 0)//这种情况最短距离在该线段的起点处

 53                     {

 54                         break;

 55                     }

 56                     double c2 = dot(v, v);

 57                     if (c2 <= c1)//这种情况最短距离在该线段的终点处                      

 58                     {

 59                         culmulateDis += Math.Sqrt(c2);

 60                         break;

 61                     }

 62 

 63                     double b = c1 / c2;

 64                     culmulateDis += Math.Sqrt(c1);

 65                     IPoint Pb = new PointClass();

 66                     Pb.X = current.FromPoint.X + b * v.X;

 67                     Pb.Y = current.FromPoint.Y + b * v.Y;

 68                     break;

 69                 }

 70             }

 71             return culmulateDis;

 72         }

 73 

 74         public static IPoint GetCentrePoint(IPolygon polygon)

 75         {

 76             IArea pArea = polygon as IArea;

 77             IPoint pt = new PointClass();

 78             pt.X = pArea.Centroid.X;

 79             pt.Y = pArea.Centroid.Y;

 80             return pt;

 81         }

 82 

 83         public static double Dist_Point_to_Segment(IPoint P, ISegment S)

 84         {

 85             Vector3d v = new Vector3d();

 86             v.X = S.ToPoint.X - S.FromPoint.X;

 87             v.Y = S.ToPoint.Y - S.FromPoint.Y;

 88 

 89             Vector3d w = new Vector3d();

 90             w.X = P.X - S.FromPoint.X;

 91             w.Y = P.Y - S.FromPoint.Y;

 92 

 93             double c1 = dot(w, v);

 94             if (c1 <= 0)

 95                 return d(P, S.FromPoint);

 96 

 97             double c2 = dot(v, v);

 98             if (c2 <= c1)

 99                 return d(P, S.ToPoint);

100 

101             double b = c1 / c2;

102             IPoint Pb = new PointClass();

103             Pb.X = S.FromPoint.X + b * v.X;

104             Pb.Y = S.FromPoint.Y + b * v.Y;

105             return d(P, Pb);

106         }

107         /// <summary>

108         /// 向量的模

109         /// </summary>

110         /// <param name="v"></param>

111         /// <returns></returns>

112         public static double norm(Vector3d v)

113         {

114             return Math.Sqrt(dot2(v, v));  // norm = length of vector

115         }

116         /// <summary>

117         /// 2D数量积，点乘

118         /// </summary>

119         /// <param name="u"></param>

120         /// <param name="v"></param>

121         /// <returns></returns>

122         public static double dot2(Vector3d u, Vector3d v)

123         {

124             return ((u).X * (v).X + (u).Y * (v).Y);

125         }

126         public static double dot(Vector3d u, Vector3d v)

127         {

128             return ((u).X * (v).X + (u).Y * (v).Y + (u).Z * (v).Z);

129         }

130 

131         public static double d(IPoint P, IPoint P1)

132         {

133             return Math.Sqrt((P1.X - P.X) * (P1.X - P.X) + (P1.Y - P.Y) * (P1.Y - P.Y));

134         }

135 

136         /// <param name="x">增量X</param>

137         /// <param name="y">增量Y</param>

138         /// <returns>象限角</returns>

139         public static double GetQuadrantAngle(double x, double y)

140         {

141             double theta = Math.Atan(y / x);

142             if (x > 0 && y == 0) return 0;

143             if (x == 0 && y > 0) return Math.PI / 2;

144             if (x < 0 && y == 0) return Math.PI;

145             if (x == 0 && y < 0) return 3 * Math.PI / 2;

146 

147             if (x > 0 && y > 0) return theta;

148             if (x > 0 && y < 0) return Math.PI * 2 + theta;

149             if (x < 0 && y > 0) return theta + Math.PI;

150             if (x < 0 && y < 0) return theta + Math.PI;

151             return theta;

152         }

153     }

154 }