ArcGis 拓扑检查——狭长角锐角代码C#

中学的时候醉心于研究怎么“逃课”，大学的时候豁然开悟——最牛逼的逃课是准时准地儿去上每一课，却不知到老师讲的啥，“大隐隐于市”大概就是这境界吧。

用到才听说有“余弦定理”这么一个东西，遂感叹“白上了大学”。

又百度了一下，高中数学……

检查角度先要根据已知的3点计算出其所组成的夹角的角度，这就需要“余弦定理”了。

其代码实现应该是下面的样子：

  private static double GetAngle(IPoint first, IPoint cen, IPoint last)
         {
             double ma_x = first.X - cen.X;
             double ma_y = first.Y - cen.Y;
             double mb_x = last.X - cen.X;
             double mb_y = last.Y - cen.Y;
             double ab_x = first.X - last.X;
             double ab_y = first.Y - last.Y;
             double ab_val2 = ab_x * ab_x + ab_y * ab_y;
             double ma_val = Math.Sqrt(ma_x * ma_x + ma_y * ma_y);
             double mb_val = Math.Sqrt(mb_x * mb_x + mb_y * mb_y);
             double cosM = (ma_val * ma_val + mb_val * mb_val - ab_val2) / ( * ma_val * mb_val);
             double angleAMB = Math.Acos(cosM) / System.Math.PI * ;
             return angleAMB;
         }

在检查方法CheckAcuteAngle中调用GetAngle方法获取角度值，CheckAcuteAngle方法传入IFeatureClass类型的要素类（应该是一个面层的）与给定的double型角度上限值。返回值是有错的要素List与其对应的角度值List。

       public static List<int> CheckAcuteAngle(IFeatureClass pFeatureClass, double acuteAngle, out List<double> listAngle)
         {
             IGraphicsContainer pGraphicsContainer = (IGraphicsContainer)m_hookHelper.FocusMap.ActiveGraphicsLayer;
             pGraphicsContainer.DeleteAllElements();
             IColor color = DisplayUtils.RGBColor(, , );
             List<int> listError = new List<int>();
             List<double> listOutAngle = new List<double>();
             IFeatureCursor pFeatureCursor = pFeatureClass.Search(null, true);
             IFeature pFeature = pFeatureCursor.NextFeature();
             try
             {
                 if (pFeature != null)
                 {
                     IPointCollection Temp_Vertices;
                     IPoint First_Point = new Point();
                     IPoint Center_Point = new Point();
                     IPoint Last_Point = new Point();
                     while (pFeature != null)
                     {
                         IGeometryCollection pGeometryCollection=pFeature.Shape as IGeometryCollection;
                         int count = pGeometryCollection.GeometryCount;
                         for (int j = ; j < count; j++)
                         {
                             IGeometry pGeometry = pGeometryCollection.get_Geometry(j);
                             Temp_Vertices = pGeometry as IPointCollection;
                             Temp_Vertices.AddPoint(Temp_Vertices.get_Point());
                             for (int i = ; i < Temp_Vertices.PointCount - ; i++)
                             {
                                 Temp_Vertices.QueryPoint(i, First_Point);
                                 Temp_Vertices.QueryPoint(i + , Center_Point);
                                 Temp_Vertices.QueryPoint(i + , Last_Point);
                                 double angle = GetAngle(First_Point, Center_Point, Last_Point);
                                 if (angle <= acuteAngle || angle >=  - acuteAngle)
                                 {
                                     listError.Add(pFeature.OID);
                                     listOutAngle.Add(angle);

                                     IPointArray pointArray = new PointArrayClass();
                                     pointArray.Add(First_Point);
                                     pointArray.Add(Center_Point);
                                     pointArray.Add(Last_Point);

                                     IElement pElement = MarkElementUtils.PointArray2LineMarkElement(pointArray, 1.0, color);
                                     pGraphicsContainer.AddElement(pElement, );
                                 }
                             }
                         }
                         pFeature = pFeatureCursor.NextFeature();
                     }
                 }
             }
             catch (Exception)
             {
                 throw new Exception("执行角度计算时发生错误，错误FeatureID为："+pFeature.OID);
             }
             finally
             {
                 Marshal.FinalReleaseComObject(pFeatureCursor);
             }
             listAngle = listOutAngle;
             return listError;
         }