1.遇到的问题：
最近遇到在线要素（矢量数据）中，一条完整的道路、河流等往往是断开的，如下图1所示：
2.思路：
在ArcGIS Desktop中没有相关的工具可以将这些断开的线要素进行自动合并，今天自己写了一个Arcmap上的一个插件，实现当点击插件按钮后，对地图窗口中断开的线要素进行合并。合并的依据是具有相同NAME属性（如长沙-张家界高速）的Polyline要素进行合并，然后存储在另一个线要素图层中。
3.程序的实现和结果：
程序运行的结果如下，这样本来属于同一段道路的多个Polyline就合并成一条Polyline：
4.程序源代码：
1 using System; 2 using System.Collections; 3 using System.Collections.Generic; 4 using System.Text; 5 using System.IO; 6 using System.Windows.Forms; 7 using ESRI.ArcGIS.ArcMapUI; 8 using ESRI.ArcGIS.Carto; 9 using ESRI.ArcGIS.Geodatabase; 10 using ESRI.ArcGIS.Geometry; 11 12 namespace MergeDisconnectPolylineAddin 13 { 14 public class MergePolyline : ESRI.ArcGIS.Desktop.AddIns.Button 15 { 16 17 IMap map = null; 18 IActiveView pActiveView = null; 19 //private List<IPolyline> DisconnPolylineList = new List<IPolyline>(); 20 21 public MergePolyline() 22 { 23 IMxDocument mxDoc = ArcMap.Application.Document as IMxDocument; 24 map = mxDoc.FocusMap; 25 pActiveView = mxDoc.ActivatedView; 26 } 27 28 protected override void OnClick() 29 { 30 // 31 // TODO: Sample code showing how to access button host 32 // 33 ArcMap.Application.CurrentTool = null; 34 35 //计算程序耗时 36 DateTime beforDT = System.DateTime.Now; 37 38 List<string> distinctString = getDistinctNAMEValue(); 39 MergePloyline(distinctString); 40 41 DateTime afterDT = System.DateTime.Now; 42 TimeSpan ts = afterDT.Subtract(beforDT); 43 MessageBox.Show("线要素合并结束，运行程序共耗时约："+ ts.Minutes+"分钟"); 44 } 45 46 public List<string> getDistinctNAMEValue() 47 { 48 IFeatureLayer featureLayer = map.get_Layer(0) as IFeatureLayer; 49 IFeatureClass featureClass = featureLayer.FeatureClass; 50 IQueryFilter queryFilter = new QueryFilterClass(); 51 queryFilter.WhereClause = ""; 52 IFeatureCursor pFeatCursor = featureClass.Search(queryFilter, false); 53 IFeature pFeature = pFeatCursor.NextFeature(); 54 ArrayList fieldArray = new ArrayList(); 55 List<string> distinctString = new List<string>(); 56 while (pFeature != null) 57 { 58 if (featureClass.ShapeType == esriGeometryType.esriGeometryPolyline) 59 { 60 IFields fields = pFeatCursor.Fields; 61 int fieldIndex = fields.FindField("NAME"); 62 string field_NAME = (string)pFeature.get_Value(fieldIndex); 63 fieldArray.Add(field_NAME); 64 } 65 pFeature = pFeatCursor.NextFeature(); 66 } 67 distinctString = removeSameString(fieldArray); 68 return distinctString; 69 } 70 71 public void MergePloyline(List<string> DistinctNameValue) 72 { 73 IFeatureLayer featureLayer = map.get_Layer(0) as IFeatureLayer; 74 IFeatureClass featureClass = featureLayer.FeatureClass; 75 76 //IDataset dataset = featureClass as IDataset; 77 //IWorkspaceEdit workspaceEdit = dataset.Workspace as IWorkspaceEdit; 78 //Type.Missing指的是空类型，因为有些方法你传null给它会出错的，必须要用Type.Missing. 79 object Missing = Type.Missing; 80 //workspaceEdit.StartEditing(true); 81 //workspaceEdit.StartEditOperation(); 82 //string field_NAME = ""; 83 84 for (int i = 0; i < DistinctNameValue.Count; i++) 85 { 86 IQueryFilter queryFilter = new QueryFilterClass(); 87 queryFilter.WhereClause = ""; 88 IFeatureCursor pFeatCursor = featureClass.Search(queryFilter, false); 89 IFeature pFeature = pFeatCursor.NextFeature(); 90 91 IFeature pFeatureFirst = pFeature; 92 //List<IPolyline> toMergePolylineList = new List<IPolyline>(); 93 94 IGeometryCollection Geometrybag = new GeometryBagClass(); 95 ITopologicalOperator2 pTopOperatorFirst = null; 96 IGeometry geometrySecond = null; 97 IGeometry pGeometryFirst = null; 98 bool bSwitch = true; 99 while (pFeature != null)100 {101 map.SelectFeature(featureLayer, pFeature);102 if (featureClass.ShapeType == esriGeometryType.esriGeometryPolyline)103 { 104 //IPolyline polyline = geometry as IPolyline;105 IFields fields = pFeatCursor.Fields;106 int fieldIndex = fields.FindField("NAME");107 string field_NAME = (string)pFeature.get_Value(fieldIndex);108 109 if (field_NAME == DistinctNameValue[i])110 {111 if (bSwitch)112 {113 //将当前name字段相同的feature中的第一个feature传给pFeatureFirst114 pFeatureFirst = pFeature;115 pGeometryFirst = pFeature.Shape;116 pTopOperatorFirst = (ITopologicalOperator2) pGeometryFirst;117 pTopOperatorFirst.IsKnownSimple_2 = false;118 pTopOperatorFirst.Simplify();119 pGeometryFirst.SnapToSpatialReference();120 bSwitch = false;121 //break;122 }123 else124 {125 //geometrySecond = pFeature.ShapeCopy;126 geometrySecond = pFeature.Shape;127 Geometrybag.AddGeometry(geometrySecond, ref Missing, ref Missing);128 //toMergePolylineList.Add(polyline);129 } 130 }131 //DisconnPolylineList.Add(polyline);132 }133 pFeature = pFeatCursor.NextFeature();134 }135 IEnumGeometry tEnumGeometry = (IEnumGeometry)Geometrybag;136 //IGeometry mergeGeomery = null;137 pTopOperatorFirst.ConstructUnion(tEnumGeometry);138 139 pTopOperatorFirst.IsKnownSimple_2 = false;140 pTopOperatorFirst.Simplify();141 pFeatureFirst.Shape = pGeometryFirst;142 //pFeatureFirst.Store();143 IFeatureLayer featureLayer2 = map.get_Layer(1) as IFeatureLayer;144 IFeatureClass featureClass2 = featureLayer2.FeatureClass;145 AddPolyline(featureClass2, pGeometryFirst);146 }147 //workspaceEdit.StopEditOperation();148 //workspaceEdit.StopEditing(true); 149 }150 private void AddPolyline(IFeatureClass pFeatureClass, IGeometry polyline)151 {152 IFeatureBuffer featureBuffer = pFeatureClass.CreateFeatureBuffer();153 IFeatureCursor featureCursor;154 featureCursor = pFeatureClass.Insert(true);155 featureBuffer.Shape = polyline;156 featureCursor.InsertFeature(featureBuffer);157 featureCursor.Flush();158 System.Runtime.InteropServices.Marshal.ReleaseComObject(featureCursor);159 }160 public List<string> removeSameString(ArrayList stringArray)161 {162 //List用于存储从数组里取出来的不相同的元素163 List<string> distinctString = new List<string>();164 foreach (string eachString in stringArray)165 {166 if (!distinctString.Contains(eachString))167 distinctString.Add(eachString);168 }169 return distinctString;170 }171 172 protected override void OnUpdate()173 {174 Enabled = ArcMap.Application != null;175 }176 }177 178 }
5.总结
这个插件还有一些不足的地方，如不是从线要素首尾点相邻的角度寻找相邻点（这种方法存在判断三条线要素交叉而形成的节点的判断和是否进行合并的问题和难点），在下一篇随笔里面会介绍从纯几何学的角度实现线要素的连接的实现。
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本文系作者GISQZC原创文章，欢迎转载，但必须注明出处，否则将追究相关法律责任！
- 4楼我也是个傻瓜
- 01.用GIS编程的思维来解决实际生产中遇到的问题，非常不错！向您学习；，02.其实您有这句话还有些不采“在ArcGIS Desktop中没有相关的工具可以将这些断开的线要素进行自动合并”；实际上，arcmap在很早之前就有这个功能了，即融合工具（Dissolve）
- Re: GISQZC
- @我也是个傻瓜，您好，感谢您帮我指出文中的错误。ArcGIS工具箱中的Dissolve工具的确可以将具有相同属性的的不同要素（相连或不相连）进行合并。但是这个工具不能满足我导师提的需求（我们拿到的数据主要是要进行道路线要素化简，在道路都是分段断开的条件下，化简的效果不好，所以需要先进行合并，再进行抽烯）。Dissolve工具是完全根据属性判断的，在节点（有3条或3条以上的线相交的点）处可能仍然是相连的。后面为了解决这个问题，就重新换了一个思路写，不通过属性，直接通过几何条件判断进行合并操作，在我后面的两篇随笔中http://www.cnblogs.com/GISQZC/p/5299820.html 。我还是在校生，有什么写的不对的地方还请您批评指正，谢谢！
- 3楼ProgrammingNobody
- 总结括号里的话表达不清
- Re: GISQZC
- @ProgrammingNobody，你好，这句话的意思是，我这样通过属性判断，Name属性相同的线要素都进行了合并。但是后来我导师要求如果有3条或者3条以上的polyline向接于同一点（称之为“节点”），就不能进行合并，只合并两条开始点或者结束点相同的两条线。这样通过同值属性的方式就不符合需求了。所以我重新写了一个通过几何上的相接关系合并的新的算法，在我今天发的日志里，你可以看一下。
- 2楼ProgrammingNobody
- 谢谢兄台！
- 1楼GISQZC
- 不客气，一起进步！