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以Network Dataset（网络数据集）方式实现的最短路径分析
转自原文 以Network Dataset（网络数据集）方式实现的最短路径分析
构建网络有两种方式，分别是网络数据集NetworkDataset和几何网络Geometric Network，这个网络结构数据的创建直接在Catalog中实现创建，进行最短路径分析，为了直接使用ArcGIS提供的功能，我选用的是NetworkDataset，主要记录下考虑单双行的最短路径的设计与实现（理想状态，不考虑转弯等要素）。
（A)对数据编辑的要求有一下几点：
（1） 添加属性字段，名称为Oneway，类型Text，默认值为空。
（2） 道路数据电子矢量化
（3） 对于单行线、禁行以及无限制通行方向道路属性值设置的要求：
由东往西或由北往南通行的单行路段，Oneway字段值设为：FT
由西往东或由南往北通行的单行路段，Oneway字段值设为：TF
禁止通行的路段，Oneway字段值为：N
双向通行的路段，Oneway字段值为：空字符
(B)路径分析的思路分为一下几步：
（1）读取shp文件和网络数据集数据
（2）创建网络分析上下文对象INAContext和网络分析对象INASolver（==IRouteNASolver）
（3）加载位置点图层，创建网络位置
（4）设置Solver参数（输出、容限值等）
（5）进行分析
（6）显示路线及结果信息
PS:对于道路走向不是正南正北，或者很难分辨是东西向还是南北向的，Oneway字段的赋值情况，还没有琢磨出万无一失的方法，有高人熟悉的，请指点。
(C)代码实现部分：
//初始化地图、网络数据集
private void Initial()
{
this.axMapControl1.ActiveView.Clear();
axMapControl1.ActiveView.Refresh();
pFeatureWorkspace =
OpenWorkspace(ConfigurationManager.ConnectionStrings["MdbPath"].ToString())
as IFeatureWorkspace;
pNetworkDataset = OpenNetworkDataset_Other(pFeatureWorkspace as IWorkspace, "TestNet_ND", "TestNet");
pNAContext = CreateNAContext(pNetworkDataset);
pInputFC = pFeatureWorkspace.OpenFeatureClass("stop");
pVertexFC = pFeatureWorkspace.OpenFeatureClass("TestNet_ND_Junctions");
IFeatureLayer pVertexFL = new FeatureLayerClass();
pVertexFL.FeatureClass = pFeatureWorkspace.OpenFeatureClass("TestNet_ND_Junctions");
pVertexFL.Name = pVertexFL.FeatureClass.AliasName;
axMapControl1.AddLayer(pVertexFL, 0);
IFeatureLayer pRoadFL = new FeatureLayerClass();
pRoadFL.FeatureClass = pFeatureWorkspace.OpenFeatureClass("道路中心线");
pRoadFL.Name = pRoadFL.FeatureClass.AliasName;
axMapControl1.AddLayer(pRoadFL,0);
ILayer pLayer;
INetworkLayer pNetworkLayer = new NetworkLayerClass();
pNetworkLayer.NetworkDataset = pNetworkDataset;
pLayer = pNetworkLayer as ILayer;
pLayer.Name = "Network Dataset";
axMapControl1.AddLayer(pLayer, 0);
//Create a Network Analysis Layer and add to ArcMap
INALayer naLayer = pNAContext.Solver.CreateLayer(pNAContext);
pLayer = naLayer as ILayer;
pLayer.Name = pNAContext.Solver.DisplayName;
axMapControl1.AddLayer(pLayer, 0);
pActiveView = axMapControl1.ActiveView;
pMap = pActiveView.FocusMap;
pGraphicsContainer = pMap as IGraphicsContainer;
}
//打开工作空间
private IWorkspace OpenWorkspace(string strMDBName)
{
IWorkspaceFactory pWorkspaceFactory = new AccessWorkspaceFactoryClass();
return pWorkspaceFactory.OpenFromFile(strMDBName, 0);
}
//打开网络数据集
private INetworkDataset OpenNetworkDataset(IWorkspace workspace,string strNDName)
{
IWorkspaceExtensionManager pWorkspaceExtensionManager;
IWorkspaceExtension pWorkspaceExtension;
IDatasetContainer2 pDatasetContainer2;
pWorkspaceExtensionManager = workspace as IWorkspaceExtensionManager;
int iCount = pWorkspaceExtensionManager.ExtensionCount;
for (int i = 0; i < iCount; i++)
{
pWorkspaceExtension = pWorkspaceExtensionManager.get_Extension(i);
if(pWorkspaceExtension.Name.Equals("Network Dataset"))
{
pDatasetContainer2=pWorkspaceExtension as IDatasetContainer2;
return
pDatasetContainer2.get_DatasetByName(esriDatasetType.esriDTNetworkDataset,
strNDName) as INetworkDataset;
}
}
return null;
}
private INetworkDataset OpenNetworkDataset_Other(IWorkspace workspace, string strNDName,string strRoadFeatureDataset)
{
IDatasetContainer3 pDatasetContainer3;
IFeatureWorkspace pFeatureWorkspace = workspace as IFeatureWorkspace;
pFeatureDataset = pFeatureWorkspace.OpenFeatureDataset(strRoadFeatureDataset);
IFeatureDatasetExtensionContainer pFeatureDatasetExtensionContainer =
pFeatureDataset as IFeatureDatasetExtensionContainer;
IFeatureDatasetExtension pFeatureDatasetExtension =
pFeatureDatasetExtensionContainer.FindExtension(esriDatasetType.esriDTNetworkDataset);
pDatasetContainer3 = pFeatureDatasetExtension as IDatasetContainer3;
if (pDatasetContainer3 == null)
return null;
IDataset pDataset = pDatasetContainer3.get_DatasetByName(esriDatasetType.esriDTNetworkDataset, strNDName);
return pDataset as INetworkDataset;
}
//创建网络分析上下文
private INAContext CreateNAContext(INetworkDataset networkDataset)
{
IDENetworkDataset pDENetworkDataset = GetDENetworkDataset(networkDataset);
INASolver pNASolver = new NARouteSolverClass();
INAContextEdit pNAContextEdit = pNASolver.CreateContext(pDENetworkDataset, pNASolver.Name) as INAContextEdit;
pNAContextEdit.Bind(networkDataset,new GPMessagesClass());
return pNAContextEdit as INAContext;
}
//根据点图层确定最短路径所用经历的点
private void LoadNANetWorkLocations(string strNAClassName, IFeatureClass inputFC, double dSnapTolerance)
{
INAClass pNAClass;
INamedSet pNamedSet;
pNamedSet = pNAContext.NAClasses;
pNAClass = pNamedSet.get_ItemByName(strNAClassName) as INAClass;
//删除已存在的位置点
pNAClass.DeleteAllRows();
//创建NAClassLoader，设置捕捉容限值
INAClassLoader pNAClassLoader = new NAClassLoaderClass();
pNAClassLoader.Locator = pNAContext.Locator;
if (dSnapTolerance > 0)
pNAClassLoader.Locator.SnapTolerance = dSnapTolerance;
pNAClassLoader.NAClass = pNAClass;
//字段匹配
INAClassFieldMap pNAClassFieldMap = new NAClassFieldMapClass();
pNAClassFieldMap.CreateMapping(pNAClass.ClassDefinition, inputFC.Fields);
pNAClassLoader.FieldMap = pNAClassFieldMap;
//pNAClassFieldMap.set_MappedField("OBJECTID", "OBJECTID");
//pNAClassLoader.FieldMap = pNAClassFieldMap;
//加载网络位置点数据
int iRows=0;
int iRowsLocated=0;
IFeatureCursor pFeatureCursor = pInputFC.Search(null, true);
pNAClassLoader.Load((ICursor)pFeatureCursor, null, ref iRows, ref iRowsLocated);
((INAContextEdit)pNAContext).ContextChanged();
}
private void SetSolverSettings()
{
//Set Route specific Settings
INASolver naSolver = pNAContext.Solver;
INARouteSolver cfSolver = naSolver as INARouteSolver;
cfSolver.OutputLines = esriNAOutputLineType.esriNAOutputLineTrueShapeWithMeasure;
// Set generic solver settings
// Set the impedance attribute
INASolverSettings naSolverSettings;
naSolverSettings = naSolver as INASolverSettings;
// Set the On
eWay Restriction if necessary
IStringArray restrictions;
restrictions = naSolverSettings.RestrictionAttributeNames;
restrictions.RemoveAll();
restrictions.Add("oneway");
naSolverSettings.RestrictionAttributeNames = restrictions;
////Restrict UTurns
//naSolverSettings.RestrictUTurns = esriNetworkForwardStarBacktrack.esriNFSBNoBacktrack;
//naSolverSettings.IgnoreInvalidLocations = true;
// Do not forget to update the context after you set your impedance
naSolver.UpdateContext(pNAContext, GetDENetworkDataset(pNAContext.NetworkDataset), new GPMessagesClass());
}
//路径分析
private void btnSolver_Click(object sender, EventArgs e)
{
this.Cursor = Cursors.WaitCursor;
lstOutput.Items.Clear();
lstOutput.Items.Add("分析中...");
LoadNANetWorkLocations("Stops", pInputFC, 80);
IGPMessages gpMessages = new GPMessagesClass();
INASolver naSolver = pNAContext.Solver;
SetSolverSettings();
pNAContext.Solver.Solve(pNAContext, gpMessages, new CancelTrackerClass());
if (gpMessages != null)
{
for (int i = 0; i < gpMessages.Count; i++)
{
switch (gpMessages.GetMessage(i).Type)
{
case esriGPMessageType.esriGPMessageTypeError:
lstOutput.Items.Add("错误 " +
gpMessages.GetMessage(i).ErrorCode.ToString() + " " +
gpMessages.GetMessage(i).Description);
break;
case esriGPMessageType.esriGPMessageTypeWarning:
lstOutput.Items.Add("警告 " + gpMessages.GetMessage(i).Description);
break;
default:
lstOutput.Items.Add("信息 " + gpMessages.GetMessage(i).Description);
break;
}
}
}
axMapControl1.Refresh();
lstOutput.Items.Add("Successful");
this.Cursor = Cursors.Default;
}
(D)上下效果图
以Network Dataset（网络数据集）方式实现的最短路径分析