利用ArcEngin进行空间分析的简单应用

一个简单的空间分析例子：vb实现在地图上画一个矩形或者
圆后,计算出该区域内的要素的数目。

创建临时图层
在临时图层上用程序或者让用户手动的创建一个矩形或者圆形
然后使用空间过滤器,spatialfilter
指定一下它的参数,进行查找就行了。
具体的使用在帮助文档里有。

在地图上画矩形或者圆形可以通过INewCircleFeedback接口实现，画矩形同理，只需转换使用的接口就可以了，以下以画圆形为例（该代码是在ArcMap的VBA环境下，建立用户控件使用的）：
Private m_pDoc As IMxDocument
Private m_pAV As IActiveView
Private m_pScrD As IScreenDisplay
Private m_pNewCircFeedback As INewCircleFeedback

Private Function UIToolControl1_Enabled() As Boolean
  'Set the ToolControl to enabled (disabled by default if any code is present in this event)
  UIToolControl1_Enabled = True
 
  'Check that we have a reference to the ActiveView and ScreenDisplay
  If m_pScrD Is Nothing Then
    Set m_pDoc = Application.Document
    Set m_pAV = m_pDoc.ActiveView
    Set m_pScrD = m_pAV.ScreenDisplay
  End If
End Function

Private Sub UIToolControl1_MouseDown(ByVal button As Long, ByVal shift As Long, ByVal x As Long, ByVal y As Long)
  Dim pPnt As IPoint
 
  ' Get the current mouse location in Map Units
  Set pPnt = m_pScrD.DisplayTransformation.ToMapPoint(x, y)
 
  ' Check that user is not using an existing feedback
  If m_pNewCircFeedback Is Nothing Then
   
    ' Create a NewCircleFeedback object
    Set m_pNewCircFeedback = New NewCircleFeedback
   
    'Set the Feedback's Display and StartPoint
    Set m_pNewCircFeedback.Display = m_pScrD
    m_pNewCircFeedback.Start pPnt
   
  End If
End Sub

Private Sub UIToolControl1_MouseMove(ByVal button As Long, ByVal shift As Long, ByVal x As Long, ByVal y As Long)
 
  ' Check if the user is currently using the feedback
  If Not m_pNewCircFeedback Is Nothing Then
    Dim pPnt As IPoint
    'Move the Feedback to the current mouse location
    Set pPnt = m_pScrD.DisplayTransformation.ToMapPoint(x, y)
    m_pNewCircFeedback.MoveTo pPnt
  End If
End Sub

Private Sub UIToolControl1_MouseUp(ByVal button As Long, ByVal shift As Long, ByVal x As Long, ByVal y As Long)
  Dim pCircArc As IGeometry
 
  ' Check if the user is currently using the feedback
  If Not m_pNewCircFeedback Is Nothing Then
    'Get the geometry (ICircularArc) returned from the feedback
    Set pCircArc = m_pNewCircFeedback.Stop
   
    ' If it is valid then create a CircleElement on the ActiveView using the 'AddCreateElement' procedure
    If Not pCircArc Is Nothing Then
      AddCreateElement pCircArc, m_pAV
      m_pAV.Refresh
    End If
   
    ' Set the feedback to nothing for the next use
    Set m_pNewCircFeedback = Nothing
  End If
End Sub

Private Sub AddCreateElement(pCircArc As ICircularArc, pAV As IActiveView)
' Takes an ICircularArc and IActiveView and creates a CircleElement in the ActiveView's BasicGraphicsLayer
  Dim pElemFillShp As IFillShapeElement
  Dim pElem As IElement
  Dim pGraCont As IGraphicsContainer
  Dim pSFSym As ISimpleFillSymbol
  Dim pRGB As IRgbColor
  Dim pSegColl As ISegmentCollection
 
  ' Create a new Polygon object and access the ISegmentCollection interface to add a segment
  Set pSegColl = New Polygon
  pSegColl.AddSegment pCircArc
 
  ' Create a new circleelement and use the IElement interface to set the its Geometry
  Set pElem = New CircleElement
  pElem.Geometry = pSegColl
 
  ' QI for the IFillShapeElement interface so that the Symbol property can be set
  Set pElemFillShp = pElem
   
  ' Create a new RGBColor
  Set pRGB = New RgbColor
  With pRGB
    .Red = 198
    .Green = 255
    .Blue = 214
  End With
   
  ' Create a new SimpleFillSymbol and set its Color and Style
  Set pSFSym = New SimpleFillSymbol
  pSFSym.Color = pRGB
  pSFSym.Style = esriSFSSolid
  pElemFillShp.Symbol = pSFSym
   
  ' QI for the IGraphicsContainer interface from the IActiveView, allows access to the BasicGraphicsLayer
  Set pGraCont = pAV
  'Add the element at Z order zero
  pGraCont.AddElement pElemFillShp, 0
End Sub
至于搜索，只需在取得pCircArc后利用ISpatialFilter即可实现，代码如下：
Dim pFilter As IspatialFilter
Set pFilter = New SpatialFilter
  With pFilter
    Set .Geometry = pCircArc
    .GeometryField = "SHAPE"
    .SpatialRel = esriSpatialRelIntersects
  End With
dim featureCount as Integer
featurecount=pFeatureClass.FeatureCount pFilter
featurecount即为要搜索的pfeatureclass中的实体个数