I would run they each of the individual segments and for each find the matching node in the complex polyline for the start as well as the end node of the section.
Now you can check if the end node number is larger than the start node number. If so the line direction of the section is the same as the direction of the polyline.
If not, the direction is reverted.
Here's some code that can help you find the node number within a polyline/polygon with only one segment:
'******************************
Function OBJFindNode( ByVal oObj As Object 'The object (polyline or polygon) to search in, only the first segment of the object will be searched
, ByVal oNode As Object 'Node position to look for
, ByVal fTolerance As Float 'Search tolerance, in meters, distance is measured using Cartesian calculation
) As Integer 'Returns the first matching node number, or 0 if no found
Dim nSegm, nNode As Integer
OnError GoTo ErrorOccured
OBJFindNode = 0
If OBJFindSegmentAndNode(oObj, oNode, fTolerance, nSegm, nNode) Then
If nSegm = 1 Then
OBJFindNode = nNode
End If
End If
Exit Function
'-------------------------
ErrorOccured:
Note Err() + " " + Error$() + ": OBJFindNode"
End Function
'************************************
Function OBJFindSegmentAndNode( ByVal oObj As Object 'The object (polyline or polygon) to search in
, ByVal oNode As Object 'Node position to look for
, ByVal fTolerance As Float 'Search tolerance, in meters, distance is measured using Cartesian calculation
, nSegmentFound As Integer 'The Segment number where the node was found
, nNodeFound As Integer 'The matching node number
) As Logical 'Returns TRUE if a matching node was found, otherwise FALSE
Dim nSegm, nNode As Integer,
fNodeX, fNodeY, fX, fY, fDistance As Float
OnError GoTo ErrorOccured
OBJFindSegmentAndNode = FALSE
If NOT ObjectInfo(oObj, OBJ_INFO_TYPE) IN (OBJ_TYPE_PLINE, OBJ_TYPE_REGION) Then
Exit Function
End If
fNodeX = CentroidX(oNode)
fNodeY = CentroidY(oNode)
For nSegm = 1 To ObjectInfo(oObj, OBJ_INFO_NPOLYGONS)
For nNode = 1 To ObjectInfo(oObj, OBJ_INFO_NPOLYGONS + nSegm)
fX = ObjectNodeX(oObj, nSegm, nNode)
fY = ObjectNodeY(oObj, nSegm, nNode)
fDistance = CartesianDistance(fNodeX, fNodeY, fX, fY, "m")
If fDistance <= fTolerance Then
nSegmentFound = nSegm
nNodeFound = nNode
OBJFindSegmentAndNode = TRUE
Exit Function
End If
Next 'nNode
Next 'nSegm
Exit Function
'-------------------------
ErrorOccured:
Note Err() + " " + Error$() + " OBJFindSegmentAndNode"
End Function
'******************************
Function OBJFindNodeBinary( ByVal oObj As Object 'The object (polyline or polygon) to search in, only the first segment of the object will be searched
, ByVal oNode As Object 'Node position to look for
, ByVal fTolerance As Float 'Search tolerance, in meters, distance is measured using Cartesian calculation
, ByVal nOffset As Integer 'Offset of 1st node in polyline based on original
) As Integer 'Returns the first matching node number, or 0 if no found
Dim objLow, objHigh As Object,
nPnts, nNode, nMid As Integer
OnError GoTo ErrorOccured
OBJFindNodeBinary = 0
nPnts = ObjectInfo(oObj, OBJ_INFO_NPNTS)
If nPnts < 100 Then
nNode = OBJFindNode( oObj, oNode, fTolerance)
If nNode > 0 Then
OBJFindNodeBinary = (nNode + nOffset)
End If
Exit Function
End If
'Determine the middle point
nMid = nPnts \ 2 + nPnts Mod 2
'Start with the lower half
objLow = ExtractNodes( oObj, 1, 1, nMid, FALSE)
If oNode Within CartesianBuffer(MBR(objLow), 25, fTolerance, "m") Then
nNode = OBJFindNodeBinary(objLow, oNode, fTolerance, nOffset)
OBJFindNodeBinary = nNode
Else
' Forget this branch
nNode = 0
End If
' If we couldn't find it in the lower, then check the upper half
If nNode = 0 Then
objHigh = ExtractNodes(oObj, 1, nMid + 1, nPnts, FALSE )
If oNode Within CartesianBuffer(MBR(objHigh), 25, fTolerance, "m") Then
nNode = OBJFindNodeBinary( objHigh, oNode, fTolerance, nOffset + nMid)
Else
' Forget this branch
nNode = 0
End If
End If
OBJFindNodeBinary = nNode
Exit Function
'-------------------------
ErrorOccured:
Print Err() + " " + Error$() + " OBJFindNodeBinary: nNode: " + nNode
End Function
The fundemental structure of the Binary search function has been made by Bill Thoen who shared it on MapInfo-L more than a year ago.
This is how to use the code above:
Dim oPolyline, oPoint, oLine As Object,
nOrder, nTolerance, nNode1, nNode2, nRowID As Integer
nTolerance = 0.2 'meters
Set CoordSys Table TABLE_WITH_LINES
Fetch First From TABLE_WITH_POLYLINES
oPolyline = TABLE_WITH_POLYLINES.OBJ
Fetch First From TABLE_WITH_LINES
Do Until EOT(TABLE_WITH_LINES)
oLine = TABLE_WITH_LINES.OBJ
nRowID = TABLE_WITH_LINES.ROWID
oPoint = CreatePoint(ObjectGeography(oLine, OBJ_GEO_LINEBEGX), ObjectGeography(oLine, OBJ_GEO_LINEBEGY))
nNode1 = OBJFindNodeBinary(oPolyline, oPoint, 0.2, 0)
oPoint = CreatePoint(ObjectGeography(oLine, OBJ_GEO_LINEENDX), ObjectGeography(oLine, OBJ_GEO_LINEENDY))
nNode2 = OBJFindNodeBinary(oPolyline, oPoint, 0.2, 0)
nOrder = 0
If nNode1 = 0 or nNode2 = 0 Then
'First of last point could not be matched to a node within the tolerance given
ElseIf nNode1 < nNode2 Then
nOrder = 1
ElseIf nNode1 > nNode2 Then
nOrder = -1
End If
Update TABLE_WITH_LINES
Set Direction = nOrder
Where ROWID = nROWID
Fetch Next From TABLE_WITH_LINES
Loop
Notice that in the sample above I'm expected you to only have one polyline. If that's not the case you need to figure out how to link the current line to the matching polyline. If the line table holds a reference ID for the polyline table, you can use this.
Best Answer
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