VECTopoConsistencyCheck()

Description

VECTopoConsistencyCheck() is used to verify that a particular area (LAYER_TYPE = TOPO_AREAS) layer, and its associated arc and node layers are topologically consistent.

Call Signature

mstring VECTopoConsistencyCheck ( int/string filespec, int segment_num [, double tolerance] )

Return Value

mstring

An mstring report of the inconsistencies. If the length of the report is zero, then there are no inconsistencies.

Arguments

int/string filespec:

This can either be the handle returned by DBOpen(), or the name of an open file.

int segment_num:

The vector layer (segment) number being accessed.

[ double tolerance ]:

The maximum distance in georeferenced units that two points may be apart, and still be considered the same location.

Remarks

For the arc layer, it checks that:

• All arcs have at least 2 vertices
• If a Node layer is linked to it, then we check if the nodes pointed to by the StartNodeId and EndNodeId attribute also point to this arc in their ArcIdList attribute and that the nodes contain the right x,y position (within a defined tolerance).
• If an Area layer is linked to it, then we check if the areas pointed to by the LeftAreaId and RightAreaId also point to this arc in their ArcIdList attribute.

For the node layer (if it exists), it checks that:

• Every arc listed in a node's ArcIdList also refers to this node in either its StartNodeId or EndNodeId attribute.
• For now, arcs do not have to be sorted in clockwise order in the ArcIdList attribute.

For the area layer (if it exists), it checks that:

• Every arc listed in an area's ArcIdList also refers to this area in its LeftAreaId or RightAreaId attribute.
• All rings are closed properly (a closed polygon can be regenerated)
• For now, arcs do not have to be sorted in clockwise order in the ArcIdList attribute.

Example

Test an area layer for topological consistency, and report to the user.

 local mstring TopoReport, int file_spec

 try
    file_spec = DBOpen( GetPCIHOME()+"/demo/irvine.pix", "r" )
    TopoReport = VECTopoConsistencyCheck( file_spec, 28 )
    call DBClose( file_spec )
    if( f$len(TopoReport) > 0 )then
        print TopoReport
    else
        print "Topology is consistent."
    endif
 onerror
    print "Error: ", GetLastErrorMessage()
 endonerror

Output:

 Topology is consistent.

See also

GDB file functions

GDB vector file functions

VECCopyWholePolygonLayer()