Splitting polygons creates double lines

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Splitting polygons creates double lines	Richard Hardin	Aug 12, 2009
Re: Splitting polygons creates double lines	Christian Degrassi	Aug 12, 2009
Re: Splitting polygons creates double lines	Richard Hardin	Aug 12, 2009
Re: Splitting polygons creates double lines	Richard Hardin	Aug 12, 2009
Re: Splitting polygons creates double lines	Richard Hardin	Aug 12, 2009
Re: Splitting polygons creates double lines	Christian Degrassi	Aug 12, 2009

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Subject	Splitting polygons creates double lines
Author	Richard Hardin
Date	Aug 12, 2009
Message	We have two situations that we are not sure if they are related and/or if it is the code that is causing the problem. When splitting polygons using ITopologicalOperator -> Cut we occasionally get a double line boundary at a previously good boundary. The lines are only .002 or .003 inches apart. We also have a situation where when snapping to a vertex or boundary through code although ArcGIS acts as though the snap worked, it appears that the snapped point is not truly on the boundary or vertex. Could this be a problem in the way the database is setup? I do not see any other parameters to use in the splitting and snapping procedures in VBA. thanks in advance, Rick

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Subject	Re: Splitting polygons creates double lines
Author	Christian Degrassi
Date	Aug 12, 2009
Message	Hi, what is the source of the features? Was it created in CAD and then inported? Are there originally splines in the polygon? Check the geodatabase tolerance/precision and also try frocing a "SnapToSpatialReference" though be carefull baceuse this operation will adjust the coordinates based on the spatial reference precision. Cheers
	Christian Degrassi, MA Senior GIS Analyst

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Subject	Re: Splitting polygons creates double lines
Author	Richard Hardin
Date	Aug 12, 2009
Message	thanks for responding, The data were constructed from scratch in an SDE geodatabase in SQL Server. We didn't import anything. There are no splines that I am aware of. The XY tolerance of the feature datasets is .001 meters and these values are lower, so they may not be snapping when the new split polygons are created. Seems to me I read once about another geodatabase tolerance/precision that is set up in the database, perhaps through SQL or SDE admin procedures. I am not our DB admin and he is out. I find it odd that a previously good boundary of a polygon gets its coordinates changed by such a small amount when the new split polygons are created. They do not align with the existing adjacent boundaries as they did prior to the cut operation. Also, this does not happen on all occasions but is not rare either. I will look into the "SnapToSpatialReference" option. thanks again and welcome any other insights, Rick

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Subject	Re: Splitting polygons creates double lines
Author	Richard Hardin
Date	Aug 12, 2009
Message	Apologies, The lines are less than the cluster tolerance apart and therefore should be one line, I believe. Also, the cluster tolerance of the topology for the feature dataset is also .001 meters and running the topoplogy seems to resolve the problem. Rick

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Subject	Re: Splitting polygons creates double lines
Author	Richard Hardin
Date	Aug 12, 2009
Message	I have tried forcing the snaptospatialreference on the input feature to be split, the line doing the splitting, and the output left and right geometries from the ITopologicalOperator:Cut method and recieve the same erroneous results. The lines appear to be ~ 0.0002 inches apart when zoomed into 1:0 scale. thanks, Rick

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Subject	Re: Splitting polygons creates double lines
Author	Christian Degrassi
Date	Aug 12, 2009
Message	Unless there is something wrong with the geometry itself (maybe the dataset is corrupted) the only other suggestion i have is to check the spatial reference precision. ArcGIS 9.2 allows to set GDB at high resolution. See here for more info: http://edndoc.esri.com/arcobjects/9.2/NET_Server_Doc/manager/geodatabase/creating_a_geodatabase/migratin344318119.htm and here it the geoprocessing tool to help you for applying the transformation: http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Upgrade%20Spatial%20Reference%20(Data%20Management) I hope this helps
	Christian Degrassi, MA Senior GIS Analyst