Map 3D Topologies – Part 2: Overlay Analysis Results


Nathan Moore from Autodesk helped resolve yesterday’s post.  Apparently, overlay analysis of topologies changes arcs into a series of line segments, this was in our example.  Here’s the kicker – it cuts the circle represented by the arc into 32 segments that match into the endpoints of the arc. 

He agreed that this can cause errors in area, networks, etc. which are generally small in the GIS world who looks at things at a grand scale.  But when used for Engineering purposes, this error is no longer negligible.  So he created what he called a “Change Request” to have developers address the issue.

So what do we do now?  Any topologies you may create should only have line segments. If you have arcs, convert them to polylines and have the DRAWING CLEANUP tool weed the arc as needed.  That way, you’ll at least match areas when comparing base topologies to overlay analysis topologies.

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About Kevin
Hi… I am a husband, father, brother and neighbor. I am employed as a Civil Engineer and have enjoyed playing the drums for the last 30+ years.

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