AutoCAD Map 3D General Discussion

AutoCAD Map 3D General Discussion

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Distinguished Contributor
cadman009
Posts: 336
Registered: ‎12-17-2003
Message 1 of 6 (327 Views)

union overlay topology > intersections detected

327 Views, 5 Replies
10-05-2005 06:33 AM
hey, y'all,

i've really appreciated the help i've gotten in the past via this discussion group. here's another problem that i'm hoping somebody knows the answer to. i'm trying to do a union overlay with 2 topologies and am getting an error message that says, "intersections detected, can't create topology". anybody know what i can do to fix this?
Distinguished Contributor
cadman009
Posts: 336
Registered: ‎12-17-2003
Message 2 of 6 (327 Views)

Re: union overlay topology > intersections detected

10-06-2005 03:40 AM in reply to: cadman009
hey, i got this to work by doing a couple of things -- i reinserted and cleaned up the main property boundary which was common to both topologies. i also manually edited some slivers out of the topologies, then i ran the topology overlay using "intersection" instead of "union". i think this error occurs when too many slivers are present in either of the topologies. getting rid of some of the slivers seemed to do the trick. does this sound about right?
New Member
MD_CAD
Posts: 1
Registered: ‎10-06-2005
Message 3 of 6 (327 Views)

Re: union overlay topology > intersections detected

10-06-2005 08:08 AM in reply to: cadman009
I've had a similar problem with a project recently except I could create the overlay topology but it was incorrect. Myself and a colleague managed to narrow down the problem. When you have line work that is supposed to be coincident but isn't. Essentially the algorithm creates sliver polygons that are so small they can't be displayed (what we have come to refer to as "nano-slivers". I have sent two different support requests to autodesk about this but they have said it is a known problem but they have no solution for it. The request went to their development team and they couldn't offer either a patch or a work-around.

It is however not a problem unique to Map. I have overlayed the same topologies using ArcView and gotten similar results. This suggests that it is infact a problem with the line work.

The only way that I have found to solve the problem is by finding the "offending" line segments and forcing them to be coincident through brute force. Unfortunately this is not a reliable method of detecting all of the "nano-slivers" and you could miss some of them and therefore end up with erroneous results. This is particularly true if you are working with very large or complex linework.

Sorry to be the bearer of bad news, but if you do find a better solution PLEASE let me know. Message was edited by: MD_CAD
Distinguished Contributor
cadman009
Posts: 336
Registered: ‎12-17-2003
Message 4 of 6 (327 Views)

Re: union overlay topology > intersections detected

10-06-2005 09:32 AM in reply to: cadman009
i just tried overlaying shapefiles using arcmap that were created in admap on the same project and they overlaid just fine. so far arcmap seems to be more forgiving than admap on overlays, but, as you say, the errors still probably exist in the linework. i'm going to keep experimenting with using arcmap more in conjunction with autodesk map and see if that can't speed things up for me a little. i spent hours yesterday trying to get 2 topologies to overlay in admap and i just did a very similar in arcmap in minutes with no glitches (so far).
New Member
gplkml
Posts: 1
Registered: ‎08-25-2012
Message 5 of 6 (207 Views)

Re: union overlay topology > intersections detected

08-25-2012 07:14 AM in reply to: cadman009

Hai Just convert the polylines to lines by explode command then convert to polygon topology hope it works

*Expert Elite*
antoniovinci
Posts: 1,750
Registered: ‎06-03-2011
Message 6 of 6 (203 Views)

Re: union overlay topology > intersections detected

08-25-2012 11:19 AM in reply to: gplkml

gplkml wrote:

hope it works


After 7 years, I guess the OP already solved his problem, sir...

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