Correcting many topology errors

1935
8
03-02-2011 05:51 AM
Occasional Contributor
Hello everyone,
I have a large polygon feature class with several thousand gap and overlap errors.  I am trying to fix them by creating new features.  If I select more than a few dozen errors at a time to create new features I get a "failed to create new feature" error, and every once in a while ArcMap will crash and ask me to send an error report.  I have 10638 errors that need fixing, so this method is rather slow going.
If anyone has any suggestions as to how to speed things up it would be much appreciated.
Thank-You,
Tags (2)
8 Replies
Regular Contributor III
To the extent that the gaps and overlaps are less than a suitable tolerance you could run an Integrate.  But I'm guessing that won't handle most of your problems.  You could run something akin to a clean which would get rid of the problems under the tolerance limit and then create new polys in the gaps and new ones to replace the overlaps.  You could then run an Eliminate to get rid of many of these.  But like any automated process you might not like the results, although by fiddling around with the settings you might get a lot of work done.

The advantage of the topology is that it identifies the errors and lets you manually fix each one the way you want it to be.

As for a clean, if you have ArcInfo, you could convert to a coverage and run a clean.  Of you could in effect do the same by converting your polygons to lines and points, and then creating polygons from the lines with the points providing the attributes.  If you don't have ArcInfo but have ETGeowizards full version you could run a clean using it.  That has the option to create a point layer showing all overlaps.
Reply
0 Kudos
Regular Contributor II
There is a developer sample written in VB6 that will export topological errors to a separate featureclass. This would help you find and edit the errors more easily. It is a DLL written for 9.2 but still works in 9.3.
Reply
0 Kudos
Occasional Contributor
I am experiencing the same problem, fixing numerous topology errors very slow and sometims does very strange things.  Using Windows 7, ArcGIS 10.0 Sp4.  Almost 1000 overlapping polygons which I either need to create features and dissolve (everything is the same for a particular attribute) or subtract and hav even more holes in the data.  The layer was created by appending two sets,created by different organizations, and many of the polygons share borders .  Yesterday with a different layer , creating features from topology errors, it took over an hour to create features for 1500 overlaps.  When done, I discovered that it had also calculated a numeric field and a character field as well.  It calculated the character field with Chinese and Japanese (according to google translate).  Also have problems with validate topology not doing anything.  No rrors, but it does not do anything
Reply
0 Kudos
by
Regular Contributor III
Apologize if you've done/know this, but couldn't tell from your post.

First try using the Integrate tool. Set a tolerance you think is reasonable, say 0.5 feet, and vertices within the tolerance will snap together. That won't solve everything, but is a start.

Not sure what you mean by Validate not doing anything. Assuming you've fixed an error, Validate doesn't 'do' anything visible except to remove the error symbology from corrected errors. When you check Error Inspector, you should have fewer errors (although once in a while a fix to one error may create another).

I don't like running the automated fixes on large numbers of errors unless I can see a bunch of contiguous identical errors, such as a subdivision line cutting through a series of parcels. There are usually a small, but non-trivial number of errors that are better fixed manually. It can be tedious to go through them all, but yields better results.

Don't know where the Asian characters would be coming from.
Reply
0 Kudos
Occasional Contributor
I have been experimenting with higher tolerances, both in geoprocessing operations used to create data and in topology checks, it helps.   I have not tried integrate, and will try that as well. The validate "not doing anything" is really strange, almost as if I did not really click on the button.   Once in an edit mode I'll opt to validate, and the validating "status" (?) bar never shows.  When I open the errors table and search, none are found.  At first I thought this happened because there were no errors, but that is not the case.  Getting validate to "work" ranges anywhere from removing/re-adding the topology toolbar, to stopping/restarting the edit session, to stopping/restarting ArcMap, to recreating the topology rules, to rebooting, to waiting and hoping that tomorrow is a better day.  The extent of the data sets I am working with:
Top 2781031.158307 m , Right  -1079966.152815 m, Bottom 2208890.238787 m, Left -1715664.866530 m
Reply
0 Kudos
by
Regular Contributor III
Have you checked or unchecked the 'Visible extent' checkbox in the Error Inspector window? I leave it unchecked myself. Also make sure you have 'Errors from all rules' selected, unless you just want to work on one type. Oh, and just to be sure, make sure the Errors checkbox is checked (duh!).
Reply
0 Kudos
New Contributor
I have a similar situation in terms of volume of errors (+100,000) almost all of them overlapping. I don't have any issues validating or running the error tool, but the dilemma lies in time consumption. I could select mass numbers of errors at a time and just create new features but I would rather not due to soiling the data with an unnecessary amount of tiny polygons. Any suggestions on how to tackle this issue in a more timely manner than going down the list error by error? Thanks
Reply
0 Kudos
Regular Contributor III
The validation (or integrate tool) would get rid of the smallest of overlaps, depending on your tolerance setting.  You could increase it until you get unacceptable movement of vertices generally.  Use copies or maybe use one in an edit session since they change the input layer.

With your larger area overlaps, you could create your many small polygons, and then use the Eliminate tool to merge the ones you select (perhaps by an area query to limit the selection to slivers and/or perhaps by selecting for polygons without attributes to get at newly created polygons) with an abutting polygon based on some input settings.  Like any automated process check your results to make sure you can live with the changes.
Reply
0 Kudos