I am using ArcGIS Desktop.

I have a feature class of polygons. At first I run topology with rule "must not have gap" error. I find 250 errors (these all are exceptions). After shifting all the features and on few places modification, I again run the topology with same rule, but now I find more errors (e.g 300). As this is very huge data so I want to find only those error (gaps) which are new and not in the old data.

How I can find these errors?

  • So the original 250 errors, did you fix them, or mark them as exceptions, or both? This is a little confusing. Do you have a backup of the prefixed data?
    – danak
    Dec 4 '18 at 16:24
  • Yes I have back up of the pefixed data, Actually before updating data I remove gaps and some are exception which are e.g 250 but after updating which include shifting whole data and somewhere modification. Now exceptions increses e,g 300 I want to find only those exceptions which are new. Most of the features are same after shifting but as they are shifted so how I select those which are similar in shape but at different location because after selection similar I can get those which are modified.
    – Bilal
    Dec 6 '18 at 8:49

If you rerun the topology validation on the pre-fixed data (don't make any corrections or mark any exceptions), you can then export the topology results. This can be added to an mxd just like a feature class. You can symbolize by type of error, so you can compare this to your current topology.

However, you cannot select or intersect a topology error layer like a normal layer, but you will be able to see differences and overlaps/gaps. You could also look at your pre-fixed layers, which will be selectable and which can be spatially selected or joined.

But you have to keep in mind that the whole topology workflow is not designed for big changes like shifting most of a dataset. After edits like that, most of your data will be marked "dirty," because data has changed, which means it will be rechecked during validation even if it was at one point marked as an exception. So new topology errors will be flagged; you can definitely get more errors after such a validation because there may be some areas of exceptions that will not be re-checked and the new error shapes will not include those pieces. In other words, you can get more but smaller error shapes. If you revalidate your fixed data from scratch, you should in theory get the simplest, fewest errors. This is easier to understand if you symbolize the dirty areas, errors, and exceptions in a map.

When I have revalidated from scratch, I had had to bring in new rules/features. There is probably a less drastic way to do it, such as selecting all your exceptions and marking them as errors.

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