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I have a couple of shapefiles, the first one is a set of points, while the second one is a set of lines. I need to regularize the shapefiles in order to be able to generate a graph (adjacency list / paths) out of them later.

The set of lines has many dangles, with both undershoot and overshoot problems. I want ArcGIS to mark the suspect points and possibly offer me a correction to apply, on an individual basis.

I've seen the tutorial "Using geodatabase topology to fix line errors", which seems to go where I want.

However, in order to create a "topology" with a "Must Not Have Dangles" rule, I need a "geodatabase". I'm very new to GIS systems, and I'm trying to figure out a way to convert my shapefile to a geodatabase. I did the following

  1. open ArcCatalog
  2. click Connect Folder to connect the folder with my shapefiles
  3. right click on connected folder, New, File Geodatabase
  4. right click on created geodatabase, New, Feature Dataset
  5. right click on created feature dataset, New, Feature Class
  6. added the shapefile with lines (I used the Import button while creating the new Feature Class - see first screenshot below).
  7. right click on the feature dataset (not the feature class), New, Topology
  8. follow the tutorial

However, after adding the "Must Not Have Dangles" rule, and running Validate, I am told there are no errors. I can see there are errors, there are obvious dangling lines, so why aren't they detected?

New Feature Class

When I'm finished creating the topology, I get this warning:

enter image description here

This is the final result:

Final result

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  • In New Feature Class wizard the last step has an Import button. I used that. See the image I added (edited OP). Is that enough?
    – Agostino
    May 18, 2015 at 23:09
  • I don't know about the attribute table, but using import > feature class seems to have done the trick. Any suggestion on how to get the program to suggest for corrections?
    – Agostino
    May 18, 2015 at 23:30
  • The tutorial you linked to covers under/overshoot correction pretty well (error inspector/fix topology tool), and those methods/manual editing will give you the highest level of control. You could consider the Integrate or Snap tools, but those come with data alteration risks (not all dangles are necessarily errors depending on your data). Otherwise I'm not sure what you mean by 'suggest for corrections'.
    – Chris W
    May 18, 2015 at 23:43
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    It's dangle not dongle; a dongle is a software key (physical device) that works with licensing software, mostly USB now but they used to be serial and parallel. There is no 'or' in topology rules.. there is a rule 'must fall on endpoint of' that will validate your points but not except them.. hence exporting the error points then remove the ones that coincide, then visit the error points.
    – Michael Stimson
    May 18, 2015 at 23:52
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    So far as I know, it isn't possible to do or combinations of rules. You have to run both rules (and yes, endpoint must be covered by is one and the other you'd need). You'd get false positives, which is why you have to go through them all manually (note you can mark errors as exceptions, which should hold until the topology is rebuilt). A line covered by a point would excuse it from dangle, but I imagine you'll have a lot of other lines that don't dangle but aren't covered by a point either.
    – Chris W
    May 19, 2015 at 0:00

1 Answer 1

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Shapefiles do not support topology directly, as you have discovered. The data must first be imported in to a geodatabase, and specifically a feature dataset within that geodatabase. If you need to continue on in shapefile form, you'll have to export it back out once you're done topology checking and editing.

The answer to the actual/original question is that you had not imported any geometry to the feature dataset that was participating in the topology. Your step six created a new, blank feature class and the Import button you used only brought in the fields from your shapefile, not the actual lines. This is what the message in your second screenshot indicates (topology is valid, but there are no actual features participating).

To do that you need to right-click the feature dataset and rather than choosing New, choose Import > Feature Class (multiple or single depending on if you want to bring the lines and points in at the same time, but note everything in a feature dataset must be in the same coordinate system) and select the line shapefile. This will import the actual line data into the feature class within the feature dataset.

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  • Thanks. I don't get the "Dangle errors" bookmarks described in the tutorial though. Any idea about that?
    – Agostino
    May 19, 2015 at 0:56
  • You would think that ArcGis would have an inbuilt 'visit these' tool; it was the first tool I wrote (in VBA) with 8.3, then the first to get updated to VB6 in 9.0 and (hopefully finally) the first AddIn I wrote. You would need to create your own AddIn or open the topology error dialog and click on each in turn.
    – Michael Stimson
    May 19, 2015 at 1:34
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    @Agostino I'm pretty sure those are just bookmarks included in the tutorial data to get you to the right area where you can see some examples. Once you've validated the topology, you just click the Error Inspector button and it should pop up a window that lists all the errors (may have to hit Search Now to get the list to populate). Note you need to be in an Edit Session. You can right-click a specific error in the list and choose zoom to. Michael I got a surprise when I discovered the 'step through' tools I'd been using where I last worked were actually custom. So useful in lots of cases.
    – Chris W
    May 19, 2015 at 1:34

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