Anyone know if there's some secret magic parameters that need to be set for the Extend and Trim (Editing Toolbox) tools in ArcMap to run properly?

I have a dataset of about 2000 "interior" lines which have been systematically separated from their surrounding "exterior" lines, and need to be extended or trimmed in order to reconnect with their borders.

I can do this manually one each line using Extend/Trim in the Advanced Editing toolbar, but as I need to do 2000+ records (plus a possible 16 000 for another project) I really need to do it in batch mode. This would mean using the Extend/ Trim tools from the Editing Toolbox. However, I can't seem to get these tools to actually run properly.

When I run Extend (Editing Toolbox) the tool runs 'successfully' in about 0.45 s with no error messages, but doesn't actually do anything. I have several test areas where I have measured the distance of the gap between the line that needs to be extended and the next line, these gaps are 0.5-0.8m maximum. I have set the Extend distance to various lengths such as 1.0m, 1.5m, 2.0m, as well as leaving it null, which should extend all lines to the next nearest feature. It still does nothing, the lines in my test areas do not appear to be altered at all. I've read through the ArcGIS documentation and a variety of forum posts, and I still can't figure out what I'm missing. I've had a similar lack of results when using the Trim tool.

Things I have already tried: - running tool in and out of an Edit session
- running tool with lines to be extended selected or un-selected
- extending lines from one feature class to another
- extending lines from one feature class to itself
- running tool manually from toolbox
- running tool programmatically through Python window
- running FindIdentical (Editing Toolbox tools) and DeleteIdentical (Editing Toolbox) in case there are any overlapping features which are causing confusion
- running tool with and without other feature classes present in the view
- checking the geoprocessing and tool Environments to ensure that processing extent, projection, linear measurement units, etc. are logical

Anyone have any idea what I might be missing?

I am using ArcGIS for Desktop 10.2.2 with an Advanced license.

Here is an example of an area of "interior" (blue) lines that need to be extended to the "exterior" (green) lines. enter image description here

  • Perhaps upload subsets somewhere, I'd like to play with them
    – FelixIP
    Commented Dec 12, 2016 at 19:34
  • THanks @FelixIP. I'll have to check if I am allowed to do this, there may be some privacy issues involved with data sharing. Might be able to if I strip out some of the attributes first however. Commented Dec 12, 2016 at 21:55
  • Interesting. I created some mock up datasets just to test if I can get Extend/Trim working at all on something simpler. Using the mock datasets, the tools work as you would expect them to, no problem. So there is some sort of problem in my datasets themselves. I'll keep looking and post a solution once found. Commented Dec 13, 2016 at 0:15
  • Can be anything. Is one or both of them 3D ?
    – FelixIP
    Commented Dec 13, 2016 at 0:49
  • If you can't find an explanation, there is this bug: Bug BUG-000094189 - The Extend Line tool does not extend lines in some cases.. Not much detail provided.
    – GISGe
    Commented Dec 13, 2016 at 10:13

1 Answer 1


Thanks folks for your suggestions. I finally figured out what it was, it was an error I'd introduced in the pre-processing.

Basically the lines in my dataset were derived from a polygon dataset originally. So there was duplicate lines in the dataset, redundant in geometry but different in attributes, wherever two polygons had previously been touching. The duplication in line geometry was confusing the tools and made it so it couldn't recognize those lines as undershoots or dangles.

I ran a 'Duplicate Geometry Check' (Data Reviewer) to visually verify this, then used 'Delete Identical' to remove line features with identical geometry but different attributes. Once I did this, Extend and Trim both worked as originally expected! (Although it will cause me later headaches when I try to re-build the polygons from lines...but that's another issue.)

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