I have a geometric network stored in an ArcGIS 10.5 geodatabase. These lines represent all the river paths in a watershed. The lines associated with this network have the required flow direction assigned based on line digitized directions. I can manually select an end node of one stream and use the trace geometric network tool in ArcToolbox to select a single upstream path without error. My network branches and I want to select an end node and return all the connected streams that flow to that end node. If I change the parameter to Find Common Ancestors the tool returns an error 001191: No flag found from the flag junction feature class. Ultimately I need to generate a Python script to select each nodes and select all upstream line segments but I cannot make the tool work. The inputted river lines, and the end nodes from those lines each share a CRS and reside in the same feature database feature class items.

Here is a screenshot of a trace successful find uphill path result using these data. I want to select all connected lines though. enter image description here

If I use the Utilities Network Toolbar I can place a flag at an end and trace a single path like the image above. The same tools that fail using the Trace Geometric Network tool in toolbox are also grayed out in the Utilities Network Toolbar.

Is there a bug in the Find Common Ancestors parameter of the Trace Geometric Network tool?

  • Are your network and flag junction featureclass the same coordinate systems?
    – Hornbydd
    Commented Aug 22, 2018 at 20:30
  • @Hornbydd - Yes, the inputted river lines, and the end nodes from those lines each share a CRS. I edited my question and added a screen shot showing a sucessful 'Find uphill path' operation using these data.
    – GBG
    Commented Aug 22, 2018 at 21:05
  • 1
    Your network is wrong. End nodes of one line cannot sit in the middle of other line.
    – FelixIP
    Commented Aug 23, 2018 at 0:51
  • @FelixIP - If the network is wrong then why would one parameter of the Trace tool work and not another?
    – GBG
    Commented Aug 23, 2018 at 2:23
  • 1
    FelixIP - Yes, you are correct. The geometric network had single lines that were not split at some junctions. I created and uses end and start vertex and selections to identify those areas where lines intersected a line without a split. I split the lines using those points and regenerated the network. Also, having the flags reside outside of the same feature dataset as the network avoided a 99999 error on tool execution. If you create an answer I will mark it as correct. @Hornbydd - Thanks for the help. The image also included some vertices. I will provide better images in the future.
    – GBG
    Commented Aug 23, 2018 at 20:00

1 Answer 1


I was able to run the find common ancestor trace using the geoprocessing tools on a geometric network. I was able to replicate the 001191 error message and reading the help on that it was clear that my points (flags) were not snapped to the network. When I snapped the points and ran the tool again if worked without error.

So if you are using the toolbar it seems to be snapping the flags automatically but for the geo-processing tools they rely on the point be coincident to the network.

I suspect this may be your issue.

For the record in your image (always good to have images) you do not explain what the difference is between the small black points (I assume they are network nodes) and the big brown dots, what are they?

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