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I am encountering some unexpected behaviour in attempting to use linear referencing tools to produce a route event layer for a road network.

I have produced a polyline route shapefile from a previously existing segmented layer without issues, which displays as expected- all lines have been reproduced and consolidated by UID. I'm then running the Make Route Event Layer tool. When setting parameters for this tool, initially there is an error message displayed next to the Event Table Route Identifier Field (Error 00840 - The value is not a Route Measure Event), however this disappears once I have set the From and To Measure Fields. The tool runs without issue, and generates the Route Event Layer. In the attribute table, all looks as it should- the correct number of records, all attributes have been maintained, etc. This is when the irregular behaviours start occurring however:

  • The layer seems to only display a portion of the features. Panning and zooming around tends to change which features are displayed.
  • When overlayed on the routes layer, the identify tool will display the attributes from the Route Event Layer even when I click on a section which displays only as the parent route layer
  • When zoomed to full extent and a rectangle selection is dragged over the route event layer, only the segments that are displaying are highlighted as selected in the attribute table. Reversing the selection and creating a new layer creates a layer with all of the expected features in the attribute table, but no display in the project window.
  • When I export the event layer, again only a small portion of features will display, even though the attribute table contains all features. Interestingly, it seems to be a different subset of features from the event layer- each time I perform the same operation, it seems that this subset of features chosen to display changes arbitrarily. This also changes the behaviour of the identify tool- clicking on a parent route segment with the exported data layer turned on will only show attributes of the parent route segment. Additionally, the features displayed appear to be fixed, in that panning and zooming will not alter what is drawn. Opening this exported layer in QGIS displays the same set of features, again with a full attribute table.

The only conclusion I can draw from this is that something is occurring in the initial caching when the data is first drawn, both as an event layer and as an exported layer, preventing the full set of features from caching to display correctly. Can anyone shed some light onto what might be happening?

I am using ArcGIS Desktop v10.3

Another user seemed to have a similar issue here: https://community.esri.com/thread/44116

Linear Referencing irregular behaviour Figure 1:

  • Two different instances of layers exported from the Route Event layer (Blue and Green)
  • The original route layer (Yellow).

Expectation would be that both blue and green would overlay all yellow lines. Additionally, blue and green differentiate even between themselves despite having been derived from the same event layer using exactly the same process.

Before export, the Route Event layer looks similar to the blue and green layers, but using the identify tool on any of the yellow lines gives the attributes of the Route Event layer rather than the original route layer that it is being displayed as.

EDIT: Running calculate geometry on the output features shows that a lot of them have 0 length, which doesn't explain why the attributes would be showing when clicking in the area they should be, but does explain why they might not be displaying. I'm not sure why that would be though- there does not seem to be any identifiable pattern of difference in the from and to values between those that do have measurable length and those that don't.

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The solution in this instance was simple- the route event UID field was a string format, while the event table UID that it was matching to was in a numeric format. All I had to do was recast the event table UID as string format. For anyone interested, the easiest way I found of doing this was to ~ right click > export > to dBase ~ the table in the catalog window, and change the field type in the export dialogue box.

If anyone has any further information on why a discrepancy between UID field types might cause such aberrant behaviour in the output Route Event layer please feel free to edit this answer with some information- I'm at a loss.

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