Event LRS and Spatial Join Discrepancies

Question

Good Afternoon!

I snap crashes to an LRS and get the associated Route IDs and Mile Points using the "Locate Features Along Routes" tool. As you know, this tool returns a table. This table is joined back to my crash data where a "Spatial Join" is then made with roadway line segment data. Many times, at intersecting roadways, the Route IDs from Locate Features Along Routes LRS do not exactly match with Route Ids from the spatially joined segment line data. I always make sure all the point data has snapped within .05 of the routes and LRS. So, the LRS tool does not match at around 2-4% of the time. I learned at GIS-T, in Atlanta, that i could use a python code in the field calculator to obtain the Route ID and Mile Point on the LRS without having to export as an event table. Of course, I still don't think this will remedy the discrepancies. Any thoughts?

BrianVann · Answer

Ayan,

I appreciate your direction. The crashes , point features, are "snapped" to the target routes and tested with "Near" to be certain they are within 0.05' of the LRS. So, the search radius is set at that value. The Locate Features tool then executed and table joined back to the crash data. Of course, the crash data now consists of the associated Route ID and Mile Point. Since I need the remaining roadway data attached to the crashes, I use the spatial join tool, however, as discussed above, the spatial join sometimes joins the intersecting roadway even setting the search radius at 0.05.  Apologies, but I'm not really following what you are suggesting and don't understand how it would alleviate the problem.

Ayan Palit · Answer

@BrianVann This is a common linear referencing challenge that can be solved reasonably well with some guided processes.

Let's start with key references to the Locate Features Along Routes help documentation:

* Crash data may often have just coordinates to locate them on a map.  It is desirable to have a Route attribute collected with the crash data. Or perhaps a post-process to enrich the crash data with a unique route attribute.
* The above process primes the data to then allow for a selective and more accurate process. You can have a recursive script to group the crash points by the route, and then use Locate Features Along Routes tool for each set.