Locate Features Along Route returns duplicate values in event table output

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05-17-2016 11:53 AM
CraigPrisland1
New Contributor II

Hi all,

I have seen this question posed a few times through different forums but have not found a good explanation up to this point  I have around 161,000 points that I am running the Locate Features Along Routes geoprocessing tool on in ArcGIS 10.2.2 on a single route feature (centerline).  All of these points are off the centerline I have been applying a search radius.  The outputted event table returns around 850 duplicate records.  Is there a reason for this?  I've tried exporting only those points that contained duplicates in the event table into a new feature class as well as playing around with the search radius but it still returns the same duplicates.  I cannot find a pattern as to why this is.  Any information would be greatly appreciated.

Thanks in advance!

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8 Replies
NeilAyres
MVP Frequent Contributor

A look at the data might be helpful.

Are not the points locking on to the same point along the line?

What is the attribute in the point feature?

Exactly what the measure is and what the data is at the point might help.

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RichardFairhurst
MVP Honored Contributor

Duplicate events will be returned for points that fall on the concave side of a curve in a route when the point falls at the radius origin for the curve and the curve is within the search radius and is nearest to the point.  That is because all positions along the curve are exactly the same distance from the point for that route.  The tool returns all of the events that are the same offset distance for that route along the curve, because it does not know whether you prefer the beginning of the curve, the end of the curve, or at any of the points between (and it would take another step for it to decide to favor any of these options).  I usually summarize these events and take the event with the lowest measure, although the mean or highest measure are equally valid.

CraigPrisland1
New Contributor II

Thank you for this thorough explanation.  I do now understand as to why I was returning duplicate events.

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AntonioHurtado1
New Contributor

I'm having the same problem here. I read in another forum that people is getting around this by using the "Delete Identical" tool, but that doesn't work for me because I'm interested in the offset value to see if the point is to the left or to the right of the linear feature. The output is giving me duplicates with the exact same information but different signs (1 row in the output with a positive offset value and another row with a negative offset value). Any ideas on how to solve this?

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RichardFairhurst
MVP Honored Contributor

I have not observed that behavior and have created millions of events with this tool, so it is something in your Route geometry I bet.  I would need to see an example of the Route and event.  Are you sure your Route is not scrambled?  If it is a complete loop route and built using the Create Routes tool, all vertice pairs will become scrambled and flip directions and measures like crazy, resulting in very random events and meaningless outputs from the other LR tools.  A self-intersection in the Route that is very small (virtually invisible) might cause this behavior.  Anyway, you have to zoom in very tight and look at your Route Sketch Properties to find out if the Route producing this result is multi-part, contains increasing and decreasing measures, etc.  Probably the only real solution is to correct or simplify the geometry to ensure the side of the line touched does not flip.

AntonioHurtado1
New Contributor

Hi Richard. Thank you for your valuable comments. My route comes from a shapefile that represents the streets of many different cities, and the point features are Points of interest (pharmacies, restaurants, etc). The route is made of almost 3 million lines, and the points shapefile has 613. Only 6 out of those 613 points presented this duplication issue. Those 6 are related to 3 different lines in the route, and from my point of view there's nothing weird about them... The end and start points are not even close to each other, one is a straight line with no vertexes... Here's 1 example:1.jpg

2.jpg

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RichardFairhurst
MVP Honored Contributor

Since I cannot examine the sketch properties I cannot say that the route is not the problem.  Routes with the very smallest of imperfections can create an issue, and the problem is usually invisible until you zoom in extremely close.  Even an apparent two point straight line can end up being a 3 point line that doubles back on itself.

The fact that the point is virtually in line with the route shown and your tolerance must be fairly high, that could be the problem. Is that the situation for all of the points involved?  In any case, you have to find the common pattern, since I assure you this is not a purely random issue.  I have not seen this occur with the setting I use.  To figure this out I would need to see all 6 examples and the sketch properties of the routes to come up with what is really happening between the route configuration and the point location relative to the route..

TedKowal
Regular Contributor II

May want to also investigate whether or not the route has a badly formed multi-part?  Just a thought... but your in good hands with Richard (the resident LRS guru!)

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