Why are there unlocated origins that are within the search tolerance?

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07-19-2011 03:09 PM
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New Contributor
Hello,

When I was double checking the results of my OD Cost Matrix, I found some unlocated origins that were within my Search Tolerance. I was using the Measure tool in ArcMap to do this check.

I set the search tolerance to 2500m when creating the OD Cost Matrix Layer and when adding the Origin Locations. I have no restrictions, I unchecked "Exclude restricted portions of the network", and I have no Default Cutoff Value set. I'm using ArcGIS v.10.

I want to make sure I understand why this is happening before I proceed with the rest of my analysis, which will likely take a long time.

Thank you to anyone who has any suggestions or comments!

Fiona
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Occasional Contributor III
Hello, Fiona!

I'd like to clarify, just to make sure we are discussing the same thing.  Are you talking about Origins that are unlocated when loading locations?  Or are you talking about Origins that find no paths to any destination when solving the analysis?  The reason I ask is that most of your post indicates that this is an issue with loading locations, but the "Default Cutoff Value" only applies to solving the analysis.

Also, what network dataset are you using?  Is your work being done in ArcMap, or via the geoprocessing tools?

For unlocated origins, maybe you could do some experiments on those origins that did not properly locate.  I am assuming that all of this work is being done in ArcMap, and not with the geoprocessing tools.  Have you tried turning on (checking) "Exclude restricted portions", just to see if it makes a difference? Have you tried to increase the search tolerance to something clearly excessive?

Also, be sure that "Use Geometry" is selected in the Load Locations dialog.  And, be sure that on the Layer Properties dialog on the Network Locations tab, that you have checked on the network sources upon which you wish to locate.

Let me know if any of this helps,

Patrick
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Hi Patrick,

Thank you for the speedy response.

After trying out a couple of the things you suggested I realized my input data for my origins was using a Geographic Coordinate System. Could this be why the measure tool is giving me a different distance than either the "Select by Location" or "Add Locations" tools? How does the Add Locations tool calculate distances and is this accurate when using data in a geographic coordinate system? I'm not sure which is the more accurate answer, the one the measure tool gives me or the one the "Add Locations" tool gives me.

Thanks so much for the help,

Fiona
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Hi again,

Here's some other info to answer your questions above:

-my question is concerning origins that are unlocated when loading locations (the majority of the origins are located but some of the unlocated ones are within the search tolerance according to the measure tool in ArcMap)
-I'm using a network dataset I built using DMTI Spatial data
-I'm working in ArcMap now, but have also tried the geoprocessing tools in a model I built to automate the generation of the OD Cost Matrix
- I tried turning on and off "Exclude restricted portions" and it made no difference
-"Use Geometry" is selected
-I had checked on the network sources upon which I wish to locate (EDGE, MIDDLE, and SHAPE checked)

Let me know if you need any other info. Thanks again!

Fiona
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Occasional Contributor III
Did you try bumping up the search tolerance and relocating?  Perhaps set it at 10,000 meters, then 20,000 meters, etc.  If you see the number of unlocated locations going down, the issue might be the distance between those locations and the nearest located network element.

You can quickly try relocating the origins with the following steps:


  1. Open the Layer Properties dialog for your layer.

  2. Choose the Network Locations tab.

  3. Change the search tolerance in the Finding Network Locations group box.

  4. Close the Layer Properties dialog by clicking OK.

  5. Right click on the Origins class in your active OD layer.

  6. Choose "Recalculate Location Fields" and select "All"


Also, you mentioned "I had checked on the network sources upon which I wish to locate (EDGE, MIDDLE, and SHAPE checked)".  How many and what sources do you have in your network?  Which ones are checked on?
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Hi Patrick,

When I increased the search tolerance to 10,000m, the number of unlocated origins went down. However, the same issue arises, where some of the unlocated origins are within 10,000m but are still unlocated. What distance should I trust, the one the Load Locations tool is using OR the one the Measure tool is giving me?

I have 2 sources listed in the Network Locations tab under the Finding Network Locations section. The first is the road (line) feature class that I used to generate the network dataset and the other is the Junctions feature class. I have all of them checked on and I've selected "Closest" under "Snap to".

Thanks again for the help,

Fiona
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Occasional Contributor III
Do you mind sharing your data?  I'd like to take a look and see if I can get to the bottom of the problem.  How big is the network dataset?

My email is pstevens at esri.com.
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New Contributor II

I know this is a question from 4+ years ago but I was having the same problem and found a solution.  In case anyone else runs into this issue and find this post, I figured I would share. 

One I "projected" my data points into Aux Sphere (Web Mercator), the unlocated features issues was resolved.  I hope this helps someone else out there!

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