topic Re: network analyst - does not see the barriers in ArcGIS Network Analyst Questions

network analyst - does not see the barriers

yuliadenisenko — Wed, 22 Jun 2011 07:31:19 GMT

hi. i am trying to solve the route. i have network dataset with the attributes for restriction. the route is supposed to avoid traffic lights. The problem is that it does the shortest route by default but completely ignores the restriction. If i load this layer into network analyst as a barrier - it does not see it again. I tried to make search tolerance as small as possible as well as snapping all feature classes participating... what could be the problem? could someone help me please?

Re: network analyst - does not see the barriers

JaySandhu — Thu, 23 Jun 2011 15:02:55 GMT

Did you create the network dataset? Is it possible that the points you are loading as restrictions are a source in your network dataset? You can check by bringing up the properties of the network in Catalog and clicking on the source tab and see what is listed there. Normally it should be a line feature class. If the points are there as well then you should remove them and re-build your network. If that is the case, the points probably not connected to anything and then when you load your restrictions they get snapped to these stand alone junctions and do not restrict any edges.

A second thing to check is to bring up the properties of your Route layer and click on the Network Location tab and then look at the "Snap To:" settings. It should be Closest and only the streets line feature class should be checked on for Shape. DO NOT check on snapping to everything, just the streets.

A third thing that can happen is if the barrier points have pre-existing stale network locations. So when you load your barriers When you load the barriers, in the load dialog, see what is checked on under the Location Position. It should be the "Use Geometry" and not the "Use Network Location Fields"

Regards,
Jay Sandhu

Re: network analyst - does not see the barriers

yuliadenisenko — Fri, 24 Jun 2011 23:21:23 GMT

thanks, Jay. My barriers were one of the sources in network dataset. Besides, there is a data problem as well. So if i really zoom in - i can see that geometrically analyst places the route on the one lane of two lane street. It does not intersect the traffic lights because they are placed in between 2 lanes. But on general picture - it intersects lights.

Re: network analyst - does not see the barriers

BethPickman — Wed, 03 Aug 2011 18:08:17 GMT

I just sent in a new post before running across this thread.
I'm having the same problem - point barriers not being reconized. I've checked the 3 suggestions provided and I have nothing out of line. The loaded points for barriers simply will not snap to the network. I'll keep watching here for more suggestions. Keep them coming. Thks 🙂

Re: network analyst - does not see the barriers

JaySandhu — Wed, 03 Aug 2011 19:36:28 GMT

If you add your network dataset to ArcMap, create a Route layer and then can you add the point barriers by clicking on the map? i.e. Is the problem only when you use the "Load Locations" or also when you click on ArcMap? Have you tried increaing the search tolerance from the default 5000 meters to something larger, say 20000 meters?

Jay Sandhu

Re: network analyst - does not see the barriers

BethPickman — Mon, 08 Aug 2011 13:23:45 GMT

>>Is the problem only when you use the "Load Locations" or also when you click on ArcMap?
both

>>Have you tried increaing the search tolerance from the default 5000 meters to something larger, say 20000 meters?
yup

Seems the locations are identifying within any tolerance distance, but unless they physically touch the linework they will not be included in the analysis. Although this shouldn't be, I've gotten around it by building a buffer layer with a radius of the location-to-line furthest distance then used the buffer layer for 'locations'. That worked because the physical 'buffers' touch the linework. Hopefully I'm missing something and my work-around isn't necessary? Rarely do datasets from varying sources actually 'physically' line up.

Thanks.
🙂 bap

Re: network analyst - does not see the barriers

BethPickman — Tue, 16 Aug 2011 20:44:08 GMT

I've come to the conclusion the Network Analyst function is neglecting a step. After it associates the point barriers to the linework it should also globally snap those points to the linework based on the 'search tolerance' it used for the association. Without this step the association is worthless. The barriers won't be recognized as barriers unless they physically touch the linework. Pin-point accuracy? No. But using dynamic segmentation is the way to go for accuracy - if, unlike me, you have enough data to perform dynseg. Thanks all.
By the way:
Hawth's Tools
Analysis Tools > Vector Editing Tools > Snap Points To Lines

Re: network analyst - does not see the barriers

JaySandhu — Tue, 16 Aug 2011 20:55:56 GMT

That is not true.

As I said before, most likely you have these points as a point source in your network and that is making it locate on unconnected features. Not sure if you tried removing these sources from your network and rebuild the network and trying it again.

Point Barriers, Stops, Facilities etc do not need to touch the lines. If that is the only way you can make it happen then I suggest that you contact Esri tech support and have them look at your data.

Jay Sandhu

Re: network analyst - does not see the barriers

BethPickman — Tue, 16 Aug 2011 21:05:12 GMT

The points I am using are completely seperate from the nework. I'm thrilled to hear you say "...Point Barriers, Stops, Facilities etc do not need to touch the lines..." because that makes more sense for the function.
I've rebuilt the network twice with the same results. I'm stumped, but willing to rebuild it again. Thanks for the advice.
🙂 bap

Re: network analyst - does not see the barriers

JaySandhu — Tue, 16 Aug 2011 21:56:12 GMT

It's not simply re-building but making sure that there are no point feature sources in your network dataset. You can bring up the properties of your network dataset and in the sources tab you should have an edge feature source and a system junction source. Anything else should be there only if you want it to be there. If the point barriers are showing up there then remove them and re-build.
Jay Sandhu

Re: network analyst - does not see the barriers

BethPickman — Tue, 16 Aug 2011 22:00:30 GMT

Figured out my mistake !!
I had some double lines in the network (directional) and the point data associated with only one of them of course. Therefore the barrier was effective in the direction it associated to, but allowed traffic passage on the linework going the other direction. Need to clean my network.
Off and running now.
🙂 bap
---------------------------------------------------
Sources:
Edge Source: Woodburn_v2007_Base2000_link
Junction Source: ModelNetwork_ND_Junctions

Is all that is in there. Very basic