topic Re: Network Analysis with No Turns in ArcGIS Network Analyst Questions

Network Analysis with No Turns

CodyKinzett — Mon, 09 Dec 2013 23:09:45 GMT

Hello all as a PG DIP Student in NZ, I'm fairly inexperienced in Network Analysis.

My biggest problem is that the network I am producing has no turns in it, so when I do my service area place that are 28 Km's away are considered more than 3 hours away. I get the feeling its just modelling along the lines and taking one line from my service centres in a sort of spiral but not making use of connecting roads. I have about 91,000 junctions, with about 200,000 edges but zero turns... I am having a hard time understanding how this problem is occurring since there doesn't seem to be any forums on this topic.

I have seen that using the repair connectivity tools are useful but they aren't even clickable, as in never become usable. I have all the necessary licences as I have the student ArcMap 10.0 package.

Cheers in advance,

Cody K

Re: Network Analysis with No Turns

RamB — Tue, 10 Dec 2013 10:32:35 GMT

you can use the planarize tool to give a completely connectivity or selected connectivity.
If you did not define turns, by default all turns are enabled. You will see this option when building a network dataset.

regards,

Re: Network Analysis with No Turns

MelindaMorang — Tue, 10 Dec 2013 14:07:26 GMT

As bsriramak said, this is probably not a problem with Turns. Turns are just used for applying time penalties or restrictions on specific turns. By default, the network will allow you to make turns between any two connected roads at an intersection.

So, the more likely problem is that your network isn't well connected. Here's how you can investigate:
- Zoom in to an intersection that's giving you problems.
- Use the Network Identify tool (on the Network Analyst toolbar) and click on one of the roads that goes into that intersection. Does it have an endpoint at the intersection? Do the other roads that meet at that intersection show up in the adjacent edges list? You can click the adjacent edge numbers in the Network Identify window to highlight them on the map.
- If all the roads that should be connected to your road aren't actually connected, then you need to fix your network.

To fix a network that isn't well connected:
- First, open your network dataset properties and look at the connectivity tab. If your street feature class has vertices at the intersections but not end points, you might be able to fix your problems by switching to Any Vertex connectivity instead of endpoint. Read http://resources.arcgis.com/en/help/main/10.2/index.html#/Modifying_connectivity/00470000001v000000/ for some tips.
- If your street features don't have vertices there either, you might need to run the Integrate tool. This tool will create vertices at the points where features touch each other. You have to be careful, though, because it will create vertices in places where they might not belong, such as highway overpasses.