could not create service area polygon

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11-20-2010 06:25 AM
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New Contributor
Hello everyone..

I have tried to create a network dataset from shapefile for service area analysis purpose. I was succeed to load the emergency service facilities but then i failed to create the service polygon. I tried to compute 3, 5, and 10 minutes driving time from those emergency facilities, but the polygon didn't want to appear. And there is no any notification why this problem occur.

In another hand, I tried to create the geodatabase file from the shapefile which was i assumed can solve the previous problem. But the another problem occurred, the geodatabase file was not created completely. Meaning, only 1/4 of whole map that successfully exported into geodatabase and displayed on ArcMap. Im using arcGIS 9.3 and i think i already followed the step by step service area-network analysis tutorial but i dont know why this problem occur maybe i miss something. I hope anybody can help me to solve this problem.


Thank you,
Belinda Ulfa Aulia
b3ltown@gmail.com
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Esri Regular Contributor
One reason the service area polygons may not get created is bad connectivity in the network.
You can bring up the properties of the service area layer and on the Line Generation tab, check on
the generate lines option and re-solve. Do you get any service area lines?

If no lines are generated, can you do a shortes path route using the Route Analysis layer and get back a path on that network?

If you can not get a path then there is probably a connectivity issue or some attribute (Restrictions or Impedance) that are causing the solvers to not work. On the NA toolbar, the second from right icon lets you "identify" network edges. Use it to inspect some lines and see what costs (impedance attribute), restrictions are on that edge and also see if the edges are connected to all its relevant neighbors.

Jay Sandhu
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Hii Jay.. thank you for your concise and clear explanation.

As what you have explained before, i have tried 3 possibilities ways you asked me to do. Then, either re-solve by click on the line generation line nor creating the shortest path route using the Route Analysis layer still the service area polygon can not be generated. So it's true about the bad connectivity, then i checked using "network identify tool" i found that the edges is not connected each other and the "minute" and "meter" attributes is 0.

I am rookie in this matter Jay. So should I go back to the data and rearrange the polyline of road layer? or maybe you have another better suggestion?. I appreciate and looking forward for your reply.

Thank you
Belinda Ulfa Aulia
b3ltown@gmail.com
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Esri Regular Contributor
Belinda,
Since you have connectivity issues and your impedance attributes are 0, you need to do two things. First, fix the connectivity issues. You can take a look at the "Editing Source Features" section here and follow the links to the integrate tool or the topology section:

http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Ways_to_edit_network_datasets/00470000...

Once your connectivity is fixed, re-create the network and then make sure on the Attributes Tab where the impedance attribuets are listed, click on the Evaluators button and specify where the impedance attributes will get their information for each edge. If you are un-sure on what to do here, take a look at the tutorial data for San Francisco that comes with Network Analyst.
Regards,
Jay Sandhu
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