Determining Line Direction for Historical Traffic Data

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10-06-2011 06:45 AM
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New Contributor III
This question relates to my use of Network Analyst extension, but has an editing component to it. I need to determine the direction of which my street lines were created. What direction is taken from the first edited point to the last? Network Analyst is using a bunch of To and From information to create historical traffic patterns based on the street side edges. However, my Street Centerline was a file from our County government. So, I am not fully sure that they consistently have the lines flowing in the same direction. My eventual use is to compare the direction the street was digitized to determine a To/From direction for the lines. Then attribute my GPS data, with a heading, to the appropriate To/From edge of the line. Any ideas?
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Esri Regular Contributor
You can visualize the digitized direction of your streets by using a line symbol that places an arrow in the middle of the road, for example pick a line symbol like the one titled: Arrow Right Middle.

You can also draw the network dataset symbolized with the directions in which the lines are restricted based on a restriction attribute such as oneway. Bring up the properties of the network dataset (added to the ArcMAP table of contents) and click on Symbology tab and turn on edges and pick the arrow symbols and customize as needed.
More help here:
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/The_network_dataset_layer/0047000001r4...

Jay Sandhu
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New Contributor III
I am trying to do this programmatically.  I have roughly 93,000 street segments and over 10 million GPS data points.  So I need someway of generating the cardinal direction as an attribute.  Unless there is a better way to attribute the information over.
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Esri Regular Contributor
You can add an attribute to your network dataset that can return you the from and to azimuths of the edges.
This can be done by using a script evaluator. For example add a cost attribute called LineAzimuth, then click on the evaluators and for the type pick script and for the value, click on the icon on the right to bring up the script evaluators and pick Edge and then FromAzimuth (for the From-To direction of the edge) and set the Edge.ToAzimuth for the To-From direction. Click Ok and build. Now when you query, display, identify an edge you will get the from starting and to ending azimuths of each edge. You can read more about the script evaluators here:
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Assigning_evaluators/00470000002100000...

And you can get more info on the azimuth and other network edge properties here:
http://help.arcgis.com/en/sdk/10.0/arcobjects_net/componenthelp/index.html#//002500000563000000

Jay Sandhu
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