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Thread: Identify Discrete Points Along a Route

  1. #1
    Sashikanth Gurram
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    Default Identify Discrete Points Along a Route

    Hello everyone,

    I have created the shortest routes (in length) between several O-D pairs. Now, my question is, can I identify the discrete intermediate locations along the route. I need the location coordinates for the intermediate locations along the route. Is this possible?

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    Jay Sandhu

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    Default Re: Identify Discrete Points Along a Route

    I am assuming that you used the Route solver to generate the OD pairs. Once the route are solved, you can use the resulting Routes sub-layer to select the features that lie along them. The "Selection" top menu drop down has the Select by Location option to get you started.

    Another way you can generate the features along the path is to realize that when the Route solver finishes, it keeps the "traversal" results in memory. These are all the network features traversed by the routes. You can programatically access these. One way is to download and use the following AddIn:
    http://resources.arcgis.com/gallery/...4-48812C8DB8DE

    Jay Sandhu

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    Sashikanth Gurram
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    Default Re: Identify Discrete Points Along a Route

    Thanks for the reply Jay. I have downloaded the add-in and have worked with it to generate the feature information. The traversal add-in generates the Junction points along the generated routes. However, I did not quite understand as to how the Junctions were generated along a route. It appears that the total number of junction points generated for different routes are different. Did the add-in generate the junction points based on the network features? Please let me know about this.

    Further, this tool may not provide the answer to my question. I was not looking to identify the features along the route. What I actually want is the location coordinates along the route at specific intervals. For example, for a given route between an O-D pair, I want the location coordinates along it at 50 feet intervals. In other words, I would like to break the route into 50 feet segments and then record the coordinate(s) at the end of each segment. Is this possible?

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    Jay Sandhu

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    Default Re: Identify Discrete Points Along a Route

    If your goal is to either "locate" features every 50 feet or break into 50 feet segments then you can achieve that by using "linear referencing".
    When routes are generated the default option is to output them as lines with measures. Assuming that you used a "length" attribute to solve the shortest paths and assuming that the length attribute was in feet, then the output Routes lines are stored as polylineM and the M (measure) values will be in feet. Given this, you can create an "event table" and then use the GP fool "Make Route Event Layer" to create features 50 feet in length. The event table will look something like:

    RouteID FromM ToM
    1 0 50
    1 50 100
    1 100 150
    2 0 50
    2 50 100
    2 100 150

    make sure the measures go up as the length of the routes and have that many IDs as the number of routes. You can read more about this tool here:
    http://help.arcgis.com/en/arcgisdesk...0008000000.htm

    Jay Sandhu

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    Sashikanth Gurram
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    Default Re: Identify Discrete Points Along a Route

    Thanks for the suggestion and sorry for the late response.

    Will this method work if my routes are calculated based on shortest time path. I have used the roadway length and the posted speedlimit to come up with the travel time along the link. Then, I have used this Travel_Time attribute to build the network dataset and compute the shortest route. Subsequently, I have created a shape file from the routes layer and computed the length attribute in the routes layer. Now can I use this layer to create the route events layer?

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    Jay Sandhu

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    Default Re: Identify Discrete Points Along a Route

    The route layer create by solving on a time attribute will have the M measure values in terms of the time attribute.

    You will need to re-create that route based on length before you can use the linear referencing approach. You can do this by using the Create Route gp tool. The input will be the route shape file you have written out. See more about it here:
    http://help.arcgis.com/en/arcgisdesk...0005000000.htm

    Jay Sandhu

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    Sashikanth Gurram
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    Default Re: Identify Discrete Points Along a Route

    Instead of creating the event layer isn't there any other way to get the intermediate points along a route?

    For example, are there any polyline to point conversion or split polyline tools that can be used to solve this issue.

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    Sashikanth Gurram
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    Default Re: Identify Discrete Points Along a Route

    Following up, I have created another route layer using the create routes tool in linear referencing with the measure Source as Length. The help section you have posted suggested that the output route layer will have the measure M values. However, the routes output I have got does not contain any M values. Does this indicate some error ?

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    Jay Sandhu

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    Default Re: Identify Discrete Points Along a Route

    The output of that Create Routes tool should have measures unless the length field does not have any informaiton.

    Open the attribute table of the newly create feature. It should list "Polyline M" in the Shape column. If it only says "Polyline" then the tool was not executed properly.

    Jay Sandhu

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    Jay Sandhu

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    Default Re: Identify Discrete Points Along a Route

    Quote Originally Posted by sashi34u View Post
    Instead of creating the event layer isn't there any other way to get the intermediate points along a route?

    For example, are there any polyline to point conversion or split polyline tools that can be used to solve this issue.
    You could post on the geometry/genaral type forums for other solutions. As far as I am aware, the tool Split line at Vertices could be used, but how will you gurantee that their are vertices every 50 feet? You could first use the Densify tool but again there is no gurantee that the vertices are every 50 feet as the existing vertices can be anywhere before you start to densify.

    Jay Sandhu

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    Sashikanth Gurram
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    Default Re: Identify Discrete Points Along a Route

    Quote Originally Posted by jsandhu View Post
    The output of that Create Routes tool should have measures unless the length field does not have any informaiton.

    Open the attribute table of the newly create feature. It should list "Polyline M" in the Shape column. If it only says "Polyline" then the tool was not executed properly.

    Jay Sandhu
    The shape column corresponding to the new routes table has Polyline M. It has a total of 3 columns as shown below.

    FID Shape Name

    As you can see, there is no column which gives the length of the route. Is this how it is supposed to be?

  12. #12
    Jay Sandhu

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    Default Re: Identify Discrete Points Along a Route

    As you can see, there is no column which gives the length of the route. Is this how it is supposed to be?
    Yes!

    Feature classes do not automatically have length or other attributes added on to them.
    If you want to see the acutal geometry length of a line, then you can add a field and use the field calculator to display this value. Help here:
    http://help.arcgis.com/en/arcgisdesk...00000025000000

    However this is the geometry length, not the calibrated measure length of the route which can be different.

    Jay Sandhu

  13. #13
    Sashikanth Gurram
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    Default Re: Identify Discrete Points Along a Route

    Thanks a lot for your reply Jay. I was trying to create this dataset that you have mentioned. However, I have found that there is a tool available to do exactly this.

    I am sure you know about the ET Geowizards extension. In the ET Geowizards under the Point Functions there is a feature called Station Points. This tool creates points at fixed intervals along the routes (or for that matter along any polyline). This feature is free to use as well.

  14. #14
    Jay Sandhu

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    Default Re: Identify Discrete Points Along a Route

    Glad to know you found a tool! And thanks for reporting it here as others will be able to find the same solution that you did.
    Jay Sandhu

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