Latest Contributions by MelindaMorang

Hello everyone.  I just wanted to let you know about a new prototype tool from Esri's Network Analyst team which allows you to add GTFS public transit data directly to a network dataset.  You can use this network dataset with the Network Analyst tools to run time-aware analyses that incorporate the transit schedules. You can download the toolset and instructions here: http://www.arcgis.com/home/item.html?id=0fa52a75d9ba4abcad6b88bb6285fae1 Please do not hesitate to contact me at mmorang@esri.com with questions or comments about this toolset. ... View more

Do your input points actually have a geographic location on the map?  Because Points to Line should be able to do this. What is your actual analysis about?  I understand from your description the type of lines you want to create.  I'm just wondering why you are trying to create these lines.  There might be a better way to accomplish your end goal. ... View more

Can you tell me a little bit more about what you're trying to do?  What's the overall goal of this analysis?  Maybe we can find a better way to do it. ... View more

It sounds like you need the Points to Line tool: http://resources.arcgis.com/en/help/main/10.1/index.html#//00170000003s000000 It creates a line connecting the input points, and you can specify a line ID field from your input data, so you could make it produce a different line for each slope value. ... View more

Ack, sorry, I did some more experiments, and I now see that, in fact, you CAN do what I was suggesting.  You don't have to have a turn feature class with every turn digitized in to use a custom script evaluator for global turns.  It WILL work the way I originally suggested.  I think if you just fix your syntax, you should be good to go. In the mean time, I'll see what I can do about us getting some better documentation for this subject.  If I work here and can't figure it out, we clearly didn't do a very good job. ... View more

Hi Liam.  I'm afraid I was incorrect in my earlier post.  You can't actually use the default turn script evaluator effectively unless you have actual turn features drawn into your network.  If you are going to use this method, you will have to manually create all the turn features.  As you mentioned before, this would undoubtedly be quite laborious. As for why your code isn't working, it's a syntax problem.  In your if statements, you would need to use something like this: fromEdge.AttributeValueByName( "RoadClass" ) Also, you won't be able to just call "Economy" by itself.  That value is meaningless unless associated with a particular edge element.  As I mentioned before, you can't update the cost of the edge element itself based on the next edge in the route because the route doesn't know what the next edge is going to be.  The reason I suggested the turns is that turns are the only cost-associated element that has information about the edge elements it's connected to. So, unfortunately, this doesn't leave you with a lot of good options.  If you know ArcObjects, you could build your own custom evaluator, but this is not an easy process.  And, again, you can't use a custom evaluator to determine the cost of an edge based on the next edge in the route because the solver itself does not know what the next edge is going to be. I'm really sorry I don't have a better answer for you. ... View more

Okay, I think I've got it figured out. You want to create your own global turn script evaluator that will add a certain number of liters of fuel needed for each type of transition between road types (turn).  So, the fuel usage on the edges will stay the same as you have them now, but each transition between edges can add some value, based on the way you want to calculate it. First, when you create your network dataset, make sure you click the button that tells it you want to model global turns. Next, set up the global turn evaluator, as follows: - In the network dataset properties window, go to the Attributes tab. - For your fuel usage attribute, click Evaluators. - After the evaluators window pops up, go to the Default Values tab. - In the Type column next to Turn, click to get a drop-down menu where you can select "Script". - Click the Evaluator Properties button on the right (looks like a finger pointing at a piece of paper).  A dialog will appear where you can write a simple Python or VBScript that says how the solvers should calculate the fuel usage for turns in your network.  You should be able to use some if statements to give it a different value based on the road types of the fromEdge and toEdge. ... View more

Actually, I think you can use Global Turns for this.  Global Turns allow you to specify a different delay for turns between roads of different classes. http://resources.arcgis.com/en/help/main/10.1/index.html#//004700000030000000 ... View more

Hi Liam.  Unfortunately, the Network Analyst solvers don't have a way of assigning an added cost based on the previous edge traversed.  When the solver calculates the cost on an edge or junction, it doesn't know what the previous edge or junction was.  So you won't be able to do this automatically. You could potentially use a turn feature class to add your costs, but you would have to set up the turns manually for each intersection where you want the added cost. Can you describe more fully what you are trying to do?  What's the goal of this part of your project?  Maybe we can find a better way to do it so we can avoid this problem. ... View more

Thanks for the kind words, Jeremiah.  I'm glad to see that you were able to come up with a really nice solution for your project! We here at Esri are working to develop a much more advanced and useful set of tools for public transit analysis.  I am always interested in hearing from users working in this area to learn about their work, the types of analyses they want to perform, and the challenges they have with our current software.  Feel free to send me a private message if you want to talk further about public transit analyses.  You are also always welcome to contact me with complaints or suggestions about Network Analyst tools or documentation in general. Thanks, and good luck with your transit projects! ... View more

Unfortunately, there is not really a way to do what you are trying to do.  This is a difficult problem. As long as the impedance on both bus routes is exactly the same, the Network Analyst Route solver will somewhat arbitrarily choose which one to take.  We see this sometimes in cases where there are overlapping roads or loop-shaped roads where you could go either way around the loop.  However, if the impedances are exactly the same and the route segments are going to the exact same place, then the route generated will end up in the same place and show the same travel time, so the results will be "correct".  Unfortunately, if you are trying to generate directions, then you will see a difference in which bus it says to take. I wish I had a better answer. ... View more

You can do this by assigning values to the RouteName field in the Stops sublayer.  Each pair of stops needs its own, unique RouteName.  To make this easier to set up, I recommend doing this: - Add two fields to your input bus stop layer. - Populate one of these fields with the name of the stop. - Populate the other field with the name of the next stop. - Use Load Locations for the Route Stops sublayer TWICE so all your bus stops are put in twice.  Use field mapping each time to map the new fields you created to RouteName.  The first time you Load Locations, map it to the first field you created.  The second time, map it to the second field.  That way you end up with each pair of stops having a unique RouteName to themselves.  The solver will then solve a separate route between each pair of stops. ... View more

Please post the error message.  That will help us figure out what's wrong. ... View more