Latest Contributions by RobertGarrity

There isn�??t a way to use a script evaluator to get cost attribute values at a certain time, unfortunately. However, the results of your analysis won�??t change by scaling travel times by a constant value. So could you solve you problem without scaling? For instance, if you don't want people to spend more than $10 on travel costs getting to your facilities, you could convert that to a travel time and put the value as the impedance cutoff, then solve. If that doesn't work for you, there are two other options: write a custom evaluator or use a scaled-cost polygon barrier. The recommended way is writing a custom evaluator, which is capable of getting what you want, but this may take some time to set up if you�??re not familiar with how to do it. The other option is to create a scaled cost polygon barrier that covers your network, set the Attr_TravelTime field to your wage value, then solve using TravelTime as the impedance. This would work on a small network but it would take a long time to load and solve on a larger network. Thanks, Robert ... View more

Hello Paul, It sounds like you want to solve a capacitated allocation problem. The following tool should do what you want: http://www.arcgis.com/home/item.html?id=c5ae481f25604d1bb050d9bd1d6e3c06. Otherwise, you could sign up for the Beta program and use the new Maximize Capacitated Coverage problem type for the location-allocation solver. Since you're not locating facilities and allocating demand to facilities, rather, you're simply allocating demand to current (that is, "required") facilities, you would set the Facilities to Choose property to match the number of required facilities in your analysis. (If you were also locating new facilities, this parameter would be higher to choose the best candidate facilities.) Best, Robert ... View more

Hello. There is a way to edit parameters using Python, but only in ArcGIS 10.1, which isn't released yet. You can use 10.1 if you're part of the Beta program. I think you can sign up for it at betacommunity.esri.com, if you're interested. A new 10.1 Network Analyst Python module provides access to solver parameters; for example, here is a link to the help for VehicleRoutingProblemSolverProperties class. However, if you get access to 10.1, you might want to consider using the new restriction model instead. The new restrictions allow you to avoid certain edges rather than prohibit them entirely. For instance, you could choose to mark your local streets and undesireable streets as restricted, then set the Restriction Usage parameter to Avoid: Med or Avoid: High. This would allow buses to travel on those streets, but they would try to avoid them, which is similar to what it sounds like you are doing with your cost attribute parameter. Here is a 10.1 tutorial exercise on the subject. Last, I don't understand why you need to solve routes repeatedly. Are you using the VRP solver or are you running a custom VRP solution? Thanks, Robert ... View more

Hi Matt, I'm attaching an image showing how you can model the transfer times as you described. Basically, instead of using a single junction to model the transfer, expand it out to be a line (with a junction on each end). The evaluator for one side of the line, e.g. the From-To side, would have a time cost but the other side wouldn't. Robert [ATTACH=CONFIG]13275[/ATTACH] ... View more

Hello, I just want to jump in here and make sure that there wasn't a misunderstanding. It read like chunking might have been turned off in the last analysis--it should be on. Jeffrey, did you set the registry key for chunking then solve the analysis using overlapping (instead of merge)?  The point Jay was making was that chunking doesn't work with merging polygons. The merge operation is a post process which requires all the polygons to be stored in memory during the solve so that the 150 or so polygons can be merged in the end. The Overlapping option creates polygons that are completely independent of one another and allows the memory to be cleared after each "chunk". Robert ... View more

Hello Subrina, Hope you're well. Judging from the graphic you posted, there is surely a problem with the Oneway restriction attribute. It is restricting your roads in both directions, rather than just one. Furthermore, it's restricting two-way roads--probably all of them. I say this because the road you identified in the graphic was a dead end and should be two-way--I've never heard of a one-way deadend before. 🙂 You'll need to correct the logic in your evaluator for the Oneway restriction attribute. The logic should look something like what's shown in the 5th and 6th graphics in the following help topic: http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Types_of_evaluators_used_by_a_network/00470000000n000000/ You may want to go through the first Network Analyst tutorial exercise and pay particular attention to Step 24 when you choose Oneway. Also during that step, click the Properties button (on the right side of the dialog box) to get to the evaluator's logic. http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Exercise_1_Creating_a_network_dataset/00470000005t000000/ One other thing to consider is you can use the nationwide network dataset that comes with the Data & Maps DVD instead of making a network dataset yourself, and avoid some difficulties. But that's only if your study area is in North America or Europe. Best, Robert ... View more

but still why can't i do measure the network distance when the restrictions are on?? Did you take a look at the evaluator logic in the one-way restriction attribute? Post it here so I can take a look too. Maybe the evaluator is restricting roads in both directions rather than in just one. Aside from Network Identify and symbolizing restrictions, you could also try a service area analysis to see how far you can traverse on the network from your stops--just load the stops as facilities, set a reasonable break value, and see what the solver returns. I have one more q. i have 400 points from which i wanna know the distance of some hospitals. but these points are actually centroid of ZIP Codes which i created from the ZIP Code polygons. So, they are in different layers. That's why i have to take each centroid location at a time and do the OD matrix. How can i take the centroid points in one layer so that i will have the network measure in one OD matrix attribute?? Sorry, but I guess I don't understand the question. Are you trying to figure out the nearest X number of hospitals, or how many hospitals are within X distance? Or do you have a set of hospitals and, for each zip code, you want to find the distance to a specific subset of those hospitals? Thanks, Robert ... View more

You can... Double-click the Routes sublayer of the VRP layer in the table of contents. Click Symbology tab. Click Categories under Show. For Value Field choose Name. Click the Add All Values button. In the table, click the field header Symbol and choose Properties for All Symbols and set the common properties for your routes, such as width. Click OK to close the Symbol Selector dialog box. Back in the Symbology tab of the Layer Properties dialog box, click each route and choose a color. Often times with the VRP solver, users solve different problems for the same vehicle fleet, so the routes/vehicles are constant. You may want to store the symbology you just created for the routes layer then apply it to future VRP layers. To save as a layer file, right-click the Routes layer in the TOC and choose Save As Layer File. To apply the symbology use the Apply Symbology from Layer geoprocessing tool. I hope this helps. Robert ... View more

Hi Subrina, Have you tried turning off your one-way restriction on the route layer and re-solving? If you're able to solve with it off, it could be a problem with the one-way restriction evaluator. If you have other restriction attributes, also try turning them off. Consider symbolizing restrictions on your network to get a better idea of what edges are blocked. See the section entitled "Symbolizing restrictions with arrows" of this help topic. One other thing to try is the Network Identify tool on the Network Analyst toolbar. Use it to click on Fairfax Road to see the street's network attributes. In particular, see what the network cost is for the attribute you're solving on. If it's a -1 (or less), then this is causing your edge to be restricted. Good luck, and please let me know how it goes. Robert ... View more

It sounds like you can use the location-allocation solver for your study. It choses sites from candidate sites based on network impedance and other factors. The following are a couple of resources to help you get started, but I'll try to answer some of your other questions below: location-allocation help topic location-allocation tutorial exercise I currently have 2 different layers: - First: a point layer which can be consists of more than 1000 departure location for biomass transport. From each departure location, the biomass is transported to the storage site of which the location is to be determined. - Second: a layer which shows the existing road network in the study area You'll need a network dataset, so you can use the road network to create a network dataset. However, you may want to avoid this process and use an existing network dataset. See this post for a list of network dataset options, but I recommend using the one provided with the Data & Maps media to get started. The 1000 departure locations for biomass transport would be your demand points. You'll need another layer; one that represents potential "facility" sites. ("Facilities" represent biomass storage sites in your analysis.) It sounds like you don't have this information, and you want to assume a site can be located anywhere. Location-allocation can choose only from a finite number of locations, so what you can do is create a point feature class with facilities uniformly dispersed throughout your study area or along the network to home in on the best location. Another assumption is that the biomass storage site is located next to/on a road and not in the middle of example an agricultural parcel. Network Analyst always assumes facilities, demand points, etc., are located directly on the road network, so this need not be a concern for you. Even when point symbols representing facilities etc. are displayed off the network, they are treated as if they are on the nearest point of the network. To avoid any confusion about where the sites are located on the network, choose to Snap to Position along Network as shown here when you load your facilities into a location-allocation layer. Good luck, Robert ... View more

One other option to add to Alexey's list is the standard (non-premium) StreetMap data, which is available to ArcGIS users at no additional cost on the Data and Maps media. This StreetMap network doesn't have as many options and isn't as current as the premium version, but it covers North America (or Europe) and should be sufficient for what you want to do. If you don't find Data and Maps on your GIS lab's computers, maybe you can ask your lab manager to download it from the Esri Customer Care site or get the DVD, which he/she may already have, and install it. Best, Robert ... View more

I took a quick look at your mxd. It appears there are several one-way restrictions that are making the route to the stops you have infeasible. If you turn off the Oneway restriction on the route layer, you'll get a solution. It may help you to visualize the oneways (see the section entitled Symbolizing restrictions with arrows). Another point to consider is you can more precisely choose which edges your stops locate on by setting up a query (here's a link to the help) before adding the stops to the route layer. It may be that you want to locate on one overlapping edge, but not the other; in this case, the query definition will help. I tried this and located Stop 2 stop on PathLine_0, instead of PathLine_1, and got a route, even with the one-way restriction enabled. Robert ... View more

Josh, You can try the Network Analyst Traversal Result add-in that Patrick Stevens posted on the Resource Center. It outputs features that are traversed during an network analysis. From there, you can use the junctions feature class, which is ordered for you. (Note that this feature class includes points that represent stops and added-cost/scaled-cost barriers in the analysis.) Good luck, Robert ... View more

Hello. I saw in your other post that you said the following: When I did the build of my network dataset, it did not put a "ND junction" point at all these points (and I can't see any pattern in where it opted to put one vs. not put one). Any of my "POC" points that are not coincident with the ND junction points produces a standalone error. What this tells me is that the points you are creating and that are giving you the stand-alone error aren't truly coincident with the endpoint/vertex of a line. Try zooming in really close, I don't think the problem junctions you created will be coincident with the ND_junctions (AKA "system junctions"). In fact, Network Analyst shouldn't create a system junction on top of user-defined junction. Try these steps as a test: 1. Start an edit session to edit the junctions you created. 2. Add the snapping toolbar and turn on all snapping except for edge snapping. 3. select one of your problem points with the Edit Tool. 4. Drag it so that it snaps to the system junction that appears to be on top of it. 5. Stop editing and save your edits. 6. Build the network. 7. Create a route and see if you get the expected results. Please let me know if that was the issue or not. Thanks, Robert ... View more