Latest Contributions by JaySandhu

Adam, The [Shape_Length] field is the computed length based on the projection of the data. The [Shape] field used in the evaluator will compute/return the true geodesic length of the feature in the units specified (meters in this case). So these two will most likely not be the same. So one way to fix is to continue using the [Shape_Legnth] in all places by changing your settings as: AfrRoads (From-To): Field - [Shape_Length] AfrRoads (To-From): Field - [Shape_Length] OR Add a field to your street data and calculate it to the true geodesic distance by using the Haversine formula.  And then update your Len22, Len23, etc, fields based on this new field. But this will be more work. Jay Sandhu ... View more

Adam, First are you solving on Length? OR are you solving on say, travel time and accumulating Length to get the Total_Length field? Second, how was the Length attribute added/defined in the network dataset? Third, how are the length by category attributes set up? Are they based on the same "Length" attribute of that edge? Or were they set up by some other formula? Network Analyst itself is not doing any projections to figure out the lengths of the edges. And it will accumulate what ever fields you ask. There is no error in simply summing up attributes to report out the accumulation of the various attributes. Any differences have to exist in the input data. If you use the network identify tool (second icon from right on the NA toolbar), it will list out all the attribute values for that edge. Use that to see if the length and the length by category are the same. Most likely they are not same and that is source of the differences. Regards, Jay Sandhu ... View more

Depending on the version of ArcGIS you are using, you can search the resource centers online for source code to do such tasks. For example, here is one: http://resources.esri.com/help/9.3/ArcGISDesktop/dotnet/d4a90e4c-ba98-44b1-9ab5-73edfaa13513.htm Regards, Jay Sandhu ... View more

Bogdon, What network dataset are you using to computer the OD? If the 131 by 131 is returning only 1 closest the most likely there is no path from where those locations are being snapped on the network to rest of the points. Have you tried running a simple shortest path (Route) on a pair of cities and does that work. Possible reasons for not finding paths could be related to the way the network was set up. And of course make sure the OD is not set to compute only 1 closest, by default it is set to find "<All>". Regards, Jay Sandhu ... View more

Do you have multiple sources making up the network dataset? e.g. streets, bus line, rail, etc such that some source is not getting traversed and leaves a hole. If you have multiple sources, then on the SA properties, polygon tab, you have turn off or exclude sources such that they do not influence the polygon generation. You could also switch to "generalized" and not detailed polygon and it should not leave any holes. You could also turn on Line generation to see if there are any lines (especially some line ends) not getting traversed that would cause a hole to be generated. Jay Sandhu ... View more

John, If you are using Closest Facility, make sure that you put a cut off (say 10 miles) and find 5 closest stores AND make sure hierarchy is OFF. It should solve without running out of memory. However I will suggest that you use OD Cost Matrix solver and not the Closest Facility as it uses less memory (it does not need to return the true shortest path geometry) but otherwise works similarly. Just do the same settings, 10 mile cutoff, find 5 closest and Hierarchy OFF. You will be loading your 10000 customers as Origins and the 1000 stores as destinations. I did not understand your second comment: "I need to get to the point to where I can measure that all customers are 1 mile away their closest store, 2 miles from the 2nd closest store, 2.5 miles from 3 closest store, etc. You get the picture." i.e. what is that you are trying to achieve? Are you trying to open more stores such that all customers are within 1 mile? Jay Sandhu ... View more

There can be many reasons why non-zero distances can get computed for same location. it may have to do with the curb-approach and u-turn policy set in your analysis in conjunction with one way restrictions, etc. Or it could happen if your network dataset has multiple line feature sources and the the locations may get snapped to a different sourceid. But in your case the SourceId is the same so it could be the former. So I would suggest that you copy a pair of problem locations to a route analysis layer and run a shortest path and see what is the resulting shape that gets generated to get some clue on what may be causnig the non-zero distances. Regards, Jay Sandhu ... View more

Your attached zip file is not working. It cannot be un-zipped. I do not understand what you mean by "if i set breaks to 100, then there should be a whole bunch of areas, but i only get 1" If you set a break value of 100, you will get one polygon at 100. If your units are meters, do note that the default trim distance is 100 as well and that may cause the output polygon to be incorrect. So you may want to turn off the trim and see what the output looks like (or set trim to a lower value like 25). Also in your screen shot for A, the polygon break value appears to be a small number like 0.0163 So not sure how you have break value set to 100. What units are the impedance attribute in? You then say you get no output for B. Yet you attached a screen shot of B with two red and yellow lines AND there is a small green-brown polygon surrounding those two lines. Jay ... View more

Can not reproduce the problem you report. I used your mdb to create a new feature dataset called B and then imported the StreetData.shp into it, created/build a network dataset and ran a service area with breaks of 500, 1000, 1500, 2000 meters. All lines were traversed. Screen shot attached. Jay Sandhu ... View more

If you are using the street network (SDC) from ESRI, you do not have to create a network dataset from it. It is ready to use with Network Analyst. Simply bring up the Add dialog, browse to the location of the SDC data folder and add the "streets" network to ArcMap. You should be able to route on it. As far as why the create network dataset is grayed out, make sure that in ArcCatalog (and also later in ArcMap), click on the Tools menu and choose Extensions and make sure the Network Analyst is checked on. Regards, Jay Sandhu ... View more

OD Matrix does not have to be symmetric. A road network may have many one-way streets, turn restrictions or penalties and the fact that it is a directed network, so travel to and travel from impedances may be different for the same edge. All of these can cause the travel time from location 1 to location 500 be different. If you want symmetric values, then either create a network without the above mentioned things (i.e., no turn penalties, no one-way information, no restrictions, and same travel-to/from impedances) OR use one half of the matrix and fill the other side to make it symmetric after the fact. Regards, Jay Sandhu ... View more

In ArcGIS 10 Network Analyst has a new solver called Location-Allocation. You can use it to find "new" facilities to serve a set of given demand. You can load in the existing demand locations as demand points, existing facilities as "required" facilities and a set of points that you can open new or "candidate" facilities and solve solve for how many you want. Their are numerous options and goals you can set. I suggest you run through the new tutorial for location-allocation and read up on the help to use this new solver effectively. Regards, Jay Sandhu ... View more

If they are part of the network dataset (they do not have to be unless there is a reason), then they are NOT connected to the network UNLESS you choose any vertex connectivity AND there are vertices on the underlying street segments AND that is if these facilities are exactly over a street edge. So in any case, you can follow my suggestions from the previous post of either locating only on the edges OR you can use the network identify tool (second icon from right on the Network Analyst toolbar) and click on an edge and see what is it connected to. If it looks like all the streets are not connected then there is a street connectivity issue. Regards, Jay Sandhu ... View more

Have you made the incidents and facilities part of your network dataset? Then most likely that is the problem. i.e. these are not connected to the network and when you create the CF layer, your incidents/facilities are getting located on un-connected locations of the network. If this is the case, you can remove the incidents/facilities from the network dataset and re-build OR bring up the properties of the CF layer and on the network locations tab, uncheck these to location on, leaving on the street edges to locate on and re-load your locations. If the above is not the case then you may have some connectivity issue in the network edges. Jay Sandhu ... View more

You can use the Create Turn Feature Class from each of your routes. See this link: http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?id=2069&pid=2068&topicname=Create_Turn_Feature_Class_(Network_Analyst) That should help you get the turn by turn directions in a feature class. You can also read up on the whole collection of tools here: http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=An_overview_of_the_Turn_Feature_Class_toolset Having turns in your network dataset does NOT help in turn by turn directions. Turns are needed to add restrictions or delays in the network. Network Analyst will provide driving directions for a route that you solve. However you need to make sure the data for the streets and your bus routes (intermediate stops) needs to be available. I will suggest that you install the Network Analyst tutorial data and run through the tutorial exercises to get famillar with the routing/direction capabilities. Jay Sandhu ... View more