topic Re: Distance calculation between in ArcGIS Network Analyst Questions

Distance calculation between

ThomasVoets — Tue, 20 Mar 2012 12:28:14 GMT

Hello,

I will try to explain my problem by means of a the figurethat I attached in this post.

In the figure you can see the study area. Each small dot represents a biomass collection location. As you can see, the dots are divided in three different colors in order to create 3 subareas which each are visited by a truck to collect the biomass. The blue lines represents the existing road network in the study area. The large blue dot is the central biomass plant location, which is currently not relevant for the explanation of the problem.

For each of the 3 subareas, the biomass should be collected by a truck at each dot. This should be done in a way the distance to be traveled is as low as possible. Therefore, I would like to develop an algorithm which satisfies 2 important conditions:

1) After the first dot is visited, the next dot to be visited is the dot that is the closest to the first dot. The third dot, is the dot that is the clost to the second dot, and so on. In general, one could say that the next dot is the dot closest to the current dot, except dots that are already visited.
2) The sequence of the dots that are visited should afterwards be consultable for further analysis, just like the total distance and the distance that is traveled between each dot.

If possible, the distance over the existing road network should be calculated. However, since not all collection points are connected to a road network, Euclidian distance with also be satisfying.

I hope my explanation is clear !

Many thanks in advance...

Thomas Voets

Re: Distance calculation between

NaAn — Tue, 20 Mar 2012 17:32:18 GMT

Hi Thomas,

I�??m not sure why you need this rule:

1) After the first dot is visited, the next dot to be visited is the dot that is the closest to the first dot. The third dot, is the dot that is the clost to the second dot, and so on. In general, one could say that the next dot is the dot closest to the current dot, except dots that are already visited.

The lowest cost route does not necessarily visit orders in the sequence defined in your rule, unless you have some business requirement to do so.

If your objective is just to minimize the total travel distance, your problem should be solved with VRP solver. Here is the way to setup your problem:

Introduce 3 routes (also called trucks) each corresponding to one subarea, i.e. R1, R2 and R3. Assuming that trucks will return to the biomass plant location when finishing visit all biomass collection locations, you can introduce plant location as a Depot and use it as route end depot (setting it in Route �??EndDepotName�?�).

Load all biomass collection locations as Orders. For each order, set its correpsonding �??RouteName�?�, i.e. all biomass collection locations to be visited by R1 will have RouteName set to R1 (you may open order attribute table, select a bunch of orders, right click RouteName field to open �??Field Calculator�?� and do a batch set ). Set all order assignment rule to �??Preserve Route.�?�

The solver will return the low cost solution visiting all collection locations. You can find the route cost summary and other time and cost information in route properties.

Please go through the help and tutorial doc for more details on VRP solver:
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Exercise_7_Servicing_a_set_of_orders_with_a_fleet_of_vehicles/004700000062000000/
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Vehicle_routing_problem_analysis/00470000004v000000/

I hope this helps.

Thanks.

Anna

Re: Distance calculation between

ThomasVoets — Wed, 21 Mar 2012 09:18:32 GMT

Thanks a lot!

I will go through the documents and keep you updated if I can solve my problem with it.

Kind Regards,

Thomas Voets

Re: Distance calculation between

ThomasVoets — Wed, 28 Mar 2012 11:29:41 GMT

Here a short update of the status of my problem:

I have very little experience with network analyst. So, when I was opening the 'Make Vehicle Routing Problem Layer', I had to add my input analysis network. Therefore, I first created a network dataset. When I wanted to load my network dataset as the input analysis network for the Vehicle Routing Problem Layer I get following message: "Network has no cost attributes." This is quite strange because I added a cost attribute (see figures attached in this post). Can somebody help me? Which (cost) attributes should I further add to my network dataset, based on the description of my problem mentioned above?

Thanks in advance!

Thomas

Re: Distance calculation between

NaAn — Wed, 28 Mar 2012 15:22:44 GMT

Hi Thomas,

VRP solver needs a time cost attribute. The time cost attribute is used to define the traversal time along the elements of the network. This attribute is required, since the vehicle routing problem solver minimizes time.

Please search for "Time Attribute" in VRP help page for more details:
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Vehicle_routing_problem_analysis/00470000004v000000/

Here is more information for network attribute:
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Understanding_the_network_attribute/00470000000m000000/

Thanks.

Anna

Re: Distance calculation between

ThomasVoets — Thu, 29 Mar 2012 08:35:14 GMT

Thanks a lot Anna,

I've gone trough all this but I still get the same remark: " network has no cost attributes". However I added the 'meter' cost attribute

I created it like this:

I added the attribute 'Meters' with usage type 'cost', unites 'meters' and data type 'double'.
Then I createdn evaluator. It consists of 2 rows with 2 different sources:

Source 1: 'Road Segments', direction 'from-to', element 'edge', type 'field', value 'distance' (which refers to the column of the attribute table of the road segments in which the distance in meters is given)
Source 2: 'Road sgements', direction 'to-from', element 'edge', type 'field', value 'distance' (which refers to the column of the attribute table of the road segments in which the distance in meters is given)

Do you have any idea why it is still not working despite the fact I added this cost attribute? Should I add more of them for my problem in which I just want to visits different locations in a sequence that minimizes total transport distance?

Thanks again!

Thomas

Re: Distance calculation between

NaAn — Thu, 29 Mar 2012 17:03:57 GMT

Hi Thomas,

You need a "Time" cost attribute which has the unit of "seconds, minuts or hours." You may either add a new travel time field in the Road Segement feature class and use it as the time attribute source value, or just use a field evaluator to calculate the time value based on the distance field value, i.e. time = distance/60.

[ATTACH=CONFIG]13112[/ATTACH]

In addition, I noticed that you open 'Make Vehicle Routing Problem Layer' to solve VRP. Unless you want to use the model builder or write your python script to call the solver, you don't need to use this tool. In ArcMap, you will need to click Network Analyst on the Network Analyst toolbar and click New Vehicle Routing Problem to create a VRP layer. Please read the tutorial for more details:

http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Exercise_7_Servicing_a_set_of_orders_with_a_fleet_of_vehicles/004700000062000000/

If it still doesn't work, could you please post your the network dataset here?

Thanks.

Anna

Re: Distance calculation between

ThomasVoets — Fri, 30 Mar 2012 12:46:14 GMT

Thanks a lot,

But still not working...

Here are my data. The zipfile contains 5 different layers:

'Gebied A', 'Gebied B', 'Gebied C': the point layers with the locations where the biomass is collected.
'Study Area': shapefile layer of the study area
'Overpelt Fabriek': the point layer which represents the location where the biomass is centrally processed. This is also the location where the transport vehicle start to collect the biomass.
'Wegsegmenten': this means 'road segments'. This is the road network in the study area. The last column 'lengte' represents the 'length' of the different road segments.

Hope these data are the data you are looking for?

Many thanks in advance!

Thomas Voets

Re: Distance calculation between

NaAn — Fri, 30 Mar 2012 20:06:16 GMT

Hi Thomas,

I looked at the data. You didn't add the time cost attribute. I added it for you which looks like this:
[ATTACH=CONFIG]13153[/ATTACH]

In your data, each area includes more than 600 orders. Since you want one truck dedicated to each area, I would suggest you to create a VRP layer for each area and solve the three areas independently. Otherwise, you have to introduce the specialty to match orders with the dedicated vehicles (see VRP help to understand specialties).

In addition, one truck cannot finish visiting all orders a day, so you have to introduce multiple routes with each representing a day to cover all orders.

Finally, in your street segment data, there are some disconnected areas where duplicated junctions were created and each is connected to a subset of adjacent edges. I used the Integrate tool to merge them. Solving problem on a disconnected network will cause some unassigned orders.

Please find the network dataset (disconnected Dataset and fixed Dataset) and the corresponding test layers in the attachment and also watch this VRP vedio:

http://video.arcgis.com/watch/686/vehicle-routing-problem-example-appliance-delivery

Thanks.

Anna

Re: Distance calculation between

ThomasVoets — Mon, 02 Apr 2012 06:55:40 GMT

Thanks a lot,

I will deal with it this afternoon and keep you updates. Many thanks!

Thomas Voets

Re: Distance calculation between

ThomasVoets — Mon, 02 Apr 2012 08:55:46 GMT

Ok, I've gone throught it.

I support your idea of creating a VRP for each subarea. However, I should first give some further explanation concerning the background of my model.

The dots of the three subareas represent collecting locations of biomass.
The aim is now that a transport van with a mobile pyrolysis reactor on it, visits each collection location. The mobile pyrolysis reactor converts the biomass to oil, which is then 'tanked' into another van that transports the oil to the Overpelt Fabriek site. So, the van with the mobile pyrolysis reactor on it, does not return to the Overpelt Fabriek site but just visits each parcel after another, while the oil is brought to the Overpelt Site by the other van.

So, for my analysis I would just like to get the distance of the van with the mobile pyrolysis reactor on it without returning each day to the Overpelt Fabriek site. So the transport distance per subarea consists of the distance from the Overpelt Fabriek site to the first collection location plus the distance that is travelled to visit all other collection locations and then finally the distance to return to the Overpelt Fabriek site.

Is it possible to explain how I should deal with this situation in ArcGIS ? I hope my explanation is clear.

Many thanks in advance, and sorry for keeping asking questions !

Re: Distance calculation between

NaAn — Mon, 02 Apr 2012 17:36:11 GMT

Hi Thomas,

Your problem is simpler than I thought. For each area, you only need one route. You can use Overpelt Fabriek site as the start and end depot, and use the number of orders in the area as the MaxOrderCount for the route.

Since the all orders in an area will be assigned to one route, solving the problem will take a while.

Thanks.

anna

Re: Distance calculation between

ThomasVoets — Tue, 03 Apr 2012 10:52:19 GMT

Hi Thomas,

Your problem is simpler than I thought. For each area, you only need one route. You can use Overpelt Fabriek site as the start and end depot, and use the number of orders in the area as the MaxOrderCount for the route.

Since the all orders in an area will be assigned to one route, solving the problem will take a while.

Thanks.

anna

Thanks again Anna!

However, still 2 questions.

First question: when I want to use the Overpelt Fabriek site as the start and end depot, is it enough to just load it as a location for the Depots? You can see in attachment the example for route 1 for which I loaded 378 locations as the orders and the Overpelt Fabriek site as the Depot.

Second question: How can I add the number of orders in the area as the MaxOrderCount for each route?

Many thanks again! Problem is almost solved 🙂

Thomas

Re: Distance calculation between

ThomasVoets — Tue, 03 Apr 2012 13:02:36 GMT

Thanks again Anna!

However, still 2 questions.

First question: when I want to use the Overpelt Fabriek site as the start and end depot, is it enough to just load it as a location for the Depots? You can see in attachment the example for route 1 for which I loaded 378 locations as the orders and the Overpelt Fabriek site as the Depot.

Second question: How can I add the number of orders in the area as the MaxOrderCount for each route?

Many thanks again! Problem is almost solved 🙂

Thomas

Forgot attachment. It should now be included.

Re: Distance calculation between

NaAn — Tue, 03 Apr 2012 15:13:16 GMT

First question: when I want to use the Overpelt Fabriek site as the start and end depot, is it enough to just load it as a location for the Depots? You can see in attachment the example for route 1 for which I loaded 378 locations as the orders and the Overpelt Fabriek site as the Depot.

Yes. Loading it once and use it for both start and end depot.

Second question: How can I add the number of orders in the area as the MaxOrderCount for each route?

Right click Routes NA class to open Route properties and set MaxOrderCount value there.

I see you opened ArcTool dialog in the screenshot which is not needed at all. I would highly recommend you to go through the tutorial because all those questions are answered there. Also you can open the layer I created for you in my previous attachment to get a good understanding.

Good luck!

Anna