Help with GIS extension

[vidus...@gmail.com]

Hi All 

I am trying to move my agents along the roads on a multi destination trip and want to calculate total distance travelled along the road drinng whole run. I am using Path finding model using the A-star algorithm in Netlogo - GMU_roads model https://github.com/YangZhouCSS/roads/ to get coding help to get roads shapefile in NetLogo and to make my agents move to multiple locations along the roads. 

I have a global variable called total-distance-travelled to store total travel distance in one year (= one run). However, my world is quite large (i.e. whole state) as compared to the world in the GMU model (roads withing a university campus). Therefore, I am getting runtime error "your model is too large ....". 

Can anyone suggest any other approch or example model that can help me. 

I thougt of having a patch variable roads? and assign the values using gis:intersecting but it gives me error (see below my code) 

extensions [gis]

globals [ roads-dataset total-distance-travelled ]

turtles-own [ 

my-home               ; patch where turtle is generated randomly

previous-target     ; initialize as nobody updated as turtle moves i.e. next-target becomes                                       previous target after one movement 

next-target              ; turtle finds closest patch with sp-ric value > 0 as next-target 

distance-travelled  ; distance between previous-target and next-target

patches-own [ 

roads?  ; True is patch intersects roads shapefile

sp-rich ; species richness at the patch randomly assigned between 0 to 9 

               (set sp-rich random 10) 

to setup-turtles

  create- turtles   number-of-turtles ; create turtles based on slider

  ask  turtles   [

  setxy random-xcor random-ycor

  set color white

  set shape "person"

  set previous-target nobody

  set my-home patch-here

  set pcolor brown

  ]

end

to  setup-roads

  set roads-dataset gis:load-dataset  "data/roads_WA.shp"

  gis:set-world-envelope ( gis:envelope-of  roads-dataset   )

  ifelse ( patch-set  gis:intersecting  roads-dataset  ) [set roads? true ] [ set roads? false ]  

end

to go

 if ticks > 365 [ stop]

 ask beekeepers [

 move

 calculate-distance

  ]

  tick

end

to move

  ask turtles [ 

    if [sp-rich ] of patch-here = 0

  [ 

 ifelse roads? = true

   [ fd 1] [ right 360  fd 1 ]

      move-to next-target

      set distance-travelled distance previous-target next-target 

  ] ]

end

to-report next-target

 if previous-target = nobody  [

    ask turtles [ set next-target min-one-of patches with [ sp-rich > 0] [distance myself] ] 

   ]

end

Highlighted part is not working. I am not sure why.

Not sure how to update total-distance-travelled. 

Also, if I want travel-distance calculated for each turtle seperately, total-distance-travelled should be a turtle variable rather than global right? 

I would truely appreciate any help with this part of coding. 

Thank you 

Kind Regards

Vidushi

[Stephen Guerin]

Re: the error in your line:

 ifelse ( patch-set  gis:intersecting  roads-dataset  ) [set roads? true ] [ set roads? false ]  

Note in the documentation for gis:intersecting, patch-set is in italics, which means you need to provide a patch-set in its place. eg, your statement could look like:

          ask patches gis:intersecting roads-dataset [set roads? true]

Instead of dealing with roads as patch variables, it might be better to deal with the road network as a collection of turtles and links like in Yang Zhou's model that you referenced. You will need some type of network representation to use their A* approach anyway. Also, for memory issues, note how the road network was simplified in their model to optimize performance.

-Stephen
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