extensions [ gis ]
globals [ cities-dataset
          rivers-dataset
          countries-dataset
          elevation-dataset ]
breed [ city-labels city-label ]
breed [ country-labels country-label ]
breed [ country-vertices country-vertex ]
breed [ river-labels river-label ]
patches-own [ population country-name elevation ]

to setup
  ca
  ; Note that setting the coordinate system here is optional, as
  ; long as all of your datasets use the same coordinate system.
  gis:load-coordinate-system (word "data/" projection ".prj")
  ; Load all of our datasets
  set cities-dataset gis:load-dataset "data/cities.shp"
  set rivers-dataset gis:load-dataset "data/rivers.shp"
  set countries-dataset gis:load-dataset "data/countries.shp"
  set elevation-dataset gis:load-dataset "data/world-elevation.asc"
  ; Set the world envelope to the union of all of our dataset's envelopes
  gis:set-world-envelope (gis:envelope-union-of (gis:envelope-of cities-dataset)
                                                (gis:envelope-of rivers-dataset)
                                                (gis:envelope-of countries-dataset)
                                                (gis:envelope-of elevation-dataset))
end

; Drawing point data from a shapefile, and optionally loading the
; data into turtles, if label-cities is true
to display-cities
  ask city-labels [ die ]
  foreach gis:feature-list-of cities-dataset
  [ gis:set-drawing-color scale-color red (gis:property-value ? "POPULATION") 5000000 1000
    gis:fill ? 2.0
    if label-cities
    [ ; a feature in a point dataset may have multiple points, so we
      ; have a list of lists of points, which is why we need to use
      ; first twice here
      let location gis:location-of (first (first (gis:vertex-lists-of ?)))
      ; location will be an empty list if the point lies outside the
      ; bounds of the current NetLogo world, as defined by our current
      ; coordinate transformation
      if not empty? location
      [ create-city-labels 1
        [ set xcor item 0 location
          set ycor item 1 location
          set size 0
          set label gis:property-value ? "NAME" ] ] ] ]
end

; Drawing polyline data from a shapefile, and optionally loading some
; of the data into turtles, if label-rivers is true
to display-rivers
  ask river-labels [ die ]
  gis:set-drawing-color blue
  gis:draw rivers-dataset 1
  if label-rivers
  [ foreach gis:feature-list-of rivers-dataset
    [ let centroid gis:location-of gis:centroid-of ?
      ; centroid will be an empty list if it lies outside the bounds
      ; of the current NetLogo world, as defined by our current GIS
      ; coordinate transformation
      if not empty? centroid
      [ create-river-labels 1
          [ set xcor item 0 centroid
            set ycor item 1 centroid
            set size 0
            set label gis:property-value ? "NAME" ] ] ] ]
end

; Drawing polygon data from a shapefile, and optionally loading some
; of the data into turtles, if label-countries is true
to display-countries
  ask country-labels [ die ]
  gis:set-drawing-color white
  gis:draw countries-dataset 1
  if label-countries
  [ foreach gis:feature-list-of countries-dataset
    [ let centroid gis:location-of gis:centroid-of ?
      ; centroid will be an empty list if it lies outside the bounds
      ; of the current NetLogo world, as defined by our current GIS
      ; coordinate transformation
      if not empty? centroid
      [ create-country-labels 1
        [ set xcor item 0 centroid
          set ycor item 1 centroid
          set size 0
          set label gis:property-value ? "CNTRY_NAME" ] ] ] ]
end

; Loading polygon data into turtles connected by links
to display-countries-using-links
  ask country-vertices [ die ]
  foreach gis:feature-list-of countries-dataset
  [ foreach gis:vertex-lists-of ?
    [ let previous-turtle nobody
      let first-turtle nobody
      ; By convention, the first and last coordinates of polygons
      ; in a shapefile are the same, so we don't create a turtle
      ; on the last vertex of the polygon
      foreach but-last ?
      [ let location gis:location-of ?
        ; location will be an empty list if it lies outside the
        ; bounds of the current NetLogo world, as defined by our
        ; current GIS coordinate transformation
        if not empty? location
        [ create-country-vertices 1
          [ set xcor item 0 location
            set ycor item 1 location
            ifelse previous-turtle = nobody
            [ set first-turtle self ]
            [ create-link-with previous-turtle ]
            set hidden? true
            set previous-turtle self ] ] ]
      ; Link the first turtle to the last turtle to close the polygon
      if first-turtle != nobody and first-turtle != previous-turtle
      [ ask first-turtle
        [ create-link-with previous-turtle ] ] ] ]
end

; Using gis:intersecting to find the set of patches that intersects
; a given vector feature (in this case, a river).
to display-rivers-in-patches
  ask patches [ set pcolor black ]
  ask patches gis:intersecting rivers-dataset
  [ set pcolor cyan ]
end

; Using gis:apply-coverage to copy values from a polygon dataset
; to a patch variable
to display-population-in-patches
  gis:apply-coverage countries-dataset "POP_CNTRY" population
  ask patches
  [ ifelse (population > 0)
    [ set pcolor scale-color red population 500000000 100000 ]
    [ set pcolor blue ] ]
end

; Using find-one-of to find a particular VectorFeature, then using
; gis:intersects? to do something with all the features from another
; dataset that intersect that feature.
to draw-us-rivers-in-green
  let united-states gis:find-one-feature countries-dataset "CNTRY_NAME" "United States"
  gis:set-drawing-color green
  foreach gis:feature-list-of rivers-dataset
  [ if gis:intersects? ? united-states
    [ gis:draw ? 1 ] ]
end

; Using find-greater-than to find a list of VectorFeatures by value.
to highlight-large-cities
  gis:set-drawing-color yellow
  foreach gis:find-greater-than cities-dataset "POPULATION" 10000000
  [ gis:draw ? 3 ]
end

; Drawing a raster dataset to the NetLogo drawing layer, which sits
; on top of (and obscures) the patches.
to display-elevation
  gis:paint elevation-dataset 0
end

to display-elevation-in-patches
  ; This is the preferred way of copying values from a raster dataset
  ; into a patch variable: in one step, using gis:apply-raster.
  gis:apply-raster elevation-dataset elevation
  ; Now, just to make sure it worked, we'll color each patch by its
  ; elevation value.
  let min-elevation gis:minimum-of elevation-dataset
  let max-elevation gis:maximum-of elevation-dataset
  ask patches
  [ ; note the use of the "<= 0 or >= 0" technique to filter out
    ; "not a number" values, as discussed in the documentation.
    if (elevation <= 0) or (elevation >= 0)
    [ set pcolor scale-color black elevation min-elevation max-elevation ] ]
end

; This is a second way of copying values from a raster dataset into
; patches, by asking for a rectangular sample of the raster at each
; patch. This is somewhat slower, but it does produce smoother
; subsampling, which is desirable for some types of data.
to sample-elevation-with-patches
  let min-elevation gis:minimum-of elevation-dataset
  let max-elevation gis:maximum-of elevation-dataset
  ask patches
  [ set elevation gis:raster-sample elevation-dataset self
    if (elevation <= 0) or (elevation >= 0)
    [ set pcolor scale-color black elevation min-elevation max-elevation ] ]
end

; This is an example of how to select a subset of a raster dataset
; whose size and shape matches the dimensions of the NetLogo world.
; It doesn't actually draw anything; it just modifies the coordinate
; transformation to line up patch boundaries with raster cell
; boundaries. You need to call one of the other commands after calling
; this one to see its effect.
to match-cells-to-patches
  gis:set-world-envelope gis:raster-world-envelope elevation-dataset 0 0
  cd
  ct
end

; This command also demonstrates the technique of creating a new, empty
; raster dataset and filling it with values from a calculation.
;
; This command uses the gis:convolve primitive to compute the horizontal
; and vertical Sobel gradients of the elevation dataset, then combines
; them using the square root of the sum of their squares to compute an
; overall "image gradient". This is really more of an image-processing
; technique than a GIS technique, but I've included it here to show how
; it can be easily done using the GIS extension.
to display-gradient-in-patches
  let horizontal-gradient gis:convolve elevation-dataset 3 3 [ 1 0 -1 2 0 -2 1 0 -1 ] 1 1
  let vertical-gradient gis:convolve elevation-dataset 3 3 [ 1 2 1 0 0 0 -1 -2 -1 ] 1 1
  let gradient gis:create-raster gis:width-of elevation-dataset gis:height-of elevation-dataset gis:envelope-of elevation-dataset
  let x 0
  repeat (gis:width-of gradient)
  [ let y 0
    repeat (gis:height-of gradient)
    [ let gx gis:raster-value horizontal-gradient x y
      let gy gis:raster-value vertical-gradient x y
      if ((gx <= 0) or (gx >= 0)) and ((gy <= 0) or (gy >= 0))
      [ gis:set-raster-value gradient x y sqrt ((gx * gx) + (gy * gy)) ]
      set y y + 1 ]
    set x x + 1 ]
  let min-g gis:minimum-of gradient
  let max-g gis:maximum-of gradient
  gis:apply-raster gradient elevation
  ask patches
  [ if (elevation <= 0) or (elevation >= 0)
    [ set pcolor scale-color black elevation min-g max-g ] ]
end


; Public Domain:
; To the extent possible under law, Uri Wilensky has waived all
; copyright and related or neighboring rights to this model.
@#$#@#$#@
GRAPHICS-WINDOW
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ticks
30.0

BUTTON
5
100
175
133
NIL
display-cities
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1
T
OBSERVER
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NIL
NIL
NIL
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BUTTON
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display-countries
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BUTTON
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setup\n
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SWITCH
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label-cities
label-cities
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SWITCH
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label-countries
label-countries
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1
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BUTTON
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NIL
display-rivers
NIL
1
T
OBSERVER
NIL
NIL
NIL
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SWITCH
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label-rivers
label-rivers
1
1
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BUTTON
5
340
175
373
NIL
display-rivers-in-patches
NIL
1
T
OBSERVER
NIL
NIL
NIL
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BUTTON
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413
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display-population-in-patches
NIL
1
T
OBSERVER
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NIL
NIL
1

BUTTON
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373
NIL
draw-us-rivers-in-green
NIL
1
T
OBSERVER
NIL
NIL
NIL
NIL
1

BUTTON
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380
365
413
NIL
highlight-large-cities
NIL
1
T
OBSERVER
NIL
NIL
NIL
NIL
1

CHOOSER
5
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175
55
projection
projection
"WGS_84_Geographic" "US_Orthographic" "Lambert_Conformal_Conic"
0

BUTTON
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175
453
NIL
display-countries-using-links
NIL
1
T
OBSERVER
NIL
NIL
NIL
NIL
1

BUTTON
395
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580
373
NIL
display-elevation
NIL
1
T
OBSERVER
NIL
NIL
NIL
NIL
1

BUTTON
395
420
580
453
NIL
sample-elevation-with-patches
NIL
1
T
OBSERVER
NIL
NIL
NIL
NIL
1

BUTTON
395
380
580
413
NIL
display-elevation-in-patches
NIL
1
T
OBSERVER
NIL
NIL
NIL
NIL
1

BUTTON
590
380
775
413
NIL
match-cells-to-patches
NIL
1
T
OBSERVER
NIL
NIL
NIL
NIL
1

BUTTON
590
340
775
373
NIL
display-gradient-in-patches
NIL
1
T
OBSERVER
NIL
NIL
NIL
NIL
1

BUTTON
185
420
365
453
NIL
clear-drawing
NIL
1
T
OBSERVER
NIL
NIL
NIL
NIL
1

@#$#@#$#@
## WHAT IS IT?

This model was built to test and demonstrate the functionality of the GIS NetLogo extension.

## HOW IT WORKS

This model loads four different GIS datasets: a point file of world cities, a polyline file of world rivers, a polygon file of countries, and a raster file of surface elevation. It provides a collection of different ways to display and query the data, to demonstrate the capabilities of the GIS extension.

## HOW TO USE IT

Select a map projection from the projection menu, then click the setup button. You can then click on any of the other buttons to display data. See the code tab for specific information about how the different buttons work.

## THINGS TO TRY

Most of the commands in the Code tab can be easily modified to display slightly different information. For example, you could modify `display-cities` to label cities with their population instead of their name. Or you could modify `highlight-large-cities` to highlight small cities instead, by replacing `gis:find-greater-than` with `gis:find-less-than`.

## EXTENDING THE MODEL

This model doesn't do anything particularly interesting, but you can easily copy some of the code from the Code tab into a new model that uses your own data, or does something interesting with the included data. See the other GIS code example, GIS Gradient Example, for an example of this technique.

## RELATED MODELS

GIS Gradient Example provides another example of how to use the GIS extension.

## CREDITS AND REFERENCES
@#$#@#$#@
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airplane
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circle 2
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turtle
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x
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@#$#@#$#@
NetLogo 5.1.0
@#$#@#$#@
setup
display-cities
display-countries
@#$#@#$#@
@#$#@#$#@
@#$#@#$#@
@#$#@#$#@
default
0.0
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0.2 0 0.0 1.0
link direction
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Line -7500403 true 150 150 210 180

@#$#@#$#@
0
@#$#@#$#@