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Cartogram generation code

How to get started:

• Install PostgreSQL and PostGIS.

• Load the standard SRSs, if they’re not already loaded:

   psql < /usr/local/share/postgis/spatial_ref_sys.sql
  

• Add World Robinson as well:

   # from http://spatialreference.org/ref/esri/54030/postgis/
   psql <<END
   INSERT into spatial_ref_sys (
       srid, auth_name, auth_srid,
       proj4text, srtext
   ) values (
       954030, 'esri', 54030,
       '+proj=robin +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs ',
         'PROJCS["World_Robinson",GEOGCS["GCS_WGS_1984",DATUM["WGS_1984",SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Robinson"],PARAMETER["False_Easting",0],PARAMETER["False_Northing",0],PARAMETER["Central_Meridian",0],UNIT["Meter",1],AUTHORITY["EPSG","54030"]]'
   );
   END
  

• (Note that PROJ.4 < 4.8 has an error in its implementation of the Robinson projection: http://trac.osgeo.org/proj/ticket/113)

• Create the schema using sql/schema.sql and define the functions using sql/functions.sql.

• Load whatever maps you intend to use from sql/maps.sql, or define your own.

• Prepare your dataset in CSV format.

• Run bin/load-data.py to load your data into the database.

• Run bin/density-grid.py to export a density grid.

• Run cart to create a cartogram grid from it.

• Run bin/as-js.py to generate a JSON file of SVG path data.

• Use this JSON data to make a beautiful web app.

A script for making cartograms from multiple datasets might look something like this:

CART=/usr/local/cartograms  # Or wherever you have installed it
for dataset in foo bar baz # Whatever your datasets are called
do
    "$CART"/bin/delete-data.py "myproject:$dataset"  # Replace “myproject” with your project name
    "$CART"/bin/load-data.py "myproject:$dataset" "data/input/$dataset.csv" countries-10m-3.1.0 Alpha-2 Value

    "$CART"/bin/density-grid.py --dataset=myproject:"$dataset" --map=world-10m-3.1.0-robinson > data/cart/density/"$dataset".density

    cart 1500 750 data/cart/density/"$dataset".density data/cart/output/"$dataset".cart

    "$CART"/bin/as-js.py --map=world-10m-3.1.0-robinson data/cart/output/"$dataset".cart -o data/output/"$dataset".js
done