Utility to generate TopoJSON maps for Catalonia
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README.md

Utility to generate TopoJSON maps for Catalonia

This repository provides a utility to generate TopoJSON maps for Catalonia using the source maps provided by ICGC (Base municipal).

You may find this article useful to better understand what this utility does.

provincies
comarques
municipis

NOTE: Source maps are produced by ICGC and are subject to terms of use.

Preliminary requirements

Regarding software, the first requirement is the TopoJSON host tool, topojson, which in turn requires Node.js. If you are on OS X, and assuming you use brew, you can easily get both by typing:

$ brew install node
$ npm install -g topojson

In case of converting from one coordinate system to another you will also need GDAL. It can also be installed using brew:

$ brew install gdal

Getting started

To get started, clone this repository:

git clone https://github.com/teslabs/cat-topojson

Once done, you can generate the maps by simply typing:

make

The following maps are generated in the topo/ directory:

  • cat-caps.json: Location of the capital cities for each municipality
  • cat-municipis.json: Municipalities polygons
  • cat-comarques.json: Counties polygons
  • cat-provincies.json: Provinces polygons
  • cat.json: Combination of all of the above

Using the default parameters will generate projected maps (see all available parameters and their defaults below) using the Base municipal in 1:50 scale. You can open any of the examples to verify the generated maps.

Parameters

Geographical coordinates

By default projected maps are generated, as ICGC source maps are already projected. However, you can also generate maps in geographical coordinates by setting the GEO parameter. By default it will generate maps in the WGS-84 coordinate system. You can change this by setting GEO_COORD to any of the supported coordinate systems by ogr2ogr.

Dimensions

When generating projected maps, three parameters can be used to control the dimensions of the generated map: WIDTH (default to 500 px), HEIGHT and MARGIN.

Simplification and quantization

Simplification can be set using the SIMPLIFICATION parameter. It defaults to 2 px2 for projected maps and to 10-8 sr for geographic coordinates.

Quantization can be set using the QUANTIZATION parameter. It has no default, which means that topojson default (104) is used.

Maps version

ICGC maps file names are in the format bm[eeee]mv33sh1f{xx}[m]_[aaaammdd]_[c].shp where:

  • eeee is the scale (i.e., 50, 250, 1000)
  • m is the frame coordinate reference (only 1 is available, meaning EPSG:25831 - ETRS89 / UTM zone 31N)
  • aaaammdd is the maps reference date (e.g. 20150501)
  • c is the distribution revision (e.g. 0)
  • xx identifies the map (e.g. mp is for municipalities polygons)

A couple of parameters can be set to change the maps used: SCALE (default to 50) and DATE (default to 20150501). Source maps are found inside the sources folder and are subject to terms of use (see LICENSE in sources).

Examples

You can verify that the maps have been generated properly by opening any of the examples found in examples. You will first need to link or copy the generated topo folder containing the maps and launch them using an HTTP server, e.g.

cd examples/
ln -s ../topo .
python -m SimpleHTTPServer

example-proj.html requires projected maps to work properly. As already said, projected maps are generated by default. Parameters may be set like this:

make WIDTH=250 MARGIN=10 SIMPLIFICATION=10

example-geo.html requires maps in geographical coordinates to work properly. The simplest way to generate them using defaults is to just set GEO:

make GEO=1