New Leaflet plugin to handle multiple TileMill layers

My setup for the population density map of New Zealand made it easy to create new choropleth maps with New Zealand census data. This blog post explains how you can use Leaflet to switch between multiple interactive layers created with TileMill.

I wanted to create a map of the social geography of New Zealand, using the Index of Deprivation from the Department of Public Health, University of Otago. I downloaded a Excel sheet containing data for the 2006 census area units, which I also used for my population density map. I simply added the data to the same SQLite database, and created the map using the same techniques described in two previous blog posts (1, 2).

The Index of Deprivation is constructed from nine Census 2006 variables, and provides a summary deprivation score from 1 to 10. A score of 1 is allocated to the least deprived 10 percent of areas, and 10 is allocated to the most deprived 10 percent of areas. You'll find more information about the index in the Atlas of Socioeconomic Deprivation in New Zealand.

Wax allows you to easily add an interactive TileMill map to Leaflet or other mapping libraries. Adding more than one interactive layer is not that straightforward, so I wrote a Leaflet plugin:


This plugin allows you to switch between various layers (interactive or not) and it will automatically load and display map legends, and remove the elements when they're no longer needed. It's easy to use the plugin:

Include a wax property when you create a tile layer, containing a TileJSON object or an URL to a TileJSON file.  

var population = L.tileLayer('tiles/nz-popden/{z}/{x}/{y}.png', {
  attribution: 'Statistics New Zealand',
  wax: 'tiles/nz-popden.tilejson'
});

After you've created the map you simply add:

L.wax(map);
 
That's it! :-)

You can try to switch between the various basemaps using the layers control below:



Fullscreen map