One of the many geo formats that TileMill supports is a spreadsheet, specifically a comma-separated values (CSV) file. We want to start by working with a basic spreadsheet to show how easy it is to make a simple point map.
To import data into TileMill as a CSV file you need column headings on the first row. The CSV must also contain columns with latitude and longitude geographic coordinates. We have hard coded TileMill to look at the column headers for any mention of “lat” or “latitude”, so something like “geo_longitude” will even work.
If your CSV contains place names or addresses instead of lat/lon coordinates, you will have to geocode the data before it will work in TileMill. We have a plugin for Google Docs that makes geocoding easy.
In this crash course, we’ll use earthquake data from the USGS to make a map showing points for earthquakes that have occurred.
#countriesstyled with some example CartoCSS code.
earthquakesin the “ID” field. You’ll use this ID to to reference this layer in CartoCSS selectors.
http://earthquake.usgs.gov/earthquakes/feed/csv/2.5/weekinto the “Datasource” field.