Creating a basemap in WGS84

Question

I am trying to create a base map suitable for overlaying data that is in SRS EPSG:4326 using CartoDB following the projections tutorial. I have other projections working, but not one for this.

So using:

  SELECT cartodb_id, ST_Transform(the_geom, 4326) AS the_geom_webmercator
  FROM world_borders_hd 

It does not seem to return any geometries plotted in the tiles.

From a comment on the CartoDB academy issue I posted, I presume this is something to do with a scale that needs to be applied in the transformation from degrees to meters.

Can anyone advise me what I need to do in the SQL to get a zoom 0 tile that would look like this?

Answer 1

You can scale the coordinates like this to map the circumference in longitude (180 - -180 = 360) to the diameter of the earth in meters (40.075 million m) which is what web mercator uses. The conversion is 40,075,000 / 360 = 111319.44444444444444

SELECT ST_Scale(the_geom, 111319.44444444444444, 111319.44444444444444) As the_geom_webmercator 
FROM world_borders_hd