Explore all supported map projections in CARTO.

1. Create a clean dataset of map projections from PostGIS spatial_ref_sys table:

• First, apply the following query in any dataset:

  WITH a AS(
    SELECT 
      auth_srid,
      string_to_array(srtext, '"') AS sr_text
    FROM 
      spatial_ref_sys
    )
  SELECT 
    auth_srid, 
    sr_text[2] AS geogcs,
    sr_text[4] AS datum,
    sr_text[6] AS spheroid,
    sr_text[16] AS primem,
    sr_text[22] AS unit
  FROM a

• Secondly, create a new dataset from this query. Rename it as map_proj.

• Third, add a new field called notes with some comments about each projection from Wikipedia [1].

2. Create a map with the Editor with ne_50m_land dataset as the unique layer and a color background as basemap.

3. Build a CartoDB.js application with a dropdown menu in order to select a map projection*.

[1] https://en.wikipedia.org/wiki/List_of_map_projections