{"version":"1.0","type":"rich","title":"Course notes","description":"The visualization maps New York City’s census tracts, coloring each by the density of public bicycle racks. It first simplifies tract geometries using PostGIS’s `ST_SimplifyPreserveTopology`, then counts rack intersections with `ST_Intersects` to populate a numeric column, normalizing the count by `shape_area` via SQL. The final map, rendered with CartoDB’s default styling, displays the normalized rack density as a choropleth, revealing spatial patterns in bike infrastructure across neighborhoods.","provider_name":"VizHub AI Studio","provider_url":"https://next.vizhub.com","html":"<iframe src=\"https://next.vizhub.com/viz/gist-6c1f7fe885669bc2203f?mode=embed\" width=\"960\" height=\"500\" scrolling=\"no\" frameborder=\"1\"></iframe>","width":960,"height":500,"cache_age":3600}