Point-in-polygon with CARTO API

Locate which neighborhood you are working in via point-in-polygon.

Data events allow you to grab information about a point’s location, i.e. which polygon the point lies in.

This example illustrates how to set up two data events. Both take advantage of CARTO’s querying ability through the SQL API. The first one uses a nearest neighbor query to find the nearest brewery. The second example pulls in the name of the neighborhood polygon in which the point is contained.

These examples require having data stored in CARTO tables. If you are unsure of what the query should be returning, we recommend testing out example data:

https://denverstartup.carto.com/api/v2/sql?q=SELECT%20*%20FROM%20sanfran_neighborhoods%20where%20ST_Contains(the_geom,%20ST_GeomFromText(%27POINT(-122.4613380%2037.78048)%27,4326))

which returns:

{
	"rows": [{
		"cartodb_id": 801,
		"the_geom": "0106000020E61...",
		"the_geom_webmercator": "0106000020110F...",
		"restaurants": 147,
		"city": "San Francisco",
		"county": "San Francisco",
		"name": "Inner Richmond",
		"bike_park_count": 46,
		"bike_share_count": 0,
		"co_working": 0,
		"bus_stops": 131,
		"total": 324
	}]
}

Tip: To keep data private, you will want to use &api={secret_api_key} at the end of the URL

function nearestBrewery() {
	var query = 'SELECT * FROM denver_breweries ORDER BY the_geom <-> ST_Transform(CDB_LatLng(' + LONGITUDE() + ',' + LATITUDE() + '),4326) LIMIT 60';

	var options = {
    url: 'https://denverstartup.carto.com/api/v2/sql?f=geojson&q=' + encodeURIComponent(query)
  };

  REQUEST(options, function(error, response, body) {
    if (error) {
      ALERT('Error with request: ' + error);
    } else {
      data = JSON.parse(body);
      SETVALUE('nearest_brewery', data.rows[0].name);
    }
  });
}
ON('save-record', nearestBrewery);
ON('edit-record', nearestBrewery);
ON('click', 'nearest_brewery', nearestBrewery);

function identifyNeighborhood() {
	var query = "SELECT * FROM denver_neighborhoods WHERE ST_Contains(the_geom, ST_GeomFromText('POINT("+ LONGITUDE() + " " + LATITUDE()+ ")', 4326));"

	var options = {
    url: 'https://denverstartup.carto.com/api/v2/sql?f=geojson&q=' + encodeURIComponent(query)
  };

  REQUEST(options, function(error, response, body) {
    if (error) {
      ALERT('Error with request: ' + error);
    } else {
      data = JSON.parse(body);
      SETVALUE('neighborhood', data.rows[0].nbhd_name);
    }
  });
}
ON('save-record', identifyNeighborhood);
ON('edit-record', identifyNeighborhood);
ON('click', 'neighborhood', identifyNeighborhood);