Georeference by Longitude and Latitude
Georeferencing is a CARTO service that gathers location data, from many different sources, to get the geographical coordinates associated with latitude/longitude columns, city names, postal codes, administrative boundaries, IP addresses, or street addresses. Since CARTO uses coordinates to plot data, the more finite your data (such as an address), the better your results (versus a city name).
CHEATSHEET: Georeference Types
The following types of location text can be geocoded and applied to your data:
- Longitude and Latitude: Generates location points using two parameter columns, one for longitude values and one for latitude values.
- Cities: Generates location points using a single parameter column with city name values. For greater accuracy, you can specify a column to be used for the admin. region names, or alternatively, specify a column for country names. For both admin. regions and country names, you can enter custom values by typing in the name (if the data is within a single region or country. For example, manually type in and select `United States`).
- Countries: Requires a single parameter column with country names to generate location border geometries as polygons.
- Admin. Regions: Requires a single parameter column with admin. region names to generate location points. You can also specify a column to be used for country names (if all are unique), or alternatively, type in the custom country name.
- Postal Codes: If your dataset consists of a column with postal codes, this option geocodes those values to generate location points. Your input data must be a text column. You can also specify a column to be used as a country names, similar to the Admin. Regions option. For specific details about how CARTO geocodes US zip codes, see the Postal Code Geocoder section in the Data Servies API documentation.
- IP Addresses: Geocodes your data into point geometries for IP addresses. This is useful if you are analyzing location data based on a set of user’s IP addresses.
- Street Addresses: Geocodes your data into a point geometry for a street address. You can specify the column to be used for the street addresses, in addition to the columns to be used for the city, state and country. You can also specify custom fields using the Advanced Mode.
The Georeference analysis in CARTO Builder enables you to generate location coordinates directly from a map layer. For this guide, let’s convert the location of Paris addresses by latitude and longitude.
Geocode Data into Point Geometries
We will use the location of Paris addresses, provided by openaddresses.io. This example displays the intense flooding that occurred in Paris; similar to the flood that occurred in 1910. The data is derived from Open Data of Paris, and the results are applied as point coordinates.
- Import the template .carto file, packaged from “Download resources” of this guide and create the map. Builder opens with Paris data as the first map layer, Natural_water as the second map layer, and Flood_zone as the third map layer.
Click on “Download resources” from this guide to download the zip file to your local machine. Extract the zip file to view the .carto file(s) used for this guide.
Notice that the Paris map layer does not identify what type of geometry the data contains.
- Switch to the Data View of the Paris map layer and you will notice that there are various columns with address information.
The Data View and Map View appear as icons on your map visualization when a map layer is selected. Click to switch between viewing your connected dataset as a table, or show the map view of your data.
Since the original data is in French, the translation of languages may complicate the geocoding of data. We will use the
lat columns from our dataset to georeference all of the geometry coordinates.
Click the ANALYSIS tab to add an analysis to the Paris map layer.
Select Georeference from the Add a new analysis options.
Keep Longitude and Latitude selected as the Georeference TYPE.
You must enter the LATITUDE and LONGITUDE parameters before applying the analysis. For this example, select the lat and lon columns from the Paris dataset.
Click APPLY. The analysis confirmation dialog appears, which you can use to apply styling.
- Click STYLE THIS ANALYSIS to visually enhance the buildings within the flood-zone.
- Click on the SIZE value and change it to 1.5. (Be sure to click on the size, not the color, from the SIZE/COLOR options).
- Click on the COLOR. The SOLID tab opens by default. Use the color modifier to change the solid fill color to black.
- Click on the STROKE size and change the value to 0.
Optionally, download the final .carto file from the “Download resources” of this guide to see the styling options that were applied.
The analysis geocoded the Paris data into point geometries, and the Georeference analysis is linked to the map layer. You can continue to explore the point geometry data for Paris.
Geocode with the API
If you are a developer and have access to the CARTO Engine’s to manage your data, view the Geocoding Functions that can be applied with the Data Services API.
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