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Supabase Backend as a Service · Lesson

Advanced Geospatial Data (PostGIS)

Integrate PostGIS to handle complex geospatial data, perform location-based queries, and build mapping features within your app.

Advanced Geospatial Data (PostGIS) is a free Supabase Backend as a Service lesson on CoddyKit — lesson 2 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Supabase Backend as a Service learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Unlocking Geospatial Power

Welcome to Advanced Geospatial Data (PostGIS)! In this lesson, we'll explore how to handle location-based data directly within your Supabase database.

Geospatial data is crucial for apps that deal with maps, locations, navigation, or proximity services.

What is PostGIS?

PostGIS is a powerful, open-source extension for PostgreSQL that adds support for geographic objects.

  • It transforms your database into a spatial database.
  • It allows you to store, query, and analyze location data (points, lines, polygons).
  • Supabase, being built on PostgreSQL, fully supports PostGIS.

Why Use PostGIS?

Traditional databases store locations as separate latitude/longitude columns, making complex queries difficult.

PostGIS provides specialized functions to:

  • Calculate distances between points.
  • Find locations within a specific radius.
  • Determine if points are inside an area.
  • Perform complex spatial joins and analyses.

Enabling PostGIS Extension

Before using PostGIS, you need to enable the extension in your Supabase project. This is a one-time step done via the SQL Editor in your Supabase dashboard.

Simply run the following command:

CREATE EXTENSION IF NOT EXISTS postgis;

Geospatial Data Types

PostGIS introduces new data types to store spatial information:

  • GEOMETRY: Stores data on a 2D Cartesian plane (flat earth model). Good for small-scale, local areas.
  • GEOGRAPHY: Stores data on a spherical globe (real-world coordinates). Best for large-scale, global applications.

We'll primarily use GEOMETRY for simplicity in examples, but GEOGRAPHY is often preferred for real-world distances.

Creating a Table with Spatial Data

Let's create a table to store points of interest, like coffee shops, using a GEOMETRY column. The SRID (Spatial Reference ID) 4326 is standard for latitude/longitude.

CREATE TABLE coffee_shops (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  name TEXT NOT NULL,
  location GEOMETRY(Point, 4326)
);

Inserting Geospatial Points

To insert a point, we use the ST_GeomFromText() function, which converts a Well-Known Text (WKT) representation into a PostGIS geometry object. The format is 'POINT(longitude latitude)'.

INSERT INTO coffee_shops (name, location) VALUES
('Espresso Hub', ST_GeomFromText('POINT(-0.1278 51.5074)', 4326)),
('Bean Scene', ST_GeomFromText('POINT(-0.1419 51.5085)', 4326)),
('Daily Grind', ST_GeomFromText('POINT(-0.1000 51.5200)', 4326));

Finding Nearest Locations

One common task is finding locations near a specific point. We can use ST_Distance() to calculate the distance between two geometry points. The unit of distance depends on the SRID (e.g., meters for 4326 on GEOGRAPHY type, degrees for GEOMETRY type).

Here, we find shops near a reference point (e.g., user's current location).

SELECT
  name,
  ST_Distance(
    location,
    ST_GeomFromText('POINT(-0.1300 51.5090)', 4326)
  ) AS distance_in_degrees
FROM
  coffee_shops
ORDER BY
  distance_in_degrees
LIMIT 1;

Efficient Proximity Search

For more efficient proximity searches, especially when working with GEOGRAPHY types for real-world distances, ST_DWithin() is excellent. It checks if two geometries are within a specified distance.

Let's find all coffee shops within 1000 meters of a specific point using GEOGRAPHY for accurate distance calculation.

SELECT
  name
FROM
  coffee_shops
WHERE
  ST_DWithin(
    location::geography,
    ST_GeomFromText('POINT(-0.1300 51.5090)', 4326)::geography,
    1000 -- 1000 meters
  );

PostGIS Query Check

You've learned how to enable PostGIS, create tables with spatial columns, and insert/query geospatial data.

Which PostGIS function would you typically use to find all points of interest that are located within 500 meters of a user's current position, assuming you're using the GEOGRAPHY type?

Recap: Geospatial Data

Great job! You've taken your first steps into the world of geospatial data with PostGIS and Supabase.

  • We enabled the PostGIS extension.
  • Learned about GEOMETRY and GEOGRAPHY types.
  • Created tables and inserted data using WKT.
  • Performed basic spatial queries like distance calculation and proximity searches with ST_Distance() and ST_DWithin().

PostGIS opens up a vast array of possibilities for location-aware applications!

Frequently asked questions

Is the “Advanced Geospatial Data (PostGIS)” lesson free?

Yes — the full text of “Advanced Geospatial Data (PostGIS)” is free to read here on the web, and the Supabase Backend as a Service course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Supabase Backend as a Service course, upgrade to CoddyKit PRO.

What will I learn in “Advanced Geospatial Data (PostGIS)”?

Integrate PostGIS to handle complex geospatial data, perform location-based queries, and build mapping features within your app. You practise Supabase Backend as a Service with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Supabase Backend as a Service?

No prior experience is required. Supabase Backend as a Service on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 3, so you can start here or from the beginning and move at your own pace.

How long does the “Advanced Geospatial Data (PostGIS)” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Supabase Backend as a Service lesson?

Yes. Every Supabase Backend as a Service lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Utilizing Postgres Extensions
  2. Advanced Geospatial Data (PostGIS)
  3. Full-Text Search and Vector Embeddings with pgvector
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