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高度な地理空間データ（PostGIS）

PostGISを統合し、複雑な地理空間データの処理、位置情報に基づくクエリの実行、アプリ内の地図機能の構築方法を学びます。

「高度な地理空間データ（PostGIS）」はCoddyKit上の無料Supabase Backend as a Serviceレッスンです。これはレッスン2/3です。下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。これはSupabase Backend as a Service学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Supabase Backend as a Serviceコースには全3レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

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!

よくある質問

「高度な地理空間データ（PostGIS）」レッスンは無料ですか？

はい。「高度な地理空間データ（PostGIS）」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Supabase Backend as a Serviceコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Supabase Backend as a Serviceコースには全3レッスンが含まれています。

「高度な地理空間データ（PostGIS）」で何を学びますか？

PostGISを統合し、複雑な地理空間データの処理、位置情報に基づくクエリの実行、アプリ内の地図機能の構築方法を学びます。ブラウザで直接実行するハンズオンコードでSupabase Backend as a Serviceを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Supabase Backend as a Serviceを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのSupabase Backend as a Serviceは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。これはレッスン2/3です。

「高度な地理空間データ（PostGIS）」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このSupabase Backend as a Serviceレッスンでコードを書いて実行できますか？

はい。すべてのSupabase Backend as a Serviceレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

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