DuckDB Spatial GeoJSON Analysis

A static web application that performs spatial queries and geoprocessing directly in the browser using DuckDB WebAssembly.

Overview

This application performs spatial queries of GeoJSON data without requiring server-side processing. All computations run entirely in the browser using web assembly.

Technology Stack

• DuckDB WASM: SQL engine
• Leaflet.js: Interactive map visualization
• D3.js: Dynamic table rendering and data visualization

Getting Started

Running Locally

Since this is a static web application that uses ES6 modules, you need to serve it over HTTP:

# Using Python
python -m http.server 8000

# Using Node.js
npx serve .

# Using PHP
php -S localhost:8000

Then open http://localhost:8000 in your browser.

Usage

1. Set Data Source: Enter a GeoJSON URL in the source field
2. Write Queries: Use SQL with {SOURCE} placeholder for the data source
3. Execute: Run spatial analysis queries in real-time
4. Visualize: View results in both table and map formats

Example Queries

-- Calculate areas of polygons
WITH datasource AS (SELECT * FROM ST_Read({SOURCE}))
SELECT properties.name, 
       ST_Area(geom) as area_sq_degrees,
       ST_AsGeoJSON(geom) as geometry
FROM datasource 
ORDER BY area_sq_degrees DESC 
LIMIT 10;

-- Find features within bounding box
WITH datasource AS (SELECT * FROM ST_Read({SOURCE}))
SELECT properties.name, ST_AsGeoJSON(geom) as geometry
FROM datasource 
WHERE ST_Within(geom, ST_MakeEnvelope(-123, 48, -121, 49));

-- Calculate centroids
WITH datasource AS (SELECT * FROM ST_Read({SOURCE}))
SELECT properties.name, 
       ST_AsText(ST_Centroid(geom)) as centroid
FROM datasource;

Spatial Functions

The application provides access to DuckDB's spatial extension functions:

• ST_Read() - Read spatial data from remote sources
• ST_AsGeoJSON() - Convert geometry to GeoJSON
• ST_Area() - Calculate area of geometries
• ST_Centroid() - Find centroid of geometries
• ST_Within() - Spatial containment testing
• ST_MakeEnvelope() - Create bounding box geometries
• ST_Distance() - Calculate spatial distances

Browser Requirements

• Modern browser with WebAssembly support
• JavaScript ES6 modules support
• CORS-enabled for fetching remote GeoJSON files

Development

The application consists of three main files:

• index.html - Main interface with Bootstrap UI
• script.js - JavaScript module handling DuckDB initialization and spatial operations
• style.css - Custom styling for table and map components

---