Zagreb Pub Shade Map

Interactive map showing when Zagreb pubs and bars are in sun or shade throughout the day, combined with a 3-day weather forecast.

Features

• All pubs, bars, and cafes with outdoor seating in Zagreb from OpenStreetMap
• 2.5D shadow casting using building footprints and heights at 5-minute resolution
• Visual sun/shade timeline per pub for today and the next 3 days
• 3-day weather forecast from Open-Meteo (free, no API key required)
• Interactive Leaflet.js map with dark theme
• Markers coloured by current shade status (yellow = sun, grey = shade)

How It Works

1. Building footprints and heights are fetched from OpenStreetMap and cached locally
2. Sun position (azimuth + elevation angle) is computed for Zagreb at 5-minute intervals using pysolar
3. For each time step, a shadow polygon is projected from each building footprint opposite the sun:
   • shadow_length = building_height / tan(sun_elevation)
   • Shadow polygon = convex hull of footprint vertices + offset vertices
4. Each pub is checked against shadow polygons of nearby buildings (≤ 200 m radius)
5. Results are served via FastAPI and visualised on a Leaflet map

Data Sources

Data	Source
Pubs / bars	OpenStreetMap via Overpass API
Building footprints & heights	OpenStreetMap (height / building:levels tags)
Sun position	pysolar
Weather forecast	Open-Meteo

Upgrading to Official Zagreb 3D Data

The City of Zagreb publishes high-accuracy LoD 2.2 3D building models via ArcGIS Scene Services (2022–2023 multisensor survey). These cover all 15 city districts and include precise Z_Min / Z_Max elevation per building mesh. Switching to this data source would meaningfully improve shadow accuracy.

• Hub: https://zg3d-zagreb.hub.arcgis.com/
• Base URL: https://services8.arcgis.com/Usi0jGQwMmBUpFjr/arcgis/rest/services/ZG3D_GC_{district}_2022/SceneServer
• Districts: Pescenica_Zitnjak, Gornji_Grad, Novi_Zagreb_zapad, Trnje, Brezovica, Novi_Zagreb_istok, Donja_Dubrava, Tresnjevka_jug, Crnomerec, Sesvete, Podsused_Vrapce, Gornja_Dubrava, Donji_Grad, Maksimir, Podsljeme

See backend/data_pipeline/fetch_buildings.py for integration notes.

Quick Start

# 1. Set up backend
cd backend
python -m venv venv
source venv/bin/activate
pip install -r requirements.txt

# 2. Fetch OSM data (run once, ~1-2 minutes)
python scripts/fetch_data.py

# 3. Start the API server (also serves the frontend)
uvicorn api.main:app --reload --port 8000

# 4. Open http://localhost:8000 in your browser

Architecture

pub-shade-map/
├── backend/
│   ├── data_pipeline/   # OSM data fetching & caching
│   ├── shadow/          # solar position + shadow geometry engine
│   ├── api/             # FastAPI app
│   └── scripts/         # CLI tools (fetch data, pre-compute shade)
├── frontend/
│   ├── index.html
│   ├── css/style.css
│   └── js/              # map.js, timeline.js, weather.js
└── data/                # cached GeoJSON + shade timelines (git-ignored)

Limitations & Future Work

• OSM building heights are incomplete; switching to ArcGIS ZG3D data would improve accuracy
• Shadow model is 2.5D (extruded footprints), not full 3D mesh ray-tracing
• No terrain/elevation model — all buildings treated as on flat ground
• Shade timelines are computed on demand; pre-computation script available for performance