During a casual chat in the MalaGIS WeChat group, someone asked when GIS skills become most useful in daily life. Answers ranged from food delivery route optimization to travel planning, but the most insightful response was "assessing location (including Feng Shui) for property purchases". Among factors like sunlight access—a critical yet often overlooked parameter—most standard map apps fail to provide this data, requiring specialized GIS software (refer to methods in "ArcGIS 3D Handbook: Sunlight and 3D Path Analysis"). Recently, I discovered an online WebGIS application that simulates sunlight and shadows for any global location at any date—an excellent tool worth sharing.
Official site: https://shademap.app/
ShadeMap enables browser-based simulation of mountain, building, and tree shadows at any global coordinate for customizable dates/times. Users achieve precise, interactive sunlight and shadow analysis without client installations.
Technical Principle
ShadeMap employs ray casting technology at its core.
The tool casts rays from each map pixel toward the sun. If terrain, structures, or trees obstruct these rays, pixels render as shadows; otherwise, they display direct sunlight. Additionally, ShadeMap calculates cumulative daily sunlight hours or annual totals.
Tree shadows are simulated using satellite imagery combined with ML-derived canopy height estimates. While vertical accuracy has variance (±3 meters), it enables realistic dynamic tree-shade rendering.
Tech Stack Implementation
As explained by developers on Reddit, ShadeMap leverages:
Backend:
- Cloudflare Workers + R2 Storage
- Protomaps (vector tile service)
Frontend:
- Mapbox / MapLibre GL JS (map rendering)
- ViteJS (build tool)
- React (UI framework)
ShadeMap integrates open geospatial data sources (OpenStreetMap, Overture Maps Foundation, Mapbox Streets), defaulting to 3.1-meter height values (≈one-story height) where precise elevation is unavailable. Premium LiDAR/photogrammetric data (±30 cm accuracy) is available via paid subscription.
Application Scenarios
ShadeMap delivers high value across domains:
- Gardening, landscaping & ecology: Determine plant growth zones using sun exposure metrics
- Real estate & site selection: Evaluate property/land parcel sunlight conditions
- Solar energy potential: Aid photographers, filmmakers, and event planners in lighting assessment
- Outdoor activity planning: Optimize shade/sun positions for weddings, camping, hiking, fishing, or hunting
- Academic research & agriculture: Analyze sunlight distribution for ecological/agronomic studies
- Trail planning: Supports GPX/KML uploads to generate path-specific shade profiles
Future Roadmap
Planned developments include:
- Incorporating clouds/weather for dynamic temperature modeling in shaded areas
- Integration with GIS platforms (e.g., QGIS)
- Mobile app development enabling "real-time shady route navigation"