🐻 Bearing Compass 🧭

Calculate true and magnetic bearings between waypoints on a map.

Usage: Open in your browser. Click to add waypoints, double-click to zoom.

Features

• Calculate true bearing, magnetic bearing, declination, and distance for route legs
• WMM2025 magnetic model (valid 2025-2030) embedded, no API calls
• Mobile-optimized with swipeable result cards
• Shareable URLs with encoded waypoints
• Color-coded routes

Tech Stack

• Leaflet.js - Map rendering
• OpenTopoMap - Topographic tiles
• geomagJS - WMM2025 implementation
• Single self-contained HTML file

Methodology

True Bearing: Forward azimuth formula on WGS84 ellipsoid Distance: Haversine formula (great circle) Magnetic Bearing: True bearing adjusted by WMM2025 declination

Magnetic Bearing = True Bearing - Declination

Declination accuracy: ±1°, sufficient for navigation.

Data Sources

• WMM2025: NOAA NCEI (public domain)
• Map tiles: OpenTopoMap / OpenStreetMap (CC-BY-SA 3.0)

Credits

• Christopher Weiss (@cmweiss) - geomagJS
• Vladimir Agafonkin - Leaflet.js
• NOAA NCEI - World Magnetic Model