Compass Bearing Calculator (Point to Point)

Because meridians converge: your heading is measured against local north, and local north's direction shifts as you move across the globe. A great circle is straight in the geodesic sense (no turning on the surface), but the reference grid rotates beneath it. The extreme case makes it obvious: the shortest path between two points at the same high latitude arcs over the pole — departing northeast-ish and arriving southeast-ish, having pointed 'north' in the middle.

A rhumb line (loxodrome) holds one constant bearing the whole way — it spirals on the globe but draws straight on a Mercator chart, which is exactly why Mercator invented the projection in 1569. The price: it's longer — London→New York costs ~150 extra km by rhumb. Classic practice splits the difference: compute the great circle, divide into segments, sail/fly each segment as a short rhumb with periodic heading updates. GPS-era autopilots just track the geodesic continuously.

True — referenced to the geographic pole, like all chart work. Your compass reads magnetic, offset by local declination (variation): −15° to +20° across the continental US, 0–25° across India and Europe, changing slowly as the magnetic pole wanders. Convert with: magnetic = true − declination (east declination subtracts). Look up your current local value (NOAA's WMM calculator); aviation and marine charts print it. Forgetting the conversion puts you kilometres off after an hour's travel.

Not by adding 180° to your outbound INITIAL bearing — that's the classic spherical-trig trap. The correct return initial bearing equals this tool's FINAL bearing reversed: if you arrive in New York heading 232°, you depart back on 52°. The asymmetry vanishes only for short hops (under ~100 km the difference is a fraction of a degree) and pure north-south routes. Swap the points in this calculator and it handles the bookkeeping for you.