Rhumb-line Planner

Calculate a constant-bearing spherical path and compare it with a great-circle model.

Modeling only: not for navigation, surveying, aviation, marine, or safety use. A sphere omits ellipsoidal shape, terrain, currents, magnetic variation, and datums. A finite rhumb continuation through a pole is mathematically undefined.

Path input

Input mode

Distance unit

Radius

Radius in selected unit

Start latitude °

Start longitude ° signed

Destination latitude °

Destination longitude ° signed

Longitude choice

Bearing °

Distance

Intermediate points (0–500)

Spherical model results

Rhumb points and legs

Calculated rhumb points and leg distances
#	Fraction	Latitude	Wrapped longitude	Unwrapped longitude	Leg	Cumulative

Transparent formulas

Δψ = ln(tan(π/4 + φ₂/2) / tan(π/4 + φ₁/2))
q = Δφ/Δψ; if |Δψ| is tiny, q = cos φ₁
rhumb distance = R √(Δφ² + q²Δλ²)
rhumb bearing = atan2(Δλ, Δψ)
destination: φ₂ = φ₁ + δ cos θ; Δλ = δ sin θ/q
great-circle: haversine central angle × R; initial bearing via atan2