// Package numerics provides the numerical primitives used by the trajectory
// engine: regular-grid multilinear interpolation, monotone bisection, spherical
// kinematics, and a Runge-Kutta-4 integrator with binary-search refinement of a
// termination point.
//
// Positions are carried as GeoVec (degrees and metres) and advanced with
// GeoStep, which rotates the position along a great circle. Rates are velocities
// (Rate: metres per second east/north/up), never degrees per second — a
// longitude derivative carries a 1/cos(lat) factor that diverges at the poles,
// so the singularity is absent from the formulation rather than guarded against
// by a threshold latitude. A step that reaches a pole continues down the far
// side on its own.
//
// The package has no dependencies on any domain type. Longitude wrapping into
// [0, 360) and the sphere geometry live here; unit conversions specific to a
// data source stay in the caller.
//
// All algorithms are documented in docs/numerics.tex.
package numerics