The practical navigator relies on his ability to perform two fundamentally distinct operations: fixing his position and determining the course to steer. Guidance, in the sense that he receives (or generates within his craft) signals which continually define a vector coincident with his desired track, is not normally available to him.

Certain radio aids, notably the hyperbolic navigation systems, have however, frequently been used in the guidance role where the direction in which the signals can be particularly easily interpreted happens to coincide with the course to be steered. Thus, flying down a Decca lane is an acceptable operational technique which corresponds to making the aircraft follow the locus of constant range-difference to two points at known locations. It is not in principle necessary for the craft to perform the conversion from hyperbolic to Earth coordinates in order to do this.