A precision approach guidance system that provides flying craft guidance information during a precision approach to a landing site and methods associated therewith are provided. In one embodiment, the system includes: an inertial navigation system, an onboard ranging sensor, a terrain database storing previously identified position-referenced terrain information associated with the landing site, and a position determining process. The position determining process repetitively determines a corrected position of the flying craft during the precision approach based at least in part on attitude and velocity information from an inertial navigation system, current position-referenced terrain information based on measurements from an onboard ranging sensor, and previously identified position-referenced terrain information from the terrain database.