Horizon Profile Checkpoints for Low-Altitude Aircraft

A technique for utilizing on-board sensed horizon profiles and computer stored reference horizon profiles to provide navigation checkpoints for low-altitude aircraft is described. The technique has been analyzed using digitized terrain data and computer simulations to select the best method of horizon profile comparison, to determine horizon data density requirements, and to provide performance comparisons, system error limitations, and tradeoffs. Results of these analyses are shown to support feasibility conclusions and system parameter tradeoffs.