Navigation aircraft used to be a simple business. Early pilots often used roadmaps and flew low enough to read the names of towns from water towers and grain silos. Longer-range aircraft brought with them the need for a dedicated navigator, who used the sun and stars just as shipboard navigators did for centuries.The development of satellite-based global positioning systems, however, automated the process and effectively removed the navigator from the cockpit of modern commercial aircraft. Unfortunately, GPS is vulnerable to system attack and jamming, especially since GPS signals are used for military purposes—their original purpose.Can robust, low cost and accurate aircraft navigation systems be built without reliance on GPS? Honeywell has tested a prototype system that promises to do just that.Access all episodes of This Week in Engineering on engineering.com TV along with all of our other series.