Neat article. The Pentagon has been aware of this for a while now (though as I understand, the Navy only recently brought back celestial navigation into it's cu

Neat article. The Pentagon has been aware of this for a while now (though as I understand, the Navy only recently brought back celestial navigation into it's curriculum) but what's neat to me is how we might have had say, one backup method for navigation before falling back to manual methods (usually INS, which the U.S. was a leader in). But modern computers allow for pulling together a vast array of sources like the NAVSOP system described. One method I thought was neat: I play a lot of military flight sims, with my favorite aircraft being the AJS-37 Viggen from the 1970s. A lot of aircraft of this period used TACAN for navigation supplemented by INS for missions over friendly territory. But not the Swedes. They used INS, with fixes being made by the pilot using it's ground radar to identify features on the ground that would correspond on a map. The idea was that you'd program your flight plan into the computer, with your waypoints being say, a bit of land that jutted out on a coastline, or a bridge, or a tiny lake. When you're flying, as your approach the feature, there would be a little "+" where the feature should be, which may or may not have drifted. The feature would be visible on the radar, and since the pilot knew it had to be centered on it, he would correct the waypoint and skew it back onto the feature it should be on. That would then update the rest of the waypoints in the system, correcting the drift. This is modeled in the game, and so when I'm going to hit a target, I'll have a nav fix some 20-30km from the target as the actual thing I'm hitting might not be identifiable on the radar. But my INS will be corrected just shy of the target, and I can be reasonably sure it won't drift too much when I arrive in the area. We can hit points in darkness or poor weather with no visibility, no GPS, no night vision. It's not fantastic, but it's reasonably capable, and requires no outside input. The Swedes later added TERCOM to the jet in the 90s (same thing early models of the Tomahawk used to navigate) which means the INS drift is now largely corrected automatically, but if this for some reason isn't working (in the game you can perform a TERCOM fix anywhere, but in real life the amount of ground maps that could be stored was limited, so if you were wildly off course it wouldn't be able to match where you were), we still have the radar nav fix backup. Neat stuff. =)