Slightly off topic: Early evolution of airway navigation...from railroad tracks, to bonfires, to lighted airways, to A-N ranges, to VOR, etc. Even then there was the occasional bonfire going out or lighted airway beacon going T/U. The only dependable navaid was the paper chart unless it blew out of the cockpit.
https://airandspace.si.edu/stories/editorial/guiding-light-airway-beacon-tower
COOL! Oh yes. Post WWI Pre WWII it was IFR "I follow Roads" or light beacons, akin to ship light houses. They flew light to light at night. Day time they read the towns name on Water towers, aka "Pilotage". I still look for the beacon and runway approach lights at night. 10 miles away I'd click on the airports lights and see the glow in the distance. It's fun to turn off the GPS.
My Dad WWII era Pilot, said to me as a kid, "Son in my day all we had was a Jelly Jar Compass and Map" when explaining the VOR to me when he took me flying in the AeroClubs Cherokee, aka Dead Reckoning. I got my Private Pilot Mid 80's, LORAN was around in a few rentals, and GPS was not out quite in GA planes, at least in mass. I really enjoyed pilotage and dead reckoning. Big satisfaction when you arrived over your fix on time.
"Pilotage is defined in the FAA's Pilot's Handbook as using landmarks or checkpoints, often in conjunction with Dead Reckoning, using last known fix and predicting next by knowing airspeed and heading and estimating (Deducting) ground speed and track based on wind drift. The Dead is short for deduction. Deduction Reckoning is not as catchy. I guess you are DEAD if you don't navigate properly.
Fan fact INS or (Inertial Nav System) or now IRU (Inertial Ref Unit) on Airliners and Military planes, provides accurate Nav position without any Nav Aids outside the plane of any kind and therefore is
dead Reckoning!!! The INS/IRU was simply told where it's on the ground, before moving (Initialized). From then on internal gyros and accelerometers keeps track of current position by which way you moved for how long and adds it up. The INS electric mechanical Gyros were later replaced by laser rings that measures the time difference it takes light to travel due to rotational movement in three planes (degrees of freedom). The FMC (Flt Management Computer) or NAV computer uses this position from IRU with a database to give accurate position on a map display. They early INS only gave raw data LAT/LONG/GND SPD and TRK, no moving map display.
However over time an INS or IRU will drift, lose accuracy and need updating by a Terrestrial Nav source (DME-DME for example) or GPS Nav input today. Way before GPS in early days of INS, the INS drifted more than today's solid state IRU's. The early INS required Pilots to manually check for accuracy before "coasting out" or going over the water portion of the trip. The cross checked they used land based NAV Aids or even pilotage to verify the IRU was working and accurate. If over the water for any length of time they needed to check position of INS using Celestial navigation by a sextant. This combo of INS and Celestial Nav was used in Apollo missions to get to moon. If you know the night sky you can use stars to navigate just by looking at them. (Pretty rough guess but point is that was #1 Nav aid in ancient times.)
Decades before GPS the SR71 had ASTO-NAV which was like a Star Wars R2-D2. It took star sightings automatically and computed position. It was cutting edge... Because of the SR71's speed only a machine could calculate accurate position. I believe variations are still used and would be critical in times of GPS black out.
https://www.thedrive.com/the-war-zo...ning-future-fights-in-gps-denied-environments
Celestial Nav goes back to rudimentary methods almost a millennium ago, middle ages. Even the Bible talks of star Nav. In "modern times" it goes back several centuries. The Sextant was invented Mid 1700's. Jump forward 200 years the first GPS prototype satellite was launched 1974. It soon failed, but a constellation of 11 GPS satellites launched by 1977. Then in 1985, the first 11-satellite GPS Block I constellation was in orbit which brought GPS for the masses. They are launching Block 3 series satellites now. They will be less prone to jamming and interference. Amazing time we live in.