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Near the end of SA people did figure out how to minimize its influence. Not because they could decrypt the military code, but because of differential GPS (comp

Near the end of SA people did figure out how to minimize its influence. Not because they could decrypt the military code, but because of differential GPS (compare the raw signals you receive with the raw signals at a known location called a continuously operating reference station; the reference station didn't move, so if the signals said it did, that's how wrong they are in that particular corner of the earth) and the ability to solve the navigation equation based on the actual carrier phase/doppler shift instead of only the transmitted messages. Both of these techniques are still good for removing much of GPS's error, which mostly involve the uncertainty about the "speed of light". It changes locally as the total electron content of the ionosphere changes. Measure against a reference station or between two different radio frequencies (L1/L2C), and that error can be minimized. You don't need a reference station anymore, as things like WAAS try to transmit these corrections from a satellite. If you want to play with high-precisions GPS, you can easily buy fancy u-blox modules from Sparkfun, connect them to a Windows computer running uCenter (from ublox), and get access to reference stations through your state to do full DGPS. With good sky conditions, you should be able to move your receiver a few centimeters and watch the lat/lon change accordingly. (New York State's service is here: https://cors.dot.ny.gov/ https://cors.dot.ny.gov/. It's free! They use a software suite that's designed to charge customers money for using the data, but the prices are all set to $0.) People say that the achievement of the 20th century was the Internet, but I think GPS was a lot harder. The Internet is just computers connected to each other with cables! This is atomic clocks in space sending you messages indistinguishable from noise that let you find your position in space within a centimeter. When the aliens invade, I think they'll be impressed! I am, anyway.

vlovich123 3y ago
Yup I was talking about differential GPS. As for difficulty, both are achievements and don’t undersell the difficulty of networking. At the 500ft level it’s all just wires but the actual details of doing it are incredibly difficult. It’s just that we’ve had so much experience pushing it forward that there’s a lot we can just take for granted which removes the magic from it. https://www.allaboutcircuits.com/news/ethernet-turns-50-look-back-feats-robert-metcalfe-co-inventor-of-ethernet/ https://www.allaboutcircuits.com/news/ethernet-turns-50-look... And that’s just local area networking. Networking broad area networks is even more complicated. As for people calling it the achievement of the 20th century, it’s more because of how it made the world smaller and the network effects of the changes it’s wrought to society (and from that perspective it is bigger than GPS and the computer itself).

vlovich123 3y ago

Yup I was talking about differential GPS. As for difficulty, both are achievements and don’t undersell the difficulty of networking. At the 500ft level it’s all just wires but the actual details of doing it are incredibly difficult. It’s just that we’ve had so much experience pushing it forward that there’s a lot we can just take for granted which removes the magic from it. https://www.allaboutcircuits.com/news/ethernet-turns-50-look-back-feats-robert-metcalfe-co-inventor-of-ethernet/ https://www.allaboutcircuits.com/news/ethernet-turns-50-look... And that’s just local area networking. Networking broad area networks is even more complicated. As for people calling it the achievement of the 20th century, it’s more because of how it made the world smaller and the network effects of the changes it’s wrought to society (and from that perspective it is bigger than GPS and the computer itself).