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by phkahler 2676 days ago
>> Einsteinian physics are incomplete, but it allows us to use satellites moving at roughly 10KM/s to pinpoint our location to within a few metres.

Funny. I know how GPS works and that knowing the SAT locations is critical, but I never thought about how fast they are moving. They need to transmit their own position and time with great accuracy. In particular, don't they have to transmit their time and position at the time of transmission? That is a more interesting problem than I realized.
1 comments
PeterisP 2676 days ago
GPS satellites aren't really transmitting their location at any particular time, they're transmitting the so-called ephemeris and almanac data that has information about their orbits so that you can calculate their position at the time of transmission.
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crankylinuxuser 2676 days ago
And if you have a ADALM-PLUTO, you can download the brdc file (ephermis) and spoof all 12 satellites to a location of your choosing here: ftp://cddis.gsfc.nasa.gov/gnss/data/daily/2019/brdc/

https://github.com/Mictronics/pluto-gps-sim-win32

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