Eric Walker added r/WatchandLearn - How GPS works [xpost from r/interestingasfuck] to Navigational instruments

Eric Walker added a number of topics and a number of links to Devices, machines, vehicles and robots, and added Devices, machines, vehicles and robots to Technology

Eric Walker added r/WatchandLearn - How GPS works [xpost from r/interestingasfuck] to Navigational instruments, and added Navigational instruments to Devices, machines, vehicles and robots