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==GPS receivers==

==GPS receivers==

GPS receivers are an extremely fast and easy way to navigate. With the ability to tell you where you are, where you're heading, how to get there, and where just about anything else is they are tough to beat for convenience. It is easy to come to rely on GPS with all of its features and convenience, but it is important to remember that like any other electronic device it may fail. While the GPS network itself it very robust, requiring little more than regular corrections from ground based stations, GPS receivers are small relatively fragile devices than may break or run out of power.

GPS receivers offer a fast and easy way to navigate, track locations, and more. By monitoring exact distances from multiple fixed GPS satellites, the receiver can continuously calculate its position, and therefore extrapolate its relative movement on all three axes of movement. When this data is fed into a GPS router system, a user can be provided with step-by-step navigational directions for driving, shipping, and more.

The most common use of GPS receivers is for automobile navigation, where devices from companies like Garmin and Tomtom are extremely popular. But these devices can also be used by people on foot, such as for hiking, orienteering, and geocaching.  But, being complex electronic devices, their reliability is not as good as a plain old [[map]] and [[compass]].

A very common use of GPS receivers is for automobile navigation. Dedicated devices from companies like Garmin and Tomtom are available, and some vehicles have GPS navigation systems integrated into the infotainment system. However, many people use the GPS navigation capabilities built into modern [[smartphone]]s. Many router applications require an active internet connection, but some also work independently. Such smartphones and dedicated devices can also be used by people on foot, such as for hiking, orienteering, and geocaching.  But, being complex electronic devices, their reliability is not as good as a plain old [[map]] and [[compass]]. It is easy to come to rely on GPS with all of its features and convenience, but of course like any other electronic device, such systems may fail. While the GPS network itself it very robust, requiring little more than regular corrections from ground based stations, GPS receivers are small relatively fragile devices than may break or run out of power. Of course, hostile actions from enemy nations can also cause disruptions and problems, such as Russian jamming of GPS signals during their 2024 invasion of Ukraine.

GPS receivers require that the clocks on the satellites be exquisitely well calibrated.  The reason is that an error of 5 microseconds in the clock synchronization will lead to a position error of one mile.  Achieving this accuracy requires that the clocks compensate for both the effects of [[special relativity]] (7 milliseconds per day) and [[general relativity]] (45 milliseconds per day in the opposite direction), leading to a total required correction of 38 milliseconds per day.<ref>http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html</ref>

GPS receivers require that the clocks on the satellites be exquisitely well calibrated.  The reason is that an error of 5 microseconds in the clock synchronization will lead to a position error of one mile.  Achieving this accuracy requires that the clocks compensate for both the effects of [[special relativity]] (7 milliseconds per day) and [[general relativity]] (45 milliseconds per day in the opposite direction), leading to a total required correction of 38 milliseconds per day.<ref>http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html</ref>