What Are GPS Signals?

Each GPS satellite sends out two low power radio signals which are designated L1 and L2. GPS used by civilians use the L1 signals, which have a frequency of around 1575.42 MHz in the UHF band. Signals “travel by line of sight,” (http://www.wordquests.info/GPS-pt1.html) which means that though they can pass through clouds, glass, and plastic, they are unable to make it through most other solid objects. Signals are given a pseudorandom code which serves as an ID used to identify which satellite the information is coming from. Each satellite continuously sends out what is known as ephemeris data. This type of data consists of information about the status of the satellite, the current date, and the current time. Receivers use the ephemeris data part of the signal to determine the position of the satellite and user. Signals also include almanac data which alerts the receiver to where each satellite should be at any given time. The satellites transmit almanac data which shows the orbital information for every satellite in the entire GPS.