The global positioning system (GPS) is composed of a network of 24 satellites that orbit the earth at an altitude of about 11,625 miles. Each satellite is equipped with an atomic clock which measures time by counting oscillations of a certain type of atom. This timing information is obtained by GPS receivers which require precise time to compute their distance to each satellite and ultimately their position on earth. GPS clocks utilize the same technology to determine accurate time. Contrary to ordinary GPS receivers which focus on making positioning information available to the user, GPS clocks focus on making timing information available at precise intervals. PresenTense Time Server allows you to synchronize to GPS clocks and ordinary GPS receivers via the industry standard NMEA 0183 protocol, turning your PC into an accurate time server on your local area network. A typical network time synchronization scenario using GPS technology is depicted in the diagram shown below.  In order to be compatible with PresenTense Time Server, GPS receivers must emit the GPRMC or GPGGA NMEA sentence at one or two second intervals. Special support is included for the Garmin GPS 2 Plus and the Garmin 38 hand held GPS receivers. You may use either PresenTense Server's native GPS support or the GPS support furnished by the NTP4 plug-in's reference clock support. |