The GPS system is a satellite navigation system operated by the Department of Defense. In essence, provides a free subscription civil calendar and navigation services. GPS is primarily designed as a highly accurate global positioning and navigation reference. However, a product placement accurate is that each satellite in orbit also has an integrated high-precision atomic clock synchronized unit by the U.S. Naval Observatory (USNO). Therefore, is ideal for providing a time reference of high precision timing systems computer, such as NTP. This article attempts to describe simply as network servers time can obtain accurate timing information to provide a precise reference for synchronization of computers. It also discusses how the servers NTP can use atomic time generated by the GPS system to provide a synchronization reference for computer networks.
GPS is a constellation of 24 satellites in orbit, each with timing systems of high precision atomic clock on board. The system offers a comprehensive service, which may at any place from the face of the planet. Accurate time data is transmitted continuously from each satellite. Weather data can easily be received with modern antenna under cost and receiving equipment.
Time is broadcast for each satellite in Coordinated Universal Time (UTC), which is almost identical to Greenwich Mean Time (GMT). UTC is the same worldwide, does not vary with the time zone or DST. UTC is a standard high-precision atomic clock maintained by atomic clocks located in national standards laboratories. UTC has uniform seconds as defined by International Atomic Time (TAI) Institute.
Each time the satellite broadcasts and the positioning of information as very low frequency radio transmission of energy. The U.S. Army designates two frequencies, one for civil uses coded L1 and L2 encrypted for military use. The L1 frequency is transmitted to 1575 MHz (1.575 GHz). These weak radio transmissions can easily pass through less dense materials such as plastics and glass, but are blocked by denser materials such as metal and brick. However, newest and most sensitive receptors are being developed for indoor operation.
A GPS antenna needs to have a "line of sight" view of the satellites. Therefore, roof-mounted antenna is ideal, with full 360 degree view of the sky. Often however, an antenna on the side of a building is appropriate, provided that the horizon is too obscured by trees or buildings. The antenna is essentially a signal amplifier, which enhances the signals received for transmission over a cable to a receiver. Fifty-ohm coaxial cable is generally used to transfer signal information between the antenna and receiver.
The receiver decodes the signals received by the antenna in a usable format, easy to read. The most common protocol used by receivers is NMEA, which consists of a series of sentences of transmission. Each NMEA sentence provides an information package consisting of time, date and location information. The protocol also provides additional information such as visible satellites and satellite orientation in heaven.
NTP servers use a specific receptor adapted for applications in time. Calendar receivers have additional functions and a circuit to ensure a time reference of high precision. They also perform automated site study to compare the satellite clocks synchronicity. Time servers also utilize an accurate pulse per second (PPS output) generated by the receiver. An exit PPS provides a trigger for high-precision reference for synchronization.
The GPS system provides an ideal solution for timing networks. Using the 'free-to-air "system, NTP time servers can be synchronized to within a few microseconds of UTC.
About the Author:
Dave Evans has written a number of articles on time server and network timing. Click here, if you would like more information on NTP server systems.
Article Source: ArticlesBase.com - Using GPS For NTP Server Time Synchronisation
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