Have the Olympics kept pace with precision timing?

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The accuracy of modern Olympic timing is made possible with the use of high quality timing devices, accurate synchronisation and atomic timing. Regular quartz oscillators are fairly accurate, but they still drift, which means without regular synchronisation, their accuracy would falter UY98UZDDVGGJ . To ensure all timing devices can achieve millisecond accuracy and precise synchronisation with one another, all Olympic timing devices are synchronised with GPS atomic clocks several times a day.

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Receiving GPS Time for Network Synchronisation

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To synchronise a computer network or other technology systems to GPS time, all that is required is a GPS network time server. GPS network time servers are simple to install, simple to use and can maintain accuracy for all sorts of technologies. Used by organisations as diverse as stock exchanges, air traffic control and banking systems, GPS time servers provide an efficient and cost effective solution to maintain network synchronicity.

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Competition for GPS Ever Closer

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Written by Richard N Williams for Galleon Systems

Since its release to the civilian population the Global Positioning System (GPS) has greatly improved and enhanced our world. From satellite navigation to the precise time used by NTP servers (Network Time Protocol) and much or our modern world’s technology.

And GPS has for several years been the only Global Navigation Satellite Systems (GNSS) and is used the world over, however, times are now changing.

There are now three other GNSS systems on the horizon that will not only act as competition for GPS but will also increase its precision and accuracy.

Glonass is a Russian GNSS system that was developed during the Cold War. However, after the fall of the Soviet Union the system fell into disrepair but it has finally been revamped and is now back up and running.

The Glonass system is now being used as a navigational aid by Russian airlines and their emergency services with in-car GNSS receivers also being rolled out for the general population to use. And the Glonass system is also allowing time synchronisation using NTP time servers as it uses the same atomic clock technology as GPS.

And Glonass is not the only competition for GPS either. The European Galileo system is on track with the first satellites expected to be launched at the end of 2010 and the Chinese Compass system is also expected to be online soon which will make four fully operational GNSS systems orbiting above Earth’s orbit.

And this is good news for those interested in ultra high time synchronisation as the systems should all be interoperable meaning anyone looking to GNSS satellites can use multiple systems to ensure even greater accuracy.

It is expected that interoperable GNSS NTP time servers will soon be available to make use of these new technologies.

MSF Outages for 2010

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Users of the National Physical Laboratory’s (NPL) MSF time and frequency signal are probably aware that the signal is occasionally taken off-air for scheduled maintenance.

NPL have published there scheduled maintenance for 2010 where the signal will be temporarily taken off-air. Usually the scheduled downtimes lasts for less than four hours but users need to be aware that while NPL and VT Communications, who service the antenna, make every effort to ensure the transmitter is off for a brief amount of time as possible, there can be delays.

And while NPL like to ensure all users of the MSF signal have advanced warning of possible outages, emergency repairs and other issues may lead to unscheduled outages. Any user receiving problems receiving the MSF signal should check the NPL website in case of unscheduled maintenance before contacting your time server vendor.

The dates and times of the scheduled maintenance periods for 2010 are as follows:

* 11 March 2010 from 10:00 UTC to 14:00 UTC

* 10 June 2010 from 10:00 BST to 14:00 BST (UTC + 1 hr)

* 9 September 2010 from 10:00 BST to 14:00 BST (UTC + 1 hr)

* 9 December 2010 from 10:00 UTC to 14:00 UTC

As these scheduled outages should take no longer than four hours, users of MSF referenced time servers should not notice any drop off in accuracy of their network as their shouldn’t be enough time for any device to drift.

However, for those users concerned about accuracy or require a NTP time server (Network Time Server) that doesn’t succumb to regular outages, they may wish to consider investing in a GPS time server.

GPS time servers receive the time from the orbiting navigational satellites. As these are available anywhere on the globe and the signals are never down for outages they can provide a constant accurate time signal (GPS time is not the same as UTC but is easily converted by NTP as it is exactly 17 seconds behind due to leap seconds being added to UTC and not GPS).

Why a GPS Time Server is the Number One Choice for Time Synchronization

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When it comes to synchronizing a computer network there are several choice to ensure each device is running the same time. NTP (Network Time Protocol) is the preferred choice of time synchronization protocols but there are a multitude of methods in how NTP receives the time.

The NTP Daemon is installed on most operating systems such as windows and applications such as Windows Time are quite capable of receiving a source of UTC time (Coordinated Universal Time) from across the internet.

UTC time is the preferred time source used by computer networks as it is kept true by atomic clocks. UTC, as the name suggests, is also universal and is used by computer networks all over the world as a source to synchronize too.

However, internet sources of UTC are to recommended for any organisation where security and accuracy are a concern. Not only can the distant from host (internet time server) to the client (your computer network) can never be accurately measured leading to a drop in precision. Furthermore, any source of internet time will need access through the firewall (usually through the UDP 123 port). And by leaving this port open, malicious users and hackers can take advantage and gain access to the system.

Dedicated NTP time servers are a better solution as they receive the time from an external source. There are really two types of NTP server, the radio reference time server and the GPS time server.
Radio reference time servers use signals broadcast by places like NPL (National Physical Laboratory in the UK) or NIST (National Institute of Standards and Time). While these signals are extremely accurate, precise and secure they are affected by regular maintenance on the transmitters that broadcast the signal. Also being long wave they are vulnerable to local interference.

GPS time servers on the other hand receive the time directly from GPS satellites. This GPS time is easily converted to UTC by NTP (GPS time is UTC – 17 seconds exactly as no leap seconds have been added.) As the GPS signal is available everywhere on the earth 24 hours a day, 365 days a week, there is never a risk of a loss of signal.
A single dedicated GPS time server can synchronize a computer network of hundreds, and even thousands of machines to within a few of milliseconds of UTC time.

Common Time Synchronization Pitfalls Finding UTC

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Time synchronization can be a headache for many network administrators attempting to synchronize a network for the first time. There are many pitfalls that an unaware network administrator can fall into when attempting to get every machine on a network to synchronize to the same time.

The first problem many network administrators make is the selection of the time source. UTC (Coordinated Universal Time) is a global timescale and is used throughout the world as a basis for time synchronization as it doesn’t rely on time zones enabling the global community to base itself on one timescale.

UTC is also controlled by a constellation of atomic clocks which ensures its accuracy; however, it is regularly adjusted to ensure that it matches mean solar time by the addition of leap seconds which are added to counter the natural slowing of the Earth’s rotation.

UTC is readily available as a time reference from a number of sources. The Internet is a popular location to receive a UTC time source. However, an Internet time source is located through the network firewall and security issues can arise from having to leave the UDP port open to receive the time requests.

Internet time sources can also be inaccurate and as NTP’s own security system known as NTP authentication cannot work across the Internet further security issues can arise.

A far better solution for getting a source of UTC is to use either the Global Positioning System (GPS) or the long wave radio transmissions broadcast by several national physics laboratories such as NIST in the USA and the UK’s NPL.

Dedicated NTP time servers can receive these secure and authenticated signals and then distribute them amongst all devices on a network.

How Satellite Navigation Works

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Satellite navigational systems, or sat navs, have changed the way we navigate our way around the high roads. Gone are the days when travellers had to have a glove box full of maps and gone too is the need to stop and ask a local for directions.

Satellite navigation means that we an now go from point A to point B confident our systems will take us there and while sat nav systems are not fool proof (we must have all read the stories of people driving over cliffs and into rivers etc), it has certainly revolutionised our wayfinding.

Currently there is only one Global Navigational Satellite System (GNSS) the American run Global Positioning System (GPS). Although, a rival European System (Galileo) is set to go online sometime after 2012 and a both a Russian (GLONASS) and Chinese (COMPASS) system are being developed.

However, all these GNSS networks will operate using the same technology as employed by GPS, and in fact, current GPS systems should be able to utilise these future systems without much alteration.

The GPS system is basically a constellation of satellites (currently there are 27). These satellites each contain onboard an atomic clock (actually two are on most GPS satellites but for the purpose of this explanation only one need be considered). The signals that are transmitted from the GPS satellite contain several pieces of information sent as one integer:

* The time the message was sent

* The orbital position of the satellite (known as the ephemeris)

* The general system health and orbits of the other GPS satellites (known as the almanac)

A satellite navigation receiver, the kind found on the dashbopard of your car, receives this information and using the timing information works out the exact distance from the receiver to the satellite. By using three or more of these signals the exact position can be triangulated (four signals are actually required as height above sea level has to be worked out too).

Because the triangulation works out when the time signal was sent and how long it took to arrive at the receiver, the signals have to be incredibly accurate. Even a second of inaccuracy could see the navigational information out but thousands of kilometres as light, and therefore radio signals, can travel nearly 300,000 km each second.

Currently the GPS satellite network can provide navigational accuracy to within 5 metres which goes to show just how accurate atomic clocks can be.

GPS Atomic Clock Time Signals

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It seems that nearly every car dashboard has a GPS receiver perched on the top. They have become incredibly popular as a navigational tool with many people relying on them solely to work their way around the road networks.

The Global Positioning System has been around for quite a few years now but was originally designed and built for US military applications but was extended for civilian use following an airline disaster.

Whilst it is incredibly useful and convenient a tool, the GPS systems is relatively simple in its operation. The navigation works using a constellation of 30 or so satellites (there are quite a few more that are orbiting but no longer operational).

The signals sent from the satellites contain three pieces of information that are received by the sat nav devices in our cars.

That information includes:

* The time the message was sent

* The orbital position of the satellite (known as the ephemeris)

* The general system health and orbits of the other GPS satellites (known as the almanac)

The way the navigational information is worked out is by using the information from four satellites. The time the signals left the each of the satellites is recorded by the sat nav receiver and the distance from each satellite is then worked out using this information. By using the information from four satellites it possible to work out exactly where the satellite receiver is, this process is known as triangulation.

However, working out exactly where you are in the world does rely on complete accuracy in the time signals that are broadcast by the satellites. As signals such as the GPS travel at the speed of light (approximately 300,000 km a second through a vacuum) even a one second inaccuracy could see positioning information out by 300 kilometres! Currently the GPS system is accurate to five metres which demonstrates just how accurate the timing information broadcast by the satellites is.

This high level of accuracy is possible because each GPS satellite contains atomic clocks. Atomic clocks are incredibly accurate relying on the unwavering oscillations of atoms to keep time – in fact each GPS satellite will run for over a million years before it will drift by as much as a second (compared to the average electronic watch which will drift by a second in a week or two)

Because of this high level of accuracy the atomic clocks on board GPS satellites can be used as a source of accurate time for the synchronization of computer networks and other devices that require synchronization.

Receiving this time signal requires the use of a NTP GPS server that will synchronize with the satellite and distribute the time to all devices on a network.

Time Synchronization Using the GPS Network

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The GPS (Global Positioning System) systems has revolutionized navigation for pilots, mariners and drivers a like. Nearly every brand new car is sold with an inbuilt satellite navigation system already installed and similar detachable devices continue to sell in their millions.

Yet the GPS system is a multi purpose tool thanks mainly to the technology it employs to provide navigational information. Each GPS satellite contains an atomic clock which signal is used to triangulate positioning information.

GPS has been around since the late 1970’s but it was only in 1983 that is stopped from being purely a tool of the military and was opened up to allow free commercial access following an accidental shooting down of a passenger airliner.

To utilise the GPS system as a timing reference, a GPS clock or GPS time server is required. These devices usually rely on the time protocol NTP (Network Time Protocol) to distribute the GPS time signal that arrives via the GPS antenna.

GPS time is not the same as UTC (Coordinated Universal Time) which is normally used  NTP for time synchronization via radio transmissions or the internet. GPS time did originally match UTC in 1980 during its inception but sine that time there have been leap seconds added to UTC to counteract the variations of the earth’s rotation, however the on-board satellite clocks are corrected to compensate for the difference between GPS time and UTC, which is 17seconds, as of 2009.

By utilising a GPS time server an entire computer network can be synchronized to within a few milliseconds of UTC ensuring that all computers are safe, secure and able to deal effectively with time sensitive transactions.

Dealing With Time computers synchronisation and timestamps

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Time is important for the smooth running of our day to day lives. Everything we do is either governed by or restrained because of time. Yet time is even more essential for computer systems as it is the only point of reference a computer has to distinguish between events and processes.

Everything a computer does is logged by the processor with what process was done and exactly when it was carried out. As computers can process hundreds if not thousands of transactions a second so the time stamp is vital for establishing the order of events.

Computers do not read and use the time in the same format that we do. A computer timestamp takes the form of a single digit that counts the number of seconds from a set point in time. In most systems this is known as the ‘prime epoch’ and is set from 00:00:00 UTC on January 1, 1970. So a timestamp for the date 23 June 2009 the timestamp would read: 1246277483 as this is the number of seconds from the prime epoch.

Computer timestamps are sent across networks and the internet, for instance every time an email is sent it is accompanied by a timestamp. When the email is replied to this too comes with a timestamp. Yet, when neither computer is synchronized the replied email could arrive back with an earlier code and this can cause untold confusion for a computer as according to its logs the email will have arrived back before the original was sent.

For this reason computer networks are synchronized to the global timescale UTC (Coordinated Universal Time). UTC is kept true by a constellation of atomic clocks which means that and computer network synchronised to a UTC source will be highly accurate.

Time synchronization on computers is dealt with by the protocol NTP (Network Time Protocol). Special dedicated NTP servers are available the receive a secure time code from either the GPS network or from specialist radio transmissions broadcast by national physical laboratories and then synchronize entire networks to the single time source.