The new Exactime 300 GPS Timing and Synchronization Receiver boasts waterproof protection, anti-UV, anti-acidity and anti-alkalinity properties to ensure reliable and continual communication with the GPS network.

The attractive white mushroom is smaller than conventional GPS antennas and sits just 77.5mm or 3.05-inch in height and is easily fitted and installed thanks to the inclusion of a full installation guide and CD manual.

Whilst an ideal unit for a GPS time server this industry standard antenna is also ideal for all GPS receiving needs including: Marine Navigation and Control Vehicle Tracking.

The main features of the Exactime 300 mushroom antenna are:

• Built-in patch antenna • 12 parallel tracking channels • Fast TTFF (Time to first fix) and low power consumption • On-board, rechargeable battery sustained Real-Time Clock and control • parameters memory for fast satellite acquisition during power-up • Interference filter to major VHF channels of marine radar • WAAS compliant with EGNOS support • Perfect Static Drift for both of speed and course •  Magnetic Declination compensation • Is protected against reverse polarity voltage • Support RS-232 or RS-422 interface, Support 1 PPS output.

Exacttime 300 Mushroom Antenna

GPS (Global Positioning System) is the US controlled satellite navigation system which is commonly used by motorists, airlines and seafarers to find their position. The technology is based on time signals sent from atomic clocks that are onboard each GPS satellite. Atomic clocks have to be used as GPS positioning is based on triangulation of the time signals when they arrive at a receiver. As the signals travel the speed of light a second of inaccuracy could see positioning information out by hundreds of thousands of kilometres.

What is a GPS Time Server?

A GPS time server is a dedicated server that receives the time signal from the GPS satellites and distributes it around a network. Most GPS time servers use the protocol NTP (Network Time Protocol) to distribute the time to devices and computers on a network.

How accurate is a GPS time server?

Typically, GPS time servers can provide accuracy to within a few milliseconds (thousandths of a second) but a lot depends on a network layout. Time synchronisation can be affected by distance travelled and the speed machines process information

IS GPS time the same as UTC?

No, however, Coordinated Universal Time and GPS time are both based on International Atomic Time. The difference between the two is that UTC calculates for leap seconds that are added to adjust for slowing of the Earth’s rotation due to tidal and lunar effects. Since the GPS signal went online there have been 15 leap seconds which means GPS time is exactly 15 seconds slower than UTC but most GPS time server systems account for this ensuring that GPS time is converted to UTC.

Despite the massive economic downturn, Galleon Systems are a continual success story that have recently employed native speakers in Polish, German, French, Spanish, Italian and English have now added Russian to their team of multilingual employees.

The company’s new ntp server website  is now up and running and the first Russian orders have started to come in.  Managing Director Mark Neal said: “Many companies will sell products globally without offering the relevant support. Many clients rely on our products to keep their networks and businesses running smoothly, which is why we feel it is important to offer the relevant technical support along with the actual hardware itself.

“For this reason we have ensured that any potential customers from Russia and its satellite countries will be able to communicate effectively with members of our staff.”

Atomic clocks are not just used to keep track of time. The atomic clock is an integral part of the GPS system (Global Positioning System) as each GPS satellite has its own onboard atomic clock that generates a time signal that is picked up by GPS receivers who can calculate their position by using the precise signal from three or more satellites.

Atomic clocks need to be used as the signal s from the satellites travel at the speed of light and as light travels nearly 300,000 km each second any slight inaccuracy could put navigation out by miles.

A GPS time server is a network time server that uses the time signal from the GPS network’s satellites to synchronise the time on computer networks. A GPS time server often uses NTP (Network Time Protocol) as a method of distributing time which is why these devices are often referred to as NTP GPS time servers.

Computer networks that are synchronised using a dedicated time server are normally synchronised to UTC (Coordinated Universal Time) and while the GPS signal is not UTC, GPS time, like UTC, is based on International Atomic Time (TAI) and is easily converted by NTP.

Most time servers use the protocol NTP (Network Time Protocol). NTP is one of the Internet’s oldest protocols and is used by the majority of machines that use a time server. NTP is often installed, in a basic form, in most operating systems.

A GPS time server, as the names suggests, receives a timing signal from the GPS network. GPS satellites are really nothing more than orbiting clocks. Onboard each GPS satellite is an atomic clock. The ultra-precise time from this clock is what is transmitted from the satellite (along with the satellite’s position).

A satellite navigation system works by receiving the time signal from three or more satellites and by working out the position of the satellites and how long the signals took to arrive, it can triangulate a position.

A GPS time server needs even less information and only one satellite is required in order to receive a timing reference. A GPS time server’s antenna will receive a timing signal from one of the 33 orbiting satellites via line of sight, so the best place to fix the antenna is the roof.

Most dedicated GPS NTP time servers require a good 48 hours to locate and get a steady fix on a satellite but once they have it is rare for communication to be lost.

The time relayed by GPS satellites is known as GPS time and although it differs to the official global timescale UTC (Coordinated Universal Time) as they are both based on atomic time (TAI) GPS time is easily converted by NTP.

A GPS time server is often referred to as a stratum 1 NTP device, a stratum 2 device is a machine that receives the time from the GPS time server. Stratum 2 and stratum 3 devices can also be used as a time servers and in this way a single GPS time server can operate as a timing source for an unlimited amount of computers and devices as long as the hierarchy of NTP is followed.

But GPS has more uses than just navigation as the technology that GPS utilises is based around the atomic clock. Atomic clocks are highly accurate devices, so accurate that within a billion years they will not lose a second in time.

It is this accuracy that allows satellite navigation devices to triangulate the positioning by measuring the time it takes for the GPS signals to arrive. As radio waves, such as those broadcast by the GPS satellites travel at the speed of light, an inaccuracy of just one second could see the positioning device inaccurate by 300,000 km (the speed light travels per second).

This timing signal broadcast by the satellites can also be utilised by a GPS time server. GPS time servers use the atomic clock signal and convert it into UTC (Coordinated Universal Time) which can be used by network time servers.

These time servers are often referred to as a GPS time server as they use GPS as a timing source to synchronise entire computer networks to.  GPS signals are highly accurate and available anywhere on the planet.

This is the main cause for GPS time servers to display the incorrect time. To test the accuracy of a GPS time server, you should verify the accuracy of your GPS’ displayed UTC by comparing it against an accurate time standard such as the MSF signal or by using a guaranteed source of UTC from across the Internet – details of which are posted on the NTP pool.

Reliable, precision timing is available from the Global Positioning System by using a GPS time server as they use the GPS 1PPS signal. Such units provide the current UTC to an accuracy of 1/1000 of a second or better.

Yes. The signals that are broadcast by GPS satellites contain time information and the position of the satellite it came from (and its velocity). The timing information is generated by an onboard caesium atomic clock. It is this information used by satellite navigation devices (sat navs) that enables global positioning. Sat Navs use these signals from multiple satellites to triangulate a position.

How accurate is GPS positioning?

Because the time signal generated by GPS comes from an atomic clock it is accurate to within 16 nanoseconds (16 billionths of a second). As light travels nearly 186 000 miles in a second this equates to around 16 feet (5+metres) which means a GPS positioning system is usually accurate to this much.

Is GPS time the same as UTC?

No. GPS time, like UTC (Coordinated Universal Time)is based on International Atomic Time (TAI) – the time told by atomic clocks. However as the GPS system was developed several decades ago it is now 14 seconds (and soon to be 15) behind UTC because it has missed out on the Leap Seconds added to UTC to calibrate for the Earth’s slowing rotation.

How can I use GPS as a source of UTC then?

Fortunately a GPS time server will convert GPS to the current UTC time, which as od 1 January 2009 will mean it has to add exactly 15 seconds.

The way a time server receives the time is what defines it. A radio referenced time server will receive a time signal from a national physics laboratory via a long wave radio signal. A GPS time server receives a time signal from the Global Positioning System a constellation of satellites designed to provide navigation information.

What makes GPS possible is that onboard each global positioning satellite there is an atomic clock. The time from this clock is broadcast along with the position and velocity of the satellite. It is this information that a satellite navigation receiver uses to work out position by triangulation. It receives the same data from three or more satellites and works out by the time it takes for the transmission from each satellite to reach the receiver.

While the atomic clocks onboard the GPS satellites do not broadcast UTC (Coordinated Universal Time – the civil global timescale) because it is an atomic clock signal and therefore extremely reliable, a GPS time server can easily translate the GPS time into UTC.

It is this information that is received by satellite navigation devices that can then triangulate the position of the receiver by working out how long the signal has taken to arrive from various satellites.

These time signals, like all radio transmissions travel at the speed of light (which is close to 300,000km a second). It is therefore highly important that these devices are not just accurate to a second but to a millionth of a second otherwise the navigation system would be useless.

It is this timing information that can be utilized by a GPS time server as a base for network time. Although this timing information is not in a UTC format (Coordinated Universal Time), the World’s global timescale, it easily converted because of its origin from an atomic clock.

A GPS time server can receive the signal from a GPS aerial although this does need to have a good view of the sky as the satellites relay their transmissions via line-of-sight.
Using a dedicated GPS time server a computer network can be synchronised to within a few milliseconds of NTP (milli=1000th of a second) and provide security and authentication.

Following the increase use of GPS technology over the last few years, GPS time servers are now relatively inexpensive and are simple and straight forward systems to install.

The Global Positioning System was designed and built by the US military in the late 1970’s, although it didn’t achieve initial operational capability until 1993. GPS was originally designed as a military only system but in 1983 after a USSR aircraft shot down a Korean airliner that had accidentally strayed into Soviet airspace, the then President of the United States, Ronald Reagan, vowed the system would be available for civilian use once completed.

Full Operational Capability was declared by the now named NAVSTAR GPS in April 1995 and in 1996 to fulfil his predecessors promise the U.S. President Bill Clinton issued a policy directive declaring GPS to be a dual-use system; one for US military use and one system for civilians.

Currently GPS is the World’s only GNSS (Global Navigational Satellite System) although the Russian GLONASS system that was operational during the Cold War but has since fallen into disrepair is being repaired and a European GNSS known as Galileo is expected to be operational by 2012, other systems developed by China and India are also being developed.

GPS is primarily a navigational system that transmits precise timing information via an onboard atomic clock. It is this information and the satellites location that is used to triangulate positioning. However, the GPS signal can also be used by a GPS time server as a timing source.

Most time servers receive a UTC time signal UTC (Coordinated Universal Time) yet, there are multiple places that NTP can receive a signal from but each has it downsides. The most widely used source of UTC is the Internet but no serious network administrator would dare to use the Internet as a timing source.

Internet timing sources can’t be authenticated using NTP’s security measure and an Internet timing source will exist outside a networks firewall so a TCP/IP port would need to be left open both of these problems could leave a network open to malicious attacks, abuse or even fraud. Another reason why Internet sources should not be used is that a recent survey found less than a third were accurate enough to UTC to be useful and those that were depended on the distance from the client.

Time and frequency transmissions broadcast in longwave are far more secure and far more accurate than any Internet timing source. These transmissions are broadcast by several national physics laboratories and provide a safe, secure and highly accurate method of receiving UTV. Unfortunately not every country has a timing broadcast and even in a country that does the signals are vulnerable to local geography and interference.

GPS however, is available everywhere on the planet, the only downside at all in using a GPS time server is that it needs an antenna to be situated on the roof, which in most cases is not normally an issue.

GPS is an ideal time source as a GPS signal is available anywhere on the globe. GPS stands for Global Positioning System, the GPS network is owned by the US military and controlled and run by the US air force (space wing). It is however, since the late 1980’s been opened up to the world’s civilian population as tool to aid navigation.

The GPS network is actually a constellation of 32 satellites that orbit the Earth, they do not actually provide positioning information (GPS receivers do that) but transmit from their onboard atomic clocks a timing signal.

This timing signal is what is used to work out a global position by triangulating 3-4 timing signals a receiver can work out how far and therefore the position you are from a satellite. In essence then, a global positioning satellite is just an orbiting clock and it is this information that is broadcast that can be picked up by a GPS time server and distributed amongst a network.

Whilst strictly speaking GPS time is not the same as the global timescale UTC (coordinated universal time), a GPS time server will automatically convert the time format into UTC.

A GPS time server can provide unbridled accuracy with networks able to maintain accuracy to within a few milliseconds of UTC.

A GPS time server (Global Positioning System) bought fifteen years ago would have cost somewhere in the reason of £8,000-£10,000 ($15,000-$17,000) but thanks to the growing use of the technology the price of GPS receivers has plummeted and they can be bought for as little as £350 ($600). His has made GPS the dominate form of timing references for time synchronisation.

A GPS time server will come in several forms, some are designed to be fitted into standard server racks, these rack-mountable GPS time server will take up one or two standard U spaces depending on server type.

Other GPS time servers are smaller and more discrete, ideal to be located outside a server room. While GPS time servers offer unrivalled accuracy and a signal is available literally everywhere on the planet it does have one down-side in that a GPS antenna has to have a clear view of the sky. This means that the antenna has to be situated on a roof of a building otherwise there is a possibility that the signal will be lost.

GPS is an American military controlled system that was opened up for the use of civilians following a terrible air disaster in the late 1980’s. GPS receivers used to be astronomically expensive and all but the most wealthy network administrators would use the GPS signal as a source of UTC time.

However, due to advances in technology in recent years GPS technology has dramatically dropped in price and the GPS time server is now the globally preferred method of receiving a UTC timing source.

Other methods have continually been available of course with national time and frequency transmissions such as MSF in the UK, DCF in Germany and the WWVB signal in the USA having been the most popular method over the last decade.

However, there are drawbacks to using the national time and frequency transmissions. They are all broadcast on similar long-wave frequencies and are vulnerable to topography and interference from weather and other electrical appliances. These time and signal transmissions are also only available in a select few countries and even in the country of origin the local geography can prevent the signal getting through.

One of the reasons GPS is now so popular is that no matter where you are in the world the GPS receiver will always be able to receive a signal just as long as the GPS antenna can obtain a clear view of the sky.

Currently NAVSTAR is the world’s only fully functioning GNSS, although the European Galileo system is expected to be operational in a few years and the former Russian GLONASS system is being put back into commission after it fell into disrepair following the collapse of the Soviet Union.

NAVSTAR is controlled and run by the US Air Force’s 50th Space Wing but has been available for civilian use since the late 1980’s when a Korean passenger airliner was accidently shot down.

NAVSTAR is most commonly used as a positioning and navigational tool but the information it transmits is basic timing data that is generated by an onboard atomic clock.

It is these ultra precise timing signals that a satellite navigation system will use to work out positioning but they can also be utilised by a GPS time server as a source of UTC (coordinated universal time). Strictly speaking the time signal from NAVSTAR is not in UTC format but is kept very close to UTC (within 1 microseconds).

Using NAVSTAR GPS as a timing reference means that a UTC time source can be utilised safely, securely and reliably from anywhere on the globe.

Currently NAVSTAR is the world’s only fully functioning GNSS, although the European Galileo system is expected to be operational in a few years and the former Russian GLONASS system is being put back into commission after it fell into disrepair following the collapse of the Soviet Union.

NAVSTAR is controlled and run by the US Air Force’s 50th Space Wing but has been available for civilian use since the late 1980’s when a Korean passenger airliner was accidently shot down.

NAVSTAR is most commonly used as a positioning and navigational tool but the information it transmits is basic timing data that is generated by an onboard atomic clock.

It is these ultra precise timing signals that a satellite navigation system will use to work out positioning but they can also be utilised by a GPS time server as a source of UTC (coordinated universal time). Strictly speaking the time signal from NAVSTAR is not in UTC format but is kept very close to UTC (within 1 microseconds).

Using NAVSTAR GPS as a timing reference means that a UTC time source can be utilised safely, securely and reliably from anywhere on the globe.

The GPS time server receives its timing signal from the GPS network (Global Positioning System) and has revolutionised the way computers are able to keep track of time.

The GPS network is controlled by the US military and it was due to a military accident involving an airliner that the US government allowed the GPS network to be utilised by civilians around the globe.

The GPS system works by relaying precise time information which can be calculated by a GPS receiver to work out distances. This precise timing information is generated by an onboard atomic clock in the satellite and it is this atomic clock that a GPS time server receives the time from.

Without GPS the only other alternatives to receiving a time signal that relays UTC time (coordinated universal time) would be to use the national time and frequency radio broadcasts transmitted by several national physics laboratories, although these are not available everywhere. Alternatively the only other solution is to use the Internet which means using a device external to your firewall and also a time server that cannot be proven accurate.

However, while a radio signal is limited in range and vulnerable to interference the GPS signal, transmitted from one of the 33 NAVSTAR satellites in orbit, is available literally anywhere on the globe.

For this reason the GPS time signal is now the time reference of choice for network administrators needing a source of UTC time. The only prerequisite for a GPS time server is that that GPS antenna has to have a clear view of the sky.

This does pose some problems as the only place where an antenna can view the entire sky is on the roof. The antenna is also limited in the length of cable that it can run which means in some very large buildings there may be logistical problems in running the cable from the server room to the roof.

A GPS Time server can provide highly accurate timing information in a secure and safe environment. Using a GPS time server and a network can be synchronised to within a few milliseconds of UTC.

GNSS systems like GPS are based on the same principle. A constellation of satellites orbiting the Earth each have onboard an atomic clock. These clocks are accurate to within a few microseconds and it is this time-telling accuracy that allows satellite navigation possible.

The GPS satellite continually transmits its location along with the time told by its atomic clock. It is this information that is received by a satellite navigation unit that works out how long the message took to arrive from the satellite and therefore the distance away from it. By using four or more satellites a GPS receiver can triangulate its exact position.

Atomic clocks have to be used onboard the satellites as even tiny inaccuracies in time could cause huge errors in navigation. The signals from the satellites travel at the speed of light which can manage 300,000 km every second so even a millisecond out would make the satellite navigation inaccurate by hundreds of kilometres.

Because of its accuracy, this timing signal broadcast from the onboard atomic clocks can be utilised as a source of UTC time by a GPS time server. A GPS antenna connected to a dedicated time server can synchronise a computer network to within a few milliseconds of UTC time.

One of the most common causes for problems with a GPS time server is in failure to receive a signal. While the GPS transmission is extremely impervious to weather interference and as most GPS time servers can receive a signal from between one and twelve different satellites, the transmission is very robust. If a signal is not being received then the first point of call is the antenna.

A GPS time server antenna needs to have a clear view of the sky this is because the signal from the satellites works by direct line-of-sight. While the signal is robust avoid placing the transmitter near to a satellite dish or other broadcast aerial as this could interfere with the signal. Also be aware of foliage which can creep over the antenna and block the signal. Some GPS antennas can work through a window, however the window must not have any coating on the glass such as E-glass and there must still be a direct line of sight from the window to the satellite.

The cable connecting the antenna can also cause problems. Ensure there are no breaks and that the cable is not too long for the specifications of the antenna. Too much cable and the signal may not have enough strength to make the distance.

A much rarer problem for a GPS time server would be trouble with the receiver. Fortunately most dedicated GPS time servers have a reset and test mode. If you are confident that the antenna is in fully working and operational order then reset the receiver and run the test mode.

If all the above fails it is possible that the unit is faulty and should be returned to your manufacture or supplier.

Originally built for the United States Military, it was following a major air disaster in 1985 the then President of the USA, Ronald Regan, decided to make the military positing system available for civilians to prevent future tragedies.

GPS is based on a constellation of between 24 and 32 Medium Earth Orbit satellites. These satellite all house an onboard atomic clock. Atomic clocks are the most accurate timekeeping devices keeping time to within a few hundred nanoseconds.

A  GPS receiver calculates its position on Earth by timing the signals sent by the GPS satellites. Each satellite continually transmits the time as told by its atomic clock along with information about the location of the satellite that sent it. The receiver uses the arrival time of each message to measure the distance to each satellite. By using the distance from four or more satellites the GPS receiver can work out via triangulation exactly where it is in the world.

As the onboard atomic clocks are so accurate the GPS time signals can be used by NTP time servers. The time signal can be received via a time server fitted with a GPS antenna. This time signal can then be distributed across a network. The advantage of GPS as a timing reference is that the signal is literally available anywhere in the world so long as the antenna can get a good view of the sky.

Since the early 1990’s the Global Positioning System (GPS) has been the worlds’ only fully functioning Global Navigational Satellite System (GNSS). Run by the American military, GPS (sometimes referred to as NAVSTAR) has allowed accurate timing and location finding all over the world.

To accurately pinpoint a location, all GNSS systems require an absolute time source, that is a time source as accurate as humanely possible such as that from an atomic clock. Without knowing exactly what the time is a GNSS satellite would not be able to accurately pin point a location (as the Earth, satellites and people are all moving about a location can only be defined by a position and time). Because of the distance of the satellites away from the Earth, even an inaccuracy of a second or two could mean a sat nav’s location could be miles out.

For this reason each satellite has a highly accurate atomic clock onboard which can also be used by NTP (Network Time Protocol) servers to synchronise computer networks. GPS is an ideal time and frequency source because it can provide highly accurate time anywhere in the world using relatively cheap components.

A GPS receiver decodes the signal sent from the GPS antenna to a computer readable protocol which can be utilised by most time servers and operating systems including, Windows, LINUX and UNIX.

The GPS receiver also outputs a precise pulse every second that GPS NTP servers and computer time servers may utilise to provide ultra-precise timing. The pulse-per-second timing on most receivers is accurate to within 0.001 of a second of UTC (Coordinated Universal Time or Temps Universel Coordonné).

GPS is ideal in providing NTP time servers or stand-alone computers with a highly accurate external reference for synchronisation. Even with relatively low cost equipment, accuracy of hundred nanoseconds (a nanosecond = a billionth of a second) can be reasonably achieved using GPS as an external reference.

In 2002, the European Space Agency and European Union agreed to build Europe’s own GNSS called Galileo. To compete with the new and more advanced GNSS technologies the GPS programme is currently being upgraded and it is expected that when Galileo begins relaying signals both systems will become interoperable allowing even more accuracy in timing and positioning.

Because of the advancement in satellite navigation technologies and the increased coverage of the American GPS satellite network, many more administrators are choosing GPS as a source for a timing reference to synchronize their time servers too.

This article explores the need for a GPS time server and the things to look out for when selecting one.

Traditionally many more people opted to receive a timing source from either across the Internet or via specialist national time and frequency transmissions. However, the Global Positioning System is now by far the most popular method to receive a UTC time source from.

UTC (Coordinated Universal Time) is the global timescale based on the time told by atomic clocks which are the most accurate of time keeping devices.

A GPS time server is a relatively simple piece of hardware. Normally it consists of a dedicated NTP server with software, a GPS receiver and a GPS antenna. The antenna is the only drawback in using a dedicated GPS time server as it has to be positioned on the roof to have a clear view of the sky, although some dedicated GPS time servers can still keep time synchronized if they only receive a signal for a few hours a day, although this is not the most accurate way of time synchronization.

Once connected, the GPS time server will receive the time signal from the GPS satellites and then distribute it to all devices that require synchronization.

Most time servers, whether they receive a GPS signal or not, will use Network Time Protocol (NTP) to distribute the time signal to all devices.

NTP is one of the Internet’s oldest protocols and is by far the most widespread time synchronization protocols used. NTP is under constant development and can accurately synchronise a network to within a few milliseconds of UTC time via a dedicated GPS time server.

Accuracy is of course the fundamental feature in time servers and Network Time Protocol (NTP) has been designed to ensure the highest accuracy possible is always obtainable.

Unfortunately many administrators opt to use an Internet timing source to run their time server with. Unfortunately several studies of Internet timing references discovered that nearly two thirds were inaccurate by over several seconds (almost an eternity in the world of NTP) and those that weren’t were often too far away from a client to provide reliable accuracy.

Probably the most accurate and widely used method of retrieving a reliable time reference is to use a dedicated GPS Time Server.

The Global Positioning System is ideal to provide an accurate timing reference as each global positioning satellite contains an atomic clock that beams timing information directly to Earth. As these satellites are in a relatively low and known orbit the distance the signal travels can be compensated for by the GPS time server ensuring a high level of accuracy.

Another benefit is that a GPS time server will always be able to receive a signal no matter where in the world it is situated as long as the GPS antenna can have a clear view of the sky, enabling it to communicate with a satellite.

A GPS time server are also relatively inexpensive and advances in GPS technology means the costs are perennially falling. There is a downside to a GPS server in that to ensure the antenna can spot a satellite it needs to be situated  on certain buildings this can be expensive, impractical or even impossible as the maximum cable length should never exceed 100 metres.

Many people assume that because they are running NTP then their networks are perfectly synchronised and running accurate UTC time (UTC – Coordinated Universal Time – the world’s standard timescale).

However, NTP is a protocol designed for synchronisation and does just that it synchronises. NTP can synchronise time from an atomic clock that doesn’t lose more than a second every million years or so or to a cheap plastic wrist watch that runs a minutes slow each week. A time server is therefore only as good as the timing reference that it uses to synchronise to.

Many administrators select a timing source from the Internet and automatically assume that their server is running accurate UTC time. However, many Internet timing sources are wholly inaccurate and those that are not can often be too far away from a client to provide any hope of an accurate time source, not to mention the fact that Internet timing references can’t be authenticated and can leave a system open to a malicious attack.

Fortunately there are two methods that can provide both accurate and secure timing information to a time server. The first method is to use a radio referenced time server. These simple pieces of kit receive the national time and frequency transmission that many countries broadcast. This signal can be picked up usually within a 1000km of the transmitter and provides accuracy to within a few milliseconds. unfortunately places outside the transmission’s country of origin or areas with topographical features such as mountains may struggle to receive a signal.

Fortunately a GPS time server can receive a signal anywhere on Earth as long as the antenna can see a patch of blue sky. Also a GPS time server provides slightly better accuracy than a radio referenced one. They are also relatively inexpensive, however, the antenna does normally have to go to the roof which can bring with it its own costs.

The signals broadcast by the American Military’s Global Satellite Navigation System (GNSS) has provided timing references since the late 1990’s and is used worldwide as a timing source in hundreds of thousands of GPS time servers. Now GPS is to receive competition from not just the proposed European Galileo system but the Russians and Chinese are attempting to get into the act.

Currently the GPS is the world’s only fully functioning, global navigation satellite system, however, the European Union and European Space Agency agreed in 2002 for a European alternative called Galileo which is scheduled to be fully operational by 2012-2013.

The Russian Glonass system, which was fully operational during the height of the Cold War but had fallen into disrepair after the collapse of Soviet Union, has also been vowed to be patched up and to be fully operational again by 2010. A Chinese system called Compass is also being developed although some doubt exists as to whether it will be a stand alone system or be incorporated into Europe’s Galileo network, India have also proposed there own system.

Galileo which is expected to work alongside the GPS system providing timing references from 2013. The broadcasts will be similar to those currently received by a GPS time server and the two systems should work well together as Galileo is designed to be interoperable with GPS.

This means there will be close correspondence between the signals from the two systems, and most of the frequencies used by the Galileo satellite signals will be similar to GPS signals. This will  increase accuracy of Galileo as well as increasing the capabilities of GPS as only minor software alterations will be needed for a  current GPS time server to be able to locate Galileo satellites too. The great advantage of this is that it will be able to see around twice as many satellites providing better accuracy

Although Galileo is intended to have somewhat better positioning and timing performance than the current GPS system, the difference will be reduced or even disappear with a planned modernisation of GPS, designed to ensure the US system doesn’t lag behind the next generation.

Galileo is expected to be fully operational, by 2013, with timing and positioning signals available at the same time.

But GPS is much more than a handy navigational tool. The constellation of 24 satellites each contain some of the world’s most accurate chronometers in the shape of atomic clocks. These provide such accuracy in timing that a million years could pass and not even a second would have been gained or lost

These clocks are what enable us to pinpoint our location on Earth as a GPS receiver can workout how long the timing signal took to reach it and therefore how far away from the satellite it is. Using three or four satellites means an exact location can be pin-pointed by triangulation. Atomic clocks need to be used as just one seconds inaccuracy could mean a location could be hundreds of thousands of miles out because of the vast distances radio signals can travel in that time.

These timing signals can also be utilised to provide extremely accurate synchronisation for computer networks by receiving the timing signal via a GPS antenna connected to a GPS time server. A GPS time server uses NTP (Network Time Protocol) to synchronise machines on a network.

Because of the accuracy of the atomic clocks a GPS Time Server can obtain an accuracy to within a few hundred nanoseconds of UTC time (a nano is one billionth of a second)

UTC (Coordinated Universal Time) is a global timescale developed after the invention of the atomic clock. It is a standardised time scale base on Greenwich Meantime but allows for the minute slowing of the Earth’s rotation (caused by the Moon’s gravity).

A GPS time server can also receive a timing signal from anywhere in the world (as long as it can get a clear view of the sky)

Whether it doing the shopping from our PC at home or whether we work in a global trading company. The Internet is fast becoming the world’s new high street.

Time synchronisation is therefore more vital and relevant today than it has ever been. Time synchronisation errors are commonplace, just check your inbox you may find that email that has just arrived may technically not have been sent yet. This may not cause you any problems but what happens if you book and airline ticket on a computer system that is not synchronised?  You may find the plane seat has been sold after you had bought it or you could have the last bid on an Internet auction site only to find somebody else wins the lot because their earlier bid was on a computer with a faster clock.

In some industries time synchronisation is not only essential, but without it trading would become impossible, just think of the stock exchange where millions are won and lost in seconds.

Fortunately time synchronisation is not the headache it used to be. It is now possible to connect to an accurate UTC (Coordinated Universal Time – a global standardised time scale based on the time told by atomic clocks) time source with relatively low cost equipment.

A GPS time server is a relatively inexpensive and simple device that receives a timing signal directly from a global positioning satellite. Because GPS satellites contain atomic clocks (essential in providing accurate positioning) the signal of which can be picked up and used to synchronise an entire network.

A dedicated GPS time server is relatively simple and straightforward to install and comprises of a GPS receiver equipped with NTP software (network time protocol – software used to synchronise a network) and a GPS antenna. The only difficulties faced with the installation of a GPS time server is that the antenna needs a good view of the sky to ensure it can receive the satellite information.