GPS Time Server – Common Questions Answered

What is a GPS?

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.

GPS Time Server Specialists Expand into Russia

Following success of their recent expansion into Europe, Galleon Systems have expanded their market presence with a new website in Russian. The time synchronisation and NTP server and GPS time specialist have also employed Russian speaking sales and technical support.

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.”

GPS Time Server – How they work

GPS time servers are often called many things: NTP time servers, GPS network time servers, GPS NTP servers etc. A time server is merely a device to that computer’s can contact to receive timing information from for purposes of time synchronisation.

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.

Why GPS?

Time synchronisation can be conducted in multiple ways on a computer network. There are many time protocols but NTP (Network Time Protocol) is by far the most used (probably close to 99% of networks use NTP).

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 Time Server – The First Choice for time synchronisation

GPS time servers have revolutionised the world of synchronisation. There advantages over other forms of timing references is many fold but as there are over 30 GPS satellites one will always be in range of a GPS receiver.

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 Time Server – NAVSTAR

NAVSTAR GPS is not an acronym although many people assume it is. NAVSTAR is the original name given to the US military’s Global Navigational Satellite System (GNSS).

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.

GPS Time Server – NAVSTAR

NAVSTAR GPS is not an acronym although many people assume it is. NAVSTAR is the original name given to the US military’s Global Navigational Satellite System (GNSS).

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.

GPS Time Server the Synchronisation Choice

Time servers, in reality, come in two flavours: the radio referenced time server and the GPS time server. Both are equally as good at receiving, distributing and synchronising to UTC (coordinated universal time).

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.

GPS Time Server and NTP (Network Time Protocol)

We are all used to Satellite Navigation by now. More and more people are installing those little black boxes into their cars and throwing away their old paper road maps. The advantages of satellite navigation are many fold – from constant updates keeping the maps current to being able to pin point your location miles from any landmarks or road signs but GPS has more uses than merely triangulating a position for direction finding, it can be utilized to provide time and frequency information worldwide.

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.

Choosing a dedicated GPS Time Server.

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.