Future proofing

24 April 2008

Topcon's GR-3 receiver has been used to track signals from the first Galileo satellite, which was la

Topcon's GR-3 receiver has been used to track signals from the first Galileo satellite, which was launched at the end of 2005.

The Use of Global Positioning Systems (GPS) in construction is growing rapidly in Europe as the industry recognises the efficiency, monitoring and accuracy benefits. GPS technology is now used in a wide range of construction applications from surveying and mapping through to machine control and equipment monitoring.

Rapid development of GPS receivers in the last few years has helped make the technology both easier to use and more affordable, adding to its popularity. But while ground based receivers and software are likely to continue developing, the most significant advances in satellite positioning over the next decade will probably come from new satellites.

“The US-owned Navigation Signal Timing and Ranging Global Positioning System (NAVSTAR) GPS satellites have been fully operational since 1994 but most of the development over the last 10 to 15 years has been on the ground. People tend to forget about the role of the satellites in providing GPS,” said Trimble director of worldwide sales Pete Large. “The focus of the next 10 years will be the launch of satellites offering the new L2C and L5 signals, which will improve the system for all users.”

Existing NAVSTAR satellites currently produce two signals - L1 and L2. The original L1 signal is the least accurate of the two but is freely available for civilian use with receivers such as in-car satellite navigation systems, whereas the more accurate L2 is reserved for military use.

“Although the L2 signal is encrypted for military use, the systems used by the construction industry can decode the signal and indirectly track the satellites,” said Mr Large. “Although L2 is more accurate than L1 the encryption leads to a ‘noisier’ signal, which means the information is not as accurate as it could be. New satellites will feature the L2C signal, which has dual frequency and can be directly accessed, and the faster triple frequency L5 signal.

“At present only two satellites offering L2C are available and existing satellites are only being replaced as they wear out. However, most satellites seem to be lasting almost twice as long as their original design life, so the replacement programme is slower than we’d like it to be.”

The Russian-owned Global Navigation Satellite System (GLONASS) GPS system is also being updated. Three new GLONASS satellites are due to be launched in December 2006 and another seven are expected to be launched during 2007, bringing the number of satellites in the system back up to 22. This commitment to improving coverage has led several manufacturers, including Topcon, Trimble and Leica, to offer receivers capable of using both GLONASS and NAVSTAR GPS signals.

Work is also underway in to add a third GPS constellation - the € 3 billion European-owned Galileo system is still in the testing and development phase. A test satellite, known as Giove A, for the Galileo network was launched in December 2005 and is expected to be followed by 30 operational satellites over the next few years.

Topcon launched the G3 chip, which was the first capable of tracking signals from all three GPS systems, in 2005 and is now commercially available in its GR-3 rover system and Net-G3 receiver. “The G3 technology means that users can not only track both NAVSTAR and GLONASS satellites but will also be able to start using the European funded Galileo network as it starts to come on line without the need to upgrade,” said Topcon director of international sales and marketing Mark Contino.

Topcon has successfully used its new G3 powered receivers to track signals from the test satellite and Trimble has also said that it is tracking the satellite with prototypes of it combined NAVSTAR, GLONASS and Galileo receiver.

The second test satellite - Giove B - was supposed to have been launched in autumn 2006 but has now been delayed to early 2007. This delay is expected to have a knock-on effect for deployment of the operational satellites, the first of which was planned for launch in late 2008.

Network Development

On the ground, new software is helping to improve the accuracy of existing GPS receivers. Trimble has worked with the UK-based mapping organisation Ordnance Survey to develop a Virtual Reference Station (VRS) for the UK, which allows uses to produce Real Time Kinetic (RTK) information without the need for a base station.

“The software based VRS system users feed data from Ordnance Survey’s existing reference stations and synthesises the information which an on site base station would deliver,” said Mr Large. “Logging into the system allows a wider group of users to benefit from the accuracy of RTK but without the need for additional on-site hardware.”

But users in the UK are not restricted to using hardware from one manufacturer - Leica has launched a similar service called SmartNet, which covers the city of London. The SmartNet service also uses feed data from Ordnance Survey reference stations.

According to Leica Geosystems GPS network manager Mark Burbidge, its UK system was primarily developed to improve efficiency and accuracy during construction work for the 2012 London Olympics. But other GPS users are also benefiting and SmartNet already has 160 subscribers.

“The use of fixed reference stations is growing, which opens up the possibility of developing other national VRS systems. Western Europe is the most developed with systems in Germany and Denmark already operated by national mapping agencies and Eastern European countries are also beginning to follow,” added Mr Large.

CONTROL TECHNOLOGY

One sector which is likely to benefit from VRS technology is GPS-based machine control systems that are increasingly used by the earthmoving and road building sectors. Having RTK capabilities available via VRS, rather than through an on site base station, will open up machine control for both a wider range of applications and more users.

GPS based machine control is probably one of the fastest growing uses of GPS for the built construction sector. It is enabling contractors to carry out work on site by referring to in cab displays, rather than relying on paper plans and staked cut lines and to cut to the design grade in fewer passes.

Systems are now available for almost all earthmoving equipment and are usually retro-fitted but with CANbus technology they are fully integrated into the machine’s electronics.

“Interest in three dimensional machine control, compared to two dimensional systems, is growing in Europe,” said Trimble construction sales manager Christian Luttenberger. “I have even heard of some highway contracts in Europe stating the need for three dimensional control in the tender documents.”

Almost all of the main manufacturers have launched upgraded version of their machine control systems this year to add the benefits and functionality of the latest software.

Leica now offers the PaveSmart system for concrete paving, while its GradeSmart adds the same benefits to earthworks operations and DigSmart for use with excavators.

Trimble has recently launched a new version of its GCS9000 system which can also be used with the Trimble ATS Construction Total Station to provide accuracy to within 3 mm of the design. The ATS system links the GPS machine control with an on site robotic total station to provide a higher level of accuracy than is possible with GPS alone.

This year has also seen Komatsu signed a deal with Topcon in Europe to pre-fit machine control interfaces before shipping construction equipment out to the customer. Caterpillar has been offering factory fitment of machine controls for some time and with Komatsu following suit, it is likely to become a trend that will spread to other construction equipment manufacturers and GPS suppliers over the next few years.

Sokkia has also joined forces with two other companies to provide machine control capabilities with position sensors provided by the company, but Sokkia is not planning to launch a full machine control system under its own name.

According to Topcon’s Mr Contino, some of the next developments for machine control in construction will come from other industries. “We have recently acquired Australia-based Kee Technology, which specialises in machine control for the agricultural sector,” he said. “Their agricultural systems are far more developed in terms of on board software and precision steering.

“For example, they are already being used to reduce under or over spraying of crops by automatically detecting growth patterns and switching the spraying on or off, accordingly. We are looking at the possibility of transferring the automatic steering to large construction machinery, although it is not the end for machine operators - there are too many variables on construction sites,” said Mr Contino.

Trimble is also working on a system which will allow design changes to be transferred directly for the office to the operator’s cab in real time. “We already have a US version up and running, which provides data exchange at 900 MHz,” said Mr Luttenberger. “We hope to have a European version available during 2007 but the current 450 MHz data transfer rate is not powerful enough.”

Further Developments?

Addition of new GLONASS and Galileo satellites and launch of new NAVSTAR signals will help to improve both coverage and accuracy of GPS systems. But considering the rapid advancement of hardware and software for GPS ground tools in the last few years, is there room for further developments?

According to Topcon’s Mr Contino, the potential to further improve the industry does exist and has said that the company already has something in the pipeline, which he described to CE as ‘revolutionary’. “At 2004’s Bauma exhibition we unveiled our MM GPS, and we’re expecting our latest development to make just as bigger splash at Bauma 2007,” he said.

Topcon is not likely to alone in revealing new GPS products at Bauma - both Trimble and Leica have indicated that they are working on new systems for the construction market.       ce

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