Topcon’s mm GPS gives accuracy of between 3 mm and 5 mm in the vertical plain. In effect, the level

Topcon’s mm GPS gives accuracy of between 3 mm and 5 mm in the vertical plain. In effect, the level transmitted by a laser overwrites the GPS height to increase accuracy.

With new satellites being launched, Steve Skinner looks at connectivity across the expanded GNSS (Global Navigation Satellite Systems) network, how it will influence applications in construction and where it could take the industry.

Established GNSS networks include GPS and GLONASS developed by the US and Russia respectively. The € 3,4 billion European Galileo system is scheduled to join them in 2013. China too, has aspirations to expand its Beidou navigation system to global status (Beidou-2, also known as Compass) - a project that’s already more advanced than Galileo.

“The proliferation of both networks and numbers of satellites has led Leica Geosystems to move away from calling our systems GPS,” said Craig Hill, Geomatics marketing director. “To better represent the growing networks we have migrated towards naming our products GNSS systems,” he continued.

“With four proprietary satellite networks available within the next five years, GNSS connectivity across the differing satellites will ease fixing in difficult terrain and also improve accuracy,” said Ian Stilgoe, product marketing manager for survey and GPS at Topcon.

“It’s a contentious issue stating that connectivity across the different satellite platforms improves accuracy, but we’ve done testing and we’re positive that better results can be obtained,” continued Mr Stilgoe.

Justin Walford of Leica Geosystems says of accuracy, “The antennas used to track the GNSS are crucial to accuracy and tracking performance.

“In launching our SR25 Choke ring antenna we have brought innovative 3D conic choke ring design to market, improving performance relating to multipath rejection and signal to noise ratios. The SR25 also improves tracking of satellites when in low elevation,” continued Mr Walford.

Trimble too, recently launched its GNSS choke ring geodetic antenna. With updated electronics to improve low-noise amplification and GNSS tracking, the antenna is able to track all existing and planned GNSS constellations. “Our geodetic antennas offer supreme accuracy and exceptional performance for Real Time Kinematic (RTK) networks,” said Pierre Desjardins, business manager for GNSS infrastructure business.

In conjunction with the new antenna, Trimble launched its BX960 RTK GNSS receiver in September. The BX960 is a multi-channel, multi-frequency OEM GNSS receiver harnessing the power of Trimble’s BD960 module.

“This receiver delivers proven technology with the convenience of Ethernet connectivity in a ready-to-use package that’s rugged enough for unmanned vehicles,” said John Cameron, general manager at Trimble’s Pacific Crest Corporation.

Accuracy

Total accuracy is the ultimate aim for the industry. “Typical GNSS systems currently offer accuracy of around 10 mm in the horizontal plain and 20 mm in the vertical plain,” said Mr Stilgoe. “This is where Topcon’s mm GPS laser system comes into its own because it improves accuracy to between 3 and 5 mm in the vertical plain.

“In construction projects this is critical. A +/-10 mm discrepancy in the position of a road isn’t exactly catastrophic, but a +/- 20 mm variation in the rise and fall is totally inadequate,” said Mr Stilgoe.

Topcon’s Millimetre GPS system (mm GPS) uses a GPS receiver to give the software an X, Y and Z position, while sensors also pick-up the exact height from a laser. “In effect, the level from the laser overwrites the GPS height to increase accuracy,” said Mr Stilgoe.

Leica offers a similar solution using a terrestrial positioning system (TPS) total station. “On a dozer or a grader we’re looking at Total GPS,” said Wolfgang Klanner, hexagon machine control marketing support manager. “Essentially, we combine GNSS capability with the height accuracy of a TPS system. This solution is probably best known through our Leica Power Digger 3D excavator system”

“Prisms on a machine communicate with the total station that is set-up close to the working area,” said Mr Hill. “The Total Station measures angles and distances to produce the horizontal coordinates as well as the vertical height of the machine.”

“The failing of optical or laser systems is that they require line-of-site, whereas GNSS applications only require satellite access,” said Mr Hill. “Certainly, for initial, rough road works where centimetre accuracy is sufficient, current GNSS systems are perfectly adequate. For final preparation and finish, when an operator needs greater accuracy, then a combination system is still the most viable solution.”

Compatibility

“A significant issue in the industry today is inter-compatibility of equipment,” said Dr Robert Snow, director of product marketing for Magellan. “Lack of inter-compatibility because of proprietary message protocols can lock users into a single vendor’s solution. Magellan’s Blade technology, found in the new ProMark 500 GNSS survey receiver, assures not only inter-compatibility, but also the optimal combination of accessing GPS and GLONASS.

“Our Blade technology also interacts with the Satellite Based Augmentation System (SBAS), a system that supports wide-area or regional enhancement through the use of additional satellite-broadcast messages,” said Dr Snow.

“SABS connectivity is evident on most construction systems,” said Mr Stilgoe of Topcon. “SABS is a geo-stationary system that sits above a particular continent offering atmospheric correction for the main GNSS transmissions. Only accurate to within the 1,2 m level, in Europe SABS is better known as EGNOS (European geostationary navigation overlay service).

“Clearly, compatibility of equipment is extremely important,” continued Mr Stilgoe. “A contractor may arrive on a site that already has a base station, so it’s imperative that he can access that base station, regardless of the manufacturer.

“Sure, a contractor can go on-site with a rover system, but we certainly don’t believe it’s as good a solution as using a base station system, particularly when it comes to machine control.”

Packaging

Beyond connectivity and compatibility key aspects of new systems coming to market include reliability and suitability to task. “Crucial for GPS is ruggedness, reliability and maintainability of equipment,” said Dr Snow of Magellan. “GPS can provide a cost-effective means for improving efficiency so long as failures in the field are rare.”

“Modularity of systems is certainly one of Topcon’s goals,” said Mr Stilgoe. “We operate the same hardware and software on all machines so that operators who invest in our equipment now will be able to upgrade when contracts or finances allow.”

Leica, this year, introduced it’s PowerSnap concept to its machine control systems. “Our contact free control panels simply snap on and off the docking station, and without cables there’s a minimal number of components, which improves reliability,” said Mr Hill.

Beyond position

On site transmitters and receivers may represent the work face for GNSS systems, but beyond positioning, connectivity also facilitates a host of other project functions.

“Topcon Tiera is a tracking system that connects directly to the machine control systems via a canbus,” said Ian Stilgoe. “It reads all of the machine functions, such as temperatures, pressures and fluid levels and communicates and logs all this information at a base station.”

A similar monitoring concept was introduced by Komatsu in 2005 when it launched Komtrax. 100000 machines world-wide are now equipped with Komtrax.

“Effectively, this system enables customers to see what their machines are doing from the comfort of their own office,” said Simone Scucchiari, technical support manager for excavators at Komatsu Utility Europe.

“They can also send information back to the machines which is then displayed to the operator on the LCD monitor mounted in the cab,” continued Mr Scucchiari.

Autonomous machines

“I don’t know if it’s going to be ten years, or five years, but I think we’ll see a drive towards autonomous machine operation,” said Mike Rhoda, president and CEO of Volvo’s excavator business line. “I think as the technologies develop and machine positioning systems mature, then it will become increasing feasible to envision a machine that doesn’t require an operator to run.”

A point very much supported by Mr Stilgoe of Topcon, “I think if health and safety regulations allow it, we’ll certainly see fully autonomous machines in the next five to 10 years.

“A great deal of money has already been pumped into autonomous machinery for military purposes, so that machines can be put into war zones without operators. I am sure similar technology will ultimately reach construction sites,” continued Mr Stilgoe.

“At Topcon we have looked at systems and conducted a significant amount of research and development in this area, so I think the limiting factor will be legislative rather than technological,” said Mr Stilgoe.

Somewhat at odds, Wolfgang Klanner of Leica Geosystems is more reserved when it comes to fully autonomous equipment. “Leica is not actively pursuing fully automated machine control,” said Mr Klanner. “It’s possible technically, but we think that it would only take one accident involving personal injury and the systems would be out of the window for at least 10 years.”

“Our market information leads us to believe that most people wish to have someone on the machine, even if it’s only to hit the big red button if something goes wrong,” continued Mr Klanner.

“Already in agriculture, and even in open cast mining, we have systems where operators really just watch the machine rather than actively control it,” said Mr Klanner.

“One of the things that semi-autonomous machines could do is reduce the required know-how for machine operators,” said Leica’s Craig Hill. Inexperienced machine operators could, in a matter of days or even hours, operate as precisely as people with 20 to 30 years of experience.”

Vision

Although GNSS systems are not yet mm accurate, existing combination systems are providing the construction industry with precise, fast and efficient solutions. There is little question that as more satellites come on line, additional GNSS networks are created and technology develops, those behind GNSS systems will achieve their aims of mm perfect systems. Once that’s accomplished, it’s hard to see how any contractor could compete without GNSS systems on his side.

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