GPS Machine Control Technology:The current state of its art

By Jeff Winke

Death, taxes and technology are all givens.

Eventually our clock stops ticking, taxes are everywhere, and technology continues to evolve, permeate and transform. If alive today, the innovator and inventor Ben Franklin would agree that technology has become as much a certainty as death and taxes. This is especially true in construction. Talk to any gray-headed contractor about their experience when they first started and it’s almost as dramatic as Wilbur Wright talking to a NASA engineer.

Technology has helped construction contractors work more productively and profitably. This is evident in all phases of construction and is especially dramatic in the earthmoving, excavating and grading for site prep and road building.

The stars in this dramatic, ever-changing story have been construction lasers and GPS machine control. To maintain perspective, it helps to take a snapshot – freeze the dynamic to see where we’re at … and where we’ve been and are heading.

Three technology innovators – Trimble, Topcon and Leica – and two heavy equipment manufacturers – Caterpillar and Komatsu – were asked about (1) the latest developments in machine control for site grading, (2) the applications where they are seeing the most innovative and beneficial uses of this technology, (3) the heavy equipment with the most innovative and beneficial uses of machine control, and (4) how GPS machine control is helping contractors survive the current economic malaise.

Here’s what the heavy hitters have to say about the latest technology and its impact on the earthmoving construction markets.

(1) The Latest Developments

Leica’s latest developments continue to extend its GPS machine control offering beyond the traditional grader/dozer applications to excavators and other construction equipment that need precise positioning. The company’s new dual GPS systems for dual position – position and heading – applications are intended to bring 3-D grade control to new applications, including underwater projects. These new developments are expected to complement Leica’s single GNSS+ direction sensor solutions to provide a complete range of excavator 3-D systems.

The latest development in the GPS machine control industry for Topcon is the introduction of its 3D-MC2. According to the manufacturer, this new technology “enables a dozer operator to grade twice as fast and twice as accurate over any other 3-D GPS-based system.” By replacing the dozer’s traditional slope sensor with an inertial sensor, Topcon states that its 3D-MC2 is able to take measurements up to 100 times per second, which is said to be five to 10 times faster than the older technology.

In 2009, Trimble released two new versions of its 3-D grade control system, the Trimble GCS900 Grade Control System, v11. The updates are said to expand the machine mix and system configurations, including new system options for excavators and compactors, support for towed scrapers, and enhancements for dozers and motor graders.

Trimble updates for excavators are designed to support the 2-D modes of operation in the 3-D mode to provide system flexibility. Additionally, there is support for variable boom excavator configurations, which is said to allow the technology to be used on a greater range of excavators.

For dozers and motor graders, the GCS900 updates are said to allow dynamic blade rotation for single GPS dozers and dynamic blade roll for 3-D dozers and graders. The advantage, according to Trimble, is “greater speed and accuracy because the machine operator does not need to maintain a straight or vertical blade for accurate guidance.”

According to Trimble, dozers and agricultural tractors with towed or pull-type scrapers now have support for dual GPS indicate-only, single GPS indicate and single GPS automatic lift, or automatic lift with blade slope guidance. Automating the raising and lowering of the scraper bowl is said to speed up operation and reduce operator fatigue.

Additionally, the new Trimble SNM930 on-machine cellular radio modem is designed to allow the use of  Trimble GPS machine control systems with almost any internet base station, remote base stations or other network RTK service.

PC200 & RTS customer demo_FP Komatsu America Corp. works with Topcon and Trimble to offer factory-installed, GPS-ready plug-and-play bulldozers andmotor graders in which the electrical wiring, electronic pilot control valve, plumbing and bracketry are integrated into the base machine.

In March 2009,Topcon introduced its 3DMC2 system that is designed to enable a bulldozer to grade in third gear, which is twice the speed of a conventional system. Inertial sensors with control software are said to make blade cutting-edge adjustments 10 times faster than other GPS-based system, which Komatsu reports works well with its 130-horsepower D51-22 hydrostatic transmission dozer. Trimble recently introduced its robotic total station with on-machine optical prism for applications with satellite communication interference due to tall buildings, high walls, trees, a tunnel or other obstructions. The RTS is designed to accurately measure 3-D position of bucket cutting edge to +/- 0.15 inch at 1,000 feet.

Caterpillar is now releasing new grade control offerings from the factory for its asphalt pavers, skid-steer loaders, multi-terrain loaders and compact-track loaders. Its new integrated grade and slope for Cat Asphalt Pavers is said to assist in helping contractors place the exact amount of mix on the surface, thereby controlling thickness to maximize material usage and optimize compaction performance.

A new integrated laser for Cat skid-steer loaders, multi-terrain loaders and compact track loaders is designed for working in grading applications such as building pads, roads or sports fields.

In early 2009, Caterpillar introduced the Cat AccuGrade CD700 Version 11 for its track-type tractors, hydraulic excavators, and motor graders. It provides the platform for enhancements such as the Universal Tracking System (UTS); site and laser reference support in the 3-D solution for excavators; and dynamic pitch, which is designed to allow the motor grader operator to dynamically roll the blade while maintaining accuracy.

(2) Applications with the Most Innovative and Beneficial Uses of Machine Control

Topcon reports the dozer and motor grader remain the two most widely used earthmoving machines for GPS machine control. The company claims its 3D-MC2 for the dozer market and the use of Millimeter GPS+ with Lazer Zone for the motor grader market are technologies yielding high production and accuracy for these machines.

Trimble cites two formal studies, which show that GPS-based machine control delivers significant improvements across all phases of earthmoving in time-to-completion, lower costs and improved accuracy. A Two-Roads Productivity Study compares two roads being built – one the conventional way and the other using Cat AccuGrade machine control technology. And a Two-Trenches Productivity Study compares two excavators performing trench work – one the conventional way, the other using Trimble machine control technology.

Trimble reports that that there are improvements in the rough earthworks phase. Now contractors can get up and running more quickly using their GPS grade control systems with the new Trimble SNM930 on-machine cellular radio, which allows the system to be used with almost any Internet Base Station, such as Trimble VRS networks, remote GPS base station, or other network RTK services that allow access to GPS correction information over the internet.

D51 & 3DMC2 customer demo-1_FPMore contractors across the country are using scrapers and agriculture tractors with a pull-type scraper to perform mass earthworks in site development. According to Trimble, contractors are leveraging GPS-based grade control to excavate with greater speed and accuracy and closer to grade using a bulk earthworks machine like a scraper or an ag tractor with a pull-type scraper. “GPS-based grade control is designed to provide automatic control of the scraper pan, without fear of over cutting,” Trimble says.

Contractors are using Trimble GPS-based Grade Control Systems for marine construction projects, such as sea wall construction and dredging. For sea wall construction, the typical workflow includes pushing fill material into the ocean for the seawall tip head, spreading the tip head with 2-4 x GCS900 dual GPS Dozers. Once the sea wall subbase head has been constructed, 2 x GCS900 dual GPS excavators pull up quarry material on top of the subbase tip head material. GPS-based technology is designed to allow the operator to have complete knowledge of the position of the bucket under water.

D51 & 3DMC2 smooth surface in 3F-1_FPAccording to Leica, innovative contractors are applying 3-D GPS machine control systems to excavator operations to eliminate over-digging, reduce material handling, and improve productivity with reduced efforts for layout, grade checking and as-built surveying.

Leica also reports that paving applications see a tremendous benefit through material savings that result from 3-D GPS machine control. Using a road project as an example, Leica states that the earlier that machine control is applied – in other words, the lower the layer – the better the next layers get. Less material waste and faster production multiply the benefits. On completion, the savings at each phase are like compound interest in the bank, Leica states. GPS 3-D machine control is said to be particularly well suited to large projects with its greater range and work area, especially compared with line-of-sight technologies. The company also cited the ability of GPS 3-D machine control to perform complex contours and design geometries.

(3) Equipment with the Greatest Beneficial Use of Machine Control Technology

Those surveyed agree that all types of construction equipment benefit significantly from use of grade control systems.

Caterpillar highlighted four machines and configurations benefiting from the latest technologies – soil compactors, hydraulic excavators, track-type tractors and motor graders.

Caterpillar’s AccuGrade Compaction is designed to enable smooth drum vibratory compactors to improve quality control and provide quality assurance documentation. The compaction documentation is said to mitigate risk to both the contractor and project owner. The system provides real-time pass count and Cat compaction values (CCV) mapping on the in-cab display. According to Caterpillar, this helps the operator know the exact number of passes and level of compaction. Real-time compaction data is transferred or synchronized wirelessly over site radio infrastructure back to the office for analysis and archival purposes.

Intended for bulk earthworks and excavation on steep slopes, the Cat AccuGrade for hydraulic excavators is designed to provide more accuracy and productivity gains for the contractor. New for 2009 is the ability to use a single GNSS (Global Navigation Satellite System) receiver on the excavator and still achieve the same level of accuracy for many grade-control applications. This allows contractors to re-deploy the second GPS receiver on an additional machine in their fleet while still maintaining productivity using the single GNSS configuration on the excavator.

Cat AccuGrade with automatic controls is installed on small finishing machines for smaller sites and on larger mass earthworks dozers with the expectation of achieving greater control and accuracy on sites with complex designs as well as achieving slopes on large earthworks projects such as highway and runway construction, landfill and reservoir construction, and dam building and reclamation. New for 2009 is the ability to use a single cab-mounted GNSS configuration on the D8T to D10T track-type tractors. It is intended to provide guidance for rough grading and production earthmoving machines while leaving cleanup and finish grading to the machines equipped with blade-mounted technology.

Komatsu America reports that equipment with GPS machine control achieves tighter and tighter tolerances. According to Komatsu, bulldozers and motor graders can finish grade in GPS automatic blade-control mode to typical elevation accuracy of +/- 0.6 inch. High accuracy work to +/- 0.12 inch can be achieved combining GPS laser or similar devices.

Similarly, the company states that hydraulic excavators using GPS can excavate to typical elevation accuracy of +/- 0.6 inch even in blind conditions such as underwater work. Higher accuracy can also be achieved to +/- 0.12 inch by combining GPS-laser or similar devices.

(4) Machine Control Technology Is Helping in This Recession

Trimble reports that with states starting to see U.S. Stimulus dollars being allocated for road construction projects, contractors who may not have traditionally bid on larger road projects are now leveraging Trimble GPS-based grade control systems on dozers, graders and soil compactors with the expectation of completing these projects faster and more accurately. They are using the onboard data collection capabilities to collect compaction and productivity data for grading and compaction operations analytics and reporting. Leveraging a GPS-based grade control system enables the contractor to stay competitive and continue working. For road expansion work, GPS-based grade control can be used as follows:

  • On dozers for bulk earthwork and high-accuracy material placement of the road bed’s subbase material
  • On motor graders for high-accuracy placement and grading of material lifts
  • As dual GPS with laser augmentation on motor graders for finished grading and blue topping
  • Single GPS with compaction sensor for road bed compaction and monitoring and final finished-grade compaction.

The productivity and compaction data are taken off the machine systems and used for grading and compaction productivity analysis, which determines near real-time earthworks progress. Detected problems in grading or compaction operations can be immediately addressed prior to the start of more expensive project phases, e.g., asphalt paving. According to Trimble, this information is also used to generate project reports, validating the contractor has met or exceeded the earthworks specifications once a project has been completed. The information can be submitted along with end-of-project deliverables.

Trimble also reports greater use of its GPS Site Supervisor System, which uses the new Trimble Tablet for Construction in the cab of a supervisor’s truck. The Trimble Tablet is part of its Trimble Connected Site solution. The handheld computer with built-in connectivity is said to allow jobsite supervisors, foremen, site engineers, grade checkers, construction surveyors and project managers the ability to compute in the field, connect to the office, and make decisions faster.

Leica provides a summary of how GPS machine control is helping construction contractors be productive and profitable during this severe economic downturn: “GPS machine control helps the contractor save money throughout the project. At the beginning, staking and layout times are drastically reduced. Projects can be designed more efficiently, not needing any extra features to ensure key requirements are met, and costly material ‘pads’ are eliminated. In operation, the need for manual grade checking is reduced or eliminated, along with over-work since the operator can see instantly when they have reached design grade. Operators now have the visibility to work at a higher material-handling level, leveraging their field experience to think in terms of the whole job, not just the next cut pass. GPS machine control gives the contractor more information in an easy-to-use format, reducing risk and enabling quicker reaction to any unplanned events to avoid costly impacts.”

Topcon states that in these difficult economic times, contractors who currently have jobs are trying to optimize any profit opportunities in their projects. The company states that contractors without work must change the way they do business in order to bid and work more competitively.

Accordingly, Topcon believes that GPS machine control is a solution to both scenarios. The company states that by enabling contractors to reduce staking costs by up to 90 percent, control material costs and substantially increase production, GPS machine control is the only innovation that can improve the profit potential of grading and excavating companies in tough times. Topcon reports that most GPS machine control users report recovering their initial investment on their first job using the technology.

This article originally appeared in the September 2009 issues of all the ACP publications.

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