THE PEGLESS SITE

Construction sites and survey pegs have historically gone hand-in-hand. A traditional earthworks operation firstly involves the surveyor building batter rails on both sides of the alignment to define the design edges and batter slopes. Once the bulk material is removed, additional survey pegs are required for the trimming of each alignment. Additional roadway features such as cut benches and drains also require survey pegging. However, because machine control operators have constant design guidance from within their machines, they no longer require the traditional survey pegs. Design information is loaded into the construction machinery, enabling the operator to view real-time cut and fill values and horizontal and vertical data for every millimetre of the jobsite.  They no longer have to rely on survey stakes and grade-checkers with string lines and tape.

The fact that GPS guided plant can operate independently of any survey pegging has significant cost benefits. Less survey pegs means less survey field requirements. The need for grade checkers is eliminated. There is also considerable savings in survey consumables (stakes, ribbon, etc).

Overall, the creation of a peg less construction site eliminating the need for bulk earthworks set out is undoubtedly the biggest advantage of the use of machine control over traditional forms of surveying and construction.

IMPROVED ACCURACY

Earthworks is a game of cubic meter volumes and heavy machinery. The challenge of moving earth to tolerances of millimetres is daunting to say the least. For years, mankind has managed this process with rudimentary tools like sticks and strings. This system sometimes works well but is always time consuming.

Errors are common due to leaning and disturbed pegs, slack stringlines, miss-read tape measures and 'eyeing in' information between the pegged cross-sections. Therefore, when a surveyor used to show up to check final results, there was little guarantee that the results would be within tolerance.

Machine control equipment can now eliminate all the old tools from the construction site. With constant design reference for every millimetre of the job, machine guidance enables more accurate construction than traditional survey methods.

The accuracy of the machine control systems ensures grades that are within tolerance every time. Rookie machine control operators are able to use the system to continuously check the constructed results. More experienced operators are able to achieve accuracy on the first pass.

Mid job survey works such as replacing missing and disturbed stake set out are no longer required. Survey quality-assurance checks are faster as there is rarely the need to trim off any high spots. Thus earthworks construction projects using machine guidance experience fewer errors and greater conformance.

EASY DESIGN UPDATES

Traditionally, a design change made during the progress of a project results in any survey field set out being inaccurate until the survey crews identify the changes and then became available to re-mark (or completely remove) them. Because this takes time, there is a real risk of an intended design change being missed in the field.

With machine guidance the design changes are electronically updated into the system. Design changes can be quickly and easily distributed to the machine for instant use and superseded designs can be removed. The time-consuming exercise of surveyors needing to remove and replace set out stakes to reflect design model changes is therefore eliminated.

UNPLANNED WORKS

It is a reality of construction that work does not always proceed as planned. Unpredicted delays often result in the need to move earthworks activities at the last moment. Traditionally, this involved waiting for rushed survey set out in the new work area, which in turn impacts on the survey works planned for the day.

With the electronic updates provided by machine guidance, field crews have the ability to commence (if not complete) unplanned works without the need to wait for traditional survey set out. This reduces field and machine downtime. The extents of the job are readily available, enabling better planning of such things as stockpiling and also assists the positioning of basic site infrastructure such as haul roads, site compound locations and temporary drainage.

INCREASED SAFETY

Construction sites are always hives of activity. Earth is moved using heavy machinery including repeated rounds of scrapper fleets and/or road trucks. Construction programming is continuously tightening and this pressure results in multiple operations being conducted in the same work area. The work areas themselves are often difficult to access within relatively confined spaces. There is an obvious safety concern with surveyors walking around in such conditions.

Using machine guidance reduces the need for on-the-ground survey set out and construction crew string lining, resulting in less opportunity for workplace injuries involved with these tasks.

INCREASED JOB SATISFACTION

From a surveyor's point of view, there is also an often-overlooked advantage of using machine guidance on construction sites. As survey crews are performing less of the manual and repetitive task of pegging, they are able to move on to more satisfying tasks.

Similarly, another somewhat unexpected benefit of using machine guidance is the closer working relationship between field crews and surveyors. Traditionally in the Australian construction environment, surveyors do not get involved with any earthworks planning; they are largely removed from the earthworks operation and responsible purely for setting out the intended design and then checking completed works against the design.

However, by integrating the survey systems and the construction equipment, the two groups have been forced to work closer together which has helped open up communications between crews. Consequently, the use of machine control has contributed to a reduction in project staff turnover.

With a background in engineering surveying, Steed Shepherd was first introduced to GPS machine control in 1999. Since then, Steed has been heavily involved with the use of this emerging technology within the highway, railway and mining construction sectors. Steed's company Machine Control Survey Services (MCSS) specialises in the successful implementation and support of Trimble machine guidance on small and large scale construction projects including most recently the Safelink Alliance (Ipswich Motorway Upgrade: Wacol to Darra) and CoalConnect (Northern Missing Rail Link) projects.

Contact Steed: Phone +61 401 548 760 - E-mail This e-mail address is being protected from spambots. You need JavaScript enabled to view it